Merge tag 'rpmsg' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

Pull "remoteproc/rpmsg: new subsystem" from Arnd Bergmann:
"This new subsystem provides a common way to talk to secondary
processors on an SoC, e.g. a DSP, GPU or service processor, using
virtio as the transport. In the long run, it should replace a few
dozen vendor specific ways to do the same thing, which all never made
it into the upstream kernel. There is a broad agreement that rpmsg is
the way to go here and several vendors have started working on
replacing their own subsystems.

Two branches each add one virtio protocol number. Fortunately the
numbers were agreed upon in advance, so there are only context
changes.

Signed-off-by: Arnd Bergmann <[e-mail]>"

Fixed up trivial protocol number conflict due to the mentioned additions
next to each other.

* tag 'rpmsg' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (32 commits)
remoteproc: cleanup resource table parsing paths
remoteproc: remove the hardcoded vring alignment
remoteproc/omap: remove the mbox_callback limitation
remoteproc: remove the single rpmsg vdev limitation
remoteproc: safer boot/shutdown order
remoteproc: remoteproc_rpmsg -> remoteproc_virtio
remoteproc: resource table overhaul
rpmsg: fix build warning when dma_addr_t is 64-bit
rpmsg: fix published buffer length in rpmsg_recv_done
rpmsg: validate incoming message length before propagating
rpmsg: fix name service endpoint leak
remoteproc/omap: two Kconfig fixes
remoteproc: make sure we're parsing a 32bit firmware
remoteproc: s/big switch/lookup table/
remoteproc: bail out if firmware has different endianess
remoteproc: don't use virtio's weak barriers
rpmsg: rename virtqueue_add_buf_gfp to virtqueue_add_buf
rpmsg: depend on EXPERIMENTAL
remoteproc: depend on EXPERIMENTAL
rpmsg: add Kconfig menu
...

Conflicts:
include/linux/virtio_ids.h

Documentation/ABI/testing/sysfs-bus-rpmsg

···
+What:		/sys/bus/rpmsg/devices/.../name
+Date:		June 2011
+KernelVersion:	3.3
+Contact:	Ohad Ben-Cohen <[e-mail]>
+Description:
+		Every rpmsg device is a communication channel with a remote
+		processor. Channels are identified with a (textual) name,
+		which is maximum 32 bytes long (defined as RPMSG_NAME_SIZE in
+		rpmsg.h).
+
+		This sysfs entry contains the name of this channel.
+
+What:		/sys/bus/rpmsg/devices/.../src
+Date:		June 2011
+KernelVersion:	3.3
+Contact:	Ohad Ben-Cohen <[e-mail]>
+Description:
+		Every rpmsg device is a communication channel with a remote
+		processor. Channels have a local ("source") rpmsg address,
+		and remote ("destination") rpmsg address. When an entity
+		starts listening on one end of a channel, it assigns it with
+		a unique rpmsg address (a 32 bits integer). This way when
+		inbound messages arrive to this address, the rpmsg core
+		dispatches them to the listening entity (a kernel driver).
+
+		This sysfs entry contains the src (local) rpmsg address
+		of this channel. If it contains 0xffffffff, then an address
+		wasn't assigned (can happen if no driver exists for this
+		channel).
+
+What:		/sys/bus/rpmsg/devices/.../dst
+Date:		June 2011
+KernelVersion:	3.3
+Contact:	Ohad Ben-Cohen <[e-mail]>
+Description:
+		Every rpmsg device is a communication channel with a remote
+		processor. Channels have a local ("source") rpmsg address,
+		and remote ("destination") rpmsg address. When an entity
+		starts listening on one end of a channel, it assigns it with
+		a unique rpmsg address (a 32 bits integer). This way when
+		inbound messages arrive to this address, the rpmsg core
+		dispatches them to the listening entity.
+
+		This sysfs entry contains the dst (remote) rpmsg address
+		of this channel. If it contains 0xffffffff, then an address
+		wasn't assigned (can happen if the kernel driver that
+		is attached to this channel is exposing a service to the
+		remote processor. This make it a local rpmsg server,
+		and it is listening for inbound messages that may be sent
+		from any remote rpmsg client; it is not bound to a single
+		remote entity).
+
+What:		/sys/bus/rpmsg/devices/.../announce
+Date:		June 2011
+KernelVersion:	3.3
+Contact:	Ohad Ben-Cohen <[e-mail]>
+Description:
+		Every rpmsg device is a communication channel with a remote
+		processor. Channels are identified by a textual name (see
+		/sys/bus/rpmsg/devices/.../name above) and have a local
+		("source") rpmsg address, and remote ("destination") rpmsg
+		address.
+
+		A channel is first created when an entity, whether local
+		or remote, starts listening on it for messages (and is thus
+		called an rpmsg server).
+
+		When that happens, a "name service" announcement is sent
+		to the other processor, in order to let it know about the
+		creation of the channel (this way remote clients know they
+		can start sending messages).
+
+		This sysfs entry tells us whether the channel is a local
+		server channel that is announced (values are either
+		true or false).

Documentation/remoteproc.txt

···
+Remote Processor Framework
+
+1. Introduction
+
+Modern SoCs typically have heterogeneous remote processor devices in asymmetric
+multiprocessing (AMP) configurations, which may be running different instances
+of operating system, whether it's Linux or any other flavor of real-time OS.
+
+OMAP4, for example, has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP.
+In a typical configuration, the dual cortex-A9 is running Linux in a SMP
+configuration, and each of the other three cores (two M3 cores and a DSP)
+is running its own instance of RTOS in an AMP configuration.
+
+The remoteproc framework allows different platforms/architectures to
+control (power on, load firmware, power off) those remote processors while
+abstracting the hardware differences, so the entire driver doesn't need to be
+duplicated. In addition, this framework also adds rpmsg virtio devices
+for remote processors that supports this kind of communication. This way,
+platform-specific remoteproc drivers only need to provide a few low-level
+handlers, and then all rpmsg drivers will then just work
+(for more information about the virtio-based rpmsg bus and its drivers,
+please read Documentation/rpmsg.txt).
+Registration of other types of virtio devices is now also possible. Firmwares
+just need to publish what kind of virtio devices do they support, and then
+remoteproc will add those devices. This makes it possible to reuse the
+existing virtio drivers with remote processor backends at a minimal development
+cost.
+
+2. User API
+
+  int rproc_boot(struct rproc *rproc)
+    - Boot a remote processor (i.e. load its firmware, power it on, ...).
+      If the remote processor is already powered on, this function immediately
+      returns (successfully).
+      Returns 0 on success, and an appropriate error value otherwise.
+      Note: to use this function you should already have a valid rproc
+      handle. There are several ways to achieve that cleanly (devres, pdata,
+      the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we
+      might also consider using dev_archdata for this). See also
+      rproc_get_by_name() below.
+
+  void rproc_shutdown(struct rproc *rproc)
+    - Power off a remote processor (previously booted with rproc_boot()).
+      In case @rproc is still being used by an additional user(s), then
+      this function will just decrement the power refcount and exit,
+      without really powering off the device.
+      Every call to rproc_boot() must (eventually) be accompanied by a call
+      to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
+      Notes:
+      - we're not decrementing the rproc's refcount, only the power refcount.
+        which means that the @rproc handle stays valid even after
+        rproc_shutdown() returns, and users can still use it with a subsequent
+        rproc_boot(), if needed.
+      - don't call rproc_shutdown() to unroll rproc_get_by_name(), exactly
+        because rproc_shutdown() _does not_ decrement the refcount of @rproc.
+        To decrement the refcount of @rproc, use rproc_put() (but _only_ if
+        you acquired @rproc using rproc_get_by_name()).
+
+  struct rproc *rproc_get_by_name(const char *name)
+    - Find an rproc handle using the remote processor's name, and then
+      boot it. If it's already powered on, then just immediately return
+      (successfully). Returns the rproc handle on success, and NULL on failure.
+      This function increments the remote processor's refcount, so always
+      use rproc_put() to decrement it back once rproc isn't needed anymore.
+      Note: currently rproc_get_by_name() and rproc_put() are not used anymore
+      by the rpmsg bus and its drivers. We need to scrutinize the use cases
+      that still need them, and see if we can migrate them to use the non
+      name-based boot/shutdown interface.
+
+  void rproc_put(struct rproc *rproc)
+    - Decrement @rproc's power refcount and shut it down if it reaches zero
+      (essentially by just calling rproc_shutdown), and then decrement @rproc's
+      validity refcount too.
+      After this function returns, @rproc may _not_ be used anymore, and its
+      handle should be considered invalid.
+      This function should be called _iff_ the @rproc handle was grabbed by
+      calling rproc_get_by_name().
+
+3. Typical usage
+
+#include <linux/remoteproc.h>
+
+/* in case we were given a valid 'rproc' handle */
+int dummy_rproc_example(struct rproc *my_rproc)
+{
+	int ret;
+
+	/* let's power on and boot our remote processor */
+	ret = rproc_boot(my_rproc);
+	if (ret) {
+		/*
+		 * something went wrong. handle it and leave.
+		 */
+	}
+
+	/*
+	 * our remote processor is now powered on... give it some work
+	 */
+
+	/* let's shut it down now */
+	rproc_shutdown(my_rproc);
+}
+
+4. API for implementors
+
+  struct rproc *rproc_alloc(struct device *dev, const char *name,
+				const struct rproc_ops *ops,
+				const char *firmware, int len)
+    - Allocate a new remote processor handle, but don't register
+      it yet. Required parameters are the underlying device, the
+      name of this remote processor, platform-specific ops handlers,
+      the name of the firmware to boot this rproc with, and the
+      length of private data needed by the allocating rproc driver (in bytes).
+
+      This function should be used by rproc implementations during
+      initialization of the remote processor.
+      After creating an rproc handle using this function, and when ready,
+      implementations should then call rproc_register() to complete
+      the registration of the remote processor.
+      On success, the new rproc is returned, and on failure, NULL.
+
+      Note: _never_ directly deallocate @rproc, even if it was not registered
+      yet. Instead, if you just need to unroll rproc_alloc(), use rproc_free().
+
+  void rproc_free(struct rproc *rproc)
+    - Free an rproc handle that was allocated by rproc_alloc.
+      This function should _only_ be used if @rproc was only allocated,
+      but not registered yet.
+      If @rproc was already successfully registered (by calling
+      rproc_register()), then use rproc_unregister() instead.
+
+  int rproc_register(struct rproc *rproc)
+    - Register @rproc with the remoteproc framework, after it has been
+      allocated with rproc_alloc().
+      This is called by the platform-specific rproc implementation, whenever
+      a new remote processor device is probed.
+      Returns 0 on success and an appropriate error code otherwise.
+      Note: this function initiates an asynchronous firmware loading
+      context, which will look for virtio devices supported by the rproc's
+      firmware.
+      If found, those virtio devices will be created and added, so as a result
+      of registering this remote processor, additional virtio drivers might get
+      probed.
+
+  int rproc_unregister(struct rproc *rproc)
+    - Unregister a remote processor, and decrement its refcount.
+      If its refcount drops to zero, then @rproc will be freed. If not,
+      it will be freed later once the last reference is dropped.
+
+      This function should be called when the platform specific rproc
+      implementation decides to remove the rproc device. it should
+      _only_ be called if a previous invocation of rproc_register()
+      has completed successfully.
+
+      After rproc_unregister() returns, @rproc is _not_ valid anymore and
+      it shouldn't be used. More specifically, don't call rproc_free()
+      or try to directly free @rproc after rproc_unregister() returns;
+      none of these are needed, and calling them is a bug.
+
+      Returns 0 on success and -EINVAL if @rproc isn't valid.
+
+5. Implementation callbacks
+
+These callbacks should be provided by platform-specific remoteproc
+drivers:
+
+/**
+ * struct rproc_ops - platform-specific device handlers
+ * @start:	power on the device and boot it
+ * @stop:	power off the device
+ * @kick:	kick a virtqueue (virtqueue id given as a parameter)
+ */
+struct rproc_ops {
+	int (*start)(struct rproc *rproc);
+	int (*stop)(struct rproc *rproc);
+	void (*kick)(struct rproc *rproc, int vqid);
+};
+
+Every remoteproc implementation should at least provide the ->start and ->stop
+handlers. If rpmsg/virtio functionality is also desired, then the ->kick handler
+should be provided as well.
+
+The ->start() handler takes an rproc handle and should then power on the
+device and boot it (use rproc->priv to access platform-specific private data).
+The boot address, in case needed, can be found in rproc->bootaddr (remoteproc
+core puts there the ELF entry point).
+On success, 0 should be returned, and on failure, an appropriate error code.
+
+The ->stop() handler takes an rproc handle and powers the device down.
+On success, 0 is returned, and on failure, an appropriate error code.
+
+The ->kick() handler takes an rproc handle, and an index of a virtqueue
+where new message was placed in. Implementations should interrupt the remote
+processor and let it know it has pending messages. Notifying remote processors
+the exact virtqueue index to look in is optional: it is easy (and not
+too expensive) to go through the existing virtqueues and look for new buffers
+in the used rings.
+
+6. Binary Firmware Structure
+
+At this point remoteproc only supports ELF32 firmware binaries. However,
+it is quite expected that other platforms/devices which we'd want to
+support with this framework will be based on different binary formats.
+
+When those use cases show up, we will have to decouple the binary format
+from the framework core, so we can support several binary formats without
+duplicating common code.
+
+When the firmware is parsed, its various segments are loaded to memory
+according to the specified device address (might be a physical address
+if the remote processor is accessing memory directly).
+
+In addition to the standard ELF segments, most remote processors would
+also include a special section which we call "the resource table".
+
+The resource table contains system resources that the remote processor
+requires before it should be powered on, such as allocation of physically
+contiguous memory, or iommu mapping of certain on-chip peripherals.
+Remotecore will only power up the device after all the resource table's
+requirement are met.
+
+In addition to system resources, the resource table may also contain
+resource entries that publish the existence of supported features
+or configurations by the remote processor, such as trace buffers and
+supported virtio devices (and their configurations).
+
+The resource table begins with this header:
+
+/**
+ * struct resource_table - firmware resource table header
+ * @ver: version number
+ * @num: number of resource entries
+ * @reserved: reserved (must be zero)
+ * @offset: array of offsets pointing at the various resource entries
+ *
+ * The header of the resource table, as expressed by this structure,
+ * contains a version number (should we need to change this format in the
+ * future), the number of available resource entries, and their offsets
+ * in the table.
+ */
+struct resource_table {
+	u32 ver;
+	u32 num;
+	u32 reserved[2];
+	u32 offset[0];
+} __packed;
+
+Immediately following this header are the resource entries themselves,
+each of which begins with the following resource entry header:
+
+/**
+ * struct fw_rsc_hdr - firmware resource entry header
+ * @type: resource type
+ * @data: resource data
+ *
+ * Every resource entry begins with a 'struct fw_rsc_hdr' header providing
+ * its @type. The content of the entry itself will immediately follow
+ * this header, and it should be parsed according to the resource type.
+ */
+struct fw_rsc_hdr {
+	u32 type;
+	u8 data[0];
+} __packed;
+
+Some resources entries are mere announcements, where the host is informed
+of specific remoteproc configuration. Other entries require the host to
+do something (e.g. allocate a system resource). Sometimes a negotiation
+is expected, where the firmware requests a resource, and once allocated,
+the host should provide back its details (e.g. address of an allocated
+memory region).
+
+Here are the various resource types that are currently supported:
+
+/**
+ * enum fw_resource_type - types of resource entries
+ *
+ * @RSC_CARVEOUT:   request for allocation of a physically contiguous
+ *		    memory region.
+ * @RSC_DEVMEM:     request to iommu_map a memory-based peripheral.
+ * @RSC_TRACE:	    announces the availability of a trace buffer into which
+ *		    the remote processor will be writing logs.
+ * @RSC_VDEV:       declare support for a virtio device, and serve as its
+ *		    virtio header.
+ * @RSC_LAST:       just keep this one at the end
+ *
+ * Please note that these values are used as indices to the rproc_handle_rsc
+ * lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
+ * check the validity of an index before the lookup table is accessed, so
+ * please update it as needed.
+ */
+enum fw_resource_type {
+	RSC_CARVEOUT	= 0,
+	RSC_DEVMEM	= 1,
+	RSC_TRACE	= 2,
+	RSC_VDEV	= 3,
+	RSC_LAST	= 4,
+};
+
+For more details regarding a specific resource type, please see its
+dedicated structure in include/linux/remoteproc.h.
+
+We also expect that platform-specific resource entries will show up
+at some point. When that happens, we could easily add a new RSC_PLATFORM
+type, and hand those resources to the platform-specific rproc driver to handle.
+
+7. Virtio and remoteproc
+
+The firmware should provide remoteproc information about virtio devices
+that it supports, and their configurations: a RSC_VDEV resource entry
+should specify the virtio device id (as in virtio_ids.h), virtio features,
+virtio config space, vrings information, etc.
+
+When a new remote processor is registered, the remoteproc framework
+will look for its resource table and will register the virtio devices
+it supports. A firmware may support any number of virtio devices, and
+of any type (a single remote processor can also easily support several
+rpmsg virtio devices this way, if desired).
+
+Of course, RSC_VDEV resource entries are only good enough for static
+allocation of virtio devices. Dynamic allocations will also be made possible
+using the rpmsg bus (similar to how we already do dynamic allocations of
+rpmsg channels; read more about it in rpmsg.txt).

Documentation/rpmsg.txt

···
+Remote Processor Messaging (rpmsg) Framework
+
+Note: this document describes the rpmsg bus and how to write rpmsg drivers.
+To learn how to add rpmsg support for new platforms, check out remoteproc.txt
+(also a resident of Documentation/).
+
+1. Introduction
+
+Modern SoCs typically employ heterogeneous remote processor devices in
+asymmetric multiprocessing (AMP) configurations, which may be running
+different instances of operating system, whether it's Linux or any other
+flavor of real-time OS.
+
+OMAP4, for example, has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP.
+Typically, the dual cortex-A9 is running Linux in a SMP configuration,
+and each of the other three cores (two M3 cores and a DSP) is running
+its own instance of RTOS in an AMP configuration.
+
+Typically AMP remote processors employ dedicated DSP codecs and multimedia
+hardware accelerators, and therefore are often used to offload CPU-intensive
+multimedia tasks from the main application processor.
+
+These remote processors could also be used to control latency-sensitive
+sensors, drive random hardware blocks, or just perform background tasks
+while the main CPU is idling.
+
+Users of those remote processors can either be userland apps (e.g. multimedia
+frameworks talking with remote OMX components) or kernel drivers (controlling
+hardware accessible only by the remote processor, reserving kernel-controlled
+resources on behalf of the remote processor, etc..).
+
+Rpmsg is a virtio-based messaging bus that allows kernel drivers to communicate
+with remote processors available on the system. In turn, drivers could then
+expose appropriate user space interfaces, if needed.
+
+When writing a driver that exposes rpmsg communication to userland, please
+keep in mind that remote processors might have direct access to the
+system's physical memory and other sensitive hardware resources (e.g. on
+OMAP4, remote cores and hardware accelerators may have direct access to the
+physical memory, gpio banks, dma controllers, i2c bus, gptimers, mailbox
+devices, hwspinlocks, etc..). Moreover, those remote processors might be
+running RTOS where every task can access the entire memory/devices exposed
+to the processor. To minimize the risks of rogue (or buggy) userland code
+exploiting remote bugs, and by that taking over the system, it is often
+desired to limit userland to specific rpmsg channels (see definition below)
+it can send messages on, and if possible, minimize how much control
+it has over the content of the messages.
+
+Every rpmsg device is a communication channel with a remote processor (thus
+rpmsg devices are called channels). Channels are identified by a textual name
+and have a local ("source") rpmsg address, and remote ("destination") rpmsg
+address.
+
+When a driver starts listening on a channel, its rx callback is bound with
+a unique rpmsg local address (a 32-bit integer). This way when inbound messages
+arrive, the rpmsg core dispatches them to the appropriate driver according
+to their destination address (this is done by invoking the driver's rx handler
+with the payload of the inbound message).
+
+
+2. User API
+
+  int rpmsg_send(struct rpmsg_channel *rpdev, void *data, int len);
+   - sends a message across to the remote processor on a given channel.
+     The caller should specify the channel, the data it wants to send,
+     and its length (in bytes). The message will be sent on the specified
+     channel, i.e. its source and destination address fields will be
+     set to the channel's src and dst addresses.
+
+     In case there are no TX buffers available, the function will block until
+     one becomes available (i.e. until the remote processor consumes
+     a tx buffer and puts it back on virtio's used descriptor ring),
+     or a timeout of 15 seconds elapses. When the latter happens,
+     -ERESTARTSYS is returned.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  int rpmsg_sendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst);
+   - sends a message across to the remote processor on a given channel,
+     to a destination address provided by the caller.
+     The caller should specify the channel, the data it wants to send,
+     its length (in bytes), and an explicit destination address.
+     The message will then be sent to the remote processor to which the
+     channel belongs, using the channel's src address, and the user-provided
+     dst address (thus the channel's dst address will be ignored).
+
+     In case there are no TX buffers available, the function will block until
+     one becomes available (i.e. until the remote processor consumes
+     a tx buffer and puts it back on virtio's used descriptor ring),
+     or a timeout of 15 seconds elapses. When the latter happens,
+     -ERESTARTSYS is returned.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  int rpmsg_send_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
+							void *data, int len);
+   - sends a message across to the remote processor, using the src and dst
+     addresses provided by the user.
+     The caller should specify the channel, the data it wants to send,
+     its length (in bytes), and explicit source and destination addresses.
+     The message will then be sent to the remote processor to which the
+     channel belongs, but the channel's src and dst addresses will be
+     ignored (and the user-provided addresses will be used instead).
+
+     In case there are no TX buffers available, the function will block until
+     one becomes available (i.e. until the remote processor consumes
+     a tx buffer and puts it back on virtio's used descriptor ring),
+     or a timeout of 15 seconds elapses. When the latter happens,
+     -ERESTARTSYS is returned.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  int rpmsg_trysend(struct rpmsg_channel *rpdev, void *data, int len);
+   - sends a message across to the remote processor on a given channel.
+     The caller should specify the channel, the data it wants to send,
+     and its length (in bytes). The message will be sent on the specified
+     channel, i.e. its source and destination address fields will be
+     set to the channel's src and dst addresses.
+
+     In case there are no TX buffers available, the function will immediately
+     return -ENOMEM without waiting until one becomes available.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  int rpmsg_trysendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst)
+   - sends a message across to the remote processor on a given channel,
+     to a destination address provided by the user.
+     The user should specify the channel, the data it wants to send,
+     its length (in bytes), and an explicit destination address.
+     The message will then be sent to the remote processor to which the
+     channel belongs, using the channel's src address, and the user-provided
+     dst address (thus the channel's dst address will be ignored).
+
+     In case there are no TX buffers available, the function will immediately
+     return -ENOMEM without waiting until one becomes available.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  int rpmsg_trysend_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
+							void *data, int len);
+   - sends a message across to the remote processor, using source and
+     destination addresses provided by the user.
+     The user should specify the channel, the data it wants to send,
+     its length (in bytes), and explicit source and destination addresses.
+     The message will then be sent to the remote processor to which the
+     channel belongs, but the channel's src and dst addresses will be
+     ignored (and the user-provided addresses will be used instead).
+
+     In case there are no TX buffers available, the function will immediately
+     return -ENOMEM without waiting until one becomes available.
+     The function can only be called from a process context (for now).
+     Returns 0 on success and an appropriate error value on failure.
+
+  struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
+		void (*cb)(struct rpmsg_channel *, void *, int, void *, u32),
+		void *priv, u32 addr);
+   - every rpmsg address in the system is bound to an rx callback (so when
+     inbound messages arrive, they are dispatched by the rpmsg bus using the
+     appropriate callback handler) by means of an rpmsg_endpoint struct.
+
+     This function allows drivers to create such an endpoint, and by that,
+     bind a callback, and possibly some private data too, to an rpmsg address
+     (either one that is known in advance, or one that will be dynamically
+     assigned for them).
+
+     Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
+     is already created for them when they are probed by the rpmsg bus
+     (using the rx callback they provide when they registered to the rpmsg bus).
+
+     So things should just work for simple drivers: they already have an
+     endpoint, their rx callback is bound to their rpmsg address, and when
+     relevant inbound messages arrive (i.e. messages which their dst address
+     equals to the src address of their rpmsg channel), the driver's handler
+     is invoked to process it.
+
+     That said, more complicated drivers might do need to allocate
+     additional rpmsg addresses, and bind them to different rx callbacks.
+     To accomplish that, those drivers need to call this function.
+     Drivers should provide their channel (so the new endpoint would bind
+     to the same remote processor their channel belongs to), an rx callback
+     function, an optional private data (which is provided back when the
+     rx callback is invoked), and an address they want to bind with the
+     callback. If addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
+     dynamically assign them an available rpmsg address (drivers should have
+     a very good reason why not to always use RPMSG_ADDR_ANY here).
+
+     Returns a pointer to the endpoint on success, or NULL on error.
+
+  void rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
+   - destroys an existing rpmsg endpoint. user should provide a pointer
+     to an rpmsg endpoint that was previously created with rpmsg_create_ept().
+
+  int register_rpmsg_driver(struct rpmsg_driver *rpdrv);
+   - registers an rpmsg driver with the rpmsg bus. user should provide
+     a pointer to an rpmsg_driver struct, which contains the driver's
+     ->probe() and ->remove() functions, an rx callback, and an id_table
+     specifying the names of the channels this driver is interested to
+     be probed with.
+
+  void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv);
+   - unregisters an rpmsg driver from the rpmsg bus. user should provide
+     a pointer to a previously-registered rpmsg_driver struct.
+     Returns 0 on success, and an appropriate error value on failure.
+
+
+3. Typical usage
+
+The following is a simple rpmsg driver, that sends an "hello!" message
+on probe(), and whenever it receives an incoming message, it dumps its
+content to the console.
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rpmsg.h>
+
+static void rpmsg_sample_cb(struct rpmsg_channel *rpdev, void *data, int len,
+						void *priv, u32 src)
+{
+	print_hex_dump(KERN_INFO, "incoming message:", DUMP_PREFIX_NONE,
+						16, 1, data, len, true);
+}
+
+static int rpmsg_sample_probe(struct rpmsg_channel *rpdev)
+{
+	int err;
+
+	dev_info(&rpdev->dev, "chnl: 0x%x -> 0x%x\n", rpdev->src, rpdev->dst);
+
+	/* send a message on our channel */
+	err = rpmsg_send(rpdev, "hello!", 6);
+	if (err) {
+		pr_err("rpmsg_send failed: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static void __devexit rpmsg_sample_remove(struct rpmsg_channel *rpdev)
+{
+	dev_info(&rpdev->dev, "rpmsg sample client driver is removed\n");
+}
+
+static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = {
+	{ .name	= "rpmsg-client-sample" },
+	{ },
+};
+MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_sample_id_table);
+
+static struct rpmsg_driver rpmsg_sample_client = {
+	.drv.name	= KBUILD_MODNAME,
+	.drv.owner	= THIS_MODULE,
+	.id_table	= rpmsg_driver_sample_id_table,
+	.probe		= rpmsg_sample_probe,
+	.callback	= rpmsg_sample_cb,
+	.remove		= __devexit_p(rpmsg_sample_remove),
+};
+
+static int __init init(void)
+{
+	return register_rpmsg_driver(&rpmsg_sample_client);
+}
+module_init(init);
+
+static void __exit fini(void)
+{
+	unregister_rpmsg_driver(&rpmsg_sample_client);
+}
+module_exit(fini);
+
+Note: a similar sample which can be built and loaded can be found
+in samples/rpmsg/.
+
+4. Allocations of rpmsg channels:
+
+At this point we only support dynamic allocations of rpmsg channels.
+
+This is possible only with remote processors that have the VIRTIO_RPMSG_F_NS
+virtio device feature set. This feature bit means that the remote
+processor supports dynamic name service announcement messages.
+
+When this feature is enabled, creation of rpmsg devices (i.e. channels)
+is completely dynamic: the remote processor announces the existence of a
+remote rpmsg service by sending a name service message (which contains
+the name and rpmsg addr of the remote service, see struct rpmsg_ns_msg).
+
+This message is then handled by the rpmsg bus, which in turn dynamically
+creates and registers an rpmsg channel (which represents the remote service).
+If/when a relevant rpmsg driver is registered, it will be immediately probed
+by the bus, and can then start sending messages to the remote service.
+
+The plan is also to add static creation of rpmsg channels via the virtio
+config space, but it's not implemented yet.

MAINTAINERS

···
 F:	drivers/base/regmap/
 F:	include/linux/regmap.h
 
+REMOTE PROCESSOR (REMOTEPROC) SUBSYSTEM
+M:	Ohad Ben-Cohen <[e-mail]>
+S:	Maintained
+F:	drivers/remoteproc/
+F:	Documentation/remoteproc.txt
+F:	include/linux/remoteproc.txt
+
 RFKILL
 M:	Johannes Berg <[e-mail]>
 L:	[e-mail]

arch/arm/plat-omap/include/plat/remoteproc.h

···
+/*
+ * Remote Processor - omap-specific bits
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _PLAT_REMOTEPROC_H
+#define _PLAT_REMOTEPROC_H
+
+struct rproc_ops;
+struct platform_device;
+
+/*
+ * struct omap_rproc_pdata - omap remoteproc's platform data
+ * @name: the remoteproc's name
+ * @oh_name: omap hwmod device
+ * @oh_name_opt: optional, secondary omap hwmod device
+ * @firmware: name of firmware file to load
+ * @mbox_name: name of omap mailbox device to use with this rproc
+ * @ops: start/stop rproc handlers
+ * @device_enable: omap-specific handler for enabling a device
+ * @device_shutdown: omap-specific handler for shutting down a device
+ */
+struct omap_rproc_pdata {
+	const char *name;
+	const char *oh_name;
+	const char *oh_name_opt;
+	const char *firmware;
+	const char *mbox_name;
+	const struct rproc_ops *ops;
+	int (*device_enable) (struct platform_device *pdev);
+	int (*device_shutdown) (struct platform_device *pdev);
+};
+
+#if defined(CONFIG_OMAP_REMOTEPROC) || defined(CONFIG_OMAP_REMOTEPROC_MODULE)
+
+void __init omap_rproc_reserve_cma(void);
+
+#else
+
+void __init omap_rproc_reserve_cma(void)
+{
+}
+
+#endif
+
+#endif /* _PLAT_REMOTEPROC_H */

drivers/Kconfig

···
 
 source "drivers/iommu/Kconfig"
 
+source "drivers/remoteproc/Kconfig"
+
+source "drivers/rpmsg/Kconfig"
+
 source "drivers/virt/Kconfig"
 
 source "drivers/devfreq/Kconfig"

drivers/Makefile

···
 obj-$(CONFIG_HWSPINLOCK)	+= hwspinlock/
 obj-$(CONFIG_NFC)		+= nfc/
 obj-$(CONFIG_IOMMU_SUPPORT)	+= iommu/
+obj-$(CONFIG_REMOTEPROC)	+= remoteproc/
+obj-$(CONFIG_RPMSG)		+= rpmsg/
 
 # Virtualization drivers
 obj-$(CONFIG_VIRT_DRIVERS)	+= virt/

drivers/remoteproc/Kconfig

···
+menu "Remoteproc drivers (EXPERIMENTAL)"
+
+# REMOTEPROC gets selected by whoever wants it
+config REMOTEPROC
+	tristate
+	depends on EXPERIMENTAL
+
+config OMAP_REMOTEPROC
+	tristate "OMAP remoteproc support"
+	depends on ARCH_OMAP4
+	depends on OMAP_IOMMU
+	select REMOTEPROC
+	select OMAP_MBOX_FWK
+	select RPMSG
+	help
+	  Say y here to support OMAP's remote processors (dual M3
+	  and DSP on OMAP4) via the remote processor framework.
+
+	  Currently only supported on OMAP4.
+
+	  Usually you want to say y here, in order to enable multimedia
+	  use-cases to run on your platform (multimedia codecs are
+	  offloaded to remote DSP processors using this framework).
+
+	  It's safe to say n here if you're not interested in multimedia
+	  offloading or just want a bare minimum kernel.
+
+endmenu

drivers/remoteproc/Makefile

···
+#
+# Generic framework for controlling remote processors
+#
+
+obj-$(CONFIG_REMOTEPROC)		+= remoteproc.o
+remoteproc-y				:= remoteproc_core.o
+remoteproc-y				+= remoteproc_debugfs.o
+remoteproc-y				+= remoteproc_virtio.o
+obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o

drivers/remoteproc/omap_remoteproc.c

···
+/*
+ * OMAP Remote Processor driver
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ * Fernando Guzman Lugo <[e-mail]>
+ * Mark Grosen <[e-mail]>
+ * Suman Anna <[e-mail]>
+ * Hari Kanigeri <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/remoteproc.h>
+
+#include <plat/mailbox.h>
+#include <plat/remoteproc.h>
+
+#include "omap_remoteproc.h"
+#include "remoteproc_internal.h"
+
+/**
+ * struct omap_rproc - omap remote processor state
+ * @mbox: omap mailbox handle
+ * @nb: notifier block that will be invoked on inbound mailbox messages
+ * @rproc: rproc handle
+ */
+struct omap_rproc {
+	struct omap_mbox *mbox;
+	struct notifier_block nb;
+	struct rproc *rproc;
+};
+
+/**
+ * omap_rproc_mbox_callback() - inbound mailbox message handler
+ * @this: notifier block
+ * @index: unused
+ * @data: mailbox payload
+ *
+ * This handler is invoked by omap's mailbox driver whenever a mailbox
+ * message is received. Usually, the mailbox payload simply contains
+ * the index of the virtqueue that is kicked by the remote processor,
+ * and we let remoteproc core handle it.
+ *
+ * In addition to virtqueue indices, we also have some out-of-band values
+ * that indicates different events. Those values are deliberately very
+ * big so they don't coincide with virtqueue indices.
+ */
+static int omap_rproc_mbox_callback(struct notifier_block *this,
+					unsigned long index, void *data)
+{
+	mbox_msg_t msg = (mbox_msg_t) data;
+	struct omap_rproc *oproc = container_of(this, struct omap_rproc, nb);
+	struct device *dev = oproc->rproc->dev;
+	const char *name = oproc->rproc->name;
+
+	dev_dbg(dev, "mbox msg: 0x%x\n", msg);
+
+	switch (msg) {
+	case RP_MBOX_CRASH:
+		/* just log this for now. later, we'll also do recovery */
+		dev_err(dev, "omap rproc %s crashed\n", name);
+		break;
+	case RP_MBOX_ECHO_REPLY:
+		dev_info(dev, "received echo reply from %s\n", name);
+		break;
+	default:
+		/* msg contains the index of the triggered vring */
+		if (rproc_vq_interrupt(oproc->rproc, msg) == IRQ_NONE)
+			dev_dbg(dev, "no message was found in vqid %d\n", msg);
+	}
+
+	return NOTIFY_DONE;
+}
+
+/* kick a virtqueue */
+static void omap_rproc_kick(struct rproc *rproc, int vqid)
+{
+	struct omap_rproc *oproc = rproc->priv;
+	int ret;
+
+	/* send the index of the triggered virtqueue in the mailbox payload */
+	ret = omap_mbox_msg_send(oproc->mbox, vqid);
+	if (ret)
+		dev_err(rproc->dev, "omap_mbox_msg_send failed: %d\n", ret);
+}
+
+/*
+ * Power up the remote processor.
+ *
+ * This function will be invoked only after the firmware for this rproc
+ * was loaded, parsed successfully, and all of its resource requirements
+ * were met.
+ */
+static int omap_rproc_start(struct rproc *rproc)
+{
+	struct omap_rproc *oproc = rproc->priv;
+	struct platform_device *pdev = to_platform_device(rproc->dev);
+	struct omap_rproc_pdata *pdata = pdev->dev.platform_data;
+	int ret;
+
+	oproc->nb.notifier_call = omap_rproc_mbox_callback;
+
+	/* every omap rproc is assigned a mailbox instance for messaging */
+	oproc->mbox = omap_mbox_get(pdata->mbox_name, &oproc->nb);
+	if (IS_ERR(oproc->mbox)) {
+		ret = PTR_ERR(oproc->mbox);
+		dev_err(rproc->dev, "omap_mbox_get failed: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Ping the remote processor. this is only for sanity-sake;
+	 * there is no functional effect whatsoever.
+	 *
+	 * Note that the reply will _not_ arrive immediately: this message
+	 * will wait in the mailbox fifo until the remote processor is booted.
+	 */
+	ret = omap_mbox_msg_send(oproc->mbox, RP_MBOX_ECHO_REQUEST);
+	if (ret) {
+		dev_err(rproc->dev, "omap_mbox_get failed: %d\n", ret);
+		goto put_mbox;
+	}
+
+	ret = pdata->device_enable(pdev);
+	if (ret) {
+		dev_err(rproc->dev, "omap_device_enable failed: %d\n", ret);
+		goto put_mbox;
+	}
+
+	return 0;
+
+put_mbox:
+	omap_mbox_put(oproc->mbox, &oproc->nb);
+	return ret;
+}
+
+/* power off the remote processor */
+static int omap_rproc_stop(struct rproc *rproc)
+{
+	struct platform_device *pdev = to_platform_device(rproc->dev);
+	struct omap_rproc_pdata *pdata = pdev->dev.platform_data;
+	struct omap_rproc *oproc = rproc->priv;
+	int ret;
+
+	ret = pdata->device_shutdown(pdev);
+	if (ret)
+		return ret;
+
+	omap_mbox_put(oproc->mbox, &oproc->nb);
+
+	return 0;
+}
+
+static struct rproc_ops omap_rproc_ops = {
+	.start		= omap_rproc_start,
+	.stop		= omap_rproc_stop,
+	.kick		= omap_rproc_kick,
+};
+
+static int __devinit omap_rproc_probe(struct platform_device *pdev)
+{
+	struct omap_rproc_pdata *pdata = pdev->dev.platform_data;
+	struct omap_rproc *oproc;
+	struct rproc *rproc;
+	int ret;
+
+	ret = dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
+	if (ret) {
+		dev_err(pdev->dev.parent, "dma_set_coherent_mask: %d\n", ret);
+		return ret;
+	}
+
+	rproc = rproc_alloc(&pdev->dev, pdata->name, &omap_rproc_ops,
+				pdata->firmware, sizeof(*oproc));
+	if (!rproc)
+		return -ENOMEM;
+
+	oproc = rproc->priv;
+	oproc->rproc = rproc;
+
+	platform_set_drvdata(pdev, rproc);
+
+	ret = rproc_register(rproc);
+	if (ret)
+		goto free_rproc;
+
+	return 0;
+
+free_rproc:
+	rproc_free(rproc);
+	return ret;
+}
+
+static int __devexit omap_rproc_remove(struct platform_device *pdev)
+{
+	struct rproc *rproc = platform_get_drvdata(pdev);
+
+	return rproc_unregister(rproc);
+}
+
+static struct platform_driver omap_rproc_driver = {
+	.probe = omap_rproc_probe,
+	.remove = __devexit_p(omap_rproc_remove),
+	.driver = {
+		.name = "omap-rproc",
+		.owner = THIS_MODULE,
+	},
+};
+
+module_platform_driver(omap_rproc_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("OMAP Remote Processor control driver");

drivers/remoteproc/omap_remoteproc.h

···
+/*
+ * Remote processor messaging
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ * * Neither the name Texas Instruments nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _OMAP_RPMSG_H
+#define _OMAP_RPMSG_H
+
+/*
+ * enum - Predefined Mailbox Messages
+ *
+ * @RP_MBOX_READY: informs the M3's that we're up and running. this is
+ * part of the init sequence sent that the M3 expects to see immediately
+ * after it is booted.
+ *
+ * @RP_MBOX_PENDING_MSG: informs the receiver that there is an inbound
+ * message waiting in its own receive-side vring. please note that currently
+ * this message is optional: alternatively, one can explicitly send the index
+ * of the triggered virtqueue itself. the preferred approach will be decided
+ * as we progress and experiment with those two different approaches.
+ *
+ * @RP_MBOX_CRASH: this message is sent if BIOS crashes
+ *
+ * @RP_MBOX_ECHO_REQUEST: a mailbox-level "ping" message.
+ *
+ * @RP_MBOX_ECHO_REPLY: a mailbox-level reply to a "ping"
+ *
+ * @RP_MBOX_ABORT_REQUEST: a "please crash" request, used for testing the
+ * recovery mechanism (to some extent).
+ */
+enum omap_rp_mbox_messages {
+	RP_MBOX_READY		= 0xFFFFFF00,
+	RP_MBOX_PENDING_MSG	= 0xFFFFFF01,
+	RP_MBOX_CRASH		= 0xFFFFFF02,
+	RP_MBOX_ECHO_REQUEST	= 0xFFFFFF03,
+	RP_MBOX_ECHO_REPLY	= 0xFFFFFF04,
+	RP_MBOX_ABORT_REQUEST	= 0xFFFFFF05,
+};
+
+#endif /* _OMAP_RPMSG_H */

drivers/remoteproc/remoteproc_core.c

···
+/*
+ * Remote Processor Framework
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ * Mark Grosen <[e-mail]>
+ * Fernando Guzman Lugo <[e-mail]>
+ * Suman Anna <[e-mail]>
+ * Robert Tivy <[e-mail]>
+ * Armando Uribe De Leon <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt)    "%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/dma-mapping.h>
+#include <linux/firmware.h>
+#include <linux/string.h>
+#include <linux/debugfs.h>
+#include <linux/remoteproc.h>
+#include <linux/iommu.h>
+#include <linux/klist.h>
+#include <linux/elf.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_ring.h>
+#include <asm/byteorder.h>
+
+#include "remoteproc_internal.h"
+
+static void klist_rproc_get(struct klist_node *n);
+static void klist_rproc_put(struct klist_node *n);
+
+/*
+ * klist of the available remote processors.
+ *
+ * We need this in order to support name-based lookups (needed by the
+ * rproc_get_by_name()).
+ *
+ * That said, we don't use rproc_get_by_name() at this point.
+ * The use cases that do require its existence should be
+ * scrutinized, and hopefully migrated to rproc_boot() using device-based
+ * binding.
+ *
+ * If/when this materializes, we could drop the klist (and the by_name
+ * API).
+ */
+static DEFINE_KLIST(rprocs, klist_rproc_get, klist_rproc_put);
+
+typedef int (*rproc_handle_resources_t)(struct rproc *rproc,
+				struct resource_table *table, int len);
+typedef int (*rproc_handle_resource_t)(struct rproc *rproc, void *, int avail);
+
+/*
+ * This is the IOMMU fault handler we register with the IOMMU API
+ * (when relevant; not all remote processors access memory through
+ * an IOMMU).
+ *
+ * IOMMU core will invoke this handler whenever the remote processor
+ * will try to access an unmapped device address.
+ *
+ * Currently this is mostly a stub, but it will be later used to trigger
+ * the recovery of the remote processor.
+ */
+static int rproc_iommu_fault(struct iommu_domain *domain, struct device *dev,
+		unsigned long iova, int flags)
+{
+	dev_err(dev, "iommu fault: da 0x%lx flags 0x%x\n", iova, flags);
+
+	/*
+	 * Let the iommu core know we're not really handling this fault;
+	 * we just plan to use this as a recovery trigger.
+	 */
+	return -ENOSYS;
+}
+
+static int rproc_enable_iommu(struct rproc *rproc)
+{
+	struct iommu_domain *domain;
+	struct device *dev = rproc->dev;
+	int ret;
+
+	/*
+	 * We currently use iommu_present() to decide if an IOMMU
+	 * setup is needed.
+	 *
+	 * This works for simple cases, but will easily fail with
+	 * platforms that do have an IOMMU, but not for this specific
+	 * rproc.
+	 *
+	 * This will be easily solved by introducing hw capabilities
+	 * that will be set by the remoteproc driver.
+	 */
+	if (!iommu_present(dev->bus)) {
+		dev_dbg(dev, "iommu not found\n");
+		return 0;
+	}
+
+	domain = iommu_domain_alloc(dev->bus);
+	if (!domain) {
+		dev_err(dev, "can't alloc iommu domain\n");
+		return -ENOMEM;
+	}
+
+	iommu_set_fault_handler(domain, rproc_iommu_fault);
+
+	ret = iommu_attach_device(domain, dev);
+	if (ret) {
+		dev_err(dev, "can't attach iommu device: %d\n", ret);
+		goto free_domain;
+	}
+
+	rproc->domain = domain;
+
+	return 0;
+
+free_domain:
+	iommu_domain_free(domain);
+	return ret;
+}
+
+static void rproc_disable_iommu(struct rproc *rproc)
+{
+	struct iommu_domain *domain = rproc->domain;
+	struct device *dev = rproc->dev;
+
+	if (!domain)
+		return;
+
+	iommu_detach_device(domain, dev);
+	iommu_domain_free(domain);
+
+	return;
+}
+
+/*
+ * Some remote processors will ask us to allocate them physically contiguous
+ * memory regions (which we call "carveouts"), and map them to specific
+ * device addresses (which are hardcoded in the firmware).
+ *
+ * They may then ask us to copy objects into specific device addresses (e.g.
+ * code/data sections) or expose us certain symbols in other device address
+ * (e.g. their trace buffer).
+ *
+ * This function is an internal helper with which we can go over the allocated
+ * carveouts and translate specific device address to kernel virtual addresses
+ * so we can access the referenced memory.
+ *
+ * Note: phys_to_virt(iommu_iova_to_phys(rproc->domain, da)) will work too,
+ * but only on kernel direct mapped RAM memory. Instead, we're just using
+ * here the output of the DMA API, which should be more correct.
+ */
+static void *rproc_da_to_va(struct rproc *rproc, u64 da, int len)
+{
+	struct rproc_mem_entry *carveout;
+	void *ptr = NULL;
+
+	list_for_each_entry(carveout, &rproc->carveouts, node) {
+		int offset = da - carveout->da;
+
+		/* try next carveout if da is too small */
+		if (offset < 0)
+			continue;
+
+		/* try next carveout if da is too large */
+		if (offset + len > carveout->len)
+			continue;
+
+		ptr = carveout->va + offset;
+
+		break;
+	}
+
+	return ptr;
+}
+
+/**
+ * rproc_load_segments() - load firmware segments to memory
+ * @rproc: remote processor which will be booted using these fw segments
+ * @elf_data: the content of the ELF firmware image
+ * @len: firmware size (in bytes)
+ *
+ * This function loads the firmware segments to memory, where the remote
+ * processor expects them.
+ *
+ * Some remote processors will expect their code and data to be placed
+ * in specific device addresses, and can't have them dynamically assigned.
+ *
+ * We currently support only those kind of remote processors, and expect
+ * the program header's paddr member to contain those addresses. We then go
+ * through the physically contiguous "carveout" memory regions which we
+ * allocated (and mapped) earlier on behalf of the remote processor,
+ * and "translate" device address to kernel addresses, so we can copy the
+ * segments where they are expected.
+ *
+ * Currently we only support remote processors that required carveout
+ * allocations and got them mapped onto their iommus. Some processors
+ * might be different: they might not have iommus, and would prefer to
+ * directly allocate memory for every segment/resource. This is not yet
+ * supported, though.
+ */
+static int
+rproc_load_segments(struct rproc *rproc, const u8 *elf_data, size_t len)
+{
+	struct device *dev = rproc->dev;
+	struct elf32_hdr *ehdr;
+	struct elf32_phdr *phdr;
+	int i, ret = 0;
+
+	ehdr = (struct elf32_hdr *)elf_data;
+	phdr = (struct elf32_phdr *)(elf_data + ehdr->e_phoff);
+
+	/* go through the available ELF segments */
+	for (i = 0; i < ehdr->e_phnum; i++, phdr++) {
+		u32 da = phdr->p_paddr;
+		u32 memsz = phdr->p_memsz;
+		u32 filesz = phdr->p_filesz;
+		u32 offset = phdr->p_offset;
+		void *ptr;
+
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		dev_dbg(dev, "phdr: type %d da 0x%x memsz 0x%x filesz 0x%x\n",
+					phdr->p_type, da, memsz, filesz);
+
+		if (filesz > memsz) {
+			dev_err(dev, "bad phdr filesz 0x%x memsz 0x%x\n",
+							filesz, memsz);
+			ret = -EINVAL;
+			break;
+		}
+
+		if (offset + filesz > len) {
+			dev_err(dev, "truncated fw: need 0x%x avail 0x%x\n",
+					offset + filesz, len);
+			ret = -EINVAL;
+			break;
+		}
+
+		/* grab the kernel address for this device address */
+		ptr = rproc_da_to_va(rproc, da, memsz);
+		if (!ptr) {
+			dev_err(dev, "bad phdr da 0x%x mem 0x%x\n", da, memsz);
+			ret = -EINVAL;
+			break;
+		}
+
+		/* put the segment where the remote processor expects it */
+		if (phdr->p_filesz)
+			memcpy(ptr, elf_data + phdr->p_offset, filesz);
+
+		/*
+		 * Zero out remaining memory for this segment.
+		 *
+		 * This isn't strictly required since dma_alloc_coherent already
+		 * did this for us. albeit harmless, we may consider removing
+		 * this.
+		 */
+		if (memsz > filesz)
+			memset(ptr + filesz, 0, memsz - filesz);
+	}
+
+	return ret;
+}
+
+static int
+__rproc_handle_vring(struct rproc_vdev *rvdev, struct fw_rsc_vdev *rsc, int i)
+{
+	struct rproc *rproc = rvdev->rproc;
+	struct device *dev = rproc->dev;
+	struct fw_rsc_vdev_vring *vring = &rsc->vring[i];
+	dma_addr_t dma;
+	void *va;
+	int ret, size, notifyid;
+
+	dev_dbg(dev, "vdev rsc: vring%d: da %x, qsz %d, align %d\n",
+				i, vring->da, vring->num, vring->align);
+
+	/* make sure reserved bytes are zeroes */
+	if (vring->reserved) {
+		dev_err(dev, "vring rsc has non zero reserved bytes\n");
+		return -EINVAL;
+	}
+
+	/* verify queue size and vring alignment are sane */
+	if (!vring->num || !vring->align) {
+		dev_err(dev, "invalid qsz (%d) or alignment (%d)\n",
+						vring->num, vring->align);
+		return -EINVAL;
+	}
+
+	/* actual size of vring (in bytes) */
+	size = PAGE_ALIGN(vring_size(vring->num, vring->align));
+
+	if (!idr_pre_get(&rproc->notifyids, GFP_KERNEL)) {
+		dev_err(dev, "idr_pre_get failed\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * Allocate non-cacheable memory for the vring. In the future
+	 * this call will also configure the IOMMU for us
+	 */
+	va = dma_alloc_coherent(dev, size, &dma, GFP_KERNEL);
+	if (!va) {
+		dev_err(dev, "dma_alloc_coherent failed\n");
+		return -EINVAL;
+	}
+
+	/* assign an rproc-wide unique index for this vring */
+	/* TODO: assign a notifyid for rvdev updates as well */
+	ret = idr_get_new(&rproc->notifyids, &rvdev->vring[i], &notifyid);
+	if (ret) {
+		dev_err(dev, "idr_get_new failed: %d\n", ret);
+		dma_free_coherent(dev, size, va, dma);
+		return ret;
+	}
+
+	/* let the rproc know the da and notifyid of this vring */
+	/* TODO: expose this to remote processor */
+	vring->da = dma;
+	vring->notifyid = notifyid;
+
+	dev_dbg(dev, "vring%d: va %p dma %x size %x idr %d\n", i, va,
+					dma, size, notifyid);
+
+	rvdev->vring[i].len = vring->num;
+	rvdev->vring[i].align = vring->align;
+	rvdev->vring[i].va = va;
+	rvdev->vring[i].dma = dma;
+	rvdev->vring[i].notifyid = notifyid;
+	rvdev->vring[i].rvdev = rvdev;
+
+	return 0;
+}
+
+static void __rproc_free_vrings(struct rproc_vdev *rvdev, int i)
+{
+	struct rproc *rproc = rvdev->rproc;
+
+	for (i--; i > 0; i--) {
+		struct rproc_vring *rvring = &rvdev->vring[i];
+		int size = PAGE_ALIGN(vring_size(rvring->len, rvring->align));
+
+		dma_free_coherent(rproc->dev, size, rvring->va, rvring->dma);
+		idr_remove(&rproc->notifyids, rvring->notifyid);
+	}
+}
+
+/**
+ * rproc_handle_vdev() - handle a vdev fw resource
+ * @rproc: the remote processor
+ * @rsc: the vring resource descriptor
+ * @avail: size of available data (for sanity checking the image)
+ *
+ * This resource entry requests the host to statically register a virtio
+ * device (vdev), and setup everything needed to support it. It contains
+ * everything needed to make it possible: the virtio device id, virtio
+ * device features, vrings information, virtio config space, etc...
+ *
+ * Before registering the vdev, the vrings are allocated from non-cacheable
+ * physically contiguous memory. Currently we only support two vrings per
+ * remote processor (temporary limitation). We might also want to consider
+ * doing the vring allocation only later when ->find_vqs() is invoked, and
+ * then release them upon ->del_vqs().
+ *
+ * Note: @da is currently not really handled correctly: we dynamically
+ * allocate it using the DMA API, ignoring requested hard coded addresses,
+ * and we don't take care of any required IOMMU programming. This is all
+ * going to be taken care of when the generic iommu-based DMA API will be
+ * merged. Meanwhile, statically-addressed iommu-based firmware images should
+ * use RSC_DEVMEM resource entries to map their required @da to the physical
+ * address of their base CMA region (ouch, hacky!).
+ *
+ * Returns 0 on success, or an appropriate error code otherwise
+ */
+static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
+								int avail)
+{
+	struct device *dev = rproc->dev;
+	struct rproc_vdev *rvdev;
+	int i, ret;
+
+	/* make sure resource isn't truncated */
+	if (sizeof(*rsc) + rsc->num_of_vrings * sizeof(struct fw_rsc_vdev_vring)
+			+ rsc->config_len > avail) {
+		dev_err(rproc->dev, "vdev rsc is truncated\n");
+		return -EINVAL;
+	}
+
+	/* make sure reserved bytes are zeroes */
+	if (rsc->reserved[0] || rsc->reserved[1]) {
+		dev_err(dev, "vdev rsc has non zero reserved bytes\n");
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "vdev rsc: id %d, dfeatures %x, cfg len %d, %d vrings\n",
+		rsc->id, rsc->dfeatures, rsc->config_len, rsc->num_of_vrings);
+
+	/* we currently support only two vrings per rvdev */
+	if (rsc->num_of_vrings > ARRAY_SIZE(rvdev->vring)) {
+		dev_err(dev, "too many vrings: %d\n", rsc->num_of_vrings);
+		return -EINVAL;
+	}
+
+	rvdev = kzalloc(sizeof(struct rproc_vdev), GFP_KERNEL);
+	if (!rvdev)
+		return -ENOMEM;
+
+	rvdev->rproc = rproc;
+
+	/* allocate the vrings */
+	for (i = 0; i < rsc->num_of_vrings; i++) {
+		ret = __rproc_handle_vring(rvdev, rsc, i);
+		if (ret)
+			goto free_vrings;
+	}
+
+	/* remember the device features */
+	rvdev->dfeatures = rsc->dfeatures;
+
+	list_add_tail(&rvdev->node, &rproc->rvdevs);
+
+	/* it is now safe to add the virtio device */
+	ret = rproc_add_virtio_dev(rvdev, rsc->id);
+	if (ret)
+		goto free_vrings;
+
+	return 0;
+
+free_vrings:
+	__rproc_free_vrings(rvdev, i);
+	kfree(rvdev);
+	return ret;
+}
+
+/**
+ * rproc_handle_trace() - handle a shared trace buffer resource
+ * @rproc: the remote processor
+ * @rsc: the trace resource descriptor
+ * @avail: size of available data (for sanity checking the image)
+ *
+ * In case the remote processor dumps trace logs into memory,
+ * export it via debugfs.
+ *
+ * Currently, the 'da' member of @rsc should contain the device address
+ * where the remote processor is dumping the traces. Later we could also
+ * support dynamically allocating this address using the generic
+ * DMA API (but currently there isn't a use case for that).
+ *
+ * Returns 0 on success, or an appropriate error code otherwise
+ */
+static int rproc_handle_trace(struct rproc *rproc, struct fw_rsc_trace *rsc,
+								int avail)
+{
+	struct rproc_mem_entry *trace;
+	struct device *dev = rproc->dev;
+	void *ptr;
+	char name[15];
+
+	if (sizeof(*rsc) > avail) {
+		dev_err(rproc->dev, "trace rsc is truncated\n");
+		return -EINVAL;
+	}
+
+	/* make sure reserved bytes are zeroes */
+	if (rsc->reserved) {
+		dev_err(dev, "trace rsc has non zero reserved bytes\n");
+		return -EINVAL;
+	}
+
+	/* what's the kernel address of this resource ? */
+	ptr = rproc_da_to_va(rproc, rsc->da, rsc->len);
+	if (!ptr) {
+		dev_err(dev, "erroneous trace resource entry\n");
+		return -EINVAL;
+	}
+
+	trace = kzalloc(sizeof(*trace), GFP_KERNEL);
+	if (!trace) {
+		dev_err(dev, "kzalloc trace failed\n");
+		return -ENOMEM;
+	}
+
+	/* set the trace buffer dma properties */
+	trace->len = rsc->len;
+	trace->va = ptr;
+
+	/* make sure snprintf always null terminates, even if truncating */
+	snprintf(name, sizeof(name), "trace%d", rproc->num_traces);
+
+	/* create the debugfs entry */
+	trace->priv = rproc_create_trace_file(name, rproc, trace);
+	if (!trace->priv) {
+		trace->va = NULL;
+		kfree(trace);
+		return -EINVAL;
+	}
+
+	list_add_tail(&trace->node, &rproc->traces);
+
+	rproc->num_traces++;
+
+	dev_dbg(dev, "%s added: va %p, da 0x%x, len 0x%x\n", name, ptr,
+						rsc->da, rsc->len);
+
+	return 0;
+}
+
+/**
+ * rproc_handle_devmem() - handle devmem resource entry
+ * @rproc: remote processor handle
+ * @rsc: the devmem resource entry
+ * @avail: size of available data (for sanity checking the image)
+ *
+ * Remote processors commonly need to access certain on-chip peripherals.
+ *
+ * Some of these remote processors access memory via an iommu device,
+ * and might require us to configure their iommu before they can access
+ * the on-chip peripherals they need.
+ *
+ * This resource entry is a request to map such a peripheral device.
+ *
+ * These devmem entries will contain the physical address of the device in
+ * the 'pa' member. If a specific device address is expected, then 'da' will
+ * contain it (currently this is the only use case supported). 'len' will
+ * contain the size of the physical region we need to map.
+ *
+ * Currently we just "trust" those devmem entries to contain valid physical
+ * addresses, but this is going to change: we want the implementations to
+ * tell us ranges of physical addresses the firmware is allowed to request,
+ * and not allow firmwares to request access to physical addresses that
+ * are outside those ranges.
+ */
+static int rproc_handle_devmem(struct rproc *rproc, struct fw_rsc_devmem *rsc,
+								int avail)
+{
+	struct rproc_mem_entry *mapping;
+	int ret;
+
+	/* no point in handling this resource without a valid iommu domain */
+	if (!rproc->domain)
+		return -EINVAL;
+
+	if (sizeof(*rsc) > avail) {
+		dev_err(rproc->dev, "devmem rsc is truncated\n");
+		return -EINVAL;
+	}
+
+	/* make sure reserved bytes are zeroes */
+	if (rsc->reserved) {
+		dev_err(rproc->dev, "devmem rsc has non zero reserved bytes\n");
+		return -EINVAL;
+	}
+
+	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
+	if (!mapping) {
+		dev_err(rproc->dev, "kzalloc mapping failed\n");
+		return -ENOMEM;
+	}
+
+	ret = iommu_map(rproc->domain, rsc->da, rsc->pa, rsc->len, rsc->flags);
+	if (ret) {
+		dev_err(rproc->dev, "failed to map devmem: %d\n", ret);
+		goto out;
+	}
+
+	/*
+	 * We'll need this info later when we'll want to unmap everything
+	 * (e.g. on shutdown).
+	 *
+	 * We can't trust the remote processor not to change the resource
+	 * table, so we must maintain this info independently.
+	 */
+	mapping->da = rsc->da;
+	mapping->len = rsc->len;
+	list_add_tail(&mapping->node, &rproc->mappings);
+
+	dev_dbg(rproc->dev, "mapped devmem pa 0x%x, da 0x%x, len 0x%x\n",
+					rsc->pa, rsc->da, rsc->len);
+
+	return 0;
+
+out:
+	kfree(mapping);
+	return ret;
+}
+
+/**
+ * rproc_handle_carveout() - handle phys contig memory allocation requests
+ * @rproc: rproc handle
+ * @rsc: the resource entry
+ * @avail: size of available data (for image validation)
+ *
+ * This function will handle firmware requests for allocation of physically
+ * contiguous memory regions.
+ *
+ * These request entries should come first in the firmware's resource table,
+ * as other firmware entries might request placing other data objects inside
+ * these memory regions (e.g. data/code segments, trace resource entries, ...).
+ *
+ * Allocating memory this way helps utilizing the reserved physical memory
+ * (e.g. CMA) more efficiently, and also minimizes the number of TLB entries
+ * needed to map it (in case @rproc is using an IOMMU). Reducing the TLB
+ * pressure is important; it may have a substantial impact on performance.
+ */
+static int rproc_handle_carveout(struct rproc *rproc,
+				struct fw_rsc_carveout *rsc, int avail)
+{
+	struct rproc_mem_entry *carveout, *mapping;
+	struct device *dev = rproc->dev;
+	dma_addr_t dma;
+	void *va;
+	int ret;
+
+	if (sizeof(*rsc) > avail) {
+		dev_err(rproc->dev, "carveout rsc is truncated\n");
+		return -EINVAL;
+	}
+
+	/* make sure reserved bytes are zeroes */
+	if (rsc->reserved) {
+		dev_err(dev, "carveout rsc has non zero reserved bytes\n");
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "carveout rsc: da %x, pa %x, len %x, flags %x\n",
+			rsc->da, rsc->pa, rsc->len, rsc->flags);
+
+	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
+	if (!mapping) {
+		dev_err(dev, "kzalloc mapping failed\n");
+		return -ENOMEM;
+	}
+
+	carveout = kzalloc(sizeof(*carveout), GFP_KERNEL);
+	if (!carveout) {
+		dev_err(dev, "kzalloc carveout failed\n");
+		ret = -ENOMEM;
+		goto free_mapping;
+	}
+
+	va = dma_alloc_coherent(dev, rsc->len, &dma, GFP_KERNEL);
+	if (!va) {
+		dev_err(dev, "failed to dma alloc carveout: %d\n", rsc->len);
+		ret = -ENOMEM;
+		goto free_carv;
+	}
+
+	dev_dbg(dev, "carveout va %p, dma %x, len 0x%x\n", va, dma, rsc->len);
+
+	/*
+	 * Ok, this is non-standard.
+	 *
+	 * Sometimes we can't rely on the generic iommu-based DMA API
+	 * to dynamically allocate the device address and then set the IOMMU
+	 * tables accordingly, because some remote processors might
+	 * _require_ us to use hard coded device addresses that their
+	 * firmware was compiled with.
+	 *
+	 * In this case, we must use the IOMMU API directly and map
+	 * the memory to the device address as expected by the remote
+	 * processor.
+	 *
+	 * Obviously such remote processor devices should not be configured
+	 * to use the iommu-based DMA API: we expect 'dma' to contain the
+	 * physical address in this case.
+	 */
+	if (rproc->domain) {
+		ret = iommu_map(rproc->domain, rsc->da, dma, rsc->len,
+								rsc->flags);
+		if (ret) {
+			dev_err(dev, "iommu_map failed: %d\n", ret);
+			goto dma_free;
+		}
+
+		/*
+		 * We'll need this info later when we'll want to unmap
+		 * everything (e.g. on shutdown).
+		 *
+		 * We can't trust the remote processor not to change the
+		 * resource table, so we must maintain this info independently.
+		 */
+		mapping->da = rsc->da;
+		mapping->len = rsc->len;
+		list_add_tail(&mapping->node, &rproc->mappings);
+
+		dev_dbg(dev, "carveout mapped 0x%x to 0x%x\n", rsc->da, dma);
+
+		/*
+		 * Some remote processors might need to know the pa
+		 * even though they are behind an IOMMU. E.g., OMAP4's
+		 * remote M3 processor needs this so it can control
+		 * on-chip hardware accelerators that are not behind
+		 * the IOMMU, and therefor must know the pa.
+		 *
+		 * Generally we don't want to expose physical addresses
+		 * if we don't have to (remote processors are generally
+		 * _not_ trusted), so we might want to do this only for
+		 * remote processor that _must_ have this (e.g. OMAP4's
+		 * dual M3 subsystem).
+		 */
+		rsc->pa = dma;
+	}
+
+	carveout->va = va;
+	carveout->len = rsc->len;
+	carveout->dma = dma;
+	carveout->da = rsc->da;
+
+	list_add_tail(&carveout->node, &rproc->carveouts);
+
+	return 0;
+
+dma_free:
+	dma_free_coherent(dev, rsc->len, va, dma);
+free_carv:
+	kfree(carveout);
+free_mapping:
+	kfree(mapping);
+	return ret;
+}
+
+/*
+ * A lookup table for resource handlers. The indices are defined in
+ * enum fw_resource_type.
+ */
+static rproc_handle_resource_t rproc_handle_rsc[] = {
+	[RSC_CARVEOUT] = (rproc_handle_resource_t)rproc_handle_carveout,
+	[RSC_DEVMEM] = (rproc_handle_resource_t)rproc_handle_devmem,
+	[RSC_TRACE] = (rproc_handle_resource_t)rproc_handle_trace,
+	[RSC_VDEV] = NULL, /* VDEVs were handled upon registrarion */
+};
+
+/* handle firmware resource entries before booting the remote processor */
+static int
+rproc_handle_boot_rsc(struct rproc *rproc, struct resource_table *table, int len)
+{
+	struct device *dev = rproc->dev;
+	rproc_handle_resource_t handler;
+	int ret = 0, i;
+
+	for (i = 0; i < table->num; i++) {
+		int offset = table->offset[i];
+		struct fw_rsc_hdr *hdr = (void *)table + offset;
+		int avail = len - offset - sizeof(*hdr);
+		void *rsc = (void *)hdr + sizeof(*hdr);
+
+		/* make sure table isn't truncated */
+		if (avail < 0) {
+			dev_err(dev, "rsc table is truncated\n");
+			return -EINVAL;
+		}
+
+		dev_dbg(dev, "rsc: type %d\n", hdr->type);
+
+		if (hdr->type >= RSC_LAST) {
+			dev_warn(dev, "unsupported resource %d\n", hdr->type);
+			continue;
+		}
+
+		handler = rproc_handle_rsc[hdr->type];
+		if (!handler)
+			continue;
+
+		ret = handler(rproc, rsc, avail);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/* handle firmware resource entries while registering the remote processor */
+static int
+rproc_handle_virtio_rsc(struct rproc *rproc, struct resource_table *table, int len)
+{
+	struct device *dev = rproc->dev;
+	int ret = 0, i;
+
+	for (i = 0; i < table->num; i++) {
+		int offset = table->offset[i];
+		struct fw_rsc_hdr *hdr = (void *)table + offset;
+		int avail = len - offset - sizeof(*hdr);
+		struct fw_rsc_vdev *vrsc;
+
+		/* make sure table isn't truncated */
+		if (avail < 0) {
+			dev_err(dev, "rsc table is truncated\n");
+			return -EINVAL;
+		}
+
+		dev_dbg(dev, "%s: rsc type %d\n", __func__, hdr->type);
+
+		if (hdr->type != RSC_VDEV)
+			continue;
+
+		vrsc = (struct fw_rsc_vdev *)hdr->data;
+
+		ret = rproc_handle_vdev(rproc, vrsc, avail);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/**
+ * rproc_find_rsc_table() - find the resource table
+ * @rproc: the rproc handle
+ * @elf_data: the content of the ELF firmware image
+ * @len: firmware size (in bytes)
+ * @tablesz: place holder for providing back the table size
+ *
+ * This function finds the resource table inside the remote processor's
+ * firmware. It is used both upon the registration of @rproc (in order
+ * to look for and register the supported virito devices), and when the
+ * @rproc is booted.
+ *
+ * Returns the pointer to the resource table if it is found, and write its
+ * size into @tablesz. If a valid table isn't found, NULL is returned
+ * (and @tablesz isn't set).
+ */
+static struct resource_table *
+rproc_find_rsc_table(struct rproc *rproc, const u8 *elf_data, size_t len,
+							int *tablesz)
+{
+	struct elf32_hdr *ehdr;
+	struct elf32_shdr *shdr;
+	const char *name_table;
+	struct device *dev = rproc->dev;
+	struct resource_table *table = NULL;
+	int i;
+
+	ehdr = (struct elf32_hdr *)elf_data;
+	shdr = (struct elf32_shdr *)(elf_data + ehdr->e_shoff);
+	name_table = elf_data + shdr[ehdr->e_shstrndx].sh_offset;
+
+	/* look for the resource table and handle it */
+	for (i = 0; i < ehdr->e_shnum; i++, shdr++) {
+		int size = shdr->sh_size;
+		int offset = shdr->sh_offset;
+
+		if (strcmp(name_table + shdr->sh_name, ".resource_table"))
+			continue;
+
+		table = (struct resource_table *)(elf_data + offset);
+
+		/* make sure we have the entire table */
+		if (offset + size > len) {
+			dev_err(dev, "resource table truncated\n");
+			return NULL;
+		}
+
+		/* make sure table has at least the header */
+		if (sizeof(struct resource_table) > size) {
+			dev_err(dev, "header-less resource table\n");
+			return NULL;
+		}
+
+		/* we don't support any version beyond the first */
+		if (table->ver != 1) {
+			dev_err(dev, "unsupported fw ver: %d\n", table->ver);
+			return NULL;
+		}
+
+		/* make sure reserved bytes are zeroes */
+		if (table->reserved[0] || table->reserved[1]) {
+			dev_err(dev, "non zero reserved bytes\n");
+			return NULL;
+		}
+
+		/* make sure the offsets array isn't truncated */
+		if (table->num * sizeof(table->offset[0]) +
+				sizeof(struct resource_table) > size) {
+			dev_err(dev, "resource table incomplete\n");
+			return NULL;
+		}
+
+		*tablesz = shdr->sh_size;
+		break;
+	}
+
+	return table;
+}
+
+/**
+ * rproc_resource_cleanup() - clean up and free all acquired resources
+ * @rproc: rproc handle
+ *
+ * This function will free all resources acquired for @rproc, and it
+ * is called whenever @rproc either shuts down or fails to boot.
+ */
+static void rproc_resource_cleanup(struct rproc *rproc)
+{
+	struct rproc_mem_entry *entry, *tmp;
+	struct device *dev = rproc->dev;
+
+	/* clean up debugfs trace entries */
+	list_for_each_entry_safe(entry, tmp, &rproc->traces, node) {
+		rproc_remove_trace_file(entry->priv);
+		rproc->num_traces--;
+		list_del(&entry->node);
+		kfree(entry);
+	}
+
+	/* clean up carveout allocations */
+	list_for_each_entry_safe(entry, tmp, &rproc->carveouts, node) {
+		dma_free_coherent(dev, entry->len, entry->va, entry->dma);
+		list_del(&entry->node);
+		kfree(entry);
+	}
+
+	/* clean up iommu mapping entries */
+	list_for_each_entry_safe(entry, tmp, &rproc->mappings, node) {
+		size_t unmapped;
+
+		unmapped = iommu_unmap(rproc->domain, entry->da, entry->len);
+		if (unmapped != entry->len) {
+			/* nothing much to do besides complaining */
+			dev_err(dev, "failed to unmap %u/%u\n", entry->len,
+								unmapped);
+		}
+
+		list_del(&entry->node);
+		kfree(entry);
+	}
+}
+
+/* make sure this fw image is sane */
+static int rproc_fw_sanity_check(struct rproc *rproc, const struct firmware *fw)
+{
+	const char *name = rproc->firmware;
+	struct device *dev = rproc->dev;
+	struct elf32_hdr *ehdr;
+	char class;
+
+	if (!fw) {
+		dev_err(dev, "failed to load %s\n", name);
+		return -EINVAL;
+	}
+
+	if (fw->size < sizeof(struct elf32_hdr)) {
+		dev_err(dev, "Image is too small\n");
+		return -EINVAL;
+	}
+
+	ehdr = (struct elf32_hdr *)fw->data;
+
+	/* We only support ELF32 at this point */
+	class = ehdr->e_ident[EI_CLASS];
+	if (class != ELFCLASS32) {
+		dev_err(dev, "Unsupported class: %d\n", class);
+		return -EINVAL;
+	}
+
+	/* We assume the firmware has the same endianess as the host */
+# ifdef __LITTLE_ENDIAN
+	if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB) {
+# else /* BIG ENDIAN */
+	if (ehdr->e_ident[EI_DATA] != ELFDATA2MSB) {
+# endif
+		dev_err(dev, "Unsupported firmware endianess\n");
+		return -EINVAL;
+	}
+
+	if (fw->size < ehdr->e_shoff + sizeof(struct elf32_shdr)) {
+		dev_err(dev, "Image is too small\n");
+		return -EINVAL;
+	}
+
+	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG)) {
+		dev_err(dev, "Image is corrupted (bad magic)\n");
+		return -EINVAL;
+	}
+
+	if (ehdr->e_phnum == 0) {
+		dev_err(dev, "No loadable segments\n");
+		return -EINVAL;
+	}
+
+	if (ehdr->e_phoff > fw->size) {
+		dev_err(dev, "Firmware size is too small\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * take a firmware and boot a remote processor with it.
+ */
+static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
+{
+	struct device *dev = rproc->dev;
+	const char *name = rproc->firmware;
+	struct elf32_hdr *ehdr;
+	struct resource_table *table;
+	int ret, tablesz;
+
+	ret = rproc_fw_sanity_check(rproc, fw);
+	if (ret)
+		return ret;
+
+	ehdr = (struct elf32_hdr *)fw->data;
+
+	dev_info(dev, "Booting fw image %s, size %d\n", name, fw->size);
+
+	/*
+	 * if enabling an IOMMU isn't relevant for this rproc, this is
+	 * just a nop
+	 */
+	ret = rproc_enable_iommu(rproc);
+	if (ret) {
+		dev_err(dev, "can't enable iommu: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * The ELF entry point is the rproc's boot addr (though this is not
+	 * a configurable property of all remote processors: some will always
+	 * boot at a specific hardcoded address).
+	 */
+	rproc->bootaddr = ehdr->e_entry;
+
+	/* look for the resource table */
+	table = rproc_find_rsc_table(rproc, fw->data, fw->size, &tablesz);
+	if (!table)
+		goto clean_up;
+
+	/* handle fw resources which are required to boot rproc */
+	ret = rproc_handle_boot_rsc(rproc, table, tablesz);
+	if (ret) {
+		dev_err(dev, "Failed to process resources: %d\n", ret);
+		goto clean_up;
+	}
+
+	/* load the ELF segments to memory */
+	ret = rproc_load_segments(rproc, fw->data, fw->size);
+	if (ret) {
+		dev_err(dev, "Failed to load program segments: %d\n", ret);
+		goto clean_up;
+	}
+
+	/* power up the remote processor */
+	ret = rproc->ops->start(rproc);
+	if (ret) {
+		dev_err(dev, "can't start rproc %s: %d\n", rproc->name, ret);
+		goto clean_up;
+	}
+
+	rproc->state = RPROC_RUNNING;
+
+	dev_info(dev, "remote processor %s is now up\n", rproc->name);
+
+	return 0;
+
+clean_up:
+	rproc_resource_cleanup(rproc);
+	rproc_disable_iommu(rproc);
+	return ret;
+}
+
+/*
+ * take a firmware and look for virtio devices to register.
+ *
+ * Note: this function is called asynchronously upon registration of the
+ * remote processor (so we must wait until it completes before we try
+ * to unregister the device. one other option is just to use kref here,
+ * that might be cleaner).
+ */
+static void rproc_fw_config_virtio(const struct firmware *fw, void *context)
+{
+	struct rproc *rproc = context;
+	struct resource_table *table;
+	int ret, tablesz;
+
+	if (rproc_fw_sanity_check(rproc, fw) < 0)
+		goto out;
+
+	/* look for the resource table */
+	table = rproc_find_rsc_table(rproc, fw->data, fw->size, &tablesz);
+	if (!table)
+		goto out;
+
+	/* look for virtio devices and register them */
+	ret = rproc_handle_virtio_rsc(rproc, table, tablesz);
+	if (ret)
+		goto out;
+
+out:
+	if (fw)
+		release_firmware(fw);
+	/* allow rproc_unregister() contexts, if any, to proceed */
+	complete_all(&rproc->firmware_loading_complete);
+}
+
+/**
+ * rproc_boot() - boot a remote processor
+ * @rproc: handle of a remote processor
+ *
+ * Boot a remote processor (i.e. load its firmware, power it on, ...).
+ *
+ * If the remote processor is already powered on, this function immediately
+ * returns (successfully).
+ *
+ * Returns 0 on success, and an appropriate error value otherwise.
+ */
+int rproc_boot(struct rproc *rproc)
+{
+	const struct firmware *firmware_p;
+	struct device *dev;
+	int ret;
+
+	if (!rproc) {
+		pr_err("invalid rproc handle\n");
+		return -EINVAL;
+	}
+
+	dev = rproc->dev;
+
+	ret = mutex_lock_interruptible(&rproc->lock);
+	if (ret) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
+		return ret;
+	}
+
+	/* loading a firmware is required */
+	if (!rproc->firmware) {
+		dev_err(dev, "%s: no firmware to load\n", __func__);
+		ret = -EINVAL;
+		goto unlock_mutex;
+	}
+
+	/* prevent underlying implementation from being removed */
+	if (!try_module_get(dev->driver->owner)) {
+		dev_err(dev, "%s: can't get owner\n", __func__);
+		ret = -EINVAL;
+		goto unlock_mutex;
+	}
+
+	/* skip the boot process if rproc is already powered up */
+	if (atomic_inc_return(&rproc->power) > 1) {
+		ret = 0;
+		goto unlock_mutex;
+	}
+
+	dev_info(dev, "powering up %s\n", rproc->name);
+
+	/* load firmware */
+	ret = request_firmware(&firmware_p, rproc->firmware, dev);
+	if (ret < 0) {
+		dev_err(dev, "request_firmware failed: %d\n", ret);
+		goto downref_rproc;
+	}
+
+	ret = rproc_fw_boot(rproc, firmware_p);
+
+	release_firmware(firmware_p);
+
+downref_rproc:
+	if (ret) {
+		module_put(dev->driver->owner);
+		atomic_dec(&rproc->power);
+	}
+unlock_mutex:
+	mutex_unlock(&rproc->lock);
+	return ret;
+}
+EXPORT_SYMBOL(rproc_boot);
+
+/**
+ * rproc_shutdown() - power off the remote processor
+ * @rproc: the remote processor
+ *
+ * Power off a remote processor (previously booted with rproc_boot()).
+ *
+ * In case @rproc is still being used by an additional user(s), then
+ * this function will just decrement the power refcount and exit,
+ * without really powering off the device.
+ *
+ * Every call to rproc_boot() must (eventually) be accompanied by a call
+ * to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
+ *
+ * Notes:
+ * - we're not decrementing the rproc's refcount, only the power refcount.
+ *   which means that the @rproc handle stays valid even after rproc_shutdown()
+ *   returns, and users can still use it with a subsequent rproc_boot(), if
+ *   needed.
+ * - don't call rproc_shutdown() to unroll rproc_get_by_name(), exactly
+ *   because rproc_shutdown() _does not_ decrement the refcount of @rproc.
+ *   To decrement the refcount of @rproc, use rproc_put() (but _only_ if
+ *   you acquired @rproc using rproc_get_by_name()).
+ */
+void rproc_shutdown(struct rproc *rproc)
+{
+	struct device *dev = rproc->dev;
+	int ret;
+
+	ret = mutex_lock_interruptible(&rproc->lock);
+	if (ret) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
+		return;
+	}
+
+	/* if the remote proc is still needed, bail out */
+	if (!atomic_dec_and_test(&rproc->power))
+		goto out;
+
+	/* power off the remote processor */
+	ret = rproc->ops->stop(rproc);
+	if (ret) {
+		atomic_inc(&rproc->power);
+		dev_err(dev, "can't stop rproc: %d\n", ret);
+		goto out;
+	}
+
+	/* clean up all acquired resources */
+	rproc_resource_cleanup(rproc);
+
+	rproc_disable_iommu(rproc);
+
+	rproc->state = RPROC_OFFLINE;
+
+	dev_info(dev, "stopped remote processor %s\n", rproc->name);
+
+out:
+	mutex_unlock(&rproc->lock);
+	if (!ret)
+		module_put(dev->driver->owner);
+}
+EXPORT_SYMBOL(rproc_shutdown);
+
+/**
+ * rproc_release() - completely deletes the existence of a remote processor
+ * @kref: the rproc's kref
+ *
+ * This function should _never_ be called directly.
+ *
+ * The only reasonable location to use it is as an argument when kref_put'ing
+ * @rproc's refcount.
+ *
+ * This way it will be called when no one holds a valid pointer to this @rproc
+ * anymore (and obviously after it is removed from the rprocs klist).
+ *
+ * Note: this function is not static because rproc_vdev_release() needs it when
+ * it decrements @rproc's refcount.
+ */
+void rproc_release(struct kref *kref)
+{
+	struct rproc *rproc = container_of(kref, struct rproc, refcount);
+	struct rproc_vdev *rvdev, *rvtmp;
+
+	dev_info(rproc->dev, "removing %s\n", rproc->name);
+
+	rproc_delete_debug_dir(rproc);
+
+	/* clean up remote vdev entries */
+	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node) {
+		__rproc_free_vrings(rvdev, RVDEV_NUM_VRINGS);
+		list_del(&rvdev->node);
+	}
+
+	/*
+	 * At this point no one holds a reference to rproc anymore,
+	 * so we can directly unroll rproc_alloc()
+	 */
+	rproc_free(rproc);
+}
+
+/* will be called when an rproc is added to the rprocs klist */
+static void klist_rproc_get(struct klist_node *n)
+{
+	struct rproc *rproc = container_of(n, struct rproc, node);
+
+	kref_get(&rproc->refcount);
+}
+
+/* will be called when an rproc is removed from the rprocs klist */
+static void klist_rproc_put(struct klist_node *n)
+{
+	struct rproc *rproc = container_of(n, struct rproc, node);
+
+	kref_put(&rproc->refcount, rproc_release);
+}
+
+static struct rproc *next_rproc(struct klist_iter *i)
+{
+	struct klist_node *n;
+
+	n = klist_next(i);
+	if (!n)
+		return NULL;
+
+	return container_of(n, struct rproc, node);
+}
+
+/**
+ * rproc_get_by_name() - find a remote processor by name and boot it
+ * @name: name of the remote processor
+ *
+ * Finds an rproc handle using the remote processor's name, and then
+ * boot it. If it's already powered on, then just immediately return
+ * (successfully).
+ *
+ * Returns the rproc handle on success, and NULL on failure.
+ *
+ * This function increments the remote processor's refcount, so always
+ * use rproc_put() to decrement it back once rproc isn't needed anymore.
+ *
+ * Note: currently this function (and its counterpart rproc_put()) are not
+ * being used. We need to scrutinize the use cases
+ * that still need them, and see if we can migrate them to use the non
+ * name-based boot/shutdown interface.
+ */
+struct rproc *rproc_get_by_name(const char *name)
+{
+	struct rproc *rproc;
+	struct klist_iter i;
+	int ret;
+
+	/* find the remote processor, and upref its refcount */
+	klist_iter_init(&rprocs, &i);
+	while ((rproc = next_rproc(&i)) != NULL)
+		if (!strcmp(rproc->name, name)) {
+			kref_get(&rproc->refcount);
+			break;
+		}
+	klist_iter_exit(&i);
+
+	/* can't find this rproc ? */
+	if (!rproc) {
+		pr_err("can't find remote processor %s\n", name);
+		return NULL;
+	}
+
+	ret = rproc_boot(rproc);
+	if (ret < 0) {
+		kref_put(&rproc->refcount, rproc_release);
+		return NULL;
+	}
+
+	return rproc;
+}
+EXPORT_SYMBOL(rproc_get_by_name);
+
+/**
+ * rproc_put() - decrement the refcount of a remote processor, and shut it down
+ * @rproc: the remote processor
+ *
+ * This function tries to shutdown @rproc, and it then decrements its
+ * refcount.
+ *
+ * After this function returns, @rproc may _not_ be used anymore, and its
+ * handle should be considered invalid.
+ *
+ * This function should be called _iff_ the @rproc handle was grabbed by
+ * calling rproc_get_by_name().
+ */
+void rproc_put(struct rproc *rproc)
+{
+	/* try to power off the remote processor */
+	rproc_shutdown(rproc);
+
+	/* downref rproc's refcount */
+	kref_put(&rproc->refcount, rproc_release);
+}
+EXPORT_SYMBOL(rproc_put);
+
+/**
+ * rproc_register() - register a remote processor
+ * @rproc: the remote processor handle to register
+ *
+ * Registers @rproc with the remoteproc framework, after it has been
+ * allocated with rproc_alloc().
+ *
+ * This is called by the platform-specific rproc implementation, whenever
+ * a new remote processor device is probed.
+ *
+ * Returns 0 on success and an appropriate error code otherwise.
+ *
+ * Note: this function initiates an asynchronous firmware loading
+ * context, which will look for virtio devices supported by the rproc's
+ * firmware.
+ *
+ * If found, those virtio devices will be created and added, so as a result
+ * of registering this remote processor, additional virtio drivers might be
+ * probed.
+ */
+int rproc_register(struct rproc *rproc)
+{
+	struct device *dev = rproc->dev;
+	int ret = 0;
+
+	/* expose to rproc_get_by_name users */
+	klist_add_tail(&rproc->node, &rprocs);
+
+	dev_info(rproc->dev, "%s is available\n", rproc->name);
+
+	dev_info(dev, "Note: remoteproc is still under development and considered experimental.\n");
+	dev_info(dev, "THE BINARY FORMAT IS NOT YET FINALIZED, and backward compatibility isn't yet guaranteed.\n");
+
+	/* create debugfs entries */
+	rproc_create_debug_dir(rproc);
+
+	/* rproc_unregister() calls must wait until async loader completes */
+	init_completion(&rproc->firmware_loading_complete);
+
+	/*
+	 * We must retrieve early virtio configuration info from
+	 * the firmware (e.g. whether to register a virtio device,
+	 * what virtio features does it support, ...).
+	 *
+	 * We're initiating an asynchronous firmware loading, so we can
+	 * be built-in kernel code, without hanging the boot process.
+	 */
+	ret = request_firmware_nowait(THIS_MODULE, FW_ACTION_HOTPLUG,
+					rproc->firmware, dev, GFP_KERNEL,
+					rproc, rproc_fw_config_virtio);
+	if (ret < 0) {
+		dev_err(dev, "request_firmware_nowait failed: %d\n", ret);
+		complete_all(&rproc->firmware_loading_complete);
+		klist_remove(&rproc->node);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(rproc_register);
+
+/**
+ * rproc_alloc() - allocate a remote processor handle
+ * @dev: the underlying device
+ * @name: name of this remote processor
+ * @ops: platform-specific handlers (mainly start/stop)
+ * @firmware: name of firmware file to load
+ * @len: length of private data needed by the rproc driver (in bytes)
+ *
+ * Allocates a new remote processor handle, but does not register
+ * it yet.
+ *
+ * This function should be used by rproc implementations during initialization
+ * of the remote processor.
+ *
+ * After creating an rproc handle using this function, and when ready,
+ * implementations should then call rproc_register() to complete
+ * the registration of the remote processor.
+ *
+ * On success the new rproc is returned, and on failure, NULL.
+ *
+ * Note: _never_ directly deallocate @rproc, even if it was not registered
+ * yet. Instead, if you just need to unroll rproc_alloc(), use rproc_free().
+ */
+struct rproc *rproc_alloc(struct device *dev, const char *name,
+				const struct rproc_ops *ops,
+				const char *firmware, int len)
+{
+	struct rproc *rproc;
+
+	if (!dev || !name || !ops)
+		return NULL;
+
+	rproc = kzalloc(sizeof(struct rproc) + len, GFP_KERNEL);
+	if (!rproc) {
+		dev_err(dev, "%s: kzalloc failed\n", __func__);
+		return NULL;
+	}
+
+	rproc->dev = dev;
+	rproc->name = name;
+	rproc->ops = ops;
+	rproc->firmware = firmware;
+	rproc->priv = &rproc[1];
+
+	atomic_set(&rproc->power, 0);
+
+	kref_init(&rproc->refcount);
+
+	mutex_init(&rproc->lock);
+
+	idr_init(&rproc->notifyids);
+
+	INIT_LIST_HEAD(&rproc->carveouts);
+	INIT_LIST_HEAD(&rproc->mappings);
+	INIT_LIST_HEAD(&rproc->traces);
+	INIT_LIST_HEAD(&rproc->rvdevs);
+
+	rproc->state = RPROC_OFFLINE;
+
+	return rproc;
+}
+EXPORT_SYMBOL(rproc_alloc);
+
+/**
+ * rproc_free() - free an rproc handle that was allocated by rproc_alloc
+ * @rproc: the remote processor handle
+ *
+ * This function should _only_ be used if @rproc was only allocated,
+ * but not registered yet.
+ *
+ * If @rproc was already successfully registered (by calling rproc_register()),
+ * then use rproc_unregister() instead.
+ */
+void rproc_free(struct rproc *rproc)
+{
+	idr_remove_all(&rproc->notifyids);
+	idr_destroy(&rproc->notifyids);
+
+	kfree(rproc);
+}
+EXPORT_SYMBOL(rproc_free);
+
+/**
+ * rproc_unregister() - unregister a remote processor
+ * @rproc: rproc handle to unregister
+ *
+ * Unregisters a remote processor, and decrements its refcount.
+ * If its refcount drops to zero, then @rproc will be freed. If not,
+ * it will be freed later once the last reference is dropped.
+ *
+ * This function should be called when the platform specific rproc
+ * implementation decides to remove the rproc device. it should
+ * _only_ be called if a previous invocation of rproc_register()
+ * has completed successfully.
+ *
+ * After rproc_unregister() returns, @rproc is _not_ valid anymore and
+ * it shouldn't be used. More specifically, don't call rproc_free()
+ * or try to directly free @rproc after rproc_unregister() returns;
+ * none of these are needed, and calling them is a bug.
+ *
+ * Returns 0 on success and -EINVAL if @rproc isn't valid.
+ */
+int rproc_unregister(struct rproc *rproc)
+{
+	struct rproc_vdev *rvdev;
+
+	if (!rproc)
+		return -EINVAL;
+
+	/* if rproc is just being registered, wait */
+	wait_for_completion(&rproc->firmware_loading_complete);
+
+	/* clean up remote vdev entries */
+	list_for_each_entry(rvdev, &rproc->rvdevs, node)
+		rproc_remove_virtio_dev(rvdev);
+
+	/* the rproc is downref'ed as soon as it's removed from the klist */
+	klist_del(&rproc->node);
+
+	/* the rproc will only be released after its refcount drops to zero */
+	kref_put(&rproc->refcount, rproc_release);
+
+	return 0;
+}
+EXPORT_SYMBOL(rproc_unregister);
+
+static int __init remoteproc_init(void)
+{
+	rproc_init_debugfs();
+	return 0;
+}
+module_init(remoteproc_init);
+
+static void __exit remoteproc_exit(void)
+{
+	rproc_exit_debugfs();
+}
+module_exit(remoteproc_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Generic Remote Processor Framework");

drivers/remoteproc/remoteproc_debugfs.c

···
+/*
+ * Remote Processor Framework
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Mark Grosen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ * Fernando Guzman Lugo <[e-mail]>
+ * Suman Anna <[e-mail]>
+ * Robert Tivy <[e-mail]>
+ * Armando Uribe De Leon <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt)    "%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <linux/remoteproc.h>
+#include <linux/device.h>
+
+/* remoteproc debugfs parent dir */
+static struct dentry *rproc_dbg;
+
+/*
+ * Some remote processors may support dumping trace logs into a shared
+ * memory buffer. We expose this trace buffer using debugfs, so users
+ * can easily tell what's going on remotely.
+ *
+ * We will most probably improve the rproc tracing facilities later on,
+ * but this kind of lightweight and simple mechanism is always good to have,
+ * as it provides very early tracing with little to no dependencies at all.
+ */
+static ssize_t rproc_trace_read(struct file *filp, char __user *userbuf,
+						size_t count, loff_t *ppos)
+{
+	struct rproc_mem_entry *trace = filp->private_data;
+	int len = strnlen(trace->va, trace->len);
+
+	return simple_read_from_buffer(userbuf, count, ppos, trace->va, len);
+}
+
+static int rproc_open_generic(struct inode *inode, struct file *file)
+{
+	file->private_data = inode->i_private;
+
+	return 0;
+}
+
+static const struct file_operations trace_rproc_ops = {
+	.read = rproc_trace_read,
+	.open = rproc_open_generic,
+	.llseek	= generic_file_llseek,
+};
+
+/*
+ * A state-to-string lookup table, for exposing a human readable state
+ * via debugfs. Always keep in sync with enum rproc_state
+ */
+static const char * const rproc_state_string[] = {
+	"offline",
+	"suspended",
+	"running",
+	"crashed",
+	"invalid",
+};
+
+/* expose the state of the remote processor via debugfs */
+static ssize_t rproc_state_read(struct file *filp, char __user *userbuf,
+						size_t count, loff_t *ppos)
+{
+	struct rproc *rproc = filp->private_data;
+	unsigned int state;
+	char buf[30];
+	int i;
+
+	state = rproc->state > RPROC_LAST ? RPROC_LAST : rproc->state;
+
+	i = snprintf(buf, 30, "%.28s (%d)\n", rproc_state_string[state],
+							rproc->state);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, i);
+}
+
+static const struct file_operations rproc_state_ops = {
+	.read = rproc_state_read,
+	.open = rproc_open_generic,
+	.llseek	= generic_file_llseek,
+};
+
+/* expose the name of the remote processor via debugfs */
+static ssize_t rproc_name_read(struct file *filp, char __user *userbuf,
+						size_t count, loff_t *ppos)
+{
+	struct rproc *rproc = filp->private_data;
+	/* need room for the name, a newline and a terminating null */
+	char buf[100];
+	int i;
+
+	i = snprintf(buf, sizeof(buf), "%.98s\n", rproc->name);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, i);
+}
+
+static const struct file_operations rproc_name_ops = {
+	.read = rproc_name_read,
+	.open = rproc_open_generic,
+	.llseek	= generic_file_llseek,
+};
+
+void rproc_remove_trace_file(struct dentry *tfile)
+{
+	debugfs_remove(tfile);
+}
+
+struct dentry *rproc_create_trace_file(const char *name, struct rproc *rproc,
+					struct rproc_mem_entry *trace)
+{
+	struct dentry *tfile;
+
+	tfile = debugfs_create_file(name, 0400, rproc->dbg_dir,
+						trace, &trace_rproc_ops);
+	if (!tfile) {
+		dev_err(rproc->dev, "failed to create debugfs trace entry\n");
+		return NULL;
+	}
+
+	return tfile;
+}
+
+void rproc_delete_debug_dir(struct rproc *rproc)
+{
+	if (!rproc->dbg_dir)
+		return;
+
+	debugfs_remove_recursive(rproc->dbg_dir);
+}
+
+void rproc_create_debug_dir(struct rproc *rproc)
+{
+	struct device *dev = rproc->dev;
+
+	if (!rproc_dbg)
+		return;
+
+	rproc->dbg_dir = debugfs_create_dir(dev_name(dev), rproc_dbg);
+	if (!rproc->dbg_dir)
+		return;
+
+	debugfs_create_file("name", 0400, rproc->dbg_dir,
+					rproc, &rproc_name_ops);
+	debugfs_create_file("state", 0400, rproc->dbg_dir,
+					rproc, &rproc_state_ops);
+}
+
+void __init rproc_init_debugfs(void)
+{
+	if (debugfs_initialized()) {
+		rproc_dbg = debugfs_create_dir(KBUILD_MODNAME, NULL);
+		if (!rproc_dbg)
+			pr_err("can't create debugfs dir\n");
+	}
+}
+
+void __exit rproc_exit_debugfs(void)
+{
+	if (rproc_dbg)
+		debugfs_remove(rproc_dbg);
+}

drivers/remoteproc/remoteproc_internal.h

···
+/*
+ * Remote processor framework
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef REMOTEPROC_INTERNAL_H
+#define REMOTEPROC_INTERNAL_H
+
+#include <linux/irqreturn.h>
+
+struct rproc;
+
+/* from remoteproc_core.c */
+void rproc_release(struct kref *kref);
+irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int vq_id);
+
+/* from remoteproc_virtio.c */
+int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id);
+void rproc_remove_virtio_dev(struct rproc_vdev *rvdev);
+
+/* from remoteproc_debugfs.c */
+void rproc_remove_trace_file(struct dentry *tfile);
+struct dentry *rproc_create_trace_file(const char *name, struct rproc *rproc,
+					struct rproc_mem_entry *trace);
+void rproc_delete_debug_dir(struct rproc *rproc);
+void rproc_create_debug_dir(struct rproc *rproc);
+void rproc_init_debugfs(void);
+void rproc_exit_debugfs(void);
+
+#endif /* REMOTEPROC_INTERNAL_H */

drivers/remoteproc/remoteproc_virtio.c

···
+/*
+ * Remote processor messaging transport (OMAP platform-specific bits)
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/export.h>
+#include <linux/remoteproc.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_ring.h>
+#include <linux/err.h>
+#include <linux/kref.h>
+#include <linux/slab.h>
+
+#include "remoteproc_internal.h"
+
+/* kick the remote processor, and let it know which virtqueue to poke at */
+static void rproc_virtio_notify(struct virtqueue *vq)
+{
+	struct rproc_vring *rvring = vq->priv;
+	struct rproc *rproc = rvring->rvdev->rproc;
+	int notifyid = rvring->notifyid;
+
+	dev_dbg(rproc->dev, "kicking vq index: %d\n", notifyid);
+
+	rproc->ops->kick(rproc, notifyid);
+}
+
+/**
+ * rproc_vq_interrupt() - tell remoteproc that a virtqueue is interrupted
+ * @rproc: handle to the remote processor
+ * @notifyid: index of the signalled virtqueue (unique per this @rproc)
+ *
+ * This function should be called by the platform-specific rproc driver,
+ * when the remote processor signals that a specific virtqueue has pending
+ * messages available.
+ *
+ * Returns IRQ_NONE if no message was found in the @notifyid virtqueue,
+ * and otherwise returns IRQ_HANDLED.
+ */
+irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int notifyid)
+{
+	struct rproc_vring *rvring;
+
+	dev_dbg(rproc->dev, "vq index %d is interrupted\n", notifyid);
+
+	rvring = idr_find(&rproc->notifyids, notifyid);
+	if (!rvring || !rvring->vq)
+		return IRQ_NONE;
+
+	return vring_interrupt(0, rvring->vq);
+}
+EXPORT_SYMBOL(rproc_vq_interrupt);
+
+static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
+				    unsigned id,
+				    void (*callback)(struct virtqueue *vq),
+				    const char *name)
+{
+	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
+	struct rproc *rproc = vdev_to_rproc(vdev);
+	struct rproc_vring *rvring;
+	struct virtqueue *vq;
+	void *addr;
+	int len, size;
+
+	/* we're temporarily limited to two virtqueues per rvdev */
+	if (id >= ARRAY_SIZE(rvdev->vring))
+		return ERR_PTR(-EINVAL);
+
+	rvring = &rvdev->vring[id];
+
+	addr = rvring->va;
+	len = rvring->len;
+
+	/* zero vring */
+	size = vring_size(len, rvring->align);
+	memset(addr, 0, size);
+
+	dev_dbg(rproc->dev, "vring%d: va %p qsz %d notifyid %d\n",
+					id, addr, len, rvring->notifyid);
+
+	/*
+	 * Create the new vq, and tell virtio we're not interested in
+	 * the 'weak' smp barriers, since we're talking with a real device.
+	 */
+	vq = vring_new_virtqueue(len, rvring->align, vdev, false, addr,
+					rproc_virtio_notify, callback, name);
+	if (!vq) {
+		dev_err(rproc->dev, "vring_new_virtqueue %s failed\n", name);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	rvring->vq = vq;
+	vq->priv = rvring;
+
+	return vq;
+}
+
+static void rproc_virtio_del_vqs(struct virtio_device *vdev)
+{
+	struct virtqueue *vq, *n;
+	struct rproc *rproc = vdev_to_rproc(vdev);
+	struct rproc_vring *rvring;
+
+	/* power down the remote processor before deleting vqs */
+	rproc_shutdown(rproc);
+
+	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
+		rvring = vq->priv;
+		rvring->vq = NULL;
+		vring_del_virtqueue(vq);
+	}
+}
+
+static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+		       struct virtqueue *vqs[],
+		       vq_callback_t *callbacks[],
+		       const char *names[])
+{
+	struct rproc *rproc = vdev_to_rproc(vdev);
+	int i, ret;
+
+	for (i = 0; i < nvqs; ++i) {
+		vqs[i] = rp_find_vq(vdev, i, callbacks[i], names[i]);
+		if (IS_ERR(vqs[i])) {
+			ret = PTR_ERR(vqs[i]);
+			goto error;
+		}
+	}
+
+	/* now that the vqs are all set, boot the remote processor */
+	ret = rproc_boot(rproc);
+	if (ret) {
+		dev_err(rproc->dev, "rproc_boot() failed %d\n", ret);
+		goto error;
+	}
+
+	return 0;
+
+error:
+	rproc_virtio_del_vqs(vdev);
+	return ret;
+}
+
+/*
+ * We don't support yet real virtio status semantics.
+ *
+ * The plan is to provide this via the VDEV resource entry
+ * which is part of the firmware: this way the remote processor
+ * will be able to access the status values as set by us.
+ */
+static u8 rproc_virtio_get_status(struct virtio_device *vdev)
+{
+	return 0;
+}
+
+static void rproc_virtio_set_status(struct virtio_device *vdev, u8 status)
+{
+	dev_dbg(&vdev->dev, "status: %d\n", status);
+}
+
+static void rproc_virtio_reset(struct virtio_device *vdev)
+{
+	dev_dbg(&vdev->dev, "reset !\n");
+}
+
+/* provide the vdev features as retrieved from the firmware */
+static u32 rproc_virtio_get_features(struct virtio_device *vdev)
+{
+	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
+
+	return rvdev->dfeatures;
+}
+
+static void rproc_virtio_finalize_features(struct virtio_device *vdev)
+{
+	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
+
+	/* Give virtio_ring a chance to accept features */
+	vring_transport_features(vdev);
+
+	/*
+	 * Remember the finalized features of our vdev, and provide it
+	 * to the remote processor once it is powered on.
+	 *
+	 * Similarly to the status field, we don't expose yet the negotiated
+	 * features to the remote processors at this point. This will be
+	 * fixed as part of a small resource table overhaul and then an
+	 * extension of the virtio resource entries.
+	 */
+	rvdev->gfeatures = vdev->features[0];
+}
+
+static struct virtio_config_ops rproc_virtio_config_ops = {
+	.get_features	= rproc_virtio_get_features,
+	.finalize_features = rproc_virtio_finalize_features,
+	.find_vqs	= rproc_virtio_find_vqs,
+	.del_vqs	= rproc_virtio_del_vqs,
+	.reset		= rproc_virtio_reset,
+	.set_status	= rproc_virtio_set_status,
+	.get_status	= rproc_virtio_get_status,
+};
+
+/*
+ * This function is called whenever vdev is released, and is responsible
+ * to decrement the remote processor's refcount taken when vdev was
+ * added.
+ *
+ * Never call this function directly; it will be called by the driver
+ * core when needed.
+ */
+static void rproc_vdev_release(struct device *dev)
+{
+	struct virtio_device *vdev = dev_to_virtio(dev);
+	struct rproc *rproc = vdev_to_rproc(vdev);
+
+	kref_put(&rproc->refcount, rproc_release);
+}
+
+/**
+ * rproc_add_virtio_dev() - register an rproc-induced virtio device
+ * @rvdev: the remote vdev
+ *
+ * This function registers a virtio device. This vdev's partent is
+ * the rproc device.
+ *
+ * Returns 0 on success or an appropriate error value otherwise.
+ */
+int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
+{
+	struct rproc *rproc = rvdev->rproc;
+	struct device *dev = rproc->dev;
+	struct virtio_device *vdev = &rvdev->vdev;
+	int ret;
+
+	vdev->id.device	= id,
+	vdev->config = &rproc_virtio_config_ops,
+	vdev->dev.parent = dev;
+	vdev->dev.release = rproc_vdev_release;
+
+	/*
+	 * We're indirectly making a non-temporary copy of the rproc pointer
+	 * here, because drivers probed with this vdev will indirectly
+	 * access the wrapping rproc.
+	 *
+	 * Therefore we must increment the rproc refcount here, and decrement
+	 * it _only_ when the vdev is released.
+	 */
+	kref_get(&rproc->refcount);
+
+	ret = register_virtio_device(vdev);
+	if (ret) {
+		kref_put(&rproc->refcount, rproc_release);
+		dev_err(dev, "failed to register vdev: %d\n", ret);
+		goto out;
+	}
+
+	dev_info(dev, "registered %s (type %d)\n", dev_name(&vdev->dev), id);
+
+out:
+	return ret;
+}
+
+/**
+ * rproc_remove_virtio_dev() - remove an rproc-induced virtio device
+ * @rvdev: the remote vdev
+ *
+ * This function unregisters an existing virtio device.
+ */
+void rproc_remove_virtio_dev(struct rproc_vdev *rvdev)
+{
+	unregister_virtio_device(&rvdev->vdev);
+}

drivers/rpmsg/Kconfig

···
+menu "Rpmsg drivers (EXPERIMENTAL)"
+
+# RPMSG always gets selected by whoever wants it
+config RPMSG
+	tristate
+	select VIRTIO
+	select VIRTIO_RING
+	depends on EXPERIMENTAL
+
+endmenu

drivers/rpmsg/Makefile

···
+obj-$(CONFIG_RPMSG)	+= virtio_rpmsg_bus.o

drivers/rpmsg/virtio_rpmsg_bus.c

···
+/*
+ * Virtio-based remote processor messaging bus
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/virtio.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_config.h>
+#include <linux/scatterlist.h>
+#include <linux/dma-mapping.h>
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include <linux/jiffies.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/rpmsg.h>
+#include <linux/mutex.h>
+
+/**
+ * struct virtproc_info - virtual remote processor state
+ * @vdev:	the virtio device
+ * @rvq:	rx virtqueue
+ * @svq:	tx virtqueue
+ * @rbufs:	kernel address of rx buffers
+ * @sbufs:	kernel address of tx buffers
+ * @last_sbuf:	index of last tx buffer used
+ * @bufs_dma:	dma base addr of the buffers
+ * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
+ *		sending a message might require waking up a dozing remote
+ *		processor, which involves sleeping, hence the mutex.
+ * @endpoints:	idr of local endpoints, allows fast retrieval
+ * @endpoints_lock: lock of the endpoints set
+ * @sendq:	wait queue of sending contexts waiting for a tx buffers
+ * @sleepers:	number of senders that are waiting for a tx buffer
+ * @ns_ept:	the bus's name service endpoint
+ *
+ * This structure stores the rpmsg state of a given virtio remote processor
+ * device (there might be several virtio proc devices for each physical
+ * remote processor).
+ */
+struct virtproc_info {
+	struct virtio_device *vdev;
+	struct virtqueue *rvq, *svq;
+	void *rbufs, *sbufs;
+	int last_sbuf;
+	dma_addr_t bufs_dma;
+	struct mutex tx_lock;
+	struct idr endpoints;
+	struct mutex endpoints_lock;
+	wait_queue_head_t sendq;
+	atomic_t sleepers;
+	struct rpmsg_endpoint *ns_ept;
+};
+
+/**
+ * struct rpmsg_channel_info - internal channel info representation
+ * @name: name of service
+ * @src: local address
+ * @dst: destination address
+ */
+struct rpmsg_channel_info {
+	char name[RPMSG_NAME_SIZE];
+	u32 src;
+	u32 dst;
+};
+
+#define to_rpmsg_channel(d) container_of(d, struct rpmsg_channel, dev)
+#define to_rpmsg_driver(d) container_of(d, struct rpmsg_driver, drv)
+
+/*
+ * We're allocating 512 buffers of 512 bytes for communications, and then
+ * using the first 256 buffers for RX, and the last 256 buffers for TX.
+ *
+ * Each buffer will have 16 bytes for the msg header and 496 bytes for
+ * the payload.
+ *
+ * This will require a total space of 256KB for the buffers.
+ *
+ * We might also want to add support for user-provided buffers in time.
+ * This will allow bigger buffer size flexibility, and can also be used
+ * to achieve zero-copy messaging.
+ *
+ * Note that these numbers are purely a decision of this driver - we
+ * can change this without changing anything in the firmware of the remote
+ * processor.
+ */
+#define RPMSG_NUM_BUFS		(512)
+#define RPMSG_BUF_SIZE		(512)
+#define RPMSG_TOTAL_BUF_SPACE	(RPMSG_NUM_BUFS * RPMSG_BUF_SIZE)
+
+/*
+ * Local addresses are dynamically allocated on-demand.
+ * We do not dynamically assign addresses from the low 1024 range,
+ * in order to reserve that address range for predefined services.
+ */
+#define RPMSG_RESERVED_ADDRESSES	(1024)
+
+/* Address 53 is reserved for advertising remote services */
+#define RPMSG_NS_ADDR			(53)
+
+/* sysfs show configuration fields */
+#define rpmsg_show_attr(field, path, format_string)			\
+static ssize_t								\
+field##_show(struct device *dev,					\
+			struct device_attribute *attr, char *buf)	\
+{									\
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);		\
+									\
+	return sprintf(buf, format_string, rpdev->path);		\
+}
+
+/* for more info, see Documentation/ABI/testing/sysfs-bus-rpmsg */
+rpmsg_show_attr(name, id.name, "%s\n");
+rpmsg_show_attr(src, src, "0x%x\n");
+rpmsg_show_attr(dst, dst, "0x%x\n");
+rpmsg_show_attr(announce, announce ? "true" : "false", "%s\n");
+
+/*
+ * Unique (and free running) index for rpmsg devices.
+ *
+ * Yeah, we're not recycling those numbers (yet?). will be easy
+ * to change if/when we want to.
+ */
+static unsigned int rpmsg_dev_index;
+
+static ssize_t modalias_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+
+	return sprintf(buf, RPMSG_DEVICE_MODALIAS_FMT "\n", rpdev->id.name);
+}
+
+static struct device_attribute rpmsg_dev_attrs[] = {
+	__ATTR_RO(name),
+	__ATTR_RO(modalias),
+	__ATTR_RO(dst),
+	__ATTR_RO(src),
+	__ATTR_RO(announce),
+	__ATTR_NULL
+};
+
+/* rpmsg devices and drivers are matched using the service name */
+static inline int rpmsg_id_match(const struct rpmsg_channel *rpdev,
+				  const struct rpmsg_device_id *id)
+{
+	return strncmp(id->name, rpdev->id.name, RPMSG_NAME_SIZE) == 0;
+}
+
+/* match rpmsg channel and rpmsg driver */
+static int rpmsg_dev_match(struct device *dev, struct device_driver *drv)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+	struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
+	const struct rpmsg_device_id *ids = rpdrv->id_table;
+	unsigned int i;
+
+	for (i = 0; ids[i].name[0]; i++)
+		if (rpmsg_id_match(rpdev, &ids[i]))
+			return 1;
+
+	return 0;
+}
+
+static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+
+	return add_uevent_var(env, "MODALIAS=" RPMSG_DEVICE_MODALIAS_FMT,
+					rpdev->id.name);
+}
+
+/* for more info, see below documentation of rpmsg_create_ept() */
+static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
+		struct rpmsg_channel *rpdev, rpmsg_rx_cb_t cb,
+		void *priv, u32 addr)
+{
+	int err, tmpaddr, request;
+	struct rpmsg_endpoint *ept;
+	struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
+
+	if (!idr_pre_get(&vrp->endpoints, GFP_KERNEL))
+		return NULL;
+
+	ept = kzalloc(sizeof(*ept), GFP_KERNEL);
+	if (!ept) {
+		dev_err(dev, "failed to kzalloc a new ept\n");
+		return NULL;
+	}
+
+	ept->rpdev = rpdev;
+	ept->cb = cb;
+	ept->priv = priv;
+
+	/* do we need to allocate a local address ? */
+	request = addr == RPMSG_ADDR_ANY ? RPMSG_RESERVED_ADDRESSES : addr;
+
+	mutex_lock(&vrp->endpoints_lock);
+
+	/* bind the endpoint to an rpmsg address (and allocate one if needed) */
+	err = idr_get_new_above(&vrp->endpoints, ept, request, &tmpaddr);
+	if (err) {
+		dev_err(dev, "idr_get_new_above failed: %d\n", err);
+		goto free_ept;
+	}
+
+	/* make sure the user's address request is fulfilled, if relevant */
+	if (addr != RPMSG_ADDR_ANY && tmpaddr != addr) {
+		dev_err(dev, "address 0x%x already in use\n", addr);
+		goto rem_idr;
+	}
+
+	ept->addr = tmpaddr;
+
+	mutex_unlock(&vrp->endpoints_lock);
+
+	return ept;
+
+rem_idr:
+	idr_remove(&vrp->endpoints, request);
+free_ept:
+	mutex_unlock(&vrp->endpoints_lock);
+	kfree(ept);
+	return NULL;
+}
+
+/**
+ * rpmsg_create_ept() - create a new rpmsg_endpoint
+ * @rpdev: rpmsg channel device
+ * @cb: rx callback handler
+ * @priv: private data for the driver's use
+ * @addr: local rpmsg address to bind with @cb
+ *
+ * Every rpmsg address in the system is bound to an rx callback (so when
+ * inbound messages arrive, they are dispatched by the rpmsg bus using the
+ * appropriate callback handler) by means of an rpmsg_endpoint struct.
+ *
+ * This function allows drivers to create such an endpoint, and by that,
+ * bind a callback, and possibly some private data too, to an rpmsg address
+ * (either one that is known in advance, or one that will be dynamically
+ * assigned for them).
+ *
+ * Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
+ * is already created for them when they are probed by the rpmsg bus
+ * (using the rx callback provided when they registered to the rpmsg bus).
+ *
+ * So things should just work for simple drivers: they already have an
+ * endpoint, their rx callback is bound to their rpmsg address, and when
+ * relevant inbound messages arrive (i.e. messages which their dst address
+ * equals to the src address of their rpmsg channel), the driver's handler
+ * is invoked to process it.
+ *
+ * That said, more complicated drivers might do need to allocate
+ * additional rpmsg addresses, and bind them to different rx callbacks.
+ * To accomplish that, those drivers need to call this function.
+ *
+ * Drivers should provide their @rpdev channel (so the new endpoint would belong
+ * to the same remote processor their channel belongs to), an rx callback
+ * function, an optional private data (which is provided back when the
+ * rx callback is invoked), and an address they want to bind with the
+ * callback. If @addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
+ * dynamically assign them an available rpmsg address (drivers should have
+ * a very good reason why not to always use RPMSG_ADDR_ANY here).
+ *
+ * Returns a pointer to the endpoint on success, or NULL on error.
+ */
+struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
+				rpmsg_rx_cb_t cb, void *priv, u32 addr)
+{
+	return __rpmsg_create_ept(rpdev->vrp, rpdev, cb, priv, addr);
+}
+EXPORT_SYMBOL(rpmsg_create_ept);
+
+/**
+ * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
+ * @vrp: virtproc which owns this ept
+ * @ept: endpoing to destroy
+ *
+ * An internal function which destroy an ept without assuming it is
+ * bound to an rpmsg channel. This is needed for handling the internal
+ * name service endpoint, which isn't bound to an rpmsg channel.
+ * See also __rpmsg_create_ept().
+ */
+static void
+__rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
+{
+	mutex_lock(&vrp->endpoints_lock);
+	idr_remove(&vrp->endpoints, ept->addr);
+	mutex_unlock(&vrp->endpoints_lock);
+
+	kfree(ept);
+}
+
+/**
+ * rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
+ * @ept: endpoing to destroy
+ *
+ * Should be used by drivers to destroy an rpmsg endpoint previously
+ * created with rpmsg_create_ept().
+ */
+void rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
+{
+	__rpmsg_destroy_ept(ept->rpdev->vrp, ept);
+}
+EXPORT_SYMBOL(rpmsg_destroy_ept);
+
+/*
+ * when an rpmsg driver is probed with a channel, we seamlessly create
+ * it an endpoint, binding its rx callback to a unique local rpmsg
+ * address.
+ *
+ * if we need to, we also announce about this channel to the remote
+ * processor (needed in case the driver is exposing an rpmsg service).
+ */
+static int rpmsg_dev_probe(struct device *dev)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
+	struct virtproc_info *vrp = rpdev->vrp;
+	struct rpmsg_endpoint *ept;
+	int err;
+
+	ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, rpdev->src);
+	if (!ept) {
+		dev_err(dev, "failed to create endpoint\n");
+		err = -ENOMEM;
+		goto out;
+	}
+
+	rpdev->ept = ept;
+	rpdev->src = ept->addr;
+
+	err = rpdrv->probe(rpdev);
+	if (err) {
+		dev_err(dev, "%s: failed: %d\n", __func__, err);
+		rpmsg_destroy_ept(ept);
+		goto out;
+	}
+
+	/* need to tell remote processor's name service about this channel ? */
+	if (rpdev->announce &&
+			virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
+		struct rpmsg_ns_msg nsm;
+
+		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
+		nsm.addr = rpdev->src;
+		nsm.flags = RPMSG_NS_CREATE;
+
+		err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
+		if (err)
+			dev_err(dev, "failed to announce service %d\n", err);
+	}
+
+out:
+	return err;
+}
+
+static int rpmsg_dev_remove(struct device *dev)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
+	struct virtproc_info *vrp = rpdev->vrp;
+	int err = 0;
+
+	/* tell remote processor's name service we're removing this channel */
+	if (rpdev->announce &&
+			virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
+		struct rpmsg_ns_msg nsm;
+
+		strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
+		nsm.addr = rpdev->src;
+		nsm.flags = RPMSG_NS_DESTROY;
+
+		err = rpmsg_sendto(rpdev, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
+		if (err)
+			dev_err(dev, "failed to announce service %d\n", err);
+	}
+
+	rpdrv->remove(rpdev);
+
+	rpmsg_destroy_ept(rpdev->ept);
+
+	return err;
+}
+
+static struct bus_type rpmsg_bus = {
+	.name		= "rpmsg",
+	.match		= rpmsg_dev_match,
+	.dev_attrs	= rpmsg_dev_attrs,
+	.uevent		= rpmsg_uevent,
+	.probe		= rpmsg_dev_probe,
+	.remove		= rpmsg_dev_remove,
+};
+
+/**
+ * register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
+ * @rpdrv: pointer to a struct rpmsg_driver
+ *
+ * Returns 0 on success, and an appropriate error value on failure.
+ */
+int register_rpmsg_driver(struct rpmsg_driver *rpdrv)
+{
+	rpdrv->drv.bus = &rpmsg_bus;
+	return driver_register(&rpdrv->drv);
+}
+EXPORT_SYMBOL(register_rpmsg_driver);
+
+/**
+ * unregister_rpmsg_driver() - unregister an rpmsg driver from the rpmsg bus
+ * @rpdrv: pointer to a struct rpmsg_driver
+ *
+ * Returns 0 on success, and an appropriate error value on failure.
+ */
+void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv)
+{
+	driver_unregister(&rpdrv->drv);
+}
+EXPORT_SYMBOL(unregister_rpmsg_driver);
+
+static void rpmsg_release_device(struct device *dev)
+{
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+
+	kfree(rpdev);
+}
+
+/*
+ * match an rpmsg channel with a channel info struct.
+ * this is used to make sure we're not creating rpmsg devices for channels
+ * that already exist.
+ */
+static int rpmsg_channel_match(struct device *dev, void *data)
+{
+	struct rpmsg_channel_info *chinfo = data;
+	struct rpmsg_channel *rpdev = to_rpmsg_channel(dev);
+
+	if (chinfo->src != RPMSG_ADDR_ANY && chinfo->src != rpdev->src)
+		return 0;
+
+	if (chinfo->dst != RPMSG_ADDR_ANY && chinfo->dst != rpdev->dst)
+		return 0;
+
+	if (strncmp(chinfo->name, rpdev->id.name, RPMSG_NAME_SIZE))
+		return 0;
+
+	/* found a match ! */
+	return 1;
+}
+
+/*
+ * create an rpmsg channel using its name and address info.
+ * this function will be used to create both static and dynamic
+ * channels.
+ */
+static struct rpmsg_channel *rpmsg_create_channel(struct virtproc_info *vrp,
+				struct rpmsg_channel_info *chinfo)
+{
+	struct rpmsg_channel *rpdev;
+	struct device *tmp, *dev = &vrp->vdev->dev;
+	int ret;
+
+	/* make sure a similar channel doesn't already exist */
+	tmp = device_find_child(dev, chinfo, rpmsg_channel_match);
+	if (tmp) {
+		/* decrement the matched device's refcount back */
+		put_device(tmp);
+		dev_err(dev, "channel %s:%x:%x already exist\n",
+				chinfo->name, chinfo->src, chinfo->dst);
+		return NULL;
+	}
+
+	rpdev = kzalloc(sizeof(struct rpmsg_channel), GFP_KERNEL);
+	if (!rpdev) {
+		pr_err("kzalloc failed\n");
+		return NULL;
+	}
+
+	rpdev->vrp = vrp;
+	rpdev->src = chinfo->src;
+	rpdev->dst = chinfo->dst;
+
+	/*
+	 * rpmsg server channels has predefined local address (for now),
+	 * and their existence needs to be announced remotely
+	 */
+	rpdev->announce = rpdev->src != RPMSG_ADDR_ANY ? true : false;
+
+	strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
+
+	/* very simple device indexing plumbing which is enough for now */
+	dev_set_name(&rpdev->dev, "rpmsg%d", rpmsg_dev_index++);
+
+	rpdev->dev.parent = &vrp->vdev->dev;
+	rpdev->dev.bus = &rpmsg_bus;
+	rpdev->dev.release = rpmsg_release_device;
+
+	ret = device_register(&rpdev->dev);
+	if (ret) {
+		dev_err(dev, "device_register failed: %d\n", ret);
+		put_device(&rpdev->dev);
+		return NULL;
+	}
+
+	return rpdev;
+}
+
+/*
+ * find an existing channel using its name + address properties,
+ * and destroy it
+ */
+static int rpmsg_destroy_channel(struct virtproc_info *vrp,
+					struct rpmsg_channel_info *chinfo)
+{
+	struct virtio_device *vdev = vrp->vdev;
+	struct device *dev;
+
+	dev = device_find_child(&vdev->dev, chinfo, rpmsg_channel_match);
+	if (!dev)
+		return -EINVAL;
+
+	device_unregister(dev);
+
+	put_device(dev);
+
+	return 0;
+}
+
+/* super simple buffer "allocator" that is just enough for now */
+static void *get_a_tx_buf(struct virtproc_info *vrp)
+{
+	unsigned int len;
+	void *ret;
+
+	/* support multiple concurrent senders */
+	mutex_lock(&vrp->tx_lock);
+
+	/*
+	 * either pick the next unused tx buffer
+	 * (half of our buffers are used for sending messages)
+	 */
+	if (vrp->last_sbuf < RPMSG_NUM_BUFS / 2)
+		ret = vrp->sbufs + RPMSG_BUF_SIZE * vrp->last_sbuf++;
+	/* or recycle a used one */
+	else
+		ret = virtqueue_get_buf(vrp->svq, &len);
+
+	mutex_unlock(&vrp->tx_lock);
+
+	return ret;
+}
+
+/**
+ * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
+ * @vrp: virtual remote processor state
+ *
+ * This function is called before a sender is blocked, waiting for
+ * a tx buffer to become available.
+ *
+ * If we already have blocking senders, this function merely increases
+ * the "sleepers" reference count, and exits.
+ *
+ * Otherwise, if this is the first sender to block, we also enable
+ * virtio's tx callbacks, so we'd be immediately notified when a tx
+ * buffer is consumed (we rely on virtio's tx callback in order
+ * to wake up sleeping senders as soon as a tx buffer is used by the
+ * remote processor).
+ */
+static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
+{
+	/* support multiple concurrent senders */
+	mutex_lock(&vrp->tx_lock);
+
+	/* are we the first sleeping context waiting for tx buffers ? */
+	if (atomic_inc_return(&vrp->sleepers) == 1)
+		/* enable "tx-complete" interrupts before dozing off */
+		virtqueue_enable_cb(vrp->svq);
+
+	mutex_unlock(&vrp->tx_lock);
+}
+
+/**
+ * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
+ * @vrp: virtual remote processor state
+ *
+ * This function is called after a sender, that waited for a tx buffer
+ * to become available, is unblocked.
+ *
+ * If we still have blocking senders, this function merely decreases
+ * the "sleepers" reference count, and exits.
+ *
+ * Otherwise, if there are no more blocking senders, we also disable
+ * virtio's tx callbacks, to avoid the overhead incurred with handling
+ * those (now redundant) interrupts.
+ */
+static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
+{
+	/* support multiple concurrent senders */
+	mutex_lock(&vrp->tx_lock);
+
+	/* are we the last sleeping context waiting for tx buffers ? */
+	if (atomic_dec_and_test(&vrp->sleepers))
+		/* disable "tx-complete" interrupts */
+		virtqueue_disable_cb(vrp->svq);
+
+	mutex_unlock(&vrp->tx_lock);
+}
+
+/**
+ * rpmsg_send_offchannel_raw() - send a message across to the remote processor
+ * @rpdev: the rpmsg channel
+ * @src: source address
+ * @dst: destination address
+ * @data: payload of message
+ * @len: length of payload
+ * @wait: indicates whether caller should block in case no TX buffers available
+ *
+ * This function is the base implementation for all of the rpmsg sending API.
+ *
+ * It will send @data of length @len to @dst, and say it's from @src. The
+ * message will be sent to the remote processor which the @rpdev channel
+ * belongs to.
+ *
+ * The message is sent using one of the TX buffers that are available for
+ * communication with this remote processor.
+ *
+ * If @wait is true, the caller will be blocked until either a TX buffer is
+ * available, or 15 seconds elapses (we don't want callers to
+ * sleep indefinitely due to misbehaving remote processors), and in that
+ * case -ERESTARTSYS is returned. The number '15' itself was picked
+ * arbitrarily; there's little point in asking drivers to provide a timeout
+ * value themselves.
+ *
+ * Otherwise, if @wait is false, and there are no TX buffers available,
+ * the function will immediately fail, and -ENOMEM will be returned.
+ *
+ * Normally drivers shouldn't use this function directly; instead, drivers
+ * should use the appropriate rpmsg_{try}send{to, _offchannel} API
+ * (see include/linux/rpmsg.h).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+int rpmsg_send_offchannel_raw(struct rpmsg_channel *rpdev, u32 src, u32 dst,
+					void *data, int len, bool wait)
+{
+	struct virtproc_info *vrp = rpdev->vrp;
+	struct device *dev = &rpdev->dev;
+	struct scatterlist sg;
+	struct rpmsg_hdr *msg;
+	int err;
+
+	/* bcasting isn't allowed */
+	if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
+		dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
+		return -EINVAL;
+	}
+
+	/*
+	 * We currently use fixed-sized buffers, and therefore the payload
+	 * length is limited.
+	 *
+	 * One of the possible improvements here is either to support
+	 * user-provided buffers (and then we can also support zero-copy
+	 * messaging), or to improve the buffer allocator, to support
+	 * variable-length buffer sizes.
+	 */
+	if (len > RPMSG_BUF_SIZE - sizeof(struct rpmsg_hdr)) {
+		dev_err(dev, "message is too big (%d)\n", len);
+		return -EMSGSIZE;
+	}
+
+	/* grab a buffer */
+	msg = get_a_tx_buf(vrp);
+	if (!msg && !wait)
+		return -ENOMEM;
+
+	/* no free buffer ? wait for one (but bail after 15 seconds) */
+	while (!msg) {
+		/* enable "tx-complete" interrupts, if not already enabled */
+		rpmsg_upref_sleepers(vrp);
+
+		/*
+		 * sleep until a free buffer is available or 15 secs elapse.
+		 * the timeout period is not configurable because there's
+		 * little point in asking drivers to specify that.
+		 * if later this happens to be required, it'd be easy to add.
+		 */
+		err = wait_event_interruptible_timeout(vrp->sendq,
+					(msg = get_a_tx_buf(vrp)),
+					msecs_to_jiffies(15000));
+
+		/* disable "tx-complete" interrupts if we're the last sleeper */
+		rpmsg_downref_sleepers(vrp);
+
+		/* timeout ? */
+		if (!err) {
+			dev_err(dev, "timeout waiting for a tx buffer\n");
+			return -ERESTARTSYS;
+		}
+	}
+
+	msg->len = len;
+	msg->flags = 0;
+	msg->src = src;
+	msg->dst = dst;
+	msg->reserved = 0;
+	memcpy(msg->data, data, len);
+
+	dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
+					msg->src, msg->dst, msg->len,
+					msg->flags, msg->reserved);
+	print_hex_dump(KERN_DEBUG, "rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
+					msg, sizeof(*msg) + msg->len, true);
+
+	sg_init_one(&sg, msg, sizeof(*msg) + len);
+
+	mutex_lock(&vrp->tx_lock);
+
+	/* add message to the remote processor's virtqueue */
+	err = virtqueue_add_buf(vrp->svq, &sg, 1, 0, msg, GFP_KERNEL);
+	if (err < 0) {
+		/*
+		 * need to reclaim the buffer here, otherwise it's lost
+		 * (memory won't leak, but rpmsg won't use it again for TX).
+		 * this will wait for a buffer management overhaul.
+		 */
+		dev_err(dev, "virtqueue_add_buf failed: %d\n", err);
+		goto out;
+	}
+
+	/* tell the remote processor it has a pending message to read */
+	virtqueue_kick(vrp->svq);
+
+	err = 0;
+out:
+	mutex_unlock(&vrp->tx_lock);
+	return err;
+}
+EXPORT_SYMBOL(rpmsg_send_offchannel_raw);
+
+/* called when an rx buffer is used, and it's time to digest a message */
+static void rpmsg_recv_done(struct virtqueue *rvq)
+{
+	struct rpmsg_hdr *msg;
+	unsigned int len;
+	struct rpmsg_endpoint *ept;
+	struct scatterlist sg;
+	struct virtproc_info *vrp = rvq->vdev->priv;
+	struct device *dev = &rvq->vdev->dev;
+	int err;
+
+	msg = virtqueue_get_buf(rvq, &len);
+	if (!msg) {
+		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
+		return;
+	}
+
+	dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
+					msg->src, msg->dst, msg->len,
+					msg->flags, msg->reserved);
+	print_hex_dump(KERN_DEBUG, "rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
+					msg, sizeof(*msg) + msg->len, true);
+
+	/*
+	 * We currently use fixed-sized buffers, so trivially sanitize
+	 * the reported payload length.
+	 */
+	if (len > RPMSG_BUF_SIZE ||
+		msg->len > (len - sizeof(struct rpmsg_hdr))) {
+		dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
+		return;
+	}
+
+	/* use the dst addr to fetch the callback of the appropriate user */
+	mutex_lock(&vrp->endpoints_lock);
+	ept = idr_find(&vrp->endpoints, msg->dst);
+	mutex_unlock(&vrp->endpoints_lock);
+
+	if (ept && ept->cb)
+		ept->cb(ept->rpdev, msg->data, msg->len, ept->priv, msg->src);
+	else
+		dev_warn(dev, "msg received with no recepient\n");
+
+	/* publish the real size of the buffer */
+	sg_init_one(&sg, msg, RPMSG_BUF_SIZE);
+
+	/* add the buffer back to the remote processor's virtqueue */
+	err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, msg, GFP_KERNEL);
+	if (err < 0) {
+		dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
+		return;
+	}
+
+	/* tell the remote processor we added another available rx buffer */
+	virtqueue_kick(vrp->rvq);
+}
+
+/*
+ * This is invoked whenever the remote processor completed processing
+ * a TX msg we just sent it, and the buffer is put back to the used ring.
+ *
+ * Normally, though, we suppress this "tx complete" interrupt in order to
+ * avoid the incurred overhead.
+ */
+static void rpmsg_xmit_done(struct virtqueue *svq)
+{
+	struct virtproc_info *vrp = svq->vdev->priv;
+
+	dev_dbg(&svq->vdev->dev, "%s\n", __func__);
+
+	/* wake up potential senders that are waiting for a tx buffer */
+	wake_up_interruptible(&vrp->sendq);
+}
+
+/* invoked when a name service announcement arrives */
+static void rpmsg_ns_cb(struct rpmsg_channel *rpdev, void *data, int len,
+							void *priv, u32 src)
+{
+	struct rpmsg_ns_msg *msg = data;
+	struct rpmsg_channel *newch;
+	struct rpmsg_channel_info chinfo;
+	struct virtproc_info *vrp = priv;
+	struct device *dev = &vrp->vdev->dev;
+	int ret;
+
+	print_hex_dump(KERN_DEBUG, "NS announcement: ",
+			DUMP_PREFIX_NONE, 16, 1,
+			data, len, true);
+
+	if (len != sizeof(*msg)) {
+		dev_err(dev, "malformed ns msg (%d)\n", len);
+		return;
+	}
+
+	/*
+	 * the name service ept does _not_ belong to a real rpmsg channel,
+	 * and is handled by the rpmsg bus itself.
+	 * for sanity reasons, make sure a valid rpdev has _not_ sneaked
+	 * in somehow.
+	 */
+	if (rpdev) {
+		dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
+		return;
+	}
+
+	/* don't trust the remote processor for null terminating the name */
+	msg->name[RPMSG_NAME_SIZE - 1] = '\0';
+
+	dev_info(dev, "%sing channel %s addr 0x%x\n",
+			msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
+			msg->name, msg->addr);
+
+	strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
+	chinfo.src = RPMSG_ADDR_ANY;
+	chinfo.dst = msg->addr;
+
+	if (msg->flags & RPMSG_NS_DESTROY) {
+		ret = rpmsg_destroy_channel(vrp, &chinfo);
+		if (ret)
+			dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
+	} else {
+		newch = rpmsg_create_channel(vrp, &chinfo);
+		if (!newch)
+			dev_err(dev, "rpmsg_create_channel failed\n");
+	}
+}
+
+static int rpmsg_probe(struct virtio_device *vdev)
+{
+	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
+	const char *names[] = { "input", "output" };
+	struct virtqueue *vqs[2];
+	struct virtproc_info *vrp;
+	void *bufs_va;
+	int err = 0, i;
+
+	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
+	if (!vrp)
+		return -ENOMEM;
+
+	vrp->vdev = vdev;
+
+	idr_init(&vrp->endpoints);
+	mutex_init(&vrp->endpoints_lock);
+	mutex_init(&vrp->tx_lock);
+	init_waitqueue_head(&vrp->sendq);
+
+	/* We expect two virtqueues, rx and tx (and in this order) */
+	err = vdev->config->find_vqs(vdev, 2, vqs, vq_cbs, names);
+	if (err)
+		goto free_vrp;
+
+	vrp->rvq = vqs[0];
+	vrp->svq = vqs[1];
+
+	/* allocate coherent memory for the buffers */
+	bufs_va = dma_alloc_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE,
+				&vrp->bufs_dma, GFP_KERNEL);
+	if (!bufs_va)
+		goto vqs_del;
+
+	dev_dbg(&vdev->dev, "buffers: va %p, dma 0x%llx\n", bufs_va,
+					(unsigned long long)vrp->bufs_dma);
+
+	/* half of the buffers is dedicated for RX */
+	vrp->rbufs = bufs_va;
+
+	/* and half is dedicated for TX */
+	vrp->sbufs = bufs_va + RPMSG_TOTAL_BUF_SPACE / 2;
+
+	/* set up the receive buffers */
+	for (i = 0; i < RPMSG_NUM_BUFS / 2; i++) {
+		struct scatterlist sg;
+		void *cpu_addr = vrp->rbufs + i * RPMSG_BUF_SIZE;
+
+		sg_init_one(&sg, cpu_addr, RPMSG_BUF_SIZE);
+
+		err = virtqueue_add_buf(vrp->rvq, &sg, 0, 1, cpu_addr,
+								GFP_KERNEL);
+		WARN_ON(err < 0); /* sanity check; this can't really happen */
+	}
+
+	/* suppress "tx-complete" interrupts */
+	virtqueue_disable_cb(vrp->svq);
+
+	vdev->priv = vrp;
+
+	/* if supported by the remote processor, enable the name service */
+	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
+		/* a dedicated endpoint handles the name service msgs */
+		vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
+						vrp, RPMSG_NS_ADDR);
+		if (!vrp->ns_ept) {
+			dev_err(&vdev->dev, "failed to create the ns ept\n");
+			err = -ENOMEM;
+			goto free_coherent;
+		}
+	}
+
+	/* tell the remote processor it can start sending messages */
+	virtqueue_kick(vrp->rvq);
+
+	dev_info(&vdev->dev, "rpmsg host is online\n");
+
+	return 0;
+
+free_coherent:
+	dma_free_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE, bufs_va,
+					vrp->bufs_dma);
+vqs_del:
+	vdev->config->del_vqs(vrp->vdev);
+free_vrp:
+	kfree(vrp);
+	return err;
+}
+
+static int rpmsg_remove_device(struct device *dev, void *data)
+{
+	device_unregister(dev);
+
+	return 0;
+}
+
+static void __devexit rpmsg_remove(struct virtio_device *vdev)
+{
+	struct virtproc_info *vrp = vdev->priv;
+	int ret;
+
+	vdev->config->reset(vdev);
+
+	ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
+	if (ret)
+		dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
+
+	if (vrp->ns_ept)
+		__rpmsg_destroy_ept(vrp, vrp->ns_ept);
+
+	idr_remove_all(&vrp->endpoints);
+	idr_destroy(&vrp->endpoints);
+
+	vdev->config->del_vqs(vrp->vdev);
+
+	dma_free_coherent(vdev->dev.parent, RPMSG_TOTAL_BUF_SPACE,
+					vrp->rbufs, vrp->bufs_dma);
+
+	kfree(vrp);
+}
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static unsigned int features[] = {
+	VIRTIO_RPMSG_F_NS,
+};
+
+static struct virtio_driver virtio_ipc_driver = {
+	.feature_table	= features,
+	.feature_table_size = ARRAY_SIZE(features),
+	.driver.name	= KBUILD_MODNAME,
+	.driver.owner	= THIS_MODULE,
+	.id_table	= id_table,
+	.probe		= rpmsg_probe,
+	.remove		= __devexit_p(rpmsg_remove),
+};
+
+static int __init rpmsg_init(void)
+{
+	int ret;
+
+	ret = bus_register(&rpmsg_bus);
+	if (ret) {
+		pr_err("failed to register rpmsg bus: %d\n", ret);
+		return ret;
+	}
+
+	ret = register_virtio_driver(&virtio_ipc_driver);
+	if (ret) {
+		pr_err("failed to register virtio driver: %d\n", ret);
+		bus_unregister(&rpmsg_bus);
+	}
+
+	return ret;
+}
+module_init(rpmsg_init);
+
+static void __exit rpmsg_fini(void)
+{
+	unregister_virtio_driver(&virtio_ipc_driver);
+	bus_unregister(&rpmsg_bus);
+}
+module_exit(rpmsg_fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
+MODULE_LICENSE("GPL v2");

include/linux/mod_devicetable.h

···
 			__attribute__((aligned(sizeof(kernel_ulong_t))));
 };
 
+/* rpmsg */
+
+#define RPMSG_NAME_SIZE			32
+#define RPMSG_DEVICE_MODALIAS_FMT	"rpmsg:%s"
+
+struct rpmsg_device_id {
+	char name[RPMSG_NAME_SIZE];
+};
+
 /* i2c */
 
 #define I2C_NAME_SIZE	20

include/linux/remoteproc.h

···
+/*
+ * Remote Processor Framework
+ *
+ * Copyright(c) 2011 Texas Instruments, Inc.
+ * Copyright(c) 2011 Google, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ * * Neither the name Texas Instruments nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef REMOTEPROC_H
+#define REMOTEPROC_H
+
+#include <linux/types.h>
+#include <linux/kref.h>
+#include <linux/klist.h>
+#include <linux/mutex.h>
+#include <linux/virtio.h>
+#include <linux/completion.h>
+#include <linux/idr.h>
+
+/**
+ * struct resource_table - firmware resource table header
+ * @ver: version number
+ * @num: number of resource entries
+ * @reserved: reserved (must be zero)
+ * @offset: array of offsets pointing at the various resource entries
+ *
+ * A resource table is essentially a list of system resources required
+ * by the remote processor. It may also include configuration entries.
+ * If needed, the remote processor firmware should contain this table
+ * as a dedicated ".resource_table" ELF section.
+ *
+ * Some resources entries are mere announcements, where the host is informed
+ * of specific remoteproc configuration. Other entries require the host to
+ * do something (e.g. allocate a system resource). Sometimes a negotiation
+ * is expected, where the firmware requests a resource, and once allocated,
+ * the host should provide back its details (e.g. address of an allocated
+ * memory region).
+ *
+ * The header of the resource table, as expressed by this structure,
+ * contains a version number (should we need to change this format in the
+ * future), the number of available resource entries, and their offsets
+ * in the table.
+ *
+ * Immediately following this header are the resource entries themselves,
+ * each of which begins with a resource entry header (as described below).
+ */
+struct resource_table {
+	u32 ver;
+	u32 num;
+	u32 reserved[2];
+	u32 offset[0];
+} __packed;
+
+/**
+ * struct fw_rsc_hdr - firmware resource entry header
+ * @type: resource type
+ * @data: resource data
+ *
+ * Every resource entry begins with a 'struct fw_rsc_hdr' header providing
+ * its @type. The content of the entry itself will immediately follow
+ * this header, and it should be parsed according to the resource type.
+ */
+struct fw_rsc_hdr {
+	u32 type;
+	u8 data[0];
+} __packed;
+
+/**
+ * enum fw_resource_type - types of resource entries
+ *
+ * @RSC_CARVEOUT:   request for allocation of a physically contiguous
+ *		    memory region.
+ * @RSC_DEVMEM:     request to iommu_map a memory-based peripheral.
+ * @RSC_TRACE:	    announces the availability of a trace buffer into which
+ *		    the remote processor will be writing logs.
+ * @RSC_VDEV:       declare support for a virtio device, and serve as its
+ *		    virtio header.
+ * @RSC_LAST:       just keep this one at the end
+ *
+ * For more details regarding a specific resource type, please see its
+ * dedicated structure below.
+ *
+ * Please note that these values are used as indices to the rproc_handle_rsc
+ * lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
+ * check the validity of an index before the lookup table is accessed, so
+ * please update it as needed.
+ */
+enum fw_resource_type {
+	RSC_CARVEOUT	= 0,
+	RSC_DEVMEM	= 1,
+	RSC_TRACE	= 2,
+	RSC_VDEV	= 3,
+	RSC_LAST	= 4,
+};
+
+#define FW_RSC_ADDR_ANY (0xFFFFFFFFFFFFFFFF)
+
+/**
+ * struct fw_rsc_carveout - physically contiguous memory request
+ * @da: device address
+ * @pa: physical address
+ * @len: length (in bytes)
+ * @flags: iommu protection flags
+ * @reserved: reserved (must be zero)
+ * @name: human-readable name of the requested memory region
+ *
+ * This resource entry requests the host to allocate a physically contiguous
+ * memory region.
+ *
+ * These request entries should precede other firmware resource entries,
+ * as other entries might request placing other data objects inside
+ * these memory regions (e.g. data/code segments, trace resource entries, ...).
+ *
+ * Allocating memory this way helps utilizing the reserved physical memory
+ * (e.g. CMA) more efficiently, and also minimizes the number of TLB entries
+ * needed to map it (in case @rproc is using an IOMMU). Reducing the TLB
+ * pressure is important; it may have a substantial impact on performance.
+ *
+ * If the firmware is compiled with static addresses, then @da should specify
+ * the expected device address of this memory region. If @da is set to
+ * FW_RSC_ADDR_ANY, then the host will dynamically allocate it, and then
+ * overwrite @da with the dynamically allocated address.
+ *
+ * We will always use @da to negotiate the device addresses, even if it
+ * isn't using an iommu. In that case, though, it will obviously contain
+ * physical addresses.
+ *
+ * Some remote processors needs to know the allocated physical address
+ * even if they do use an iommu. This is needed, e.g., if they control
+ * hardware accelerators which access the physical memory directly (this
+ * is the case with OMAP4 for instance). In that case, the host will
+ * overwrite @pa with the dynamically allocated physical address.
+ * Generally we don't want to expose physical addresses if we don't have to
+ * (remote processors are generally _not_ trusted), so we might want to
+ * change this to happen _only_ when explicitly required by the hardware.
+ *
+ * @flags is used to provide IOMMU protection flags, and @name should
+ * (optionally) contain a human readable name of this carveout region
+ * (mainly for debugging purposes).
+ */
+struct fw_rsc_carveout {
+	u32 da;
+	u32 pa;
+	u32 len;
+	u32 flags;
+	u32 reserved;
+	u8 name[32];
+} __packed;
+
+/**
+ * struct fw_rsc_devmem - iommu mapping request
+ * @da: device address
+ * @pa: physical address
+ * @len: length (in bytes)
+ * @flags: iommu protection flags
+ * @reserved: reserved (must be zero)
+ * @name: human-readable name of the requested region to be mapped
+ *
+ * This resource entry requests the host to iommu map a physically contiguous
+ * memory region. This is needed in case the remote processor requires
+ * access to certain memory-based peripherals; _never_ use it to access
+ * regular memory.
+ *
+ * This is obviously only needed if the remote processor is accessing memory
+ * via an iommu.
+ *
+ * @da should specify the required device address, @pa should specify
+ * the physical address we want to map, @len should specify the size of
+ * the mapping and @flags is the IOMMU protection flags. As always, @name may
+ * (optionally) contain a human readable name of this mapping (mainly for
+ * debugging purposes).
+ *
+ * Note: at this point we just "trust" those devmem entries to contain valid
+ * physical addresses, but this isn't safe and will be changed: eventually we
+ * want remoteproc implementations to provide us ranges of physical addresses
+ * the firmware is allowed to request, and not allow firmwares to request
+ * access to physical addresses that are outside those ranges.
+ */
+struct fw_rsc_devmem {
+	u32 da;
+	u32 pa;
+	u32 len;
+	u32 flags;
+	u32 reserved;
+	u8 name[32];
+} __packed;
+
+/**
+ * struct fw_rsc_trace - trace buffer declaration
+ * @da: device address
+ * @len: length (in bytes)
+ * @reserved: reserved (must be zero)
+ * @name: human-readable name of the trace buffer
+ *
+ * This resource entry provides the host information about a trace buffer
+ * into which the remote processor will write log messages.
+ *
+ * @da specifies the device address of the buffer, @len specifies
+ * its size, and @name may contain a human readable name of the trace buffer.
+ *
+ * After booting the remote processor, the trace buffers are exposed to the
+ * user via debugfs entries (called trace0, trace1, etc..).
+ */
+struct fw_rsc_trace {
+	u32 da;
+	u32 len;
+	u32 reserved;
+	u8 name[32];
+} __packed;
+
+/**
+ * struct fw_rsc_vdev_vring - vring descriptor entry
+ * @da: device address
+ * @align: the alignment between the consumer and producer parts of the vring
+ * @num: num of buffers supported by this vring (must be power of two)
+ * @notifyid is a unique rproc-wide notify index for this vring. This notify
+ * index is used when kicking a remote processor, to let it know that this
+ * vring is triggered.
+ * @reserved: reserved (must be zero)
+ *
+ * This descriptor is not a resource entry by itself; it is part of the
+ * vdev resource type (see below).
+ *
+ * Note that @da should either contain the device address where
+ * the remote processor is expecting the vring, or indicate that
+ * dynamically allocation of the vring's device address is supported.
+ */
+struct fw_rsc_vdev_vring {
+	u32 da;
+	u32 align;
+	u32 num;
+	u32 notifyid;
+	u32 reserved;
+} __packed;
+
+/**
+ * struct fw_rsc_vdev - virtio device header
+ * @id: virtio device id (as in virtio_ids.h)
+ * @notifyid is a unique rproc-wide notify index for this vdev. This notify
+ * index is used when kicking a remote processor, to let it know that the
+ * status/features of this vdev have changes.
+ * @dfeatures specifies the virtio device features supported by the firmware
+ * @gfeatures is a place holder used by the host to write back the
+ * negotiated features that are supported by both sides.
+ * @config_len is the size of the virtio config space of this vdev. The config
+ * space lies in the resource table immediate after this vdev header.
+ * @status is a place holder where the host will indicate its virtio progress.
+ * @num_of_vrings indicates how many vrings are described in this vdev header
+ * @reserved: reserved (must be zero)
+ * @vring is an array of @num_of_vrings entries of 'struct fw_rsc_vdev_vring'.
+ *
+ * This resource is a virtio device header: it provides information about
+ * the vdev, and is then used by the host and its peer remote processors
+ * to negotiate and share certain virtio properties.
+ *
+ * By providing this resource entry, the firmware essentially asks remoteproc
+ * to statically allocate a vdev upon registration of the rproc (dynamic vdev
+ * allocation is not yet supported).
+ *
+ * Note: unlike virtualization systems, the term 'host' here means
+ * the Linux side which is running remoteproc to control the remote
+ * processors. We use the name 'gfeatures' to comply with virtio's terms,
+ * though there isn't really any virtualized guest OS here: it's the host
+ * which is responsible for negotiating the final features.
+ * Yeah, it's a bit confusing.
+ *
+ * Note: immediately following this structure is the virtio config space for
+ * this vdev (which is specific to the vdev; for more info, read the virtio
+ * spec). the size of the config space is specified by @config_len.
+ */
+struct fw_rsc_vdev {
+	u32 id;
+	u32 notifyid;
+	u32 dfeatures;
+	u32 gfeatures;
+	u32 config_len;
+	u8 status;
+	u8 num_of_vrings;
+	u8 reserved[2];
+	struct fw_rsc_vdev_vring vring[0];
+} __packed;
+
+/**
+ * struct rproc_mem_entry - memory entry descriptor
+ * @va:	virtual address
+ * @dma: dma address
+ * @len: length, in bytes
+ * @da: device address
+ * @priv: associated data
+ * @node: list node
+ */
+struct rproc_mem_entry {
+	void *va;
+	dma_addr_t dma;
+	int len;
+	u32 da;
+	void *priv;
+	struct list_head node;
+};
+
+struct rproc;
+
+/**
+ * struct rproc_ops - platform-specific device handlers
+ * @start:	power on the device and boot it
+ * @stop:	power off the device
+ * @kick:	kick a virtqueue (virtqueue id given as a parameter)
+ */
+struct rproc_ops {
+	int (*start)(struct rproc *rproc);
+	int (*stop)(struct rproc *rproc);
+	void (*kick)(struct rproc *rproc, int vqid);
+};
+
+/**
+ * enum rproc_state - remote processor states
+ * @RPROC_OFFLINE:	device is powered off
+ * @RPROC_SUSPENDED:	device is suspended; needs to be woken up to receive
+ *			a message.
+ * @RPROC_RUNNING:	device is up and running
+ * @RPROC_CRASHED:	device has crashed; need to start recovery
+ * @RPROC_LAST:		just keep this one at the end
+ *
+ * Please note that the values of these states are used as indices
+ * to rproc_state_string, a state-to-name lookup table,
+ * so please keep the two synchronized. @RPROC_LAST is used to check
+ * the validity of an index before the lookup table is accessed, so
+ * please update it as needed too.
+ */
+enum rproc_state {
+	RPROC_OFFLINE	= 0,
+	RPROC_SUSPENDED	= 1,
+	RPROC_RUNNING	= 2,
+	RPROC_CRASHED	= 3,
+	RPROC_LAST	= 4,
+};
+
+/**
+ * struct rproc - represents a physical remote processor device
+ * @node: klist node of this rproc object
+ * @domain: iommu domain
+ * @name: human readable name of the rproc
+ * @firmware: name of firmware file to be loaded
+ * @priv: private data which belongs to the platform-specific rproc module
+ * @ops: platform-specific start/stop rproc handlers
+ * @dev: underlying device
+ * @refcount: refcount of users that have a valid pointer to this rproc
+ * @power: refcount of users who need this rproc powered up
+ * @state: state of the device
+ * @lock: lock which protects concurrent manipulations of the rproc
+ * @dbg_dir: debugfs directory of this rproc device
+ * @traces: list of trace buffers
+ * @num_traces: number of trace buffers
+ * @carveouts: list of physically contiguous memory allocations
+ * @mappings: list of iommu mappings we initiated, needed on shutdown
+ * @firmware_loading_complete: marks e/o asynchronous firmware loading
+ * @bootaddr: address of first instruction to boot rproc with (optional)
+ * @rvdevs: list of remote virtio devices
+ * @notifyids: idr for dynamically assigning rproc-wide unique notify ids
+ */
+struct rproc {
+	struct klist_node node;
+	struct iommu_domain *domain;
+	const char *name;
+	const char *firmware;
+	void *priv;
+	const struct rproc_ops *ops;
+	struct device *dev;
+	struct kref refcount;
+	atomic_t power;
+	unsigned int state;
+	struct mutex lock;
+	struct dentry *dbg_dir;
+	struct list_head traces;
+	int num_traces;
+	struct list_head carveouts;
+	struct list_head mappings;
+	struct completion firmware_loading_complete;
+	u32 bootaddr;
+	struct list_head rvdevs;
+	struct idr notifyids;
+};
+
+/* we currently support only two vrings per rvdev */
+#define RVDEV_NUM_VRINGS 2
+
+/**
+ * struct rproc_vring - remoteproc vring state
+ * @va:	virtual address
+ * @dma: dma address
+ * @len: length, in bytes
+ * @da: device address
+ * @align: vring alignment
+ * @notifyid: rproc-specific unique vring index
+ * @rvdev: remote vdev
+ * @vq: the virtqueue of this vring
+ */
+struct rproc_vring {
+	void *va;
+	dma_addr_t dma;
+	int len;
+	u32 da;
+	u32 align;
+	int notifyid;
+	struct rproc_vdev *rvdev;
+	struct virtqueue *vq;
+};
+
+/**
+ * struct rproc_vdev - remoteproc state for a supported virtio device
+ * @node: list node
+ * @rproc: the rproc handle
+ * @vdev: the virio device
+ * @vring: the vrings for this vdev
+ * @dfeatures: virtio device features
+ * @gfeatures: virtio guest features
+ */
+struct rproc_vdev {
+	struct list_head node;
+	struct rproc *rproc;
+	struct virtio_device vdev;
+	struct rproc_vring vring[RVDEV_NUM_VRINGS];
+	unsigned long dfeatures;
+	unsigned long gfeatures;
+};
+
+struct rproc *rproc_get_by_name(const char *name);
+void rproc_put(struct rproc *rproc);
+
+struct rproc *rproc_alloc(struct device *dev, const char *name,
+				const struct rproc_ops *ops,
+				const char *firmware, int len);
+void rproc_free(struct rproc *rproc);
+int rproc_register(struct rproc *rproc);
+int rproc_unregister(struct rproc *rproc);
+
+int rproc_boot(struct rproc *rproc);
+void rproc_shutdown(struct rproc *rproc);
+
+static inline struct rproc_vdev *vdev_to_rvdev(struct virtio_device *vdev)
+{
+	return container_of(vdev, struct rproc_vdev, vdev);
+}
+
+static inline struct rproc *vdev_to_rproc(struct virtio_device *vdev)
+{
+	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
+
+	return rvdev->rproc;
+}
+
+#endif /* REMOTEPROC_H */

include/linux/rpmsg.h

···
+/*
+ * Remote processor messaging
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ * * Neither the name Texas Instruments nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _LINUX_RPMSG_H
+#define _LINUX_RPMSG_H
+
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+
+/* The feature bitmap for virtio rpmsg */
+#define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
+
+/**
+ * struct rpmsg_hdr - common header for all rpmsg messages
+ * @src: source address
+ * @dst: destination address
+ * @reserved: reserved for future use
+ * @len: length of payload (in bytes)
+ * @flags: message flags
+ * @data: @len bytes of message payload data
+ *
+ * Every message sent(/received) on the rpmsg bus begins with this header.
+ */
+struct rpmsg_hdr {
+	u32 src;
+	u32 dst;
+	u32 reserved;
+	u16 len;
+	u16 flags;
+	u8 data[0];
+} __packed;
+
+/**
+ * struct rpmsg_ns_msg - dynamic name service announcement message
+ * @name: name of remote service that is published
+ * @addr: address of remote service that is published
+ * @flags: indicates whether service is created or destroyed
+ *
+ * This message is sent across to publish a new service, or announce
+ * about its removal. When we receive these messages, an appropriate
+ * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
+ * or ->remove() handler of the appropriate rpmsg driver will be invoked
+ * (if/as-soon-as one is registered).
+ */
+struct rpmsg_ns_msg {
+	char name[RPMSG_NAME_SIZE];
+	u32 addr;
+	u32 flags;
+} __packed;
+
+/**
+ * enum rpmsg_ns_flags - dynamic name service announcement flags
+ *
+ * @RPMSG_NS_CREATE: a new remote service was just created
+ * @RPMSG_NS_DESTROY: a known remote service was just destroyed
+ */
+enum rpmsg_ns_flags {
+	RPMSG_NS_CREATE		= 0,
+	RPMSG_NS_DESTROY	= 1,
+};
+
+#define RPMSG_ADDR_ANY		0xFFFFFFFF
+
+struct virtproc_info;
+
+/**
+ * rpmsg_channel - devices that belong to the rpmsg bus are called channels
+ * @vrp: the remote processor this channel belongs to
+ * @dev: the device struct
+ * @id: device id (used to match between rpmsg drivers and devices)
+ * @src: local address
+ * @dst: destination address
+ * @ept: the rpmsg endpoint of this channel
+ * @announce: if set, rpmsg will announce the creation/removal of this channel
+ */
+struct rpmsg_channel {
+	struct virtproc_info *vrp;
+	struct device dev;
+	struct rpmsg_device_id id;
+	u32 src;
+	u32 dst;
+	struct rpmsg_endpoint *ept;
+	bool announce;
+};
+
+typedef void (*rpmsg_rx_cb_t)(struct rpmsg_channel *, void *, int, void *, u32);
+
+/**
+ * struct rpmsg_endpoint - binds a local rpmsg address to its user
+ * @rpdev: rpmsg channel device
+ * @cb: rx callback handler
+ * @addr: local rpmsg address
+ * @priv: private data for the driver's use
+ *
+ * In essence, an rpmsg endpoint represents a listener on the rpmsg bus, as
+ * it binds an rpmsg address with an rx callback handler.
+ *
+ * Simple rpmsg drivers shouldn't use this struct directly, because
+ * things just work: every rpmsg driver provides an rx callback upon
+ * registering to the bus, and that callback is then bound to its rpmsg
+ * address when the driver is probed. When relevant inbound messages arrive
+ * (i.e. messages which their dst address equals to the src address of
+ * the rpmsg channel), the driver's handler is invoked to process it.
+ *
+ * More complicated drivers though, that do need to allocate additional rpmsg
+ * addresses, and bind them to different rx callbacks, must explicitly
+ * create additional endpoints by themselves (see rpmsg_create_ept()).
+ */
+struct rpmsg_endpoint {
+	struct rpmsg_channel *rpdev;
+	rpmsg_rx_cb_t cb;
+	u32 addr;
+	void *priv;
+};
+
+/**
+ * struct rpmsg_driver - rpmsg driver struct
+ * @drv: underlying device driver
+ * @id_table: rpmsg ids serviced by this driver
+ * @probe: invoked when a matching rpmsg channel (i.e. device) is found
+ * @remove: invoked when the rpmsg channel is removed
+ * @callback: invoked when an inbound message is received on the channel
+ */
+struct rpmsg_driver {
+	struct device_driver drv;
+	const struct rpmsg_device_id *id_table;
+	int (*probe)(struct rpmsg_channel *dev);
+	void (*remove)(struct rpmsg_channel *dev);
+	void (*callback)(struct rpmsg_channel *, void *, int, void *, u32);
+};
+
+int register_rpmsg_device(struct rpmsg_channel *dev);
+void unregister_rpmsg_device(struct rpmsg_channel *dev);
+int register_rpmsg_driver(struct rpmsg_driver *drv);
+void unregister_rpmsg_driver(struct rpmsg_driver *drv);
+void rpmsg_destroy_ept(struct rpmsg_endpoint *);
+struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *,
+				rpmsg_rx_cb_t cb, void *priv, u32 addr);
+int
+rpmsg_send_offchannel_raw(struct rpmsg_channel *, u32, u32, void *, int, bool);
+
+/**
+ * rpmsg_send() - send a message across to the remote processor
+ * @rpdev: the rpmsg channel
+ * @data: payload of message
+ * @len: length of payload
+ *
+ * This function sends @data of length @len on the @rpdev channel.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to, using @rpdev's source and destination addresses.
+ * In case there are no TX buffers available, the function will block until
+ * one becomes available, or a timeout of 15 seconds elapses. When the latter
+ * happens, -ERESTARTSYS is returned.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline int rpmsg_send(struct rpmsg_channel *rpdev, void *data, int len)
+{
+	u32 src = rpdev->src, dst = rpdev->dst;
+
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
+}
+
+/**
+ * rpmsg_sendto() - send a message across to the remote processor, specify dst
+ * @rpdev: the rpmsg channel
+ * @data: payload of message
+ * @len: length of payload
+ * @dst: destination address
+ *
+ * This function sends @data of length @len to the remote @dst address.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to, using @rpdev's source address.
+ * In case there are no TX buffers available, the function will block until
+ * one becomes available, or a timeout of 15 seconds elapses. When the latter
+ * happens, -ERESTARTSYS is returned.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline
+int rpmsg_sendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst)
+{
+	u32 src = rpdev->src;
+
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
+}
+
+/**
+ * rpmsg_send_offchannel() - send a message using explicit src/dst addresses
+ * @rpdev: the rpmsg channel
+ * @src: source address
+ * @dst: destination address
+ * @data: payload of message
+ * @len: length of payload
+ *
+ * This function sends @data of length @len to the remote @dst address,
+ * and uses @src as the source address.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to.
+ * In case there are no TX buffers available, the function will block until
+ * one becomes available, or a timeout of 15 seconds elapses. When the latter
+ * happens, -ERESTARTSYS is returned.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline
+int rpmsg_send_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
+							void *data, int len)
+{
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
+}
+
+/**
+ * rpmsg_send() - send a message across to the remote processor
+ * @rpdev: the rpmsg channel
+ * @data: payload of message
+ * @len: length of payload
+ *
+ * This function sends @data of length @len on the @rpdev channel.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to, using @rpdev's source and destination addresses.
+ * In case there are no TX buffers available, the function will immediately
+ * return -ENOMEM without waiting until one becomes available.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline
+int rpmsg_trysend(struct rpmsg_channel *rpdev, void *data, int len)
+{
+	u32 src = rpdev->src, dst = rpdev->dst;
+
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
+}
+
+/**
+ * rpmsg_sendto() - send a message across to the remote processor, specify dst
+ * @rpdev: the rpmsg channel
+ * @data: payload of message
+ * @len: length of payload
+ * @dst: destination address
+ *
+ * This function sends @data of length @len to the remote @dst address.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to, using @rpdev's source address.
+ * In case there are no TX buffers available, the function will immediately
+ * return -ENOMEM without waiting until one becomes available.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline
+int rpmsg_trysendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst)
+{
+	u32 src = rpdev->src;
+
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
+}
+
+/**
+ * rpmsg_send_offchannel() - send a message using explicit src/dst addresses
+ * @rpdev: the rpmsg channel
+ * @src: source address
+ * @dst: destination address
+ * @data: payload of message
+ * @len: length of payload
+ *
+ * This function sends @data of length @len to the remote @dst address,
+ * and uses @src as the source address.
+ * The message will be sent to the remote processor which the @rpdev
+ * channel belongs to.
+ * In case there are no TX buffers available, the function will immediately
+ * return -ENOMEM without waiting until one becomes available.
+ *
+ * Can only be called from process context (for now).
+ *
+ * Returns 0 on success and an appropriate error value on failure.
+ */
+static inline
+int rpmsg_trysend_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
+							void *data, int len)
+{
+	return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
+}
+
+#endif /* _LINUX_RPMSG_H */

include/linux/virtio_ids.h

···
 #define VIRTIO_ID_CONSOLE	3 /* virtio console */
 #define VIRTIO_ID_RNG		4 /* virtio ring */
 #define VIRTIO_ID_BALLOON	5 /* virtio balloon */
+#define VIRTIO_ID_RPMSG		7 /* virtio remote processor messaging */
 #define VIRTIO_ID_SCSI		8 /* virtio scsi */
 #define VIRTIO_ID_9P		9 /* 9p virtio console */
 

samples/Kconfig

···
 	  Build an example of how to dynamically add the hello
 	  command to the kdb shell.
 
+config SAMPLE_RPMSG_CLIENT
+	tristate "Build rpmsg client sample -- loadable modules only"
+	depends on RPMSG && m
+	help
+	  Build an rpmsg client sample driver, which demonstrates how
+	  to communicate with an AMP-configured remote processor over
+	  the rpmsg bus.
+
 endif # SAMPLES

samples/Makefile

···
 # Makefile for Linux samples code
 
 obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/ \
-			   hw_breakpoint/ kfifo/ kdb/ hidraw/
+			   hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/

samples/rpmsg/Makefile

···
+obj-$(CONFIG_SAMPLE_RPMSG_CLIENT) += rpmsg_client_sample.o

samples/rpmsg/rpmsg_client_sample.c

···
+/*
+ * Remote processor messaging - sample client driver
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Ohad Ben-Cohen <[e-mail]>
+ * Brian Swetland <[e-mail]>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rpmsg.h>
+
+#define MSG		"hello world!"
+#define MSG_LIMIT	100
+
+static void rpmsg_sample_cb(struct rpmsg_channel *rpdev, void *data, int len,
+						void *priv, u32 src)
+{
+	int ret;
+	static int rx_count;
+
+	dev_info(&rpdev->dev, "incoming msg %d (src: 0x%x)\n", ++rx_count, src);
+
+	print_hex_dump(KERN_DEBUG, __func__, DUMP_PREFIX_NONE, 16, 1,
+		       data, len,  true);
+
+	/* samples should not live forever */
+	if (rx_count >= MSG_LIMIT) {
+		dev_info(&rpdev->dev, "goodbye!\n");
+		return;
+	}
+
+	/* send a new message now */
+	ret = rpmsg_send(rpdev, MSG, strlen(MSG));
+	if (ret)
+		dev_err(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
+}
+
+static int rpmsg_sample_probe(struct rpmsg_channel *rpdev)
+{
+	int ret;
+
+	dev_info(&rpdev->dev, "new channel: 0x%x -> 0x%x!\n",
+					rpdev->src, rpdev->dst);
+
+	/* send a message to our remote processor */
+	ret = rpmsg_send(rpdev, MSG, strlen(MSG));
+	if (ret) {
+		dev_err(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __devexit rpmsg_sample_remove(struct rpmsg_channel *rpdev)
+{
+	dev_info(&rpdev->dev, "rpmsg sample client driver is removed\n");
+}
+
+static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = {
+	{ .name	= "rpmsg-client-sample" },
+	{ },
+};
+MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_sample_id_table);
+
+static struct rpmsg_driver rpmsg_sample_client = {
+	.drv.name	= KBUILD_MODNAME,
+	.drv.owner	= THIS_MODULE,
+	.id_table	= rpmsg_driver_sample_id_table,
+	.probe		= rpmsg_sample_probe,
+	.callback	= rpmsg_sample_cb,
+	.remove		= __devexit_p(rpmsg_sample_remove),
+};
+
+static int __init rpmsg_client_sample_init(void)
+{
+	return register_rpmsg_driver(&rpmsg_sample_client);
+}
+module_init(rpmsg_client_sample_init);
+
+static void __exit rpmsg_client_sample_fini(void)
+{
+	unregister_rpmsg_driver(&rpmsg_sample_client);
+}
+module_exit(rpmsg_client_sample_fini);
+
+MODULE_DESCRIPTION("Remote processor messaging sample client driver");
+MODULE_LICENSE("GPL v2");