WSL2-Linux-Kernel/drivers/media/media-entity.c

/*
 * Media entity
 *
 * Copyright (C) 2010 Nokia Corporation
 *
 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *	     Sakari Ailus <sakari.ailus@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/bitmap.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <media/media-entity.h>
#include <media/media-device.h>

static inline const char *gobj_type(enum media_gobj_type type)
{
	switch (type) {
	case MEDIA_GRAPH_ENTITY:
		return "entity";
	case MEDIA_GRAPH_PAD:
		return "pad";
	case MEDIA_GRAPH_LINK:
		return "link";
	case MEDIA_GRAPH_INTF_DEVNODE:
		return "intf-devnode";
	default:
		return "unknown";
	}
}

static inline const char *intf_type(struct media_interface *intf)
{
	switch (intf->type) {
	case MEDIA_INTF_T_DVB_FE:
		return "frontend";
	case MEDIA_INTF_T_DVB_DEMUX:
		return "demux";
	case MEDIA_INTF_T_DVB_DVR:
		return "DVR";
	case MEDIA_INTF_T_DVB_CA:
		return  "CA";
	case MEDIA_INTF_T_DVB_NET:
		return "dvbnet";
	case MEDIA_INTF_T_V4L_VIDEO:
		return "video";
	case MEDIA_INTF_T_V4L_VBI:
		return "vbi";
	case MEDIA_INTF_T_V4L_RADIO:
		return "radio";
	case MEDIA_INTF_T_V4L_SUBDEV:
		return "v4l2-subdev";
	case MEDIA_INTF_T_V4L_SWRADIO:
		return "swradio";
	case MEDIA_INTF_T_ALSA_PCM_CAPTURE:
		return "pcm-capture";
	case MEDIA_INTF_T_ALSA_PCM_PLAYBACK:
		return "pcm-playback";
	case MEDIA_INTF_T_ALSA_CONTROL:
		return "alsa-control";
	case MEDIA_INTF_T_ALSA_COMPRESS:
		return "compress";
	case MEDIA_INTF_T_ALSA_RAWMIDI:
		return "rawmidi";
	case MEDIA_INTF_T_ALSA_HWDEP:
		return "hwdep";
	case MEDIA_INTF_T_ALSA_SEQUENCER:
		return "sequencer";
	case MEDIA_INTF_T_ALSA_TIMER:
		return "timer";
	default:
		return "unknown-intf";
	}
};

__must_check int __media_entity_enum_init(struct media_entity_enum *ent_enum,
					  int idx_max)
{
	idx_max = ALIGN(idx_max, BITS_PER_LONG);
	ent_enum->bmap = kcalloc(idx_max / BITS_PER_LONG, sizeof(long),
				 GFP_KERNEL);
	if (!ent_enum->bmap)
		return -ENOMEM;

	bitmap_zero(ent_enum->bmap, idx_max);
	ent_enum->idx_max = idx_max;

	return 0;
}
EXPORT_SYMBOL_GPL(__media_entity_enum_init);

void media_entity_enum_cleanup(struct media_entity_enum *ent_enum)
{
	kfree(ent_enum->bmap);
}
EXPORT_SYMBOL_GPL(media_entity_enum_cleanup);

/**
 *  dev_dbg_obj - Prints in debug mode a change on some object
 *
 * @event_name:	Name of the event to report. Could be __func__
 * @gobj:	Pointer to the object
 *
 * Enabled only if DEBUG or CONFIG_DYNAMIC_DEBUG. Otherwise, it
 * won't produce any code.
 */
static void dev_dbg_obj(const char *event_name,  struct media_gobj *gobj)
{
#if defined(DEBUG) || defined (CONFIG_DYNAMIC_DEBUG)
	switch (media_type(gobj)) {
	case MEDIA_GRAPH_ENTITY:
		dev_dbg(gobj->mdev->dev,
			"%s id %u: entity '%s'\n",
			event_name, media_id(gobj),
			gobj_to_entity(gobj)->name);
		break;
	case MEDIA_GRAPH_LINK:
	{
		struct media_link *link = gobj_to_link(gobj);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: %s link id %u ==> id %u\n",
			event_name, media_id(gobj),
			media_type(link->gobj0) == MEDIA_GRAPH_PAD ?
				"data" : "interface",
			media_id(link->gobj0),
			media_id(link->gobj1));
		break;
	}
	case MEDIA_GRAPH_PAD:
	{
		struct media_pad *pad = gobj_to_pad(gobj);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: %s%spad '%s':%d\n",
			event_name, media_id(gobj),
			pad->flags & MEDIA_PAD_FL_SINK   ? "sink " : "",
			pad->flags & MEDIA_PAD_FL_SOURCE ? "source " : "",
			pad->entity->name, pad->index);
		break;
	}
	case MEDIA_GRAPH_INTF_DEVNODE:
	{
		struct media_interface *intf = gobj_to_intf(gobj);
		struct media_intf_devnode *devnode = intf_to_devnode(intf);

		dev_dbg(gobj->mdev->dev,
			"%s id %u: intf_devnode %s - major: %d, minor: %d\n",
			event_name, media_id(gobj),
			intf_type(intf),
			devnode->major, devnode->minor);
		break;
	}
	}
#endif
}

void media_gobj_create(struct media_device *mdev,
			   enum media_gobj_type type,
			   struct media_gobj *gobj)
{
	BUG_ON(!mdev);

	gobj->mdev = mdev;

	/* Create a per-type unique object ID */
	gobj->id = media_gobj_gen_id(type, ++mdev->id);

	switch (type) {
	case MEDIA_GRAPH_ENTITY:
		list_add_tail(&gobj->list, &mdev->entities);
		break;
	case MEDIA_GRAPH_PAD:
		list_add_tail(&gobj->list, &mdev->pads);
		break;
	case MEDIA_GRAPH_LINK:
		list_add_tail(&gobj->list, &mdev->links);
		break;
	case MEDIA_GRAPH_INTF_DEVNODE:
		list_add_tail(&gobj->list, &mdev->interfaces);
		break;
	}

	mdev->topology_version++;

	dev_dbg_obj(__func__, gobj);
}

void media_gobj_destroy(struct media_gobj *gobj)
{
	dev_dbg_obj(__func__, gobj);

	gobj->mdev->topology_version++;

	/* Remove the object from mdev list */
	list_del(&gobj->list);
}

int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
			   struct media_pad *pads)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	unsigned int i;

	entity->num_pads = num_pads;
	entity->pads = pads;

	if (mdev)
		spin_lock(&mdev->lock);

	for (i = 0; i < num_pads; i++) {
		pads[i].entity = entity;
		pads[i].index = i;
		if (mdev)
			media_gobj_create(mdev, MEDIA_GRAPH_PAD,
					&entity->pads[i].graph_obj);
	}

	if (mdev)
		spin_unlock(&mdev->lock);

	return 0;
}
EXPORT_SYMBOL_GPL(media_entity_pads_init);

/* -----------------------------------------------------------------------------
 * Graph traversal
 */

static struct media_entity *
media_entity_other(struct media_entity *entity, struct media_link *link)
{
	if (link->source->entity == entity)
		return link->sink->entity;
	else
		return link->source->entity;
}

/* push an entity to traversal stack */
static void stack_push(struct media_entity_graph *graph,
		       struct media_entity *entity)
{
	if (graph->top == MEDIA_ENTITY_ENUM_MAX_DEPTH - 1) {
		WARN_ON(1);
		return;
	}
	graph->top++;
	graph->stack[graph->top].link = entity->links.next;
	graph->stack[graph->top].entity = entity;
}

static struct media_entity *stack_pop(struct media_entity_graph *graph)
{
	struct media_entity *entity;

	entity = graph->stack[graph->top].entity;
	graph->top--;

	return entity;
}

#define link_top(en)	((en)->stack[(en)->top].link)
#define stack_top(en)	((en)->stack[(en)->top].entity)

/*
 * TODO: Get rid of this.
 */
#define MEDIA_ENTITY_MAX_PADS		512

/**
 * media_entity_graph_walk_init - Allocate resources for graph walk
 * @graph: Media graph structure that will be used to walk the graph
 * @mdev: Media device
 *
 * Reserve resources for graph walk in media device's current
 * state. The memory must be released using
 * media_entity_graph_walk_free().
 *
 * Returns error on failure, zero on success.
 */
__must_check int media_entity_graph_walk_init(
	struct media_entity_graph *graph, struct media_device *mdev)
{
	return media_entity_enum_init(&graph->ent_enum, mdev);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_init);

/**
 * media_entity_graph_walk_cleanup - Release resources related to graph walking
 * @graph: Media graph structure that was used to walk the graph
 */
void media_entity_graph_walk_cleanup(struct media_entity_graph *graph)
{
	media_entity_enum_cleanup(&graph->ent_enum);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_cleanup);

void media_entity_graph_walk_start(struct media_entity_graph *graph,
				   struct media_entity *entity)
{
	media_entity_enum_zero(&graph->ent_enum);
	media_entity_enum_set(&graph->ent_enum, entity);

	graph->top = 0;
	graph->stack[graph->top].entity = NULL;
	stack_push(graph, entity);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_start);

struct media_entity *
media_entity_graph_walk_next(struct media_entity_graph *graph)
{
	if (stack_top(graph) == NULL)
		return NULL;

	/*
	 * Depth first search. Push entity to stack and continue from
	 * top of the stack until no more entities on the level can be
	 * found.
	 */
	while (link_top(graph) != &stack_top(graph)->links) {
		struct media_entity *entity = stack_top(graph);
		struct media_link *link;
		struct media_entity *next;

		link = list_entry(link_top(graph), typeof(*link), list);

		/* The link is not enabled so we do not follow. */
		if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
			link_top(graph) = link_top(graph)->next;
			continue;
		}

		/* Get the entity in the other end of the link . */
		next = media_entity_other(entity, link);

		/* Has the entity already been visited? */
		if (media_entity_enum_test_and_set(&graph->ent_enum, next)) {
			link_top(graph) = link_top(graph)->next;
			continue;
		}

		/* Push the new entity to stack and start over. */
		link_top(graph) = link_top(graph)->next;
		stack_push(graph, next);
	}

	return stack_pop(graph);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_next);

/* -----------------------------------------------------------------------------
 * Pipeline management
 */

__must_check int __media_entity_pipeline_start(struct media_entity *entity,
					       struct media_pipeline *pipe)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	struct media_entity_graph *graph = &pipe->graph;
	struct media_entity *entity_err = entity;
	struct media_link *link;
	int ret;

	if (!pipe->streaming_count++) {
		ret = media_entity_graph_walk_init(&pipe->graph, mdev);
		if (ret)
			goto error_graph_walk_start;
	}

	media_entity_graph_walk_start(&pipe->graph, entity);

	while ((entity = media_entity_graph_walk_next(graph))) {
		DECLARE_BITMAP(active, MEDIA_ENTITY_MAX_PADS);
		DECLARE_BITMAP(has_no_links, MEDIA_ENTITY_MAX_PADS);

		entity->stream_count++;

		if (WARN_ON(entity->pipe && entity->pipe != pipe)) {
			ret = -EBUSY;
			goto error;
		}

		entity->pipe = pipe;

		/* Already streaming --- no need to check. */
		if (entity->stream_count > 1)
			continue;

		if (!entity->ops || !entity->ops->link_validate)
			continue;

		bitmap_zero(active, entity->num_pads);
		bitmap_fill(has_no_links, entity->num_pads);

		list_for_each_entry(link, &entity->links, list) {
			struct media_pad *pad = link->sink->entity == entity
						? link->sink : link->source;

			/* Mark that a pad is connected by a link. */
			bitmap_clear(has_no_links, pad->index, 1);

			/*
			 * Pads that either do not need to connect or
			 * are connected through an enabled link are
			 * fine.
			 */
			if (!(pad->flags & MEDIA_PAD_FL_MUST_CONNECT) ||
			    link->flags & MEDIA_LNK_FL_ENABLED)
				bitmap_set(active, pad->index, 1);

			/*
			 * Link validation will only take place for
			 * sink ends of the link that are enabled.
			 */
			if (link->sink != pad ||
			    !(link->flags & MEDIA_LNK_FL_ENABLED))
				continue;

			ret = entity->ops->link_validate(link);
			if (ret < 0 && ret != -ENOIOCTLCMD) {
				dev_dbg(entity->graph_obj.mdev->dev,
					"link validation failed for \"%s\":%u -> \"%s\":%u, error %d\n",
					link->source->entity->name,
					link->source->index,
					entity->name, link->sink->index, ret);
				goto error;
			}
		}

		/* Either no links or validated links are fine. */
		bitmap_or(active, active, has_no_links, entity->num_pads);

		if (!bitmap_full(active, entity->num_pads)) {
			ret = -EPIPE;
			dev_dbg(entity->graph_obj.mdev->dev,
				"\"%s\":%u must be connected by an enabled link\n",
				entity->name,
				(unsigned)find_first_zero_bit(
					active, entity->num_pads));
			goto error;
		}
	}

	return 0;

error:
	/*
	 * Link validation on graph failed. We revert what we did and
	 * return the error.
	 */
	media_entity_graph_walk_start(graph, entity_err);

	while ((entity_err = media_entity_graph_walk_next(graph))) {
		/* don't let the stream_count go negative */
		if (entity->stream_count > 0) {
			entity_err->stream_count--;
			if (entity_err->stream_count == 0)
				entity_err->pipe = NULL;
		}

		/*
		 * We haven't increased stream_count further than this
		 * so we quit here.
		 */
		if (entity_err == entity)
			break;
	}

error_graph_walk_start:
	if (!--pipe->streaming_count)
		media_entity_graph_walk_cleanup(graph);

	return ret;
}
EXPORT_SYMBOL_GPL(__media_entity_pipeline_start);

__must_check int media_entity_pipeline_start(struct media_entity *entity,
					     struct media_pipeline *pipe)
{
	struct media_device *mdev = entity->graph_obj.mdev;
	int ret;

	mutex_lock(&mdev->graph_mutex);
	ret = __media_entity_pipeline_start(entity, pipe);
	mutex_unlock(&mdev->graph_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(media_entity_pipeline_start);

void __media_entity_pipeline_stop(struct media_entity *entity)
{
	struct media_entity_graph *graph = &entity->pipe->graph;
	struct media_pipeline *pipe = entity->pipe;


	WARN_ON(!pipe->streaming_count);
	media_entity_graph_walk_start(graph, entity);

	while ((entity = media_entity_graph_walk_next(graph))) {
		/* don't let the stream_count go negative */
		if (entity->stream_count > 0) {
			entity->stream_count--;
			if (entity->stream_count == 0)
				entity->pipe = NULL;
		}
	}

	if (!--pipe->streaming_count)
		media_entity_graph_walk_cleanup(graph);

}
EXPORT_SYMBOL_GPL(__media_entity_pipeline_stop);

void media_entity_pipeline_stop(struct media_entity *entity)
{
	struct media_device *mdev = entity->graph_obj.mdev;

	mutex_lock(&mdev->graph_mutex);
	__media_entity_pipeline_stop(entity);
	mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_entity_pipeline_stop);

/* -----------------------------------------------------------------------------
 * Module use count
 */

struct media_entity *media_entity_get(struct media_entity *entity)
{
	if (entity == NULL)
		return NULL;

	if (entity->graph_obj.mdev->dev &&
	    !try_module_get(entity->graph_obj.mdev->dev->driver->owner))
		return NULL;

	return entity;
}
EXPORT_SYMBOL_GPL(media_entity_get);

void media_entity_put(struct media_entity *entity)
{
	if (entity == NULL)
		return;

	if (entity->graph_obj.mdev->dev)
		module_put(entity->graph_obj.mdev->dev->driver->owner);
}
EXPORT_SYMBOL_GPL(media_entity_put);

/* -----------------------------------------------------------------------------
 * Links management
 */

static struct media_link *media_add_link(struct list_head *head)
{
	struct media_link *link;

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

	list_add_tail(&link->list, head);

	return link;
}

static void __media_entity_remove_link(struct media_entity *entity,
				       struct media_link *link)
{
	struct media_link *rlink, *tmp;
	struct media_entity *remote;

	if (link->source->entity == entity)
		remote = link->sink->entity;
	else
		remote = link->source->entity;

	list_for_each_entry_safe(rlink, tmp, &remote->links, list) {
		if (rlink != link->reverse)
			continue;

		if (link->source->entity == entity)
			remote->num_backlinks--;

		/* Remove the remote link */
		list_del(&rlink->list);
		media_gobj_destroy(&rlink->graph_obj);
		kfree(rlink);

		if (--remote->num_links == 0)
			break;
	}
	list_del(&link->list);
	media_gobj_destroy(&link->graph_obj);
	kfree(link);
}

int
media_create_pad_link(struct media_entity *source, u16 source_pad,
			 struct media_entity *sink, u16 sink_pad, u32 flags)
{
	struct media_link *link;
	struct media_link *backlink;

	BUG_ON(source == NULL || sink == NULL);
	BUG_ON(source_pad >= source->num_pads);
	BUG_ON(sink_pad >= sink->num_pads);

	link = media_add_link(&source->links);
	if (link == NULL)
		return -ENOMEM;

	link->source = &source->pads[source_pad];
	link->sink = &sink->pads[sink_pad];
	link->flags = flags & ~MEDIA_LNK_FL_INTERFACE_LINK;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(source->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&link->graph_obj);

	/* Create the backlink. Backlinks are used to help graph traversal and
	 * are not reported to userspace.
	 */
	backlink = media_add_link(&sink->links);
	if (backlink == NULL) {
		__media_entity_remove_link(source, link);
		return -ENOMEM;
	}

	backlink->source = &source->pads[source_pad];
	backlink->sink = &sink->pads[sink_pad];
	backlink->flags = flags;
	backlink->is_backlink = true;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(sink->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&backlink->graph_obj);

	link->reverse = backlink;
	backlink->reverse = link;

	sink->num_backlinks++;
	sink->num_links++;
	source->num_links++;

	return 0;
}
EXPORT_SYMBOL_GPL(media_create_pad_link);

int media_create_pad_links(const struct media_device *mdev,
			   const u32 source_function,
			   struct media_entity *source,
			   const u16 source_pad,
			   const u32 sink_function,
			   struct media_entity *sink,
			   const u16 sink_pad,
			   u32 flags,
			   const bool allow_both_undefined)
{
	struct media_entity *entity;
	unsigned function;
	int ret;

	/* Trivial case: 1:1 relation */
	if (source && sink)
		return media_create_pad_link(source, source_pad,
					     sink, sink_pad, flags);

	/* Worse case scenario: n:n relation */
	if (!source && !sink) {
		if (!allow_both_undefined)
			return 0;
		media_device_for_each_entity(source, mdev) {
			if (source->function != source_function)
				continue;
			media_device_for_each_entity(sink, mdev) {
				if (sink->function != sink_function)
					continue;
				ret = media_create_pad_link(source, source_pad,
							    sink, sink_pad,
							    flags);
				if (ret)
					return ret;
				flags &= ~(MEDIA_LNK_FL_ENABLED |
					   MEDIA_LNK_FL_IMMUTABLE);
			}
		}
		return 0;
	}

	/* Handle 1:n and n:1 cases */
	if (source)
		function = sink_function;
	else
		function = source_function;

	media_device_for_each_entity(entity, mdev) {
		if (entity->function != function)
			continue;

		if (source)
			ret = media_create_pad_link(source, source_pad,
						    entity, sink_pad, flags);
		else
			ret = media_create_pad_link(entity, source_pad,
						    sink, sink_pad, flags);
		if (ret)
			return ret;
		flags &= ~(MEDIA_LNK_FL_ENABLED | MEDIA_LNK_FL_IMMUTABLE);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(media_create_pad_links);

void __media_entity_remove_links(struct media_entity *entity)
{
	struct media_link *link, *tmp;

	list_for_each_entry_safe(link, tmp, &entity->links, list)
		__media_entity_remove_link(entity, link);

	entity->num_links = 0;
	entity->num_backlinks = 0;
}
EXPORT_SYMBOL_GPL(__media_entity_remove_links);

void media_entity_remove_links(struct media_entity *entity)
{
	struct media_device *mdev = entity->graph_obj.mdev;

	/* Do nothing if the entity is not registered. */
	if (mdev == NULL)
		return;

	spin_lock(&mdev->lock);
	__media_entity_remove_links(entity);
	spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_entity_remove_links);

static int __media_entity_setup_link_notify(struct media_link *link, u32 flags)
{
	int ret;

	/* Notify both entities. */
	ret = media_entity_call(link->source->entity, link_setup,
				link->source, link->sink, flags);
	if (ret < 0 && ret != -ENOIOCTLCMD)
		return ret;

	ret = media_entity_call(link->sink->entity, link_setup,
				link->sink, link->source, flags);
	if (ret < 0 && ret != -ENOIOCTLCMD) {
		media_entity_call(link->source->entity, link_setup,
				  link->source, link->sink, link->flags);
		return ret;
	}

	link->flags = flags;
	link->reverse->flags = link->flags;

	return 0;
}

int __media_entity_setup_link(struct media_link *link, u32 flags)
{
	const u32 mask = MEDIA_LNK_FL_ENABLED;
	struct media_device *mdev;
	struct media_entity *source, *sink;
	int ret = -EBUSY;

	if (link == NULL)
		return -EINVAL;

	/* The non-modifiable link flags must not be modified. */
	if ((link->flags & ~mask) != (flags & ~mask))
		return -EINVAL;

	if (link->flags & MEDIA_LNK_FL_IMMUTABLE)
		return link->flags == flags ? 0 : -EINVAL;

	if (link->flags == flags)
		return 0;

	source = link->source->entity;
	sink = link->sink->entity;

	if (!(link->flags & MEDIA_LNK_FL_DYNAMIC) &&
	    (source->stream_count || sink->stream_count))
		return -EBUSY;

	mdev = source->graph_obj.mdev;

	if (mdev->link_notify) {
		ret = mdev->link_notify(link, flags,
					MEDIA_DEV_NOTIFY_PRE_LINK_CH);
		if (ret < 0)
			return ret;
	}

	ret = __media_entity_setup_link_notify(link, flags);

	if (mdev->link_notify)
		mdev->link_notify(link, flags, MEDIA_DEV_NOTIFY_POST_LINK_CH);

	return ret;
}
EXPORT_SYMBOL_GPL(__media_entity_setup_link);

int media_entity_setup_link(struct media_link *link, u32 flags)
{
	int ret;

	mutex_lock(&link->graph_obj.mdev->graph_mutex);
	ret = __media_entity_setup_link(link, flags);
	mutex_unlock(&link->graph_obj.mdev->graph_mutex);

	return ret;
}
EXPORT_SYMBOL_GPL(media_entity_setup_link);

struct media_link *
media_entity_find_link(struct media_pad *source, struct media_pad *sink)
{
	struct media_link *link;

	list_for_each_entry(link, &source->entity->links, list) {
		if (link->source->entity == source->entity &&
		    link->source->index == source->index &&
		    link->sink->entity == sink->entity &&
		    link->sink->index == sink->index)
			return link;
	}

	return NULL;
}
EXPORT_SYMBOL_GPL(media_entity_find_link);

struct media_pad *media_entity_remote_pad(struct media_pad *pad)
{
	struct media_link *link;

	list_for_each_entry(link, &pad->entity->links, list) {
		if (!(link->flags & MEDIA_LNK_FL_ENABLED))
			continue;

		if (link->source == pad)
			return link->sink;

		if (link->sink == pad)
			return link->source;
	}

	return NULL;

}
EXPORT_SYMBOL_GPL(media_entity_remote_pad);

static void media_interface_init(struct media_device *mdev,
				 struct media_interface *intf,
				 u32 gobj_type,
				 u32 intf_type, u32 flags)
{
	intf->type = intf_type;
	intf->flags = flags;
	INIT_LIST_HEAD(&intf->links);

	media_gobj_create(mdev, gobj_type, &intf->graph_obj);
}

/* Functions related to the media interface via device nodes */

struct media_intf_devnode *media_devnode_create(struct media_device *mdev,
						u32 type, u32 flags,
						u32 major, u32 minor)
{
	struct media_intf_devnode *devnode;

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

	devnode->major = major;
	devnode->minor = minor;

	media_interface_init(mdev, &devnode->intf, MEDIA_GRAPH_INTF_DEVNODE,
			     type, flags);

	return devnode;
}
EXPORT_SYMBOL_GPL(media_devnode_create);

void media_devnode_remove(struct media_intf_devnode *devnode)
{
	media_remove_intf_links(&devnode->intf);
	media_gobj_destroy(&devnode->intf.graph_obj);
	kfree(devnode);
}
EXPORT_SYMBOL_GPL(media_devnode_remove);

struct media_link *media_create_intf_link(struct media_entity *entity,
					    struct media_interface *intf,
					    u32 flags)
{
	struct media_link *link;

	link = media_add_link(&intf->links);
	if (link == NULL)
		return NULL;

	link->intf = intf;
	link->entity = entity;
	link->flags = flags | MEDIA_LNK_FL_INTERFACE_LINK;

	/* Initialize graph object embedded at the new link */
	media_gobj_create(intf->graph_obj.mdev, MEDIA_GRAPH_LINK,
			&link->graph_obj);

	return link;
}
EXPORT_SYMBOL_GPL(media_create_intf_link);

void __media_remove_intf_link(struct media_link *link)
{
	list_del(&link->list);
	media_gobj_destroy(&link->graph_obj);
	kfree(link);
}
EXPORT_SYMBOL_GPL(__media_remove_intf_link);

void media_remove_intf_link(struct media_link *link)
{
	struct media_device *mdev = link->graph_obj.mdev;

	/* Do nothing if the intf is not registered. */
	if (mdev == NULL)
		return;

	spin_lock(&mdev->lock);
	__media_remove_intf_link(link);
	spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_remove_intf_link);

void __media_remove_intf_links(struct media_interface *intf)
{
	struct media_link *link, *tmp;

	list_for_each_entry_safe(link, tmp, &intf->links, list)
		__media_remove_intf_link(link);

}
EXPORT_SYMBOL_GPL(__media_remove_intf_links);

void media_remove_intf_links(struct media_interface *intf)
{
	struct media_device *mdev = intf->graph_obj.mdev;

	/* Do nothing if the intf is not registered. */
	if (mdev == NULL)
		return;

	spin_lock(&mdev->lock);
	__media_remove_intf_links(intf);
	spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_remove_intf_links);