drivers/rpmsg/mtk_rpmsg.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 //
 // Copyright 2019 Google LLC.

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/remoteproc.h>
 #include <linux/rpmsg/mtk_rpmsg.h>
 #include <linux/workqueue.h>

 #include "rpmsg_internal.h"

 struct mtk_rpmsg_rproc_subdev {
 	struct platform_device *pdev;
 	struct mtk_rpmsg_info *info;
 	struct rpmsg_endpoint *ns_ept;
 	struct rproc_subdev subdev;

 	struct work_struct register_work;
 	struct list_head channels;
 	struct mutex channels_lock;
 };

 #define to_mtk_subdev(d) container_of(d, struct mtk_rpmsg_rproc_subdev, subdev)

 struct mtk_rpmsg_channel_info {
 	struct rpmsg_channel_info info;
 	bool registered;
 	struct list_head list;
 };

 /**
  * 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
  *
  * This message is sent across to publish a new service. When we receive these
  * messages, an appropriate rpmsg channel (i.e device) is created. In turn, the
  * ->probe() 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;
 } __packed;

 struct mtk_rpmsg_device {
 	struct rpmsg_device rpdev;
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev;
 };

 struct mtk_rpmsg_endpoint {
 	struct rpmsg_endpoint ept;
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev;
 };

 #define to_mtk_rpmsg_device(r) container_of(r, struct mtk_rpmsg_device, rpdev)
 #define to_mtk_rpmsg_endpoint(r) container_of(r, struct mtk_rpmsg_endpoint, ept)

 static const struct rpmsg_endpoint_ops mtk_rpmsg_endpoint_ops;

 static void __mtk_ept_release(struct kref *kref)
 {
 	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
 						  refcount);
 	kfree(to_mtk_rpmsg_endpoint(ept));
 }

 static void mtk_rpmsg_ipi_handler(void *data, unsigned int len, void *priv)
 {
 	struct mtk_rpmsg_endpoint *mept = priv;
 	struct rpmsg_endpoint *ept = &mept->ept;
 	int ret;

 	ret = (*ept->cb)(ept->rpdev, data, len, ept->priv, ept->addr);
 	if (ret)
 		dev_warn(&ept->rpdev->dev, "rpmsg handler return error = %d",
 			 ret);
 }

 static struct rpmsg_endpoint *
 __mtk_create_ept(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
 		 struct rpmsg_device *rpdev, rpmsg_rx_cb_t cb, void *priv,
 		 u32 id)
 {
 	struct mtk_rpmsg_endpoint *mept;
 	struct rpmsg_endpoint *ept;
 	struct platform_device *pdev = mtk_subdev->pdev;
 	int ret;

 	mept = kzalloc(sizeof(*mept), GFP_KERNEL);
 	if (!mept)
 		return NULL;
 	mept->mtk_subdev = mtk_subdev;

 	ept = &mept->ept;
 	kref_init(&ept->refcount);

 	ept->rpdev = rpdev;
 	ept->cb = cb;
 	ept->priv = priv;
 	ept->ops = &mtk_rpmsg_endpoint_ops;
 	ept->addr = id;

 	ret = mtk_subdev->info->register_ipi(pdev, id, mtk_rpmsg_ipi_handler,
 					     mept);
 	if (ret) {
 		dev_err(&pdev->dev, "IPI register failed, id = %d", id);
 		kref_put(&ept->refcount, __mtk_ept_release);
 		return NULL;
 	}

 	return ept;
 }

 static struct rpmsg_endpoint *
 mtk_rpmsg_create_ept(struct rpmsg_device *rpdev, rpmsg_rx_cb_t cb, void *priv,
 		     struct rpmsg_channel_info chinfo)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_device(rpdev)->mtk_subdev;

 	return __mtk_create_ept(mtk_subdev, rpdev, cb, priv, chinfo.src);
 }

 static void mtk_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

 	mtk_subdev->info->unregister_ipi(mtk_subdev->pdev, ept->addr);
 	kref_put(&ept->refcount, __mtk_ept_release);
 }

 static int mtk_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

 	return mtk_subdev->info->send_ipi(mtk_subdev->pdev, ept->addr, data,
 					  len, 0);
 }

 static int mtk_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
 		to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

 	/*
 	 * TODO: This currently is same as mtk_rpmsg_send, and wait until SCP
 	 * received the last command.
 	 */
 	return mtk_subdev->info->send_ipi(mtk_subdev->pdev, ept->addr, data,
 					  len, 0);
 }

 static const struct rpmsg_endpoint_ops mtk_rpmsg_endpoint_ops = {
 	.destroy_ept = mtk_rpmsg_destroy_ept,
 	.send = mtk_rpmsg_send,
 	.trysend = mtk_rpmsg_trysend,
 };

 static void mtk_rpmsg_release_device(struct device *dev)
 {
 	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
 	struct mtk_rpmsg_device *mdev = to_mtk_rpmsg_device(rpdev);

 	kfree(mdev);
 }

 static const struct rpmsg_device_ops mtk_rpmsg_device_ops = {
 	.create_ept = mtk_rpmsg_create_ept,
 };

 static struct device_node *
 mtk_rpmsg_match_device_subnode(struct device_node *node, const char *channel)
 {
 	struct device_node *child;
 	const char *name;
 	int ret;

 	for_each_available_child_of_node(node, child) {
 		ret = of_property_read_string(child, "mtk,rpmsg-name", &name);
 		if (ret)
 			continue;

 		if (strcmp(name, channel) == 0)
 			return child;
 	}

 	return NULL;
 }

 static int mtk_rpmsg_register_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
 				     struct rpmsg_channel_info *info)
 {
 	struct rpmsg_device *rpdev;
 	struct mtk_rpmsg_device *mdev;
 	struct platform_device *pdev = mtk_subdev->pdev;
 	int ret;

 	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
 	if (!mdev)
 		return -ENOMEM;

 	mdev->mtk_subdev = mtk_subdev;

 	rpdev = &mdev->rpdev;
 	rpdev->ops = &mtk_rpmsg_device_ops;
 	rpdev->src = info->src;
 	rpdev->dst = info->dst;
 	strscpy(rpdev->id.name, info->name, RPMSG_NAME_SIZE);

 	rpdev->dev.of_node =
 		mtk_rpmsg_match_device_subnode(pdev->dev.of_node, info->name);
 	rpdev->dev.parent = &pdev->dev;
 	rpdev->dev.release = mtk_rpmsg_release_device;

 	ret = rpmsg_register_device(rpdev);
 	if (ret) {
 		kfree(mdev);
 		return ret;
 	}

 	return 0;
 }

 static void mtk_register_device_work_function(struct work_struct *register_work)
 {
 	struct mtk_rpmsg_rproc_subdev *subdev = container_of(
 		register_work, struct mtk_rpmsg_rproc_subdev, register_work);
 	struct platform_device *pdev = subdev->pdev;
 	struct mtk_rpmsg_channel_info *info;
 	int ret;

 	mutex_lock(&subdev->channels_lock);
 	list_for_each_entry(info, &subdev->channels, list) {
 		if (info->registered)
 			continue;

 		ret = mtk_rpmsg_register_device(subdev, &info->info);
 		if (ret) {
 			dev_err(&pdev->dev, "Can't create rpmsg_device\n");
 			continue;
 		}

 		info->registered = true;
 	}
 	mutex_unlock(&subdev->channels_lock);
 }

 static int mtk_rpmsg_create_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
 				   char *name, u32 addr)
 {
 	struct mtk_rpmsg_channel_info *info;

 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;

 	strscpy(info->info.name, name, RPMSG_NAME_SIZE);
 	info->info.src = addr;
 	info->info.dst = RPMSG_ADDR_ANY;
 	mutex_lock(&mtk_subdev->channels_lock);
 	list_add(&info->list, &mtk_subdev->channels);
 	mutex_unlock(&mtk_subdev->channels_lock);

 	schedule_work(&mtk_subdev->register_work);
 	return 0;
 }

 static int mtk_rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
 			   void *priv, u32 src)
 {
 	struct rpmsg_ns_msg *msg = data;
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev = priv;
 	struct device *dev = &mtk_subdev->pdev->dev;

 	int ret;

 	if (len != sizeof(*msg)) {
 		dev_err(dev, "malformed ns msg (%d)\n", len);
 		return -EINVAL;
 	}

 	/*
 	 * 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 -EINVAL;
 	}

 	/* don't trust the remote processor for null terminating the name */
 	msg->name[RPMSG_NAME_SIZE - 1] = '\0';

 	dev_info(dev, "creating channel %s addr 0x%x\n", msg->name, msg->addr);

 	ret = mtk_rpmsg_create_device(mtk_subdev, msg->name, msg->addr);
 	if (ret) {
 		dev_err(dev, "create rpmsg device failed\n");
 		return ret;
 	}

 	return 0;
 }

 static int mtk_rpmsg_prepare(struct rproc_subdev *subdev)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

 	/* a dedicated endpoint handles the name service msgs */
 	if (mtk_subdev->info->ns_ipi_id >= 0) {
 		mtk_subdev->ns_ept =
 			__mtk_create_ept(mtk_subdev, NULL, mtk_rpmsg_ns_cb,
 					 mtk_subdev,
 					 mtk_subdev->info->ns_ipi_id);
 		if (!mtk_subdev->ns_ept) {
 			dev_err(&mtk_subdev->pdev->dev,
 				"failed to create name service endpoint\n");
 			return -ENOMEM;
 		}
 	}

 	return 0;
 }

 static void mtk_rpmsg_unprepare(struct rproc_subdev *subdev)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

 	if (mtk_subdev->ns_ept) {
 		mtk_rpmsg_destroy_ept(mtk_subdev->ns_ept);
 		mtk_subdev->ns_ept = NULL;
 	}
 }

 static void mtk_rpmsg_stop(struct rproc_subdev *subdev, bool crashed)
 {
 	struct mtk_rpmsg_channel_info *info, *next;
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);
 	struct device *dev = &mtk_subdev->pdev->dev;

 	/*
 	 * Destroy the name service endpoint here, to avoid new channel being
 	 * created after the rpmsg_unregister_device loop below.
 	 */
 	if (mtk_subdev->ns_ept) {
 		mtk_rpmsg_destroy_ept(mtk_subdev->ns_ept);
 		mtk_subdev->ns_ept = NULL;
 	}

 	cancel_work_sync(&mtk_subdev->register_work);

 	mutex_lock(&mtk_subdev->channels_lock);
 	list_for_each_entry(info, &mtk_subdev->channels, list) {
 		if (!info->registered)
 			continue;
 		if (rpmsg_unregister_device(dev, &info->info)) {
 			dev_warn(
 				dev,
 				"rpmsg_unregister_device failed for %s.%d.%d\n",
 				info->info.name, info->info.src,
 				info->info.dst);
 		}
 	}

 	list_for_each_entry_safe(info, next,
 				 &mtk_subdev->channels, list) {
 		list_del(&info->list);
 		kfree(info);
 	}
 	mutex_unlock(&mtk_subdev->channels_lock);
 }

 struct rproc_subdev *
 mtk_rpmsg_create_rproc_subdev(struct platform_device *pdev,
 			      struct mtk_rpmsg_info *info)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev;

 	mtk_subdev = kzalloc(sizeof(*mtk_subdev), GFP_KERNEL);
 	if (!mtk_subdev)
 		return NULL;

 	mtk_subdev->pdev = pdev;
 	mtk_subdev->subdev.prepare = mtk_rpmsg_prepare;
 	mtk_subdev->subdev.stop = mtk_rpmsg_stop;
 	mtk_subdev->subdev.unprepare = mtk_rpmsg_unprepare;
 	mtk_subdev->info = info;
 	INIT_LIST_HEAD(&mtk_subdev->channels);
 	INIT_WORK(&mtk_subdev->register_work,
 		  mtk_register_device_work_function);
 	mutex_init(&mtk_subdev->channels_lock);

 	return &mtk_subdev->subdev;
 }
 EXPORT_SYMBOL_GPL(mtk_rpmsg_create_rproc_subdev);

 void mtk_rpmsg_destroy_rproc_subdev(struct rproc_subdev *subdev)
 {
 	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

 	kfree(mtk_subdev);
 }
 EXPORT_SYMBOL_GPL(mtk_rpmsg_destroy_rproc_subdev);

 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("MediaTek scp rpmsg driver");
	// SPDX-License-Identifier: GPL-2.0
	//
	// Copyright 2019 Google LLC.

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/remoteproc.h>
	#include <linux/rpmsg/mtk_rpmsg.h>
	#include <linux/workqueue.h>

	#include "rpmsg_internal.h"

	struct mtk_rpmsg_rproc_subdev {
	struct platform_device *pdev;
	struct mtk_rpmsg_info *info;
	struct rpmsg_endpoint *ns_ept;
	struct rproc_subdev subdev;

	struct work_struct register_work;
	struct list_head channels;
	struct mutex channels_lock;
	};

	#define to_mtk_subdev(d) container_of(d, struct mtk_rpmsg_rproc_subdev, subdev)

	struct mtk_rpmsg_channel_info {
	struct rpmsg_channel_info info;
	bool registered;
	struct list_head list;
	};

	/**
	* 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
	*
	* This message is sent across to publish a new service. When we receive these
	* messages, an appropriate rpmsg channel (i.e device) is created. In turn, the
	* ->probe() 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;
	} __packed;

	struct mtk_rpmsg_device {
	struct rpmsg_device rpdev;
	struct mtk_rpmsg_rproc_subdev *mtk_subdev;
	};

	struct mtk_rpmsg_endpoint {
	struct rpmsg_endpoint ept;
	struct mtk_rpmsg_rproc_subdev *mtk_subdev;
	};

	#define to_mtk_rpmsg_device(r) container_of(r, struct mtk_rpmsg_device, rpdev)
	#define to_mtk_rpmsg_endpoint(r) container_of(r, struct mtk_rpmsg_endpoint, ept)

	static const struct rpmsg_endpoint_ops mtk_rpmsg_endpoint_ops;

	static void __mtk_ept_release(struct kref *kref)
	{
	struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
	refcount);
	kfree(to_mtk_rpmsg_endpoint(ept));
	}

	static void mtk_rpmsg_ipi_handler(void data, unsigned int len, void priv)
	{
	struct mtk_rpmsg_endpoint *mept = priv;
	struct rpmsg_endpoint *ept = &mept->ept;
	int ret;

	ret = (*ept->cb)(ept->rpdev, data, len, ept->priv, ept->addr);
	if (ret)
	dev_warn(&ept->rpdev->dev, "rpmsg handler return error = %d",
	ret);
	}

	static struct rpmsg_endpoint *
	__mtk_create_ept(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
	struct rpmsg_device rpdev, rpmsg_rx_cb_t cb, void priv,
	u32 id)
	{
	struct mtk_rpmsg_endpoint *mept;
	struct rpmsg_endpoint *ept;
	struct platform_device *pdev = mtk_subdev->pdev;
	int ret;

	mept = kzalloc(sizeof(*mept), GFP_KERNEL);
	if (!mept)
	return NULL;
	mept->mtk_subdev = mtk_subdev;

	ept = &mept->ept;
	kref_init(&ept->refcount);

	ept->rpdev = rpdev;
	ept->cb = cb;
	ept->priv = priv;
	ept->ops = &mtk_rpmsg_endpoint_ops;
	ept->addr = id;

	ret = mtk_subdev->info->register_ipi(pdev, id, mtk_rpmsg_ipi_handler,
	mept);
	if (ret) {
	dev_err(&pdev->dev, "IPI register failed, id = %d", id);
	kref_put(&ept->refcount, __mtk_ept_release);
	return NULL;
	}

	return ept;
	}

	static struct rpmsg_endpoint *
	mtk_rpmsg_create_ept(struct rpmsg_device rpdev, rpmsg_rx_cb_t cb, void priv,
	struct rpmsg_channel_info chinfo)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
	to_mtk_rpmsg_device(rpdev)->mtk_subdev;

	return __mtk_create_ept(mtk_subdev, rpdev, cb, priv, chinfo.src);
	}

	static void mtk_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
	to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

	mtk_subdev->info->unregister_ipi(mtk_subdev->pdev, ept->addr);
	kref_put(&ept->refcount, __mtk_ept_release);
	}

	static int mtk_rpmsg_send(struct rpmsg_endpoint ept, void data, int len)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
	to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

	return mtk_subdev->info->send_ipi(mtk_subdev->pdev, ept->addr, data,
	len, 0);
	}

	static int mtk_rpmsg_trysend(struct rpmsg_endpoint ept, void data, int len)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev =
	to_mtk_rpmsg_endpoint(ept)->mtk_subdev;

	/*
	* TODO: This currently is same as mtk_rpmsg_send, and wait until SCP
	* received the last command.
	*/
	return mtk_subdev->info->send_ipi(mtk_subdev->pdev, ept->addr, data,
	len, 0);
	}

	static const struct rpmsg_endpoint_ops mtk_rpmsg_endpoint_ops = {
	.destroy_ept = mtk_rpmsg_destroy_ept,
	.send = mtk_rpmsg_send,
	.trysend = mtk_rpmsg_trysend,
	};

	static void mtk_rpmsg_release_device(struct device *dev)
	{
	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
	struct mtk_rpmsg_device *mdev = to_mtk_rpmsg_device(rpdev);

	kfree(mdev);
	}

	static const struct rpmsg_device_ops mtk_rpmsg_device_ops = {
	.create_ept = mtk_rpmsg_create_ept,
	};

	static struct device_node *
	mtk_rpmsg_match_device_subnode(struct device_node node, const char channel)
	{
	struct device_node *child;
	const char *name;
	int ret;

	for_each_available_child_of_node(node, child) {
	ret = of_property_read_string(child, "mtk,rpmsg-name", &name);
	if (ret)
	continue;

	if (strcmp(name, channel) == 0)
	return child;
	}

	return NULL;
	}

	static int mtk_rpmsg_register_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
	struct rpmsg_channel_info *info)
	{
	struct rpmsg_device *rpdev;
	struct mtk_rpmsg_device *mdev;
	struct platform_device *pdev = mtk_subdev->pdev;
	int ret;

	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
	if (!mdev)
	return -ENOMEM;

	mdev->mtk_subdev = mtk_subdev;

	rpdev = &mdev->rpdev;
	rpdev->ops = &mtk_rpmsg_device_ops;
	rpdev->src = info->src;
	rpdev->dst = info->dst;
	strscpy(rpdev->id.name, info->name, RPMSG_NAME_SIZE);

	rpdev->dev.of_node =
	mtk_rpmsg_match_device_subnode(pdev->dev.of_node, info->name);
	rpdev->dev.parent = &pdev->dev;
	rpdev->dev.release = mtk_rpmsg_release_device;

	ret = rpmsg_register_device(rpdev);
	if (ret) {
	kfree(mdev);
	return ret;
	}

	return 0;
	}

	static void mtk_register_device_work_function(struct work_struct *register_work)
	{
	struct mtk_rpmsg_rproc_subdev *subdev = container_of(
	register_work, struct mtk_rpmsg_rproc_subdev, register_work);
	struct platform_device *pdev = subdev->pdev;
	struct mtk_rpmsg_channel_info *info;
	int ret;

	mutex_lock(&subdev->channels_lock);
	list_for_each_entry(info, &subdev->channels, list) {
	if (info->registered)
	continue;

	ret = mtk_rpmsg_register_device(subdev, &info->info);
	if (ret) {
	dev_err(&pdev->dev, "Can't create rpmsg_device\n");
	continue;
	}

	info->registered = true;
	}
	mutex_unlock(&subdev->channels_lock);
	}

	static int mtk_rpmsg_create_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
	char *name, u32 addr)
	{
	struct mtk_rpmsg_channel_info *info;

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;

	strscpy(info->info.name, name, RPMSG_NAME_SIZE);
	info->info.src = addr;
	info->info.dst = RPMSG_ADDR_ANY;
	mutex_lock(&mtk_subdev->channels_lock);
	list_add(&info->list, &mtk_subdev->channels);
	mutex_unlock(&mtk_subdev->channels_lock);

	schedule_work(&mtk_subdev->register_work);
	return 0;
	}

	static int mtk_rpmsg_ns_cb(struct rpmsg_device rpdev, void data, int len,
	void *priv, u32 src)
	{
	struct rpmsg_ns_msg *msg = data;
	struct mtk_rpmsg_rproc_subdev *mtk_subdev = priv;
	struct device *dev = &mtk_subdev->pdev->dev;

	int ret;

	if (len != sizeof(*msg)) {
	dev_err(dev, "malformed ns msg (%d)\n", len);
	return -EINVAL;
	}

	/*
	* 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 -EINVAL;
	}

	/* don't trust the remote processor for null terminating the name */
	msg->name[RPMSG_NAME_SIZE - 1] = '\0';

	dev_info(dev, "creating channel %s addr 0x%x\n", msg->name, msg->addr);

	ret = mtk_rpmsg_create_device(mtk_subdev, msg->name, msg->addr);
	if (ret) {
	dev_err(dev, "create rpmsg device failed\n");
	return ret;
	}

	return 0;
	}

	static int mtk_rpmsg_prepare(struct rproc_subdev *subdev)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

	/* a dedicated endpoint handles the name service msgs */
	if (mtk_subdev->info->ns_ipi_id >= 0) {
	mtk_subdev->ns_ept =
	__mtk_create_ept(mtk_subdev, NULL, mtk_rpmsg_ns_cb,
	mtk_subdev,
	mtk_subdev->info->ns_ipi_id);
	if (!mtk_subdev->ns_ept) {
	dev_err(&mtk_subdev->pdev->dev,
	"failed to create name service endpoint\n");
	return -ENOMEM;
	}
	}

	return 0;
	}

	static void mtk_rpmsg_unprepare(struct rproc_subdev *subdev)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

	if (mtk_subdev->ns_ept) {
	mtk_rpmsg_destroy_ept(mtk_subdev->ns_ept);
	mtk_subdev->ns_ept = NULL;
	}
	}

	static void mtk_rpmsg_stop(struct rproc_subdev *subdev, bool crashed)
	{
	struct mtk_rpmsg_channel_info info, next;
	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);
	struct device *dev = &mtk_subdev->pdev->dev;

	/*
	* Destroy the name service endpoint here, to avoid new channel being
	* created after the rpmsg_unregister_device loop below.
	*/
	if (mtk_subdev->ns_ept) {
	mtk_rpmsg_destroy_ept(mtk_subdev->ns_ept);
	mtk_subdev->ns_ept = NULL;
	}

	cancel_work_sync(&mtk_subdev->register_work);

	mutex_lock(&mtk_subdev->channels_lock);
	list_for_each_entry(info, &mtk_subdev->channels, list) {
	if (!info->registered)
	continue;
	if (rpmsg_unregister_device(dev, &info->info)) {
	dev_warn(
	dev,
	"rpmsg_unregister_device failed for %s.%d.%d\n",
	info->info.name, info->info.src,
	info->info.dst);
	}
	}

	list_for_each_entry_safe(info, next,
	&mtk_subdev->channels, list) {
	list_del(&info->list);
	kfree(info);
	}
	mutex_unlock(&mtk_subdev->channels_lock);
	}

	struct rproc_subdev *
	mtk_rpmsg_create_rproc_subdev(struct platform_device *pdev,
	struct mtk_rpmsg_info *info)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev;

	mtk_subdev = kzalloc(sizeof(*mtk_subdev), GFP_KERNEL);
	if (!mtk_subdev)
	return NULL;

	mtk_subdev->pdev = pdev;
	mtk_subdev->subdev.prepare = mtk_rpmsg_prepare;
	mtk_subdev->subdev.stop = mtk_rpmsg_stop;
	mtk_subdev->subdev.unprepare = mtk_rpmsg_unprepare;
	mtk_subdev->info = info;
	INIT_LIST_HEAD(&mtk_subdev->channels);
	INIT_WORK(&mtk_subdev->register_work,
	mtk_register_device_work_function);
	mutex_init(&mtk_subdev->channels_lock);

	return &mtk_subdev->subdev;
	}
	EXPORT_SYMBOL_GPL(mtk_rpmsg_create_rproc_subdev);

	void mtk_rpmsg_destroy_rproc_subdev(struct rproc_subdev *subdev)
	{
	struct mtk_rpmsg_rproc_subdev *mtk_subdev = to_mtk_subdev(subdev);

	kfree(mtk_subdev);
	}
	EXPORT_SYMBOL_GPL(mtk_rpmsg_destroy_rproc_subdev);

	MODULE_LICENSE("GPL v2");
	MODULE_DESCRIPTION("MediaTek scp rpmsg driver");