firmware_loader: Add firmware-upload support

Extend the firmware subsystem to support a persistent sysfs interface that
userspace may use to initiate a firmware update. For example, FPGA based
PCIe cards load firmware and FPGA images from local FLASH when the card
boots. The images in FLASH may be updated with new images provided by the
user at his/her convenience.

A device driver may call firmware_upload_register() to expose persistent
"loading" and "data" sysfs files. These files are used in the same way as
the fallback sysfs "loading" and "data" files. When 0 is written to
"loading" to complete the write of firmware data, the data is transferred
to the lower-level driver using pre-registered call-back functions. The
data transfer is done in the context of a kernel worker thread.

Reviewed-by: Luis Chamberlain <[e-mail]>
Reviewed-by: Tianfei zhang <[e-mail]>
Tested-by: Matthew Gerlach <[e-mail]>
Signed-off-by: Russ Weight <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/ABI/testing/sysfs-class-firmware

···
+What: 		/sys/class/firmware/.../data
+Date:		July 2022
+KernelVersion:	5.19
+Contact:	Russ Weight <[e-mail]>
+Description:	The data sysfs file is used for firmware-fallback and for
+		firmware uploads. Cat a firmware image to this sysfs file
+		after you echo 1 to the loading sysfs file. When the firmware
+		image write is complete, echo 0 to the loading sysfs file. This
+		sequence will signal the completion of the firmware write and
+		signal the lower-level driver that the firmware data is
+		available.
+
+What: 		/sys/class/firmware/.../loading
+Date:		July 2022
+KernelVersion:	5.19
+Contact:	Russ Weight <[e-mail]>
+Description:	The loading sysfs file is used for both firmware-fallback and
+		for firmware uploads. Echo 1 onto the loading file to indicate
+		you are writing a firmware file to the data sysfs node. Echo
+		-1 onto this file to abort the data write or echo 0 onto this
+		file to indicate that the write is complete. For firmware
+		uploads, the zero value also triggers the transfer of the
+		firmware data to the lower-level device driver.
+
+What: 		/sys/class/firmware/.../timeout
+Date:		July 2022
+KernelVersion:	5.19
+Contact:	Russ Weight <[e-mail]>
+Description:	This file supports the timeout mechanism for firmware
+		fallback.  This file has no affect on firmware uploads. For
+		more information on timeouts please see the documentation
+		for firmware fallback.

Documentation/driver-api/firmware/fw_upload.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
+Firmware Upload API
+===================
+
+A device driver that registers with the firmware loader will expose
+persistent sysfs nodes to enable users to initiate firmware updates for
+that device.  It is the responsibility of the device driver and/or the
+device itself to perform any validation on the data received. Firmware
+upload uses the same *loading* and *data* sysfs files described in the
+documentation for firmware fallback.
+
+Register for firmware upload
+============================
+
+A device driver registers for firmware upload by calling
+firmware_upload_register(). Among the parameter list is a name to
+identify the device under /sys/class/firmware. A user may initiate a
+firmware upload by echoing a 1 to the *loading* sysfs file for the target
+device. Next, the user writes the firmware image to the *data* sysfs
+file. After writing the firmware data, the user echos 0 to the *loading*
+sysfs file to signal completion. Echoing 0 to *loading* also triggers the
+transfer of the firmware to the lower-lever device driver in the context
+of a kernel worker thread.
+
+To use the firmware upload API, write a driver that implements a set of
+ops.  The probe function calls firmware_upload_register() and the remove
+function calls firmware_upload_unregister() such as::
+
+	static const struct fw_upload_ops m10bmc_ops = {
+		.prepare = m10bmc_sec_prepare,
+		.write = m10bmc_sec_write,
+		.poll_complete = m10bmc_sec_poll_complete,
+		.cancel = m10bmc_sec_cancel,
+		.cleanup = m10bmc_sec_cleanup,
+	};
+
+	static int m10bmc_sec_probe(struct platform_device *pdev)
+	{
+		const char *fw_name, *truncate;
+		struct m10bmc_sec *sec;
+		struct fw_upload *fwl;
+		unsigned int len;
+
+		sec = devm_kzalloc(&pdev->dev, sizeof(*sec), GFP_KERNEL);
+		if (!sec)
+			return -ENOMEM;
+
+		sec->dev = &pdev->dev;
+		sec->m10bmc = dev_get_drvdata(pdev->dev.parent);
+		dev_set_drvdata(&pdev->dev, sec);
+
+		fw_name = dev_name(sec->dev);
+		truncate = strstr(fw_name, ".auto");
+		len = (truncate) ? truncate - fw_name : strlen(fw_name);
+		sec->fw_name = kmemdup_nul(fw_name, len, GFP_KERNEL);
+
+		fwl = firmware_upload_register(sec->dev, sec->fw_name, &m10bmc_ops, sec);
+		if (IS_ERR(fwl)) {
+			dev_err(sec->dev, "Firmware Upload driver failed to start\n");
+			kfree(sec->fw_name);
+			return PTR_ERR(fwl);
+		}
+
+		sec->fwl = fwl;
+		return 0;
+	}
+
+	static int m10bmc_sec_remove(struct platform_device *pdev)
+	{
+		struct m10bmc_sec *sec = dev_get_drvdata(&pdev->dev);
+
+		firmware_upload_unregister(sec->fwl);
+		kfree(sec->fw_name);
+		return 0;
+	}
+
+firmware_upload_register
+------------------------
+.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.c
+   :identifiers: firmware_upload_register
+
+firmware_upload_unregister
+--------------------------
+.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.c
+   :identifiers: firmware_upload_unregister
+
+Firmware Upload Ops
+-------------------
+.. kernel-doc:: include/linux/firmware.h
+   :identifiers: fw_upload_ops
+
+Firmware Upload Progress Codes
+------------------------------
+The following progress codes are used internally by the firmware loader:
+
+.. kernel-doc:: drivers/base/firmware_loader/sysfs_upload.h
+   :identifiers: fw_upload_prog
+
+Firmware Upload Error Codes
+---------------------------
+The following error codes may be returned by the driver ops in case of
+failure:
+
+.. kernel-doc:: include/linux/firmware.h
+   :identifiers: fw_upload_err

Documentation/driver-api/firmware/index.rst

···
    core
    efi/index
    request_firmware
+   fw_upload
    other_interfaces
 
 .. only::  subproject and html

drivers/base/firmware_loader/Kconfig

···
 
 	  If unsure, say Y.
 
+config FW_UPLOAD
+	bool "Enable users to initiate firmware updates using sysfs"
+	select FW_LOADER_SYSFS
+	select FW_LOADER_PAGED_BUF
+	help
+	  Enabling this option will allow device drivers to expose a persistent
+	  sysfs interface that allows firmware updates to be initiated from
+	  userspace. For example, FPGA based PCIe cards load firmware and FPGA
+	  images from local FLASH when the card boots. The images in FLASH may
+	  be updated with new images provided by the user. Enable this device
+	  to support cards that rely on user-initiated updates for firmware files.
+
+	  If unsure, say N.
+
 endif # FW_LOADER
 endmenu

drivers/base/firmware_loader/Makefile

···
 firmware_class-$(CONFIG_FW_LOADER_USER_HELPER) += fallback.o
 firmware_class-$(CONFIG_EFI_EMBEDDED_FIRMWARE) += fallback_platform.o
 firmware_class-$(CONFIG_FW_LOADER_SYSFS) += sysfs.o
+firmware_class-$(CONFIG_FW_UPLOAD) += sysfs_upload.o
 
 obj-y += builtin/

drivers/base/firmware_loader/firmware.h

···
 };
 
 extern struct mutex fw_lock;
+extern struct firmware_cache fw_cache;
 
 static inline bool __fw_state_check(struct fw_priv *fw_priv,
 				    enum fw_status status)
···
 	return __fw_state_check(fw_priv, FW_STATUS_LOADING);
 }
 
+int alloc_lookup_fw_priv(const char *fw_name, struct firmware_cache *fwc,
+			 struct fw_priv **fw_priv, void *dbuf, size_t size,
+			 size_t offset, u32 opt_flags);
 int assign_fw(struct firmware *fw, struct device *device);
+void free_fw_priv(struct fw_priv *fw_priv);
+void fw_state_init(struct fw_priv *fw_priv);
 
 #ifdef CONFIG_FW_LOADER
 bool firmware_is_builtin(const struct firmware *fw);

drivers/base/firmware_loader/main.c

···
  * guarding for corner cases a global lock should be OK */
 DEFINE_MUTEX(fw_lock);
 
-static struct firmware_cache fw_cache;
+struct firmware_cache fw_cache;
 
-static void fw_state_init(struct fw_priv *fw_priv)
+void fw_state_init(struct fw_priv *fw_priv)
 {
 	struct fw_state *fw_st = &fw_priv->fw_st;
 
···
 }
 
 /* Returns 1 for batching firmware requests with the same name */
-static int alloc_lookup_fw_priv(const char *fw_name,
-				struct firmware_cache *fwc,
-				struct fw_priv **fw_priv,
-				void *dbuf,
-				size_t size,
-				size_t offset,
-				u32 opt_flags)
+int alloc_lookup_fw_priv(const char *fw_name, struct firmware_cache *fwc,
+			 struct fw_priv **fw_priv, void *dbuf, size_t size,
+			 size_t offset, u32 opt_flags)
 {
 	struct fw_priv *tmp;
 
···
 	kfree(fw_priv);
 }
 
-static void free_fw_priv(struct fw_priv *fw_priv)
+void free_fw_priv(struct fw_priv *fw_priv)
 {
 	struct firmware_cache *fwc = fw_priv->fwc;
 	spin_lock(&fwc->lock);

drivers/base/firmware_loader/sysfs.c

···
 #include <linux/slab.h>
 #include <linux/types.h>
 
-#include "firmware.h"
 #include "sysfs.h"
+#include "sysfs_upload.h"
 
 /*
  * sysfs support for firmware loader
···
 {
 	struct fw_sysfs *fw_sysfs = to_fw_sysfs(dev);
 
+	if (fw_sysfs->fw_upload_priv) {
+		free_fw_priv(fw_sysfs->fw_priv);
+		kfree(fw_sysfs->fw_upload_priv);
+	}
 	kfree(fw_sysfs);
 }
 
···
 				written = rc;
 			} else {
 				fw_state_done(fw_priv);
+
+				/*
+				 * If this is a user-initiated firmware upload
+				 * then start the upload in a worker thread now.
+				 */
+				rc = fw_upload_start(fw_sysfs);
+				if (rc)
+					written = rc;
 			}
 			break;
 		}
···
 		fallthrough;
 	case -1:
 		fw_load_abort(fw_sysfs);
+		if (fw_sysfs->fw_upload_priv)
+			fw_state_init(fw_sysfs->fw_priv);
+
 		break;
 	}
 out:
···
 	return written;
 }
 
-static DEVICE_ATTR(loading, 0644, firmware_loading_show, firmware_loading_store);
+DEVICE_ATTR(loading, 0644, firmware_loading_show, firmware_loading_store);
 
 static void firmware_rw_data(struct fw_priv *fw_priv, char *buffer,
 			     loff_t offset, size_t count, bool read)

drivers/base/firmware_loader/sysfs.h

···
 
 #include <linux/device.h>
 
+#include "firmware.h"
+
 MODULE_IMPORT_NS(FIRMWARE_LOADER_PRIVATE);
 
 extern struct firmware_fallback_config fw_fallback_config;
+extern struct device_attribute dev_attr_loading;
 
 #ifdef CONFIG_FW_LOADER_USER_HELPER
 /**
···
 	struct device dev;
 	struct fw_priv *fw_priv;
 	struct firmware *fw;
+	void *fw_upload_priv;
 };
 
 static inline struct fw_sysfs *to_fw_sysfs(struct device *dev)

drivers/base/firmware_loader/sysfs_upload.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#include "sysfs.h"
+#include "sysfs_upload.h"
+
+/*
+ * Support for user-space to initiate a firmware upload to a device.
+ */
+
+static void fw_upload_update_progress(struct fw_upload_priv *fwlp,
+				      enum fw_upload_prog new_progress)
+{
+	mutex_lock(&fwlp->lock);
+	fwlp->progress = new_progress;
+	mutex_unlock(&fwlp->lock);
+}
+
+static void fw_upload_set_error(struct fw_upload_priv *fwlp,
+				enum fw_upload_err err_code)
+{
+	mutex_lock(&fwlp->lock);
+	fwlp->err_progress = fwlp->progress;
+	fwlp->err_code = err_code;
+	mutex_unlock(&fwlp->lock);
+}
+
+static void fw_upload_prog_complete(struct fw_upload_priv *fwlp)
+{
+	mutex_lock(&fwlp->lock);
+	fwlp->progress = FW_UPLOAD_PROG_IDLE;
+	mutex_unlock(&fwlp->lock);
+}
+
+static void fw_upload_main(struct work_struct *work)
+{
+	struct fw_upload_priv *fwlp;
+	struct fw_sysfs *fw_sysfs;
+	u32 written = 0, offset = 0;
+	enum fw_upload_err ret;
+	struct device *fw_dev;
+	struct fw_upload *fwl;
+
+	fwlp = container_of(work, struct fw_upload_priv, work);
+	fwl = fwlp->fw_upload;
+	fw_sysfs = (struct fw_sysfs *)fwl->priv;
+	fw_dev = &fw_sysfs->dev;
+
+	fw_upload_update_progress(fwlp, FW_UPLOAD_PROG_PREPARING);
+	ret = fwlp->ops->prepare(fwl, fwlp->data, fwlp->remaining_size);
+	if (ret != FW_UPLOAD_ERR_NONE) {
+		fw_upload_set_error(fwlp, ret);
+		goto putdev_exit;
+	}
+
+	fw_upload_update_progress(fwlp, FW_UPLOAD_PROG_TRANSFERRING);
+	while (fwlp->remaining_size) {
+		ret = fwlp->ops->write(fwl, fwlp->data, offset,
+					fwlp->remaining_size, &written);
+		if (ret != FW_UPLOAD_ERR_NONE || !written) {
+			if (ret == FW_UPLOAD_ERR_NONE) {
+				dev_warn(fw_dev, "write-op wrote zero data\n");
+				ret = FW_UPLOAD_ERR_RW_ERROR;
+			}
+			fw_upload_set_error(fwlp, ret);
+			goto done;
+		}
+
+		fwlp->remaining_size -= written;
+		offset += written;
+	}
+
+	fw_upload_update_progress(fwlp, FW_UPLOAD_PROG_PROGRAMMING);
+	ret = fwlp->ops->poll_complete(fwl);
+	if (ret != FW_UPLOAD_ERR_NONE)
+		fw_upload_set_error(fwlp, ret);
+
+done:
+	if (fwlp->ops->cleanup)
+		fwlp->ops->cleanup(fwl);
+
+putdev_exit:
+	put_device(fw_dev->parent);
+
+	/*
+	 * Note: fwlp->remaining_size is left unmodified here to provide
+	 * additional information on errors. It will be reinitialized when
+	 * the next firmeware upload begins.
+	 */
+	mutex_lock(&fw_lock);
+	fw_free_paged_buf(fw_sysfs->fw_priv);
+	fw_state_init(fw_sysfs->fw_priv);
+	mutex_unlock(&fw_lock);
+	fwlp->data = NULL;
+	fw_upload_prog_complete(fwlp);
+}
+
+/*
+ * Start a worker thread to upload data to the parent driver.
+ * Must be called with fw_lock held.
+ */
+int fw_upload_start(struct fw_sysfs *fw_sysfs)
+{
+	struct fw_priv *fw_priv = fw_sysfs->fw_priv;
+	struct device *fw_dev = &fw_sysfs->dev;
+	struct fw_upload_priv *fwlp;
+
+	if (!fw_sysfs->fw_upload_priv)
+		return 0;
+
+	if (!fw_priv->size) {
+		fw_free_paged_buf(fw_priv);
+		fw_state_init(fw_sysfs->fw_priv);
+		return 0;
+	}
+
+	fwlp = fw_sysfs->fw_upload_priv;
+	mutex_lock(&fwlp->lock);
+
+	/* Do not interfere with an on-going fw_upload */
+	if (fwlp->progress != FW_UPLOAD_PROG_IDLE) {
+		mutex_unlock(&fwlp->lock);
+		return -EBUSY;
+	}
+
+	get_device(fw_dev->parent); /* released in fw_upload_main */
+
+	fwlp->progress = FW_UPLOAD_PROG_RECEIVING;
+	fwlp->err_code = 0;
+	fwlp->remaining_size = fw_priv->size;
+	fwlp->data = fw_priv->data;
+
+	pr_debug("%s: fw-%s fw_priv=%p data=%p size=%u\n",
+		 __func__, fw_priv->fw_name,
+		 fw_priv, fw_priv->data,
+		 (unsigned int)fw_priv->size);
+
+	queue_work(system_long_wq, &fwlp->work);
+	mutex_unlock(&fwlp->lock);
+
+	return 0;
+}
+
+/**
+ * firmware_upload_register() - register for the firmware upload sysfs API
+ * @parent: parent device instantiating firmware upload
+ * @name: firmware name to be associated with this device
+ * @ops: pointer to structure of firmware upload ops
+ * @dd_handle: pointer to parent driver private data
+ *
+ *	@name must be unique among all users of firmware upload. The firmware
+ *	sysfs files for this device will be found at /sys/class/firmware/@name.
+ *
+ *	Return: struct fw_upload pointer or ERR_PTR()
+ *
+ **/
+struct fw_upload *
+firmware_upload_register(struct module *module, struct device *parent,
+			 const char *name, const struct fw_upload_ops *ops,
+			 void *dd_handle)
+{
+	u32 opt_flags = FW_OPT_NOCACHE;
+	struct fw_upload *fw_upload;
+	struct fw_upload_priv *fw_upload_priv;
+	struct fw_sysfs *fw_sysfs;
+	struct fw_priv *fw_priv;
+	struct device *fw_dev;
+	int ret;
+
+	if (!name || name[0] == '\0')
+		return ERR_PTR(-EINVAL);
+
+	if (!ops || !ops->cancel || !ops->prepare ||
+	    !ops->write || !ops->poll_complete) {
+		dev_err(parent, "Attempt to register without all required ops\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!try_module_get(module))
+		return ERR_PTR(-EFAULT);
+
+	fw_upload = kzalloc(sizeof(*fw_upload), GFP_KERNEL);
+	if (!fw_upload) {
+		ret = -ENOMEM;
+		goto exit_module_put;
+	}
+
+	fw_upload_priv = kzalloc(sizeof(*fw_upload_priv), GFP_KERNEL);
+	if (!fw_upload_priv) {
+		ret = -ENOMEM;
+		goto free_fw_upload;
+	}
+
+	fw_upload_priv->fw_upload = fw_upload;
+	fw_upload_priv->ops = ops;
+	mutex_init(&fw_upload_priv->lock);
+	fw_upload_priv->module = module;
+	fw_upload_priv->name = name;
+	fw_upload_priv->err_code = 0;
+	fw_upload_priv->progress = FW_UPLOAD_PROG_IDLE;
+	INIT_WORK(&fw_upload_priv->work, fw_upload_main);
+	fw_upload->dd_handle = dd_handle;
+
+	fw_sysfs = fw_create_instance(NULL, name, parent, opt_flags);
+	if (IS_ERR(fw_sysfs)) {
+		ret = PTR_ERR(fw_sysfs);
+		goto free_fw_upload_priv;
+	}
+	fw_upload->priv = fw_sysfs;
+	fw_sysfs->fw_upload_priv = fw_upload_priv;
+	fw_dev = &fw_sysfs->dev;
+
+	ret = alloc_lookup_fw_priv(name, &fw_cache, &fw_priv,  NULL, 0, 0,
+				   FW_OPT_NOCACHE);
+	if (ret != 0) {
+		if (ret > 0)
+			ret = -EINVAL;
+		goto free_fw_sysfs;
+	}
+	fw_priv->is_paged_buf = true;
+	fw_sysfs->fw_priv = fw_priv;
+
+	ret = device_add(fw_dev);
+	if (ret) {
+		dev_err(fw_dev, "%s: device_register failed\n", __func__);
+		put_device(fw_dev);
+		goto exit_module_put;
+	}
+
+	return fw_upload;
+
+free_fw_sysfs:
+	kfree(fw_sysfs);
+
+free_fw_upload_priv:
+	kfree(fw_upload_priv);
+
+free_fw_upload:
+	kfree(fw_upload);
+
+exit_module_put:
+	module_put(module);
+
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(firmware_upload_register);
+
+/**
+ * firmware_upload_unregister() - Unregister firmware upload interface
+ * @fw_upload: pointer to struct fw_upload
+ **/
+void firmware_upload_unregister(struct fw_upload *fw_upload)
+{
+	struct fw_sysfs *fw_sysfs = fw_upload->priv;
+	struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
+
+	mutex_lock(&fw_upload_priv->lock);
+	if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
+		mutex_unlock(&fw_upload_priv->lock);
+		goto unregister;
+	}
+
+	fw_upload_priv->ops->cancel(fw_upload);
+	mutex_unlock(&fw_upload_priv->lock);
+
+	/* Ensure lower-level device-driver is finished */
+	flush_work(&fw_upload_priv->work);
+
+unregister:
+	device_unregister(&fw_sysfs->dev);
+	module_put(fw_upload_priv->module);
+}
+EXPORT_SYMBOL_GPL(firmware_upload_unregister);

drivers/base/firmware_loader/sysfs_upload.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __FIRMWARE_UPLOAD_H
+#define __FIRMWARE_UPLOAD_H
+
+#include <linux/device.h>
+
+/**
+ * enum fw_upload_prog - firmware upload progress codes
+ * @FW_UPLOAD_PROG_IDLE: there is no firmware upload in progress
+ * @FW_UPLOAD_PROG_RECEIVING: worker thread is receiving firmware data
+ * @FW_UPLOAD_PROG_PREPARING: target device is preparing for firmware upload
+ * @FW_UPLOAD_PROG_TRANSFERRING: data is being copied to the device
+ * @FW_UPLOAD_PROG_PROGRAMMING: device is performing the firmware update
+ * @FW_UPLOAD_PROG_MAX: Maximum progress code marker
+ */
+enum fw_upload_prog {
+	FW_UPLOAD_PROG_IDLE,
+	FW_UPLOAD_PROG_RECEIVING,
+	FW_UPLOAD_PROG_PREPARING,
+	FW_UPLOAD_PROG_TRANSFERRING,
+	FW_UPLOAD_PROG_PROGRAMMING,
+	FW_UPLOAD_PROG_MAX
+};
+
+struct fw_upload_priv {
+	struct fw_upload *fw_upload;
+	struct module *module;
+	const char *name;
+	const struct fw_upload_ops *ops;
+	struct mutex lock;		  /* protect data structure contents */
+	struct work_struct work;
+	const u8 *data;			  /* pointer to update data */
+	u32 remaining_size;		  /* size remaining to transfer */
+	enum fw_upload_prog progress;
+	enum fw_upload_prog err_progress; /* progress at time of failure */
+	enum fw_upload_err err_code;	  /* security manager error code */
+};
+
+#ifdef CONFIG_FW_UPLOAD
+int fw_upload_start(struct fw_sysfs *fw_sysfs);
+umode_t fw_upload_is_visible(struct kobject *kobj, struct attribute *attr, int n);
+#else
+static inline int fw_upload_start(struct fw_sysfs *fw_sysfs)
+{
+	return 0;
+}
+#endif
+
+#endif /* __FIRMWARE_UPLOAD_H */

include/linux/firmware.h

···
 	void *priv;
 };
 
+/**
+ * enum fw_upload_err - firmware upload error codes
+ * @FW_UPLOAD_ERR_NONE: returned to indicate success
+ * @FW_UPLOAD_ERR_HW_ERROR: error signalled by hardware, see kernel log
+ * @FW_UPLOAD_ERR_TIMEOUT: SW timed out on handshake with HW/firmware
+ * @FW_UPLOAD_ERR_CANCELED: upload was cancelled by the user
+ * @FW_UPLOAD_ERR_BUSY: there is an upload operation already in progress
+ * @FW_UPLOAD_ERR_INVALID_SIZE: invalid firmware image size
+ * @FW_UPLOAD_ERR_RW_ERROR: read or write to HW failed, see kernel log
+ * @FW_UPLOAD_ERR_WEAROUT: FLASH device is approaching wear-out, wait & retry
+ * @FW_UPLOAD_ERR_MAX: Maximum error code marker
+ */
+enum fw_upload_err {
+	FW_UPLOAD_ERR_NONE,
+	FW_UPLOAD_ERR_HW_ERROR,
+	FW_UPLOAD_ERR_TIMEOUT,
+	FW_UPLOAD_ERR_CANCELED,
+	FW_UPLOAD_ERR_BUSY,
+	FW_UPLOAD_ERR_INVALID_SIZE,
+	FW_UPLOAD_ERR_RW_ERROR,
+	FW_UPLOAD_ERR_WEAROUT,
+	FW_UPLOAD_ERR_MAX
+};
+
+struct fw_upload {
+	void *dd_handle; /* reference to parent driver */
+	void *priv;	 /* firmware loader private fields */
+};
+
+/**
+ * struct fw_upload_ops - device specific operations to support firmware upload
+ * @prepare:		  Required: Prepare secure update
+ * @write:		  Required: The write() op receives the remaining
+ *			  size to be written and must return the actual
+ *			  size written or a negative error code. The write()
+ *			  op will be called repeatedly until all data is
+ *			  written.
+ * @poll_complete:	  Required: Check for the completion of the
+ *			  HW authentication/programming process.
+ * @cancel:		  Required: Request cancellation of update. This op
+ *			  is called from the context of a different kernel
+ *			  thread, so race conditions need to be considered.
+ * @cleanup:		  Optional: Complements the prepare()
+ *			  function and is called at the completion
+ *			  of the update, on success or failure, if the
+ *			  prepare function succeeded.
+ */
+struct fw_upload_ops {
+	enum fw_upload_err (*prepare)(struct fw_upload *fw_upload,
+				      const u8 *data, u32 size);
+	enum fw_upload_err (*write)(struct fw_upload *fw_upload,
+				    const u8 *data, u32 offset,
+				    u32 size, u32 *written);
+	enum fw_upload_err (*poll_complete)(struct fw_upload *fw_upload);
+	void (*cancel)(struct fw_upload *fw_upload);
+	void (*cleanup)(struct fw_upload *fw_upload);
+};
+
 struct module;
 struct device;
 
···
 					 void *buf, size_t size, size_t offset)
 {
 	return -EINVAL;
+}
+
+#endif
+
+#ifdef CONFIG_FW_UPLOAD
+
+struct fw_upload *
+firmware_upload_register(struct module *module, struct device *parent,
+			 const char *name, const struct fw_upload_ops *ops,
+			 void *dd_handle);
+void firmware_upload_unregister(struct fw_upload *fw_upload);
+
+#else
+
+static inline struct fw_upload *
+firmware_upload_register(struct module *module, struct device *parent,
+			 const char *name, const struct fw_upload_ops *ops,
+			 void *dd_handle)
+{
+		return ERR_PTR(-EINVAL);
+}
+
+static inline void firmware_upload_unregister(struct fw_upload *fw_upload)
+{
 }
 
 #endif