Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1611 insertions, 0 deletions

diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
new file mode 100644
index 0000000000..83468d4a44
--- /dev/null
+++ b/drivers/media/mc/mc-entity.c
@@ -0,0 +1,1611 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Media entity
+ *
+ * Copyright (C) 2010 Nokia Corporation
+ *
+ * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ *	     Sakari Ailus <sakari.ailus@iki.fi>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/list.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <media/media-entity.h>
+#include <media/media-device.h>
+
+static inline const char *intf_type(struct media_interface *intf)
+{
+	switch (intf->type) {
+	case MEDIA_INTF_T_DVB_FE:
+		return "dvb-frontend";
+	case MEDIA_INTF_T_DVB_DEMUX:
+		return "dvb-demux";
+	case MEDIA_INTF_T_DVB_DVR:
+		return "dvb-dvr";
+	case MEDIA_INTF_T_DVB_CA:
+		return  "dvb-ca";
+	case MEDIA_INTF_T_DVB_NET:
+		return "dvb-net";
+	case MEDIA_INTF_T_V4L_VIDEO:
+		return "v4l-video";
+	case MEDIA_INTF_T_V4L_VBI:
+		return "v4l-vbi";
+	case MEDIA_INTF_T_V4L_RADIO:
+		return "v4l-radio";
+	case MEDIA_INTF_T_V4L_SUBDEV:
+		return "v4l-subdev";
+	case MEDIA_INTF_T_V4L_SWRADIO:
+		return "v4l-swradio";
+	case MEDIA_INTF_T_V4L_TOUCH:
+		return "v4l-touch";
+	default:
+		return "unknown-intf";
+	}
+};
+
+static inline const char *link_type_name(struct media_link *link)
+{
+	switch (link->flags & MEDIA_LNK_FL_LINK_TYPE) {
+	case MEDIA_LNK_FL_DATA_LINK:
+		return "data";
+	case MEDIA_LNK_FL_INTERFACE_LINK:
+		return "interface";
+	case MEDIA_LNK_FL_ANCILLARY_LINK:
+		return "ancillary";
+	default:
+		return "unknown";
+	}
+}
+
+__must_check int media_entity_enum_init(struct media_entity_enum *ent_enum,
+					struct media_device *mdev)
+{
+	int idx_max;
+
+	idx_max = ALIGN(mdev->entity_internal_idx_max + 1, BITS_PER_LONG);
+	ent_enum->bmap = bitmap_zalloc(idx_max, GFP_KERNEL);
+	if (!ent_enum->bmap)
+		return -ENOMEM;
+
+	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)
+{
+	bitmap_free(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), link_type_name(link),
+			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)
+{
+	/* Do nothing if the object is not linked. */
+	if (gobj->mdev == NULL)
+		return;
+
+	dev_dbg_obj(__func__, gobj);
+
+	gobj->mdev->topology_version++;
+
+	/* Remove the object from mdev list */
+	list_del(&gobj->list);
+
+	gobj->mdev = NULL;
+}
+
+/*
+ * TODO: Get rid of this.
+ */
+#define MEDIA_ENTITY_MAX_PADS		512
+
+int media_entity_pads_init(struct media_entity *entity, u16 num_pads,
+			   struct media_pad *pads)
+{
+	struct media_device *mdev = entity->graph_obj.mdev;
+	struct media_pad *iter;
+	unsigned int i = 0;
+
+	if (num_pads >= MEDIA_ENTITY_MAX_PADS)
+		return -E2BIG;
+
+	entity->num_pads = num_pads;
+	entity->pads = pads;
+
+	if (mdev)
+		mutex_lock(&mdev->graph_mutex);
+
+	media_entity_for_each_pad(entity, iter) {
+		iter->entity = entity;
+		iter->index = i++;
+		if (mdev)
+			media_gobj_create(mdev, MEDIA_GRAPH_PAD,
+					  &iter->graph_obj);
+	}
+
+	if (mdev)
+		mutex_unlock(&mdev->graph_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(media_entity_pads_init);
+
+/* -----------------------------------------------------------------------------
+ * Graph traversal
+ */
+
+/**
+ * media_entity_has_pad_interdep - Check interdependency between two pads
+ *
+ * @entity: The entity
+ * @pad0: The first pad index
+ * @pad1: The second pad index
+ *
+ * This function checks the interdependency inside the entity between @pad0
+ * and @pad1. If two pads are interdependent they are part of the same pipeline
+ * and enabling one of the pads means that the other pad will become "locked"
+ * and doesn't allow configuration changes.
+ *
+ * This function uses the &media_entity_operations.has_pad_interdep() operation
+ * to check the dependency inside the entity between @pad0 and @pad1. If the
+ * has_pad_interdep operation is not implemented, all pads of the entity are
+ * considered to be interdependent.
+ *
+ * One of @pad0 and @pad1 must be a sink pad and the other one a source pad.
+ * The function returns false if both pads are sinks or sources.
+ *
+ * The caller must hold entity->graph_obj.mdev->mutex.
+ *
+ * Return: true if the pads are connected internally and false otherwise.
+ */
+static bool media_entity_has_pad_interdep(struct media_entity *entity,
+					  unsigned int pad0, unsigned int pad1)
+{
+	if (pad0 >= entity->num_pads || pad1 >= entity->num_pads)
+		return false;
+
+	if (entity->pads[pad0].flags & entity->pads[pad1].flags &
+	    (MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_SOURCE))
+		return false;
+
+	if (!entity->ops || !entity->ops->has_pad_interdep)
+		return true;
+
+	return entity->ops->has_pad_interdep(entity, pad0, pad1);
+}
+
+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_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_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)
+
+/**
+ * media_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_graph_walk_cleanup().
+ *
+ * Returns error on failure, zero on success.
+ */
+__must_check int media_graph_walk_init(
+	struct media_graph *graph, struct media_device *mdev)
+{
+	return media_entity_enum_init(&graph->ent_enum, mdev);
+}
+EXPORT_SYMBOL_GPL(media_graph_walk_init);
+
+/**
+ * media_graph_walk_cleanup - Release resources related to graph walking
+ * @graph: Media graph structure that was used to walk the graph
+ */
+void media_graph_walk_cleanup(struct media_graph *graph)
+{
+	media_entity_enum_cleanup(&graph->ent_enum);
+}
+EXPORT_SYMBOL_GPL(media_graph_walk_cleanup);
+
+void media_graph_walk_start(struct media_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);
+	dev_dbg(entity->graph_obj.mdev->dev,
+		"begin graph walk at '%s'\n", entity->name);
+}
+EXPORT_SYMBOL_GPL(media_graph_walk_start);
+
+static void media_graph_walk_iter(struct media_graph *graph)
+{
+	struct media_entity *entity = stack_top(graph);
+	struct media_link *link;
+	struct media_entity *next;
+
+	link = list_entry(link_top(graph), typeof(*link), list);
+
+	/* If the link is not a data link, don't follow it */
+	if ((link->flags & MEDIA_LNK_FL_LINK_TYPE) != MEDIA_LNK_FL_DATA_LINK) {
+		link_top(graph) = link_top(graph)->next;
+		return;
+	}
+
+	/* The link is not enabled so we do not follow. */
+	if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
+		link_top(graph) = link_top(graph)->next;
+		dev_dbg(entity->graph_obj.mdev->dev,
+			"walk: skipping disabled link '%s':%u -> '%s':%u\n",
+			link->source->entity->name, link->source->index,
+			link->sink->entity->name, link->sink->index);
+		return;
+	}
+
+	/* Get the entity at 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;
+		dev_dbg(entity->graph_obj.mdev->dev,
+			"walk: skipping entity '%s' (already seen)\n",
+			next->name);
+		return;
+	}
+
+	/* Push the new entity to stack and start over. */
+	link_top(graph) = link_top(graph)->next;
+	stack_push(graph, next);
+	dev_dbg(entity->graph_obj.mdev->dev, "walk: pushing '%s' on stack\n",
+		next->name);
+	lockdep_assert_held(&entity->graph_obj.mdev->graph_mutex);
+}
+
+struct media_entity *media_graph_walk_next(struct media_graph *graph)
+{
+	struct media_entity *entity;
+
+	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)
+		media_graph_walk_iter(graph);
+
+	entity = stack_pop(graph);
+	dev_dbg(entity->graph_obj.mdev->dev,
+		"walk: returning entity '%s'\n", entity->name);
+
+	return entity;
+}
+EXPORT_SYMBOL_GPL(media_graph_walk_next);
+
+/* -----------------------------------------------------------------------------
+ * Pipeline management
+ */
+
+/*
+ * The pipeline traversal stack stores pads that are reached during graph
+ * traversal, with a list of links to be visited to continue the traversal.
+ * When a new pad is reached, an entry is pushed on the top of the stack and
+ * points to the incoming pad and the first link of the entity.
+ *
+ * To find further pads in the pipeline, the traversal algorithm follows
+ * internal pad dependencies in the entity, and then links in the graph. It
+ * does so by iterating over all links of the entity, and following enabled
+ * links that originate from a pad that is internally connected to the incoming
+ * pad, as reported by the media_entity_has_pad_interdep() function.
+ */
+
+/**
+ * struct media_pipeline_walk_entry - Entry in the pipeline traversal stack
+ *
+ * @pad: The media pad being visited
+ * @links: Links left to be visited
+ */
+struct media_pipeline_walk_entry {
+	struct media_pad *pad;
+	struct list_head *links;
+};
+
+/**
+ * struct media_pipeline_walk - State used by the media pipeline traversal
+ *				algorithm
+ *
+ * @mdev: The media device
+ * @stack: Depth-first search stack
+ * @stack.size: Number of allocated entries in @stack.entries
+ * @stack.top: Index of the top stack entry (-1 if the stack is empty)
+ * @stack.entries: Stack entries
+ */
+struct media_pipeline_walk {
+	struct media_device *mdev;
+
+	struct {
+		unsigned int size;
+		int top;
+		struct media_pipeline_walk_entry *entries;
+	} stack;
+};
+
+#define MEDIA_PIPELINE_STACK_GROW_STEP		16
+
+static struct media_pipeline_walk_entry *
+media_pipeline_walk_top(struct media_pipeline_walk *walk)
+{
+	return &walk->stack.entries[walk->stack.top];
+}
+
+static bool media_pipeline_walk_empty(struct media_pipeline_walk *walk)
+{
+	return walk->stack.top == -1;
+}
+
+/* Increase the stack size by MEDIA_PIPELINE_STACK_GROW_STEP elements. */
+static int media_pipeline_walk_resize(struct media_pipeline_walk *walk)
+{
+	struct media_pipeline_walk_entry *entries;
+	unsigned int new_size;
+
+	/* Safety check, to avoid stack overflows in case of bugs. */
+	if (walk->stack.size >= 256)
+		return -E2BIG;
+
+	new_size = walk->stack.size + MEDIA_PIPELINE_STACK_GROW_STEP;
+
+	entries = krealloc(walk->stack.entries,
+			   new_size * sizeof(*walk->stack.entries),
+			   GFP_KERNEL);
+	if (!entries)
+		return -ENOMEM;
+
+	walk->stack.entries = entries;
+	walk->stack.size = new_size;
+
+	return 0;
+}
+
+/* Push a new entry on the stack. */
+static int media_pipeline_walk_push(struct media_pipeline_walk *walk,
+				    struct media_pad *pad)
+{
+	struct media_pipeline_walk_entry *entry;
+	int ret;
+
+	if (walk->stack.top + 1 >= walk->stack.size) {
+		ret = media_pipeline_walk_resize(walk);
+		if (ret)
+			return ret;
+	}
+
+	walk->stack.top++;
+	entry = media_pipeline_walk_top(walk);
+	entry->pad = pad;
+	entry->links = pad->entity->links.next;
+
+	dev_dbg(walk->mdev->dev,
+		"media pipeline: pushed entry %u: '%s':%u\n",
+		walk->stack.top, pad->entity->name, pad->index);
+
+	return 0;
+}
+
+/*
+ * Move the top entry link cursor to the next link. If all links of the entry
+ * have been visited, pop the entry itself.
+ */
+static void media_pipeline_walk_pop(struct media_pipeline_walk *walk)
+{
+	struct media_pipeline_walk_entry *entry;
+
+	if (WARN_ON(walk->stack.top < 0))
+		return;
+
+	entry = media_pipeline_walk_top(walk);
+
+	if (entry->links->next == &entry->pad->entity->links) {
+		dev_dbg(walk->mdev->dev,
+			"media pipeline: entry %u has no more links, popping\n",
+			walk->stack.top);
+
+		walk->stack.top--;
+		return;
+	}
+
+	entry->links = entry->links->next;
+
+	dev_dbg(walk->mdev->dev,
+		"media pipeline: moved entry %u to next link\n",
+		walk->stack.top);
+}
+
+/* Free all memory allocated while walking the pipeline. */
+static void media_pipeline_walk_destroy(struct media_pipeline_walk *walk)
+{
+	kfree(walk->stack.entries);
+}
+
+/* Add a pad to the pipeline and push it to the stack. */
+static int media_pipeline_add_pad(struct media_pipeline *pipe,
+				  struct media_pipeline_walk *walk,
+				  struct media_pad *pad)
+{
+	struct media_pipeline_pad *ppad;
+
+	list_for_each_entry(ppad, &pipe->pads, list) {
+		if (ppad->pad == pad) {
+			dev_dbg(pad->graph_obj.mdev->dev,
+				"media pipeline: already contains pad '%s':%u\n",
+				pad->entity->name, pad->index);
+			return 0;
+		}
+	}
+
+	ppad = kzalloc(sizeof(*ppad), GFP_KERNEL);
+	if (!ppad)
+		return -ENOMEM;
+
+	ppad->pipe = pipe;
+	ppad->pad = pad;
+
+	list_add_tail(&ppad->list, &pipe->pads);
+
+	dev_dbg(pad->graph_obj.mdev->dev,
+		"media pipeline: added pad '%s':%u\n",
+		pad->entity->name, pad->index);
+
+	return media_pipeline_walk_push(walk, pad);
+}
+
+/* Explore the next link of the entity at the top of the stack. */
+static int media_pipeline_explore_next_link(struct media_pipeline *pipe,
+					    struct media_pipeline_walk *walk)
+{
+	struct media_pipeline_walk_entry *entry = media_pipeline_walk_top(walk);
+	struct media_pad *pad;
+	struct media_link *link;
+	struct media_pad *local;
+	struct media_pad *remote;
+	int ret;
+
+	pad = entry->pad;
+	link = list_entry(entry->links, typeof(*link), list);
+	media_pipeline_walk_pop(walk);
+
+	dev_dbg(walk->mdev->dev,
+		"media pipeline: exploring link '%s':%u -> '%s':%u\n",
+		link->source->entity->name, link->source->index,
+		link->sink->entity->name, link->sink->index);
+
+	/* Skip links that are not enabled. */
+	if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
+		dev_dbg(walk->mdev->dev,
+			"media pipeline: skipping link (disabled)\n");
+		return 0;
+	}
+
+	/* Get the local pad and remote pad. */
+	if (link->source->entity == pad->entity) {
+		local = link->source;
+		remote = link->sink;
+	} else {
+		local = link->sink;
+		remote = link->source;
+	}
+
+	/*
+	 * Skip links that originate from a different pad than the incoming pad
+	 * that is not connected internally in the entity to the incoming pad.
+	 */
+	if (pad != local &&
+	    !media_entity_has_pad_interdep(pad->entity, pad->index, local->index)) {
+		dev_dbg(walk->mdev->dev,
+			"media pipeline: skipping link (no route)\n");
+		return 0;
+	}
+
+	/*
+	 * Add the local and remote pads of the link to the pipeline and push
+	 * them to the stack, if they're not already present.
+	 */
+	ret = media_pipeline_add_pad(pipe, walk, local);
+	if (ret)
+		return ret;
+
+	ret = media_pipeline_add_pad(pipe, walk, remote);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void media_pipeline_cleanup(struct media_pipeline *pipe)
+{
+	while (!list_empty(&pipe->pads)) {
+		struct media_pipeline_pad *ppad;
+
+		ppad = list_first_entry(&pipe->pads, typeof(*ppad), list);
+		list_del(&ppad->list);
+		kfree(ppad);
+	}
+}
+
+static int media_pipeline_populate(struct media_pipeline *pipe,
+				   struct media_pad *pad)
+{
+	struct media_pipeline_walk walk = { };
+	struct media_pipeline_pad *ppad;
+	int ret;
+
+	/*
+	 * Populate the media pipeline by walking the media graph, starting
+	 * from @pad.
+	 */
+	INIT_LIST_HEAD(&pipe->pads);
+	pipe->mdev = pad->graph_obj.mdev;
+
+	walk.mdev = pipe->mdev;
+	walk.stack.top = -1;
+	ret = media_pipeline_add_pad(pipe, &walk, pad);
+	if (ret)
+		goto done;
+
+	/*
+	 * Use a depth-first search algorithm: as long as the stack is not
+	 * empty, explore the next link of the top entry. The
+	 * media_pipeline_explore_next_link() function will either move to the
+	 * next link, pop the entry if fully visited, or add new entries on
+	 * top.
+	 */
+	while (!media_pipeline_walk_empty(&walk)) {
+		ret = media_pipeline_explore_next_link(pipe, &walk);
+		if (ret)
+			goto done;
+	}
+
+	dev_dbg(pad->graph_obj.mdev->dev,
+		"media pipeline populated, found pads:\n");
+
+	list_for_each_entry(ppad, &pipe->pads, list)
+		dev_dbg(pad->graph_obj.mdev->dev, "- '%s':%u\n",
+			ppad->pad->entity->name, ppad->pad->index);
+
+	WARN_ON(walk.stack.top != -1);
+
+	ret = 0;
+
+done:
+	media_pipeline_walk_destroy(&walk);
+
+	if (ret)
+		media_pipeline_cleanup(pipe);
+
+	return ret;
+}
+
+__must_check int __media_pipeline_start(struct media_pad *pad,
+					struct media_pipeline *pipe)
+{
+	struct media_device *mdev = pad->graph_obj.mdev;
+	struct media_pipeline_pad *err_ppad;
+	struct media_pipeline_pad *ppad;
+	int ret;
+
+	lockdep_assert_held(&mdev->graph_mutex);
+
+	/*
+	 * If the pad is already part of a pipeline, that pipeline must be the
+	 * same as the pipe given to media_pipeline_start().
+	 */
+	if (WARN_ON(pad->pipe && pad->pipe != pipe))
+		return -EINVAL;
+
+	/*
+	 * If the pipeline has already been started, it is guaranteed to be
+	 * valid, so just increase the start count.
+	 */
+	if (pipe->start_count) {
+		pipe->start_count++;
+		return 0;
+	}
+
+	/*
+	 * Populate the pipeline. This populates the media_pipeline pads list
+	 * with media_pipeline_pad instances for each pad found during graph
+	 * walk.
+	 */
+	ret = media_pipeline_populate(pipe, pad);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now that all the pads in the pipeline have been gathered, perform
+	 * the validation steps.
+	 */
+
+	list_for_each_entry(ppad, &pipe->pads, list) {
+		struct media_pad *pad = ppad->pad;
+		struct media_entity *entity = pad->entity;
+		bool has_enabled_link = false;
+		bool has_link = false;
+		struct media_link *link;
+
+		dev_dbg(mdev->dev, "Validating pad '%s':%u\n", pad->entity->name,
+			pad->index);
+
+		/*
+		 * 1. Ensure that the pad doesn't already belong to a different
+		 * pipeline.
+		 */
+		if (pad->pipe) {
+			dev_dbg(mdev->dev, "Failed to start pipeline: pad '%s':%u busy\n",
+				pad->entity->name, pad->index);
+			ret = -EBUSY;
+			goto error;
+		}
+
+		/*
+		 * 2. Validate all active links whose sink is the current pad.
+		 * Validation of the source pads is performed in the context of
+		 * the connected sink pad to avoid duplicating checks.
+		 */
+		for_each_media_entity_data_link(entity, link) {
+			/* Skip links unrelated to the current pad. */
+			if (link->sink != pad && link->source != pad)
+				continue;
+
+			/* Record if the pad has links and enabled links. */
+			if (link->flags & MEDIA_LNK_FL_ENABLED)
+				has_enabled_link = true;
+			has_link = true;
+
+			/*
+			 * Validate the link if it's enabled and has the
+			 * current pad as its sink.
+			 */
+			if (!(link->flags & MEDIA_LNK_FL_ENABLED))
+				continue;
+
+			if (link->sink != pad)
+				continue;
+
+			if (!entity->ops || !entity->ops->link_validate)
+				continue;
+
+			ret = entity->ops->link_validate(link);
+			if (ret) {
+				dev_dbg(mdev->dev,
+					"Link '%s':%u -> '%s':%u failed validation: %d\n",
+					link->source->entity->name,
+					link->source->index,
+					link->sink->entity->name,
+					link->sink->index, ret);
+				goto error;
+			}
+
+			dev_dbg(mdev->dev,
+				"Link '%s':%u -> '%s':%u is valid\n",
+				link->source->entity->name,
+				link->source->index,
+				link->sink->entity->name,
+				link->sink->index);
+		}
+
+		/*
+		 * 3. If the pad has the MEDIA_PAD_FL_MUST_CONNECT flag set,
+		 * ensure that it has either no link or an enabled link.
+		 */
+		if ((pad->flags & MEDIA_PAD_FL_MUST_CONNECT) && has_link &&
+		    !has_enabled_link) {
+			dev_dbg(mdev->dev,
+				"Pad '%s':%u must be connected by an enabled link\n",
+				pad->entity->name, pad->index);
+			ret = -ENOLINK;
+			goto error;
+		}
+
+		/* Validation passed, store the pipe pointer in the pad. */
+		pad->pipe = pipe;
+	}
+
+	pipe->start_count++;
+
+	return 0;
+
+error:
+	/*
+	 * Link validation on graph failed. We revert what we did and
+	 * return the error.
+	 */
+
+	list_for_each_entry(err_ppad, &pipe->pads, list) {
+		if (err_ppad == ppad)
+			break;
+
+		err_ppad->pad->pipe = NULL;
+	}
+
+	media_pipeline_cleanup(pipe);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__media_pipeline_start);
+
+__must_check int media_pipeline_start(struct media_pad *pad,
+				      struct media_pipeline *pipe)
+{
+	struct media_device *mdev = pad->graph_obj.mdev;
+	int ret;
+
+	mutex_lock(&mdev->graph_mutex);
+	ret = __media_pipeline_start(pad, pipe);
+	mutex_unlock(&mdev->graph_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(media_pipeline_start);
+
+void __media_pipeline_stop(struct media_pad *pad)
+{
+	struct media_pipeline *pipe = pad->pipe;
+	struct media_pipeline_pad *ppad;
+
+	/*
+	 * If the following check fails, the driver has performed an
+	 * unbalanced call to media_pipeline_stop()
+	 */
+	if (WARN_ON(!pipe))
+		return;
+
+	if (--pipe->start_count)
+		return;
+
+	list_for_each_entry(ppad, &pipe->pads, list)
+		ppad->pad->pipe = NULL;
+
+	media_pipeline_cleanup(pipe);
+
+	if (pipe->allocated)
+		kfree(pipe);
+}
+EXPORT_SYMBOL_GPL(__media_pipeline_stop);
+
+void media_pipeline_stop(struct media_pad *pad)
+{
+	struct media_device *mdev = pad->graph_obj.mdev;
+
+	mutex_lock(&mdev->graph_mutex);
+	__media_pipeline_stop(pad);
+	mutex_unlock(&mdev->graph_mutex);
+}
+EXPORT_SYMBOL_GPL(media_pipeline_stop);
+
+__must_check int media_pipeline_alloc_start(struct media_pad *pad)
+{
+	struct media_device *mdev = pad->graph_obj.mdev;
+	struct media_pipeline *new_pipe = NULL;
+	struct media_pipeline *pipe;
+	int ret;
+
+	mutex_lock(&mdev->graph_mutex);
+
+	/*
+	 * Is the pad already part of a pipeline? If not, we need to allocate
+	 * a pipe.
+	 */
+	pipe = media_pad_pipeline(pad);
+	if (!pipe) {
+		new_pipe = kzalloc(sizeof(*new_pipe), GFP_KERNEL);
+		if (!new_pipe) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		pipe = new_pipe;
+		pipe->allocated = true;
+	}
+
+	ret = __media_pipeline_start(pad, pipe);
+	if (ret)
+		kfree(new_pipe);
+
+out:
+	mutex_unlock(&mdev->graph_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(media_pipeline_alloc_start);
+
+struct media_pad *
+__media_pipeline_pad_iter_next(struct media_pipeline *pipe,
+			       struct media_pipeline_pad_iter *iter,
+			       struct media_pad *pad)
+{
+	if (!pad)
+		iter->cursor = pipe->pads.next;
+
+	if (iter->cursor == &pipe->pads)
+		return NULL;
+
+	pad = list_entry(iter->cursor, struct media_pipeline_pad, list)->pad;
+	iter->cursor = iter->cursor->next;
+
+	return pad;
+}
+EXPORT_SYMBOL_GPL(__media_pipeline_pad_iter_next);
+
+int media_pipeline_entity_iter_init(struct media_pipeline *pipe,
+				    struct media_pipeline_entity_iter *iter)
+{
+	return media_entity_enum_init(&iter->ent_enum, pipe->mdev);
+}
+EXPORT_SYMBOL_GPL(media_pipeline_entity_iter_init);
+
+void media_pipeline_entity_iter_cleanup(struct media_pipeline_entity_iter *iter)
+{
+	media_entity_enum_cleanup(&iter->ent_enum);
+}
+EXPORT_SYMBOL_GPL(media_pipeline_entity_iter_cleanup);
+
+struct media_entity *
+__media_pipeline_entity_iter_next(struct media_pipeline *pipe,
+				  struct media_pipeline_entity_iter *iter,
+				  struct media_entity *entity)
+{
+	if (!entity)
+		iter->cursor = pipe->pads.next;
+
+	while (iter->cursor != &pipe->pads) {
+		struct media_pipeline_pad *ppad;
+		struct media_entity *entity;
+
+		ppad = list_entry(iter->cursor, struct media_pipeline_pad, list);
+		entity = ppad->pad->entity;
+		iter->cursor = iter->cursor->next;
+
+		if (!media_entity_enum_test_and_set(&iter->ent_enum, entity))
+			return entity;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(__media_pipeline_entity_iter_next);
+
+/* -----------------------------------------------------------------------------
+ * 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;
+
+	/* Remove the reverse links for a data link. */
+	if ((link->flags & MEDIA_LNK_FL_LINK_TYPE) == MEDIA_LNK_FL_DATA_LINK) {
+		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_get_pad_index(struct media_entity *entity, u32 pad_type,
+			enum media_pad_signal_type sig_type)
+{
+	unsigned int i;
+
+	if (!entity)
+		return -EINVAL;
+
+	for (i = 0; i < entity->num_pads; i++) {
+		if ((entity->pads[i].flags &
+		     (MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_SOURCE)) != pad_type)
+			continue;
+
+		if (entity->pads[i].sig_type == sig_type)
+			return i;
+	}
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(media_get_pad_index);
+
+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;
+
+	if (WARN_ON(!source || !sink) ||
+	    WARN_ON(source_pad >= source->num_pads) ||
+	    WARN_ON(sink_pad >= sink->num_pads))
+		return -EINVAL;
+	if (WARN_ON(!(source->pads[source_pad].flags & MEDIA_PAD_FL_SOURCE)))
+		return -EINVAL;
+	if (WARN_ON(!(sink->pads[sink_pad].flags & MEDIA_PAD_FL_SINK)))
+		return -EINVAL;
+
+	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;
+
+	mutex_lock(&mdev->graph_mutex);
+	__media_entity_remove_links(entity);
+	mutex_unlock(&mdev->graph_mutex);
+}
+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_pad *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;
+	sink = link->sink;
+
+	if (!(link->flags & MEDIA_LNK_FL_DYNAMIC) &&
+	    (media_pad_is_streaming(source) || media_pad_is_streaming(sink)))
+		return -EBUSY;
+
+	mdev = source->graph_obj.mdev;
+
+	if (mdev->ops && mdev->ops->link_notify) {
+		ret = mdev->ops->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->ops && mdev->ops->link_notify)
+		mdev->ops->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;
+
+	for_each_media_entity_data_link(source->entity, link) {
+		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_pad_remote_pad_first(const struct media_pad *pad)
+{
+	struct media_link *link;
+
+	for_each_media_entity_data_link(pad->entity, link) {
+		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_pad_remote_pad_first);
+
+struct media_pad *
+media_entity_remote_pad_unique(const struct media_entity *entity,
+			       unsigned int type)
+{
+	struct media_pad *pad = NULL;
+	struct media_link *link;
+
+	list_for_each_entry(link, &entity->links, list) {
+		struct media_pad *local_pad;
+		struct media_pad *remote_pad;
+
+		if (((link->flags & MEDIA_LNK_FL_LINK_TYPE) !=
+		     MEDIA_LNK_FL_DATA_LINK) ||
+		    !(link->flags & MEDIA_LNK_FL_ENABLED))
+			continue;
+
+		if (type == MEDIA_PAD_FL_SOURCE) {
+			local_pad = link->sink;
+			remote_pad = link->source;
+		} else {
+			local_pad = link->source;
+			remote_pad = link->sink;
+		}
+
+		if (local_pad->entity == entity) {
+			if (pad)
+				return ERR_PTR(-ENOTUNIQ);
+
+			pad = remote_pad;
+		}
+	}
+
+	if (!pad)
+		return ERR_PTR(-ENOLINK);
+
+	return pad;
+}
+EXPORT_SYMBOL_GPL(media_entity_remote_pad_unique);
+
+struct media_pad *media_pad_remote_pad_unique(const struct media_pad *pad)
+{
+	struct media_pad *found_pad = NULL;
+	struct media_link *link;
+
+	list_for_each_entry(link, &pad->entity->links, list) {
+		struct media_pad *remote_pad;
+
+		if (!(link->flags & MEDIA_LNK_FL_ENABLED))
+			continue;
+
+		if (link->sink == pad)
+			remote_pad = link->source;
+		else if (link->source == pad)
+			remote_pad = link->sink;
+		else
+			continue;
+
+		if (found_pad)
+			return ERR_PTR(-ENOTUNIQ);
+
+		found_pad = remote_pad;
+	}
+
+	if (!found_pad)
+		return ERR_PTR(-ENOLINK);
+
+	return found_pad;
+}
+EXPORT_SYMBOL_GPL(media_pad_remote_pad_unique);
+
+int media_entity_get_fwnode_pad(struct media_entity *entity,
+				const struct fwnode_handle *fwnode,
+				unsigned long direction_flags)
+{
+	struct fwnode_endpoint endpoint;
+	unsigned int i;
+	int ret;
+
+	if (!entity->ops || !entity->ops->get_fwnode_pad) {
+		for (i = 0; i < entity->num_pads; i++) {
+			if (entity->pads[i].flags & direction_flags)
+				return i;
+		}
+
+		return -ENXIO;
+	}
+
+	ret = fwnode_graph_parse_endpoint(fwnode, &endpoint);
+	if (ret)
+		return ret;
+
+	ret = entity->ops->get_fwnode_pad(entity, &endpoint);
+	if (ret < 0)
+		return ret;
+
+	if (ret >= entity->num_pads)
+		return -ENXIO;
+
+	if (!(entity->pads[ret].flags & direction_flags))
+		return -ENXIO;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(media_entity_get_fwnode_pad);
+
+struct media_pipeline *media_entity_pipeline(struct media_entity *entity)
+{
+	struct media_pad *pad;
+
+	media_entity_for_each_pad(entity, pad) {
+		if (pad->pipe)
+			return pad->pipe;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(media_entity_pipeline);
+
+struct media_pipeline *media_pad_pipeline(struct media_pad *pad)
+{
+	return pad->pipe;
+}
+EXPORT_SYMBOL_GPL(media_pad_pipeline);
+
+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;
+
+	mutex_lock(&mdev->graph_mutex);
+	__media_remove_intf_link(link);
+	mutex_unlock(&mdev->graph_mutex);
+}
+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;
+
+	mutex_lock(&mdev->graph_mutex);
+	__media_remove_intf_links(intf);
+	mutex_unlock(&mdev->graph_mutex);
+}
+EXPORT_SYMBOL_GPL(media_remove_intf_links);
+
+struct media_link *media_create_ancillary_link(struct media_entity *primary,
+					       struct media_entity *ancillary)
+{
+	struct media_link *link;
+
+	link = media_add_link(&primary->links);
+	if (!link)
+		return ERR_PTR(-ENOMEM);
+
+	link->gobj0 = &primary->graph_obj;
+	link->gobj1 = &ancillary->graph_obj;
+	link->flags = MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED |
+		      MEDIA_LNK_FL_ANCILLARY_LINK;
+
+	/* Initialize graph object embedded in the new link */
+	media_gobj_create(primary->graph_obj.mdev, MEDIA_GRAPH_LINK,
+			  &link->graph_obj);
+
+	return link;
+}
+EXPORT_SYMBOL_GPL(media_create_ancillary_link);
+
+struct media_link *__media_entity_next_link(struct media_entity *entity,
+					    struct media_link *link,
+					    unsigned long link_type)
+{
+	link = link ? list_next_entry(link, list)
+		    : list_first_entry(&entity->links, typeof(*link), list);
+
+	list_for_each_entry_from(link, &entity->links, list)
+		if ((link->flags & MEDIA_LNK_FL_LINK_TYPE) == link_type)
+			return link;
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(__media_entity_next_link);