// 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/property.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 "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";
        }
};

__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)
{
        /* 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;
        unsigned int i;

        if (num_pads >= MEDIA_ENTITY_MAX_PADS)
                return -E2BIG;

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

        if (mdev)
                mutex_lock(&mdev->graph_mutex);

        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)
                mutex_unlock(&mdev->graph_mutex);

        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_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_free().
 *
 * 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);

        /* 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);

int media_entity_get_fwnode_pad(struct media_entity *entity,
                                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);

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

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

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

        media_graph_walk_start(&pipe->graph, entity);

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

                entity->stream_count++;

                if (entity->pipe && entity->pipe != pipe) {
                        pr_err("Pipe active for %s. Can't start for %s\n",
                                entity->name,
                                entity_err->name);
                        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 = -ENOLINK;
                        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_graph_walk_start(graph, entity_err);

        while ((entity_err = media_graph_walk_next(graph))) {
                /* Sanity check for negative stream_count */
                if (!WARN_ON_ONCE(entity_err->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_graph_walk_cleanup(graph);

        return ret;
}
EXPORT_SYMBOL_GPL(__media_pipeline_start);

__must_check int media_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_pipeline_start(entity, pipe);
        mutex_unlock(&mdev->graph_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(media_pipeline_start);

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

        /*
         * If the following check fails, the driver has performed an
         * unbalanced call to media_pipeline_stop()
         */
        if (WARN_ON(!pipe))
                return;

        media_graph_walk_start(graph, entity);

        while ((entity = media_graph_walk_next(graph))) {
                /* Sanity check for negative stream_count */
                if (!WARN_ON_ONCE(entity->stream_count <= 0)) {
                        entity->stream_count--;
                        if (entity->stream_count == 0)
                                entity->pipe = NULL;
                }
        }

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

}
EXPORT_SYMBOL_GPL(__media_pipeline_stop);

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

        mutex_lock(&mdev->graph_mutex);
        __media_pipeline_stop(entity);
        mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_pipeline_stop);

/* -----------------------------------------------------------------------------
 * 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_get_pad_index(struct media_entity *entity, bool is_sink,
                        enum media_pad_signal_type sig_type)
{
        int i;
        bool pad_is_sink;

        if (!entity)
                return -EINVAL;

        for (i = 0; i < entity->num_pads; i++) {
                if (entity->pads[i].flags & MEDIA_PAD_FL_SINK)
                        pad_is_sink = true;
                else if (entity->pads[i].flags & MEDIA_PAD_FL_SOURCE)
                        pad_is_sink = false;
                else
                        continue;       /* This is an error! */

                if (pad_is_sink != is_sink)
                        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_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->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;

        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(const 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;

        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);