drivers/media/v4l2-core/v4l2-mc.c - arm/linux - Git at Google

 /*
  * Media Controller ancillary functions
  *
  * Copyright (c) 2016 Mauro Carvalho Chehab <mchehab@kernel.org>
  * Copyright (C) 2016 Shuah Khan <shuahkh@osg.samsung.com>
  * Copyright (C) 2006-2010 Nokia Corporation
  * Copyright (c) 2016 Intel Corporation.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  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/module.h>
 #include <linux/pci.h>
 #include <linux/usb.h>
 #include <media/media-device.h>
 #include <media/media-entity.h>
 #include <media/v4l2-fh.h>
 #include <media/v4l2-mc.h>
 #include <media/v4l2-subdev.h>
 #include <media/media-device.h>
 #include <media/v4l2-mc.h>
 #include <media/videobuf2-core.h>

 int v4l2_mc_create_media_graph(struct media_device *mdev)

 {
 	struct media_entity *entity;
 	struct media_entity *if_vid = NULL, *if_aud = NULL;
 	struct media_entity *tuner = NULL, *decoder = NULL;
 	struct media_entity *io_v4l = NULL, *io_vbi = NULL, *io_swradio = NULL;
 	bool is_webcam = false;
 	u32 flags;
 	int ret;

 	if (!mdev)
 		return 0;

 	media_device_for_each_entity(entity, mdev) {
 		switch (entity->function) {
 		case MEDIA_ENT_F_IF_VID_DECODER:
 			if_vid = entity;
 			break;
 		case MEDIA_ENT_F_IF_AUD_DECODER:
 			if_aud = entity;
 			break;
 		case MEDIA_ENT_F_TUNER:
 			tuner = entity;
 			break;
 		case MEDIA_ENT_F_ATV_DECODER:
 			decoder = entity;
 			break;
 		case MEDIA_ENT_F_IO_V4L:
 			io_v4l = entity;
 			break;
 		case MEDIA_ENT_F_IO_VBI:
 			io_vbi = entity;
 			break;
 		case MEDIA_ENT_F_IO_SWRADIO:
 			io_swradio = entity;
 			break;
 		case MEDIA_ENT_F_CAM_SENSOR:
 			is_webcam = true;
 			break;
 		}
 	}

 	/* It should have at least one I/O entity */
 	if (!io_v4l && !io_vbi && !io_swradio)
 		return -EINVAL;

 	/*
 	 * Here, webcams are modelled on a very simple way: the sensor is
 	 * connected directly to the I/O entity. All dirty details, like
 	 * scaler and crop HW are hidden. While such mapping is not enough
 	 * for mc-centric hardware, it is enough for v4l2 interface centric
 	 * PC-consumer's hardware.
 	 */
 	if (is_webcam) {
 		if (!io_v4l)
 			return -EINVAL;

 		media_device_for_each_entity(entity, mdev) {
 			if (entity->function != MEDIA_ENT_F_CAM_SENSOR)
 				continue;
 			ret = media_create_pad_link(entity, 0,
 						    io_v4l, 0,
 						    MEDIA_LNK_FL_ENABLED);
 			if (ret)
 				return ret;
 		}
 		if (!decoder)
 			return 0;
 	}

 	/* The device isn't a webcam. So, it should have a decoder */
 	if (!decoder)
 		return -EINVAL;

 	/* Link the tuner and IF video output pads */
 	if (tuner) {
 		if (if_vid) {
 			ret = media_create_pad_link(tuner, TUNER_PAD_OUTPUT,
 						    if_vid,
 						    IF_VID_DEC_PAD_IF_INPUT,
 						    MEDIA_LNK_FL_ENABLED);
 			if (ret)
 				return ret;
 			ret = media_create_pad_link(if_vid, IF_VID_DEC_PAD_OUT,
 						decoder, DEMOD_PAD_IF_INPUT,
 						MEDIA_LNK_FL_ENABLED);
 			if (ret)
 				return ret;
 		} else {
 			ret = media_create_pad_link(tuner, TUNER_PAD_OUTPUT,
 						decoder, DEMOD_PAD_IF_INPUT,
 						MEDIA_LNK_FL_ENABLED);
 			if (ret)
 				return ret;
 		}

 		if (if_aud) {
 			ret = media_create_pad_link(tuner, TUNER_PAD_AUD_OUT,
 						    if_aud,
 						    IF_AUD_DEC_PAD_IF_INPUT,
 						    MEDIA_LNK_FL_ENABLED);
 			if (ret)
 				return ret;
 		} else {
 			if_aud = tuner;
 		}

 	}

 	/* Create demod to V4L, VBI and SDR radio links */
 	if (io_v4l) {
 		ret = media_create_pad_link(decoder, DEMOD_PAD_VID_OUT,
 					io_v4l, 0,
 					MEDIA_LNK_FL_ENABLED);
 		if (ret)
 			return ret;
 	}

 	if (io_swradio) {
 		ret = media_create_pad_link(decoder, DEMOD_PAD_VID_OUT,
 					io_swradio, 0,
 					MEDIA_LNK_FL_ENABLED);
 		if (ret)
 			return ret;
 	}

 	if (io_vbi) {
 		ret = media_create_pad_link(decoder, DEMOD_PAD_VBI_OUT,
 					    io_vbi, 0,
 					    MEDIA_LNK_FL_ENABLED);
 		if (ret)
 			return ret;
 	}

 	/* Create links for the media connectors */
 	flags = MEDIA_LNK_FL_ENABLED;
 	media_device_for_each_entity(entity, mdev) {
 		switch (entity->function) {
 		case MEDIA_ENT_F_CONN_RF:
 			if (!tuner)
 				continue;

 			ret = media_create_pad_link(entity, 0, tuner,
 						    TUNER_PAD_RF_INPUT,
 						    flags);
 			break;
 		case MEDIA_ENT_F_CONN_SVIDEO:
 		case MEDIA_ENT_F_CONN_COMPOSITE:
 			ret = media_create_pad_link(entity, 0, decoder,
 						    DEMOD_PAD_IF_INPUT,
 						    flags);
 			break;
 		default:
 			continue;
 		}
 		if (ret)
 			return ret;

 		flags = 0;
 	}

 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_mc_create_media_graph);

 int v4l_enable_media_source(struct video_device *vdev)
 {
 	struct media_device *mdev = vdev->entity.graph_obj.mdev;
 	int ret = 0, err;

 	if (!mdev)
 		return 0;

 	mutex_lock(&mdev->graph_mutex);
 	if (!mdev->enable_source)
 		goto end;
 	err = mdev->enable_source(&vdev->entity, &vdev->pipe);
 	if (err)
 		ret = -EBUSY;
 end:
 	mutex_unlock(&mdev->graph_mutex);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(v4l_enable_media_source);

 void v4l_disable_media_source(struct video_device *vdev)
 {
 	struct media_device *mdev = vdev->entity.graph_obj.mdev;

 	if (mdev) {
 		mutex_lock(&mdev->graph_mutex);
 		if (mdev->disable_source)
 			mdev->disable_source(&vdev->entity);
 		mutex_unlock(&mdev->graph_mutex);
 	}
 }
 EXPORT_SYMBOL_GPL(v4l_disable_media_source);

 int v4l_vb2q_enable_media_source(struct vb2_queue *q)
 {
 	struct v4l2_fh *fh = q->owner;

 	if (fh && fh->vdev)
 		return v4l_enable_media_source(fh->vdev);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l_vb2q_enable_media_source);

 /* -----------------------------------------------------------------------------
  * Pipeline power management
  *
  * Entities must be powered up when part of a pipeline that contains at least
  * one open video device node.
  *
  * To achieve this use the entity use_count field to track the number of users.
  * For entities corresponding to video device nodes the use_count field stores
  * the users count of the node. For entities corresponding to subdevs the
  * use_count field stores the total number of users of all video device nodes
  * in the pipeline.
  *
  * The v4l2_pipeline_pm_use() function must be called in the open() and
  * close() handlers of video device nodes. It increments or decrements the use
  * count of all subdev entities in the pipeline.
  *
  * To react to link management on powered pipelines, the link setup notification
  * callback updates the use count of all entities in the source and sink sides
  * of the link.
  */

 /*
  * pipeline_pm_use_count - Count the number of users of a pipeline
  * @entity: The entity
  *
  * Return the total number of users of all video device nodes in the pipeline.
  */
 static int pipeline_pm_use_count(struct media_entity *entity,
 	struct media_graph *graph)
 {
 	int use = 0;

 	media_graph_walk_start(graph, entity);

 	while ((entity = media_graph_walk_next(graph))) {
 		if (is_media_entity_v4l2_video_device(entity))
 			use += entity->use_count;
 	}

 	return use;
 }

 /*
  * pipeline_pm_power_one - Apply power change to an entity
  * @entity: The entity
  * @change: Use count change
  *
  * Change the entity use count by @change. If the entity is a subdev update its
  * power state by calling the core::s_power operation when the use count goes
  * from 0 to != 0 or from != 0 to 0.
  *
  * Return 0 on success or a negative error code on failure.
  */
 static int pipeline_pm_power_one(struct media_entity *entity, int change)
 {
 	struct v4l2_subdev *subdev;
 	int ret;

 	subdev = is_media_entity_v4l2_subdev(entity)
 	       ? media_entity_to_v4l2_subdev(entity) : NULL;

 	if (entity->use_count == 0 && change > 0 && subdev != NULL) {
 		ret = v4l2_subdev_call(subdev, core, s_power, 1);
 		if (ret < 0 && ret != -ENOIOCTLCMD)
 			return ret;
 	}

 	entity->use_count += change;
 	WARN_ON(entity->use_count < 0);

 	if (entity->use_count == 0 && change < 0 && subdev != NULL)
 		v4l2_subdev_call(subdev, core, s_power, 0);

 	return 0;
 }

 /*
  * pipeline_pm_power - Apply power change to all entities in a pipeline
  * @entity: The entity
  * @change: Use count change
  *
  * Walk the pipeline to update the use count and the power state of all non-node
  * entities.
  *
  * Return 0 on success or a negative error code on failure.
  */
 static int pipeline_pm_power(struct media_entity *entity, int change,
 	struct media_graph *graph)
 {
 	struct media_entity *first = entity;
 	int ret = 0;

 	if (!change)
 		return 0;

 	media_graph_walk_start(graph, entity);

 	while (!ret && (entity = media_graph_walk_next(graph)))
 		if (is_media_entity_v4l2_subdev(entity))
 			ret = pipeline_pm_power_one(entity, change);

 	if (!ret)
 		return ret;

 	media_graph_walk_start(graph, first);

 	while ((first = media_graph_walk_next(graph))
 	       && first != entity)
 		if (is_media_entity_v4l2_subdev(first))
 			pipeline_pm_power_one(first, -change);

 	return ret;
 }

 int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
 {
 	struct media_device *mdev = entity->graph_obj.mdev;
 	int change = use ? 1 : -1;
 	int ret;

 	mutex_lock(&mdev->graph_mutex);

 	/* Apply use count to node. */
 	entity->use_count += change;
 	WARN_ON(entity->use_count < 0);

 	/* Apply power change to connected non-nodes. */
 	ret = pipeline_pm_power(entity, change, &mdev->pm_count_walk);
 	if (ret < 0)
 		entity->use_count -= change;

 	mutex_unlock(&mdev->graph_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_use);

 int v4l2_pipeline_link_notify(struct media_link *link, u32 flags,
 			      unsigned int notification)
 {
 	struct media_graph *graph = &link->graph_obj.mdev->pm_count_walk;
 	struct media_entity *source = link->source->entity;
 	struct media_entity *sink = link->sink->entity;
 	int source_use;
 	int sink_use;
 	int ret = 0;

 	source_use = pipeline_pm_use_count(source, graph);
 	sink_use = pipeline_pm_use_count(sink, graph);

 	if (notification == MEDIA_DEV_NOTIFY_POST_LINK_CH &&
 	    !(flags & MEDIA_LNK_FL_ENABLED)) {
 		/* Powering off entities is assumed to never fail. */
 		pipeline_pm_power(source, -sink_use, graph);
 		pipeline_pm_power(sink, -source_use, graph);
 		return 0;
 	}

 	if (notification == MEDIA_DEV_NOTIFY_PRE_LINK_CH &&
 		(flags & MEDIA_LNK_FL_ENABLED)) {

 		ret = pipeline_pm_power(source, sink_use, graph);
 		if (ret < 0)
 			return ret;

 		ret = pipeline_pm_power(sink, source_use, graph);
 		if (ret < 0)
 			pipeline_pm_power(source, -sink_use, graph);
 	}

 	return ret;
 }
 EXPORT_SYMBOL_GPL(v4l2_pipeline_link_notify);
	/*
	* Media Controller ancillary functions
	*
	* Copyright (c) 2016 Mauro Carvalho Chehab <mchehab@kernel.org>
	* Copyright (C) 2016 Shuah Khan <shuahkh@osg.samsung.com>
	* Copyright (C) 2006-2010 Nokia Corporation
	* Copyright (c) 2016 Intel Corporation.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* 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/module.h>
	#include <linux/pci.h>
	#include <linux/usb.h>
	#include <media/media-device.h>
	#include <media/media-entity.h>
	#include <media/v4l2-fh.h>
	#include <media/v4l2-mc.h>
	#include <media/v4l2-subdev.h>
	#include <media/media-device.h>
	#include <media/v4l2-mc.h>
	#include <media/videobuf2-core.h>

	int v4l2_mc_create_media_graph(struct media_device *mdev)

	{
	struct media_entity *entity;
	struct media_entity if_vid = NULL, if_aud = NULL;
	struct media_entity tuner = NULL, decoder = NULL;
	struct media_entity io_v4l = NULL, io_vbi = NULL, *io_swradio = NULL;
	bool is_webcam = false;
	u32 flags;
	int ret;

	if (!mdev)
	return 0;

	media_device_for_each_entity(entity, mdev) {
	switch (entity->function) {
	case MEDIA_ENT_F_IF_VID_DECODER:
	if_vid = entity;
	break;
	case MEDIA_ENT_F_IF_AUD_DECODER:
	if_aud = entity;
	break;
	case MEDIA_ENT_F_TUNER:
	tuner = entity;
	break;
	case MEDIA_ENT_F_ATV_DECODER:
	decoder = entity;
	break;
	case MEDIA_ENT_F_IO_V4L:
	io_v4l = entity;
	break;
	case MEDIA_ENT_F_IO_VBI:
	io_vbi = entity;
	break;
	case MEDIA_ENT_F_IO_SWRADIO:
	io_swradio = entity;
	break;
	case MEDIA_ENT_F_CAM_SENSOR:
	is_webcam = true;
	break;
	}
	}

	/* It should have at least one I/O entity */
	if (!io_v4l && !io_vbi && !io_swradio)
	return -EINVAL;

	/*
	* Here, webcams are modelled on a very simple way: the sensor is
	* connected directly to the I/O entity. All dirty details, like
	* scaler and crop HW are hidden. While such mapping is not enough
	* for mc-centric hardware, it is enough for v4l2 interface centric
	* PC-consumer's hardware.
	*/
	if (is_webcam) {
	if (!io_v4l)
	return -EINVAL;

	media_device_for_each_entity(entity, mdev) {
	if (entity->function != MEDIA_ENT_F_CAM_SENSOR)
	continue;
	ret = media_create_pad_link(entity, 0,
	io_v4l, 0,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	}
	if (!decoder)
	return 0;
	}

	/* The device isn't a webcam. So, it should have a decoder */
	if (!decoder)
	return -EINVAL;

	/* Link the tuner and IF video output pads */
	if (tuner) {
	if (if_vid) {
	ret = media_create_pad_link(tuner, TUNER_PAD_OUTPUT,
	if_vid,
	IF_VID_DEC_PAD_IF_INPUT,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	ret = media_create_pad_link(if_vid, IF_VID_DEC_PAD_OUT,
	decoder, DEMOD_PAD_IF_INPUT,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	} else {
	ret = media_create_pad_link(tuner, TUNER_PAD_OUTPUT,
	decoder, DEMOD_PAD_IF_INPUT,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	}

	if (if_aud) {
	ret = media_create_pad_link(tuner, TUNER_PAD_AUD_OUT,
	if_aud,
	IF_AUD_DEC_PAD_IF_INPUT,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	} else {
	if_aud = tuner;
	}

	}

	/* Create demod to V4L, VBI and SDR radio links */
	if (io_v4l) {
	ret = media_create_pad_link(decoder, DEMOD_PAD_VID_OUT,
	io_v4l, 0,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	}

	if (io_swradio) {
	ret = media_create_pad_link(decoder, DEMOD_PAD_VID_OUT,
	io_swradio, 0,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	}

	if (io_vbi) {
	ret = media_create_pad_link(decoder, DEMOD_PAD_VBI_OUT,
	io_vbi, 0,
	MEDIA_LNK_FL_ENABLED);
	if (ret)
	return ret;
	}

	/* Create links for the media connectors */
	flags = MEDIA_LNK_FL_ENABLED;
	media_device_for_each_entity(entity, mdev) {
	switch (entity->function) {
	case MEDIA_ENT_F_CONN_RF:
	if (!tuner)
	continue;

	ret = media_create_pad_link(entity, 0, tuner,
	TUNER_PAD_RF_INPUT,
	flags);
	break;
	case MEDIA_ENT_F_CONN_SVIDEO:
	case MEDIA_ENT_F_CONN_COMPOSITE:
	ret = media_create_pad_link(entity, 0, decoder,
	DEMOD_PAD_IF_INPUT,
	flags);
	break;
	default:
	continue;
	}
	if (ret)
	return ret;

	flags = 0;
	}

	return 0;
	}
	EXPORT_SYMBOL_GPL(v4l2_mc_create_media_graph);

	int v4l_enable_media_source(struct video_device *vdev)
	{
	struct media_device *mdev = vdev->entity.graph_obj.mdev;
	int ret = 0, err;

	if (!mdev)
	return 0;

	mutex_lock(&mdev->graph_mutex);
	if (!mdev->enable_source)
	goto end;
	err = mdev->enable_source(&vdev->entity, &vdev->pipe);
	if (err)
	ret = -EBUSY;
	end:
	mutex_unlock(&mdev->graph_mutex);
	return ret;
	}
	EXPORT_SYMBOL_GPL(v4l_enable_media_source);

	void v4l_disable_media_source(struct video_device *vdev)
	{
	struct media_device *mdev = vdev->entity.graph_obj.mdev;

	if (mdev) {
	mutex_lock(&mdev->graph_mutex);
	if (mdev->disable_source)
	mdev->disable_source(&vdev->entity);
	mutex_unlock(&mdev->graph_mutex);
	}
	}
	EXPORT_SYMBOL_GPL(v4l_disable_media_source);

	int v4l_vb2q_enable_media_source(struct vb2_queue *q)
	{
	struct v4l2_fh *fh = q->owner;

	if (fh && fh->vdev)
	return v4l_enable_media_source(fh->vdev);
	return 0;
	}
	EXPORT_SYMBOL_GPL(v4l_vb2q_enable_media_source);

	/* -----------------------------------------------------------------------------
	* Pipeline power management
	*
	* Entities must be powered up when part of a pipeline that contains at least
	* one open video device node.
	*
	* To achieve this use the entity use_count field to track the number of users.
	* For entities corresponding to video device nodes the use_count field stores
	* the users count of the node. For entities corresponding to subdevs the
	* use_count field stores the total number of users of all video device nodes
	* in the pipeline.
	*
	* The v4l2_pipeline_pm_use() function must be called in the open() and
	* close() handlers of video device nodes. It increments or decrements the use
	* count of all subdev entities in the pipeline.
	*
	* To react to link management on powered pipelines, the link setup notification
	* callback updates the use count of all entities in the source and sink sides
	* of the link.
	*/

	/*
	* pipeline_pm_use_count - Count the number of users of a pipeline
	* @entity: The entity
	*
	* Return the total number of users of all video device nodes in the pipeline.
	*/
	static int pipeline_pm_use_count(struct media_entity *entity,
	struct media_graph *graph)
	{
	int use = 0;

	media_graph_walk_start(graph, entity);

	while ((entity = media_graph_walk_next(graph))) {
	if (is_media_entity_v4l2_video_device(entity))
	use += entity->use_count;
	}

	return use;
	}

	/*
	* pipeline_pm_power_one - Apply power change to an entity
	* @entity: The entity
	* @change: Use count change
	*
	* Change the entity use count by @change. If the entity is a subdev update its
	* power state by calling the core::s_power operation when the use count goes
	* from 0 to != 0 or from != 0 to 0.
	*
	* Return 0 on success or a negative error code on failure.
	*/
	static int pipeline_pm_power_one(struct media_entity *entity, int change)
	{
	struct v4l2_subdev *subdev;
	int ret;

	subdev = is_media_entity_v4l2_subdev(entity)
	? media_entity_to_v4l2_subdev(entity) : NULL;

	if (entity->use_count == 0 && change > 0 && subdev != NULL) {
	ret = v4l2_subdev_call(subdev, core, s_power, 1);
	if (ret < 0 && ret != -ENOIOCTLCMD)
	return ret;
	}

	entity->use_count += change;
	WARN_ON(entity->use_count < 0);

	if (entity->use_count == 0 && change < 0 && subdev != NULL)
	v4l2_subdev_call(subdev, core, s_power, 0);

	return 0;
	}

	/*
	* pipeline_pm_power - Apply power change to all entities in a pipeline
	* @entity: The entity
	* @change: Use count change
	*
	* Walk the pipeline to update the use count and the power state of all non-node
	* entities.
	*
	* Return 0 on success or a negative error code on failure.
	*/
	static int pipeline_pm_power(struct media_entity *entity, int change,
	struct media_graph *graph)
	{
	struct media_entity *first = entity;
	int ret = 0;

	if (!change)
	return 0;

	media_graph_walk_start(graph, entity);

	while (!ret && (entity = media_graph_walk_next(graph)))
	if (is_media_entity_v4l2_subdev(entity))
	ret = pipeline_pm_power_one(entity, change);

	if (!ret)
	return ret;

	media_graph_walk_start(graph, first);

	while ((first = media_graph_walk_next(graph))
	&& first != entity)
	if (is_media_entity_v4l2_subdev(first))
	pipeline_pm_power_one(first, -change);

	return ret;
	}

	int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
	{
	struct media_device *mdev = entity->graph_obj.mdev;
	int change = use ? 1 : -1;
	int ret;

	mutex_lock(&mdev->graph_mutex);

	/* Apply use count to node. */
	entity->use_count += change;
	WARN_ON(entity->use_count < 0);

	/* Apply power change to connected non-nodes. */
	ret = pipeline_pm_power(entity, change, &mdev->pm_count_walk);
	if (ret < 0)
	entity->use_count -= change;

	mutex_unlock(&mdev->graph_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_use);

	int v4l2_pipeline_link_notify(struct media_link *link, u32 flags,
	unsigned int notification)
	{
	struct media_graph *graph = &link->graph_obj.mdev->pm_count_walk;
	struct media_entity *source = link->source->entity;
	struct media_entity *sink = link->sink->entity;
	int source_use;
	int sink_use;
	int ret = 0;

	source_use = pipeline_pm_use_count(source, graph);
	sink_use = pipeline_pm_use_count(sink, graph);

	if (notification == MEDIA_DEV_NOTIFY_POST_LINK_CH &&
	!(flags & MEDIA_LNK_FL_ENABLED)) {
	/* Powering off entities is assumed to never fail. */
	pipeline_pm_power(source, -sink_use, graph);
	pipeline_pm_power(sink, -source_use, graph);
	return 0;
	}

	if (notification == MEDIA_DEV_NOTIFY_PRE_LINK_CH &&
	(flags & MEDIA_LNK_FL_ENABLED)) {

	ret = pipeline_pm_power(source, sink_use, graph);
	if (ret < 0)
	return ret;

	ret = pipeline_pm_power(sink, source_use, graph);
	if (ret < 0)
	pipeline_pm_power(source, -sink_use, graph);
	}

	return ret;
	}
	EXPORT_SYMBOL_GPL(v4l2_pipeline_link_notify);