drivers/rpmsg/rpmsg_core.c - kernel/msm-4.19 - Gitiles

 /*
  * remote processor messaging bus
  *
  * Copyright (C) 2011 Texas Instruments, Inc.
  * Copyright (C) 2011 Google, Inc.
  *
  * Ohad Ben-Cohen <ohad@wizery.com>
  * Brian Swetland <swetland@google.com>
  *
  * 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/rpmsg.h>
 #include <linux/of_device.h>
 #include <linux/slab.h>

 #include "rpmsg_internal.h"

 /**
  * rpmsg_create_ept() - create a new rpmsg_endpoint
  * @rpdev: rpmsg channel device
  * @cb: rx callback handler
  * @priv: private data for the driver's use
  * @chinfo: channel_info with the 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_device *rpdev,
 					rpmsg_rx_cb_t cb, void *priv,
 					struct rpmsg_channel_info chinfo)
 {
 	return rpdev->ops->create_ept(rpdev, cb, priv, chinfo);
 }
 EXPORT_SYMBOL(rpmsg_create_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)
 {
 	ept->ops->destroy_ept(ept);
 }
 EXPORT_SYMBOL(rpmsg_destroy_ept);

 /**
  * rpmsg_send() - send a message across to the remote processor
  * @ept: the rpmsg endpoint
  * @data: payload of message
  * @len: length of payload
  *
  * This function sends @data of length @len on the @ept endpoint.
  * The message will be sent to the remote processor which the @ept
  * endpoint belongs to, using @ept's address and its associated rpmsg
  * device 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.
  */
 int rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 {
 	return ept->ops->send(ept, data, len);
 }
 EXPORT_SYMBOL(rpmsg_send);

 /**
  * rpmsg_sendto() - send a message across to the remote processor, specify dst
  * @ept: the rpmsg endpoint
  * @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 @ept
  * endpoint belongs to, using @ept's address as source.
  * 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.
  */
 int rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
 {
 	return ept->ops->sendto(ept, data, len, dst);
 }
 EXPORT_SYMBOL(rpmsg_sendto);

 /**
  * rpmsg_send_offchannel() - send a message using explicit src/dst addresses
  * @ept: the rpmsg endpoint
  * @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 @ept
  * endpoint 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.
  */
 int rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
 			  void *data, int len)
 {
 	return ept->ops->send_offchannel(ept, src, dst, data, len);
 }
 EXPORT_SYMBOL(rpmsg_send_offchannel);

 /**
  * rpmsg_send() - send a message across to the remote processor
  * @ept: the rpmsg endpoint
  * @data: payload of message
  * @len: length of payload
  *
  * This function sends @data of length @len on the @ept endpoint.
  * The message will be sent to the remote processor which the @ept
  * endpoint belongs to, using @ept's address as source and its associated
  * rpdev's address as destination.
  * 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.
  */
 int rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 {
 	return ept->ops->trysend(ept, data, len);
 }
 EXPORT_SYMBOL(rpmsg_trysend);

 /**
  * rpmsg_sendto() - send a message across to the remote processor, specify dst
  * @ept: the rpmsg endpoint
  * @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 @ept
  * endpoint belongs to, using @ept's address as source.
  * 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.
  */
 int rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data, int len, u32 dst)
 {
 	return ept->ops->trysendto(ept, data, len, dst);
 }
 EXPORT_SYMBOL(rpmsg_trysendto);

 /**
  * rpmsg_send_offchannel() - send a message using explicit src/dst addresses
  * @ept: the rpmsg endpoint
  * @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 @ept
  * endpoint 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.
  */
 int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
 			     void *data, int len)
 {
 	return ept->ops->trysend_offchannel(ept, src, dst, data, len);
 }
 EXPORT_SYMBOL(rpmsg_trysend_offchannel);

 /*
  * 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_device_match(struct device *dev, void *data)
 {
 	struct rpmsg_channel_info *chinfo = data;
 	struct rpmsg_device *rpdev = to_rpmsg_device(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;
 }

 struct device *rpmsg_find_device(struct device *parent,
 				 struct rpmsg_channel_info *chinfo)
 {
 	return device_find_child(parent, chinfo, rpmsg_device_match);

 }
 EXPORT_SYMBOL(rpmsg_find_device);

 /* 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_device *rpdev = to_rpmsg_device(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");

 static ssize_t modalias_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
 	struct rpmsg_device *rpdev = to_rpmsg_device(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_device *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_device *rpdev = to_rpmsg_device(dev);
 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
 	const struct rpmsg_device_id *ids = rpdrv->id_table;
 	unsigned int i;

 	if (ids)
 		for (i = 0; ids[i].name[0]; i++)
 			if (rpmsg_id_match(rpdev, &ids[i]))
 				return 1;

 	return of_driver_match_device(dev, drv);
 }

 static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);

 	return add_uevent_var(env, "MODALIAS=" RPMSG_DEVICE_MODALIAS_FMT,
 					rpdev->id.name);
 }

 /*
  * 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_device *rpdev = to_rpmsg_device(dev);
 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 	struct rpmsg_channel_info chinfo = {};
 	struct rpmsg_endpoint *ept;
 	int err;

 	strncpy(chinfo.name, rpdev->id.name, RPMSG_NAME_SIZE);
 	chinfo.src = rpdev->src;
 	chinfo.dst = RPMSG_ADDR_ANY;

 	ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, chinfo);
 	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;
 	}

 	if (rpdev->ops->announce_create)
 		err = rpdev->ops->announce_create(rpdev);
 out:
 	return err;
 }

 static int rpmsg_dev_remove(struct device *dev)
 {
 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
 	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
 	int err = 0;

 	if (rpdev->ops->announce_destroy)
 		err = rpdev->ops->announce_destroy(rpdev);

 	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,
 };

 static void rpmsg_release_device(struct device *dev)
 {
 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);

 	kfree(rpdev);
 }

 int rpmsg_register_device(struct rpmsg_device *rpdev)
 {
 	struct device *dev = &rpdev->dev;
 	int ret;

 	dev_set_name(&rpdev->dev, "%s:%s",
 		     dev_name(dev->parent), rpdev->id.name);

 	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 ret;
 }
 EXPORT_SYMBOL(rpmsg_register_device);

 /*
  * find an existing channel using its name + address properties,
  * and destroy it
  */
 int rpmsg_unregister_device(struct device *parent,
 			    struct rpmsg_channel_info *chinfo)
 {
 	struct device *dev;

 	dev = rpmsg_find_device(parent, chinfo);
 	if (!dev)
 		return -EINVAL;

 	device_unregister(dev);

 	put_device(dev);

 	return 0;
 }
 EXPORT_SYMBOL(rpmsg_unregister_device);

 /**
  * __register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
  * @rpdrv: pointer to a struct rpmsg_driver
  * @owner: owning module/driver
  *
  * Returns 0 on success, and an appropriate error value on failure.
  */
 int __register_rpmsg_driver(struct rpmsg_driver *rpdrv, struct module *owner)
 {
 	rpdrv->drv.bus = &rpmsg_bus;
 	rpdrv->drv.owner = owner;
 	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 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;
 }
 postcore_initcall(rpmsg_init);

 static void __exit rpmsg_fini(void)
 {
 	bus_unregister(&rpmsg_bus);
 }
 module_exit(rpmsg_fini);

 MODULE_DESCRIPTION("remote processor messaging bus");
 MODULE_LICENSE("GPL v2");
	/*
	* remote processor messaging bus
	*
	* Copyright (C) 2011 Texas Instruments, Inc.
	* Copyright (C) 2011 Google, Inc.
	*
	* Ohad Ben-Cohen <ohad@wizery.com>
	* Brian Swetland <swetland@google.com>
	*
	* 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/rpmsg.h>
	#include <linux/of_device.h>
	#include <linux/slab.h>

	#include "rpmsg_internal.h"

	/**
	* rpmsg_create_ept() - create a new rpmsg_endpoint
	* @rpdev: rpmsg channel device
	* @cb: rx callback handler
	* @priv: private data for the driver's use
	* @chinfo: channel_info with the 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_device rpdev,
	rpmsg_rx_cb_t cb, void *priv,
	struct rpmsg_channel_info chinfo)
	{
	return rpdev->ops->create_ept(rpdev, cb, priv, chinfo);
	}
	EXPORT_SYMBOL(rpmsg_create_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)
	{
	ept->ops->destroy_ept(ept);
	}
	EXPORT_SYMBOL(rpmsg_destroy_ept);

	/**
	* rpmsg_send() - send a message across to the remote processor
	* @ept: the rpmsg endpoint
	* @data: payload of message
	* @len: length of payload
	*
	* This function sends @data of length @len on the @ept endpoint.
	* The message will be sent to the remote processor which the @ept
	* endpoint belongs to, using @ept's address and its associated rpmsg
	* device 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.
	*/
	int rpmsg_send(struct rpmsg_endpoint ept, void data, int len)
	{
	return ept->ops->send(ept, data, len);
	}
	EXPORT_SYMBOL(rpmsg_send);

	/**
	* rpmsg_sendto() - send a message across to the remote processor, specify dst
	* @ept: the rpmsg endpoint
	* @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 @ept
	* endpoint belongs to, using @ept's address as source.
	* 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.
	*/
	int rpmsg_sendto(struct rpmsg_endpoint ept, void data, int len, u32 dst)
	{
	return ept->ops->sendto(ept, data, len, dst);
	}
	EXPORT_SYMBOL(rpmsg_sendto);

	/**
	* rpmsg_send_offchannel() - send a message using explicit src/dst addresses
	* @ept: the rpmsg endpoint
	* @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 @ept
	* endpoint 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.
	*/
	int rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
	void *data, int len)
	{
	return ept->ops->send_offchannel(ept, src, dst, data, len);
	}
	EXPORT_SYMBOL(rpmsg_send_offchannel);

	/**
	* rpmsg_send() - send a message across to the remote processor
	* @ept: the rpmsg endpoint
	* @data: payload of message
	* @len: length of payload
	*
	* This function sends @data of length @len on the @ept endpoint.
	* The message will be sent to the remote processor which the @ept
	* endpoint belongs to, using @ept's address as source and its associated
	* rpdev's address as destination.
	* 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.
	*/
	int rpmsg_trysend(struct rpmsg_endpoint ept, void data, int len)
	{
	return ept->ops->trysend(ept, data, len);
	}
	EXPORT_SYMBOL(rpmsg_trysend);

	/**
	* rpmsg_sendto() - send a message across to the remote processor, specify dst
	* @ept: the rpmsg endpoint
	* @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 @ept
	* endpoint belongs to, using @ept's address as source.
	* 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.
	*/
	int rpmsg_trysendto(struct rpmsg_endpoint ept, void data, int len, u32 dst)
	{
	return ept->ops->trysendto(ept, data, len, dst);
	}
	EXPORT_SYMBOL(rpmsg_trysendto);

	/**
	* rpmsg_send_offchannel() - send a message using explicit src/dst addresses
	* @ept: the rpmsg endpoint
	* @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 @ept
	* endpoint 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.
	*/
	int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst,
	void *data, int len)
	{
	return ept->ops->trysend_offchannel(ept, src, dst, data, len);
	}
	EXPORT_SYMBOL(rpmsg_trysend_offchannel);

	/*
	* 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_device_match(struct device dev, void data)
	{
	struct rpmsg_channel_info *chinfo = data;
	struct rpmsg_device *rpdev = to_rpmsg_device(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;
	}

	struct device rpmsg_find_device(struct device parent,
	struct rpmsg_channel_info *chinfo)
	{
	return device_find_child(parent, chinfo, rpmsg_device_match);

	}
	EXPORT_SYMBOL(rpmsg_find_device);

	/* 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_device *rpdev = to_rpmsg_device(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");

	static ssize_t modalias_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct rpmsg_device *rpdev = to_rpmsg_device(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_device *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_device *rpdev = to_rpmsg_device(dev);
	struct rpmsg_driver *rpdrv = to_rpmsg_driver(drv);
	const struct rpmsg_device_id *ids = rpdrv->id_table;
	unsigned int i;

	if (ids)
	for (i = 0; ids[i].name[0]; i++)
	if (rpmsg_id_match(rpdev, &ids[i]))
	return 1;

	return of_driver_match_device(dev, drv);
	}

	static int rpmsg_uevent(struct device dev, struct kobj_uevent_env env)
	{
	struct rpmsg_device *rpdev = to_rpmsg_device(dev);

	return add_uevent_var(env, "MODALIAS=" RPMSG_DEVICE_MODALIAS_FMT,
	rpdev->id.name);
	}

	/*
	* 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_device *rpdev = to_rpmsg_device(dev);
	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
	struct rpmsg_channel_info chinfo = {};
	struct rpmsg_endpoint *ept;
	int err;

	strncpy(chinfo.name, rpdev->id.name, RPMSG_NAME_SIZE);
	chinfo.src = rpdev->src;
	chinfo.dst = RPMSG_ADDR_ANY;

	ept = rpmsg_create_ept(rpdev, rpdrv->callback, NULL, chinfo);
	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;
	}

	if (rpdev->ops->announce_create)
	err = rpdev->ops->announce_create(rpdev);
	out:
	return err;
	}

	static int rpmsg_dev_remove(struct device *dev)
	{
	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
	struct rpmsg_driver *rpdrv = to_rpmsg_driver(rpdev->dev.driver);
	int err = 0;

	if (rpdev->ops->announce_destroy)
	err = rpdev->ops->announce_destroy(rpdev);

	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,
	};

	static void rpmsg_release_device(struct device *dev)
	{
	struct rpmsg_device *rpdev = to_rpmsg_device(dev);

	kfree(rpdev);
	}

	int rpmsg_register_device(struct rpmsg_device *rpdev)
	{
	struct device *dev = &rpdev->dev;
	int ret;

	dev_set_name(&rpdev->dev, "%s:%s",
	dev_name(dev->parent), rpdev->id.name);

	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 ret;
	}
	EXPORT_SYMBOL(rpmsg_register_device);

	/*
	* find an existing channel using its name + address properties,
	* and destroy it
	*/
	int rpmsg_unregister_device(struct device *parent,
	struct rpmsg_channel_info *chinfo)
	{
	struct device *dev;

	dev = rpmsg_find_device(parent, chinfo);
	if (!dev)
	return -EINVAL;

	device_unregister(dev);

	put_device(dev);

	return 0;
	}
	EXPORT_SYMBOL(rpmsg_unregister_device);

	/**
	* __register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
	* @rpdrv: pointer to a struct rpmsg_driver
	* @owner: owning module/driver
	*
	* Returns 0 on success, and an appropriate error value on failure.
	*/
	int __register_rpmsg_driver(struct rpmsg_driver rpdrv, struct module owner)
	{
	rpdrv->drv.bus = &rpmsg_bus;
	rpdrv->drv.owner = owner;
	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 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;
	}
	postcore_initcall(rpmsg_init);

	static void __exit rpmsg_fini(void)
	{
	bus_unregister(&rpmsg_bus);
	}
	module_exit(rpmsg_fini);

	MODULE_DESCRIPTION("remote processor messaging bus");
	MODULE_LICENSE("GPL v2");