usb: gadget: f_fs: add capability for dfu functional descriptor

Add the ability for the USB FunctionFS (FFS) gadget driver to be able
to create Device Firmware Upgrade (DFU) functional descriptors. [1]

This patch allows implementation of DFU in userspace using the
FFS gadget. The DFU protocol uses the control pipe (ep0) for all
messaging so only the addition of the DFU functional descriptor
is needed in the kernel driver.

The DFU functional descriptor is written to the ep0 file along with
any other descriptors during FFS setup. DFU requires an interface
descriptor followed by the DFU functional descriptor.

This patch includes documentation of the added descriptor for DFU
and conversion of some existing documentation to kernel-doc format
so that it can be included in the generated docs.

An implementation of DFU 1.1 that implements just the runtime descriptor
using the FunctionFS gadget (with rebooting into u-boot for DFU mode)
has been tested on an i.MX8 Nano.

An implementation of DFU 1.1 that implements both runtime and DFU mode
using the FunctionFS gadget has been tested on Xilinx Zynq UltraScale+.
Note that for the best performance of firmware update file transfers, the
userspace program should respond as quick as possible to the setup packets.

[1] https://www.usb.org/sites/default/files/DFU_1.1.pdf

Signed-off-by: David Sands <[e-mail]>
Co-developed-by: Chris Wulff <[e-mail]>
Signed-off-by: Chris Wulff <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/usb/functionfs-desc.rst

···
+======================
+FunctionFS Descriptors
+======================
+
+Some of the descriptors that can be written to the FFS gadget are
+described below. Device and configuration descriptors are handled
+by the composite gadget and are not written by the user to the
+FFS gadget.
+
+Descriptors are written to the "ep0" file in the FFS gadget
+following the descriptor header.
+
+.. kernel-doc:: include/uapi/linux/usb/functionfs.h
+   :doc: descriptors
+
+Interface Descriptors
+---------------------
+
+Standard USB interface descriptors may be written. The class/subclass of the
+most recent interface descriptor determines what type of class-specific
+descriptors are accepted.
+
+Class-Specific Descriptors
+--------------------------
+
+Class-specific descriptors are accepted only for the class/subclass of the
+most recent interface descriptor. The following are some of the
+class-specific descriptors that are supported.
+
+DFU Functional Descriptor
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When the interface class is USB_CLASS_APP_SPEC and the interface subclass
+is USB_SUBCLASS_DFU, a DFU functional descriptor can be provided.
+The DFU functional descriptor is a described in the USB specification for
+Device Firmware Upgrade (DFU), version 1.1 as of this writing.
+
+.. kernel-doc:: include/uapi/linux/usb/functionfs.h
+   :doc: usb_dfu_functional_descriptor

Documentation/usb/functionfs.rst

···
 them as needed also handling situation when numbers differ in
 different configurations.
 
+For more information about FunctionFS descriptors see :doc:`functionfs-desc`
+
 When descriptors and strings are written "ep#" files appear
 (one for each declared endpoint) which handle communication on
 a single endpoint.  Again, FunctionFS takes care of the real

Documentation/usb/index.rst

···
     dwc3
     ehci
     functionfs
+    functionfs-desc
     gadget_configfs
     gadget_hid
     gadget_multi

drivers/usb/gadget/function/f_fs.c

···
 
 static int __must_check ffs_do_single_desc(char *data, unsigned len,
 					   ffs_entity_callback entity,
-					   void *priv, int *current_class)
+					   void *priv, int *current_class, int *current_subclass)
 {
 	struct usb_descriptor_header *_ds = (void *)data;
 	u8 length;
···
 		if (ds->iInterface)
 			__entity(STRING, ds->iInterface);
 		*current_class = ds->bInterfaceClass;
+		*current_subclass = ds->bInterfaceSubClass;
 	}
 		break;
 
···
 		} else if (*current_class == USB_INTERFACE_CLASS_CCID) {
 			pr_vdebug("ccid descriptor\n");
 			if (length != sizeof(struct ccid_descriptor))
+				goto inv_length;
+			break;
+		} else if (*current_class == USB_CLASS_APP_SPEC &&
+			   *current_subclass == USB_SUBCLASS_DFU) {
+			pr_vdebug("dfu functional descriptor\n");
+			if (length != sizeof(struct usb_dfu_functional_descriptor))
 				goto inv_length;
 			break;
 		} else {
···
 	const unsigned _len = len;
 	unsigned long num = 0;
 	int current_class = -1;
+	int current_subclass = -1;
 
 	for (;;) {
 		int ret;
···
 			return _len - len;
 
 		ret = ffs_do_single_desc(data, len, entity, priv,
-			&current_class);
+			&current_class, &current_subclass);
 		if (ret < 0) {
 			pr_debug("%s returns %d\n", __func__, ret);
 			return ret;

include/uapi/linux/usb/ch9.h

···
 #define USB_DT_DEVICE_CAPABILITY	0x10
 #define USB_DT_WIRELESS_ENDPOINT_COMP	0x11
 #define USB_DT_WIRE_ADAPTER		0x21
+/* From USB Device Firmware Upgrade Specification, Revision 1.1 */
+#define USB_DT_DFU_FUNCTIONAL		0x21
+/* these are from the Wireless USB spec */
 #define USB_DT_RPIPE			0x22
 #define USB_DT_CS_RADIO_CONTROL		0x23
 /* From the T10 UAS specification */
···
 #define USB_CLASS_USB_TYPE_C_BRIDGE	0x12
 #define USB_CLASS_MISC			0xef
 #define USB_CLASS_APP_SPEC		0xfe
-#define USB_CLASS_VENDOR_SPEC		0xff
+#define USB_SUBCLASS_DFU			0x01
 
-#define USB_SUBCLASS_VENDOR_SPEC	0xff
+#define USB_CLASS_VENDOR_SPEC		0xff
+#define USB_SUBCLASS_VENDOR_SPEC		0xff
 
 /*-------------------------------------------------------------------------*/
 

include/uapi/linux/usb/functionfs.h

···
 #define _UAPI__LINUX_FUNCTIONFS_H__
 
 
+#include <linux/const.h>
 #include <linux/types.h>
 #include <linux/ioctl.h>
 
···
 	__le16 wMaxPacketSize;
 	__u8  bInterval;
 } __attribute__((packed));
+
+/**
+ * struct usb_dfu_functional_descriptor - DFU Functional descriptor
+ * @bLength:		Size of the descriptor (bytes)
+ * @bDescriptorType:	USB_DT_DFU_FUNCTIONAL
+ * @bmAttributes:	DFU attributes
+ * @wDetachTimeOut:	Maximum time to wait after DFU_DETACH (ms, le16)
+ * @wTransferSize:	Maximum number of bytes per control-write (le16)
+ * @bcdDFUVersion:	DFU Spec version (BCD, le16)
+ */
+struct usb_dfu_functional_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bmAttributes;
+	__le16 wDetachTimeOut;
+	__le16 wTransferSize;
+	__le16 bcdDFUVersion;
+} __attribute__ ((packed));
+
+/* from DFU functional descriptor bmAttributes */
+#define DFU_FUNC_ATT_CAN_DOWNLOAD	_BITUL(0)
+#define DFU_FUNC_ATT_CAN_UPLOAD		_BITUL(1)
+#define DFU_FUNC_ATT_MANIFEST_TOLERANT	_BITUL(2)
+#define DFU_FUNC_ATT_WILL_DETACH	_BITUL(3)
+
 
 struct usb_functionfs_descs_head_v2 {
 	__le32 magic;
···
 
 #ifndef __KERNEL__
 
-/*
+/**
+ * DOC: descriptors
+ *
  * Descriptors format:
  *
+ * +-----+-----------+--------------+--------------------------------------+
  * | off | name      | type         | description                          |
- * |-----+-----------+--------------+--------------------------------------|
+ * +-----+-----------+--------------+--------------------------------------+
  * |   0 | magic     | LE32         | FUNCTIONFS_DESCRIPTORS_MAGIC_V2      |
+ * +-----+-----------+--------------+--------------------------------------+
  * |   4 | length    | LE32         | length of the whole data chunk       |
+ * +-----+-----------+--------------+--------------------------------------+
  * |   8 | flags     | LE32         | combination of functionfs_flags      |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | eventfd   | LE32         | eventfd file descriptor              |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | fs_count  | LE32         | number of full-speed descriptors     |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | hs_count  | LE32         | number of high-speed descriptors     |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | ss_count  | LE32         | number of super-speed descriptors    |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | os_count  | LE32         | number of MS OS descriptors          |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | fs_descrs | Descriptor[] | list of full-speed descriptors       |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | hs_descrs | Descriptor[] | list of high-speed descriptors       |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | ss_descrs | Descriptor[] | list of super-speed descriptors      |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | os_descrs | OSDesc[]     | list of MS OS descriptors            |
+ * +-----+-----------+--------------+--------------------------------------+
  *
  * Depending on which flags are set, various fields may be missing in the
  * structure.  Any flags that are not recognised cause the whole block to be
···
  *
  * Legacy descriptors format (deprecated as of 3.14):
  *
+ * +-----+-----------+--------------+--------------------------------------+
  * | off | name      | type         | description                          |
- * |-----+-----------+--------------+--------------------------------------|
+ * +-----+-----------+--------------+--------------------------------------+
  * |   0 | magic     | LE32         | FUNCTIONFS_DESCRIPTORS_MAGIC         |
+ * +-----+-----------+--------------+--------------------------------------+
  * |   4 | length    | LE32         | length of the whole data chunk       |
+ * +-----+-----------+--------------+--------------------------------------+
  * |   8 | fs_count  | LE32         | number of full-speed descriptors     |
+ * +-----+-----------+--------------+--------------------------------------+
  * |  12 | hs_count  | LE32         | number of high-speed descriptors     |
+ * +-----+-----------+--------------+--------------------------------------+
  * |  16 | fs_descrs | Descriptor[] | list of full-speed descriptors       |
+ * +-----+-----------+--------------+--------------------------------------+
  * |     | hs_descrs | Descriptor[] | list of high-speed descriptors       |
+ * +-----+-----------+--------------+--------------------------------------+
  *
  * All numbers must be in little endian order.
  *
  * Descriptor[] is an array of valid USB descriptors which have the following
  * format:
  *
+ * +-----+-----------------+------+--------------------------+
  * | off | name            | type | description              |
- * |-----+-----------------+------+--------------------------|
+ * +-----+-----------------+------+--------------------------+
  * |   0 | bLength         | U8   | length of the descriptor |
+ * +-----+-----------------+------+--------------------------+
  * |   1 | bDescriptorType | U8   | descriptor type          |
+ * +-----+-----------------+------+--------------------------+
  * |   2 | payload         |      | descriptor's payload     |
+ * +-----+-----------------+------+--------------------------+
  *
  * OSDesc[] is an array of valid MS OS Feature Descriptors which have one of
  * the following formats:
  *
+ * +-----+-----------------+------+--------------------------+
  * | off | name            | type | description              |
- * |-----+-----------------+------+--------------------------|
+ * +-----+-----------------+------+--------------------------+
  * |   0 | inteface        | U8   | related interface number |
+ * +-----+-----------------+------+--------------------------+
  * |   1 | dwLength        | U32  | length of the descriptor |
+ * +-----+-----------------+------+--------------------------+
  * |   5 | bcdVersion      | U16  | currently supported: 1   |
+ * +-----+-----------------+------+--------------------------+
  * |   7 | wIndex          | U16  | currently supported: 4   |
+ * +-----+-----------------+------+--------------------------+
  * |   9 | bCount          | U8   | number of ext. compat.   |
+ * +-----+-----------------+------+--------------------------+
  * |  10 | Reserved        | U8   | 0                        |
+ * +-----+-----------------+------+--------------------------+
  * |  11 | ExtCompat[]     |      | list of ext. compat. d.  |
+ * +-----+-----------------+------+--------------------------+
  *
+ * +-----+-----------------+------+--------------------------+
  * | off | name            | type | description              |
- * |-----+-----------------+------+--------------------------|
+ * +-----+-----------------+------+--------------------------+
  * |   0 | inteface        | U8   | related interface number |
+ * +-----+-----------------+------+--------------------------+
  * |   1 | dwLength        | U32  | length of the descriptor |
+ * +-----+-----------------+------+--------------------------+
  * |   5 | bcdVersion      | U16  | currently supported: 1   |
+ * +-----+-----------------+------+--------------------------+
  * |   7 | wIndex          | U16  | currently supported: 5   |
+ * +-----+-----------------+------+--------------------------+
  * |   9 | wCount          | U16  | number of ext. compat.   |
+ * +-----+-----------------+------+--------------------------+
  * |  11 | ExtProp[]       |      | list of ext. prop. d.    |
+ * +-----+-----------------+------+--------------------------+
  *
  * ExtCompat[] is an array of valid Extended Compatiblity descriptors
  * which have the following format:
  *
+ * +-----+-----------------------+------+-------------------------------------+
  * | off | name                  | type | description                         |
- * |-----+-----------------------+------+-------------------------------------|
+ * +-----+-----------------------+------+-------------------------------------+
  * |   0 | bFirstInterfaceNumber | U8   | index of the interface or of the 1st|
+ * +-----+-----------------------+------+-------------------------------------+
  * |     |                       |      | interface in an IAD group           |
+ * +-----+-----------------------+------+-------------------------------------+
  * |   1 | Reserved              | U8   | 1                                   |
+ * +-----+-----------------------+------+-------------------------------------+
  * |   2 | CompatibleID          | U8[8]| compatible ID string                |
+ * +-----+-----------------------+------+-------------------------------------+
  * |  10 | SubCompatibleID       | U8[8]| subcompatible ID string             |
+ * +-----+-----------------------+------+-------------------------------------+
  * |  18 | Reserved              | U8[6]| 0                                   |
+ * +-----+-----------------------+------+-------------------------------------+
  *
  * ExtProp[] is an array of valid Extended Properties descriptors
  * which have the following format:
  *
+ * +-----+-----------------------+------+-------------------------------------+
  * | off | name                  | type | description                         |
- * |-----+-----------------------+------+-------------------------------------|
+ * +-----+-----------------------+------+-------------------------------------+
  * |   0 | dwSize                | U32  | length of the descriptor            |
+ * +-----+-----------------------+------+-------------------------------------+
  * |   4 | dwPropertyDataType    | U32  | 1..7                                |
+ * +-----+-----------------------+------+-------------------------------------+
  * |   8 | wPropertyNameLength   | U16  | bPropertyName length (NL)           |
+ * +-----+-----------------------+------+-------------------------------------+
  * |  10 | bPropertyName         |U8[NL]| name of this property               |
+ * +-----+-----------------------+------+-------------------------------------+
  * |10+NL| dwPropertyDataLength  | U32  | bPropertyData length (DL)           |
+ * +-----+-----------------------+------+-------------------------------------+
  * |14+NL| bProperty             |U8[DL]| payload of this property            |
+ * +-----+-----------------------+------+-------------------------------------+
  */
 
 struct usb_functionfs_strings_head {