Avoid beyond bounds copy while caching ACL

[zen-stable.git] / 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/module.h>
#include <linux/slab.h>
#include <media/media-entity.h>
#include <media/media-device.h>

/**
 * media_entity_init - Initialize a media entity
 *
 * @num_pads: Total number of sink and source pads.
 * @extra_links: Initial estimate of the number of extra links.
 * @pads: Array of 'num_pads' pads.
 *
 * The total number of pads is an intrinsic property of entities known by the
 * entity driver, while the total number of links depends on hardware design
 * and is an extrinsic property unknown to the entity driver. However, in most
 * use cases the entity driver can guess the number of links which can safely
 * be assumed to be equal to or larger than the number of pads.
 *
 * For those reasons the links array can be preallocated based on the entity
 * driver guess and will be reallocated later if extra links need to be
 * created.
 *
 * This function allocates a links array with enough space to hold at least
 * 'num_pads' + 'extra_links' elements. The media_entity::max_links field will
 * be set to the number of allocated elements.
 *
 * The pads array is managed by the entity driver and passed to
 * media_entity_init() where its pointer will be stored in the entity structure.
 */
int
media_entity_init(struct media_entity *entity, u16 num_pads,
                  struct media_pad *pads, u16 extra_links)
{
        struct media_link *links;
        unsigned int max_links = num_pads + extra_links;
        unsigned int i;

        links = kzalloc(max_links * sizeof(links[0]), GFP_KERNEL);
        if (links == NULL)
                return -ENOMEM;

        entity->group_id = 0;
        entity->max_links = max_links;
        entity->num_links = 0;
        entity->num_backlinks = 0;
        entity->num_pads = num_pads;
        entity->pads = pads;
        entity->links = links;

        for (i = 0; i < num_pads; i++) {
                pads[i].entity = entity;
                pads[i].index = i;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(media_entity_init);

void
media_entity_cleanup(struct media_entity *entity)
{
        kfree(entity->links);
}
EXPORT_SYMBOL_GPL(media_entity_cleanup);

/* -----------------------------------------------------------------------------
 * 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 = 0;
        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 stack_peek(en)  ((en)->stack[(en)->top - 1].entity)
#define link_top(en)    ((en)->stack[(en)->top].link)
#define stack_top(en)   ((en)->stack[(en)->top].entity)

/**
 * media_entity_graph_walk_start - Start walking the media graph at a given entity
 * @graph: Media graph structure that will be used to walk the graph
 * @entity: Starting entity
 *
 * This function initializes the graph traversal structure to walk the entities
 * graph starting at the given entity. The traversal structure must not be
 * modified by the caller during graph traversal. When done the structure can
 * safely be freed.
 */
void media_entity_graph_walk_start(struct media_entity_graph *graph,
                                   struct media_entity *entity)
{
        graph->top = 0;
        graph->stack[graph->top].entity = NULL;
        stack_push(graph, entity);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_start);

/**
 * media_entity_graph_walk_next - Get the next entity in the graph
 * @graph: Media graph structure
 *
 * Perform a depth-first traversal of the given media entities graph.
 *
 * The graph structure must have been previously initialized with a call to
 * media_entity_graph_walk_start().
 *
 * Return the next entity in the graph or NULL if the whole graph have been
 * traversed.
 */
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)->num_links) {
                struct media_entity *entity = stack_top(graph);
                struct media_link *link = &entity->links[link_top(graph)];
                struct media_entity *next;

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

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

                /* Was it the entity we came here from? */
                if (next == stack_peek(graph)) {
                        link_top(graph)++;
                        continue;
                }

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

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

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

/**
 * media_entity_pipeline_start - Mark a pipeline as streaming
 * @entity: Starting entity
 * @pipe: Media pipeline to be assigned to all entities in the pipeline.
 *
 * Mark all entities connected to a given entity through enabled links, either
 * directly or indirectly, as streaming. The given pipeline object is assigned to
 * every entity in the pipeline and stored in the media_entity pipe field.
 *
 * Calls to this function can be nested, in which case the same number of
 * media_entity_pipeline_stop() calls will be required to stop streaming. The
 * pipeline pointer must be identical for all nested calls to
 * media_entity_pipeline_start().
 */
void media_entity_pipeline_start(struct media_entity *entity,
                                 struct media_pipeline *pipe)
{
        struct media_device *mdev = entity->parent;
        struct media_entity_graph graph;

        mutex_lock(&mdev->graph_mutex);

        media_entity_graph_walk_start(&graph, entity);

        while ((entity = media_entity_graph_walk_next(&graph))) {
                entity->stream_count++;
                WARN_ON(entity->pipe && entity->pipe != pipe);
                entity->pipe = pipe;
        }

        mutex_unlock(&mdev->graph_mutex);
}
EXPORT_SYMBOL_GPL(media_entity_pipeline_start);

/**
 * media_entity_pipeline_stop - Mark a pipeline as not streaming
 * @entity: Starting entity
 *
 * Mark all entities connected to a given entity through enabled links, either
 * directly or indirectly, as not streaming. The media_entity pipe field is
 * reset to NULL.
 *
 * If multiple calls to media_entity_pipeline_start() have been made, the same
 * number of calls to this function are required to mark the pipeline as not
 * streaming.
 */
void media_entity_pipeline_stop(struct media_entity *entity)
{
        struct media_device *mdev = entity->parent;
        struct media_entity_graph graph;

        mutex_lock(&mdev->graph_mutex);

        media_entity_graph_walk_start(&graph, entity);

        while ((entity = media_entity_graph_walk_next(&graph))) {
                entity->stream_count--;
                if (entity->stream_count == 0)
                        entity->pipe = NULL;
        }

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

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

/*
 * media_entity_get - Get a reference to the parent module
 * @entity: The entity
 *
 * Get a reference to the parent media device module.
 *
 * The function will return immediately if @entity is NULL.
 *
 * Return a pointer to the entity on success or NULL on failure.
 */
struct media_entity *media_entity_get(struct media_entity *entity)
{
        if (entity == NULL)
                return NULL;

        if (entity->parent->dev &&
            !try_module_get(entity->parent->dev->driver->owner))
                return NULL;

        return entity;
}
EXPORT_SYMBOL_GPL(media_entity_get);

/*
 * media_entity_put - Release the reference to the parent module
 * @entity: The entity
 *
 * Release the reference count acquired by media_entity_get().
 *
 * The function will return immediately if @entity is NULL.
 */
void media_entity_put(struct media_entity *entity)
{
        if (entity == NULL)
                return;

        if (entity->parent->dev)
                module_put(entity->parent->dev->driver->owner);
}
EXPORT_SYMBOL_GPL(media_entity_put);

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

static struct media_link *media_entity_add_link(struct media_entity *entity)
{
        if (entity->num_links >= entity->max_links) {
                struct media_link *links = entity->links;
                unsigned int max_links = entity->max_links + 2;
                unsigned int i;

                links = krealloc(links, max_links * sizeof(*links), GFP_KERNEL);
                if (links == NULL)
                        return NULL;

                for (i = 0; i < entity->num_links; i++)
                        links[i].reverse->reverse = &links[i];

                entity->max_links = max_links;
                entity->links = links;
        }

        return &entity->links[entity->num_links++];
}

int
media_entity_create_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_entity_add_link(source);
        if (link == NULL)
                return -ENOMEM;

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

        /* Create the backlink. Backlinks are used to help graph traversal and
         * are not reported to userspace.
         */
        backlink = media_entity_add_link(sink);
        if (backlink == NULL) {
                source->num_links--;
                return -ENOMEM;
        }

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

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

        sink->num_backlinks++;

        return 0;
}
EXPORT_SYMBOL_GPL(media_entity_create_link);

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;
}

/**
 * __media_entity_setup_link - Configure a media link
 * @link: The link being configured
 * @flags: Link configuration flags
 *
 * The bulk of link setup is handled by the two entities connected through the
 * link. This function notifies both entities of the link configuration change.
 *
 * If the link is immutable or if the current and new configuration are
 * identical, return immediately.
 *
 * The user is expected to hold link->source->parent->mutex. If not,
 * media_entity_setup_link() should be used instead.
 */
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->parent;

        if ((flags & MEDIA_LNK_FL_ENABLED) && mdev->link_notify) {
                ret = mdev->link_notify(link->source, link->sink,
                                        MEDIA_LNK_FL_ENABLED);
                if (ret < 0)
                        return ret;
        }

        ret = __media_entity_setup_link_notify(link, flags);
        if (ret < 0)
                goto err;

        if (!(flags & MEDIA_LNK_FL_ENABLED) && mdev->link_notify)
                mdev->link_notify(link->source, link->sink, 0);

        return 0;

err:
        if ((flags & MEDIA_LNK_FL_ENABLED) && mdev->link_notify)
                mdev->link_notify(link->source, link->sink, 0);

        return ret;
}

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

        mutex_lock(&link->source->entity->parent->graph_mutex);
        ret = __media_entity_setup_link(link, flags);
        mutex_unlock(&link->source->entity->parent->graph_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(media_entity_setup_link);

/**
 * media_entity_find_link - Find a link between two pads
 * @source: Source pad
 * @sink: Sink pad
 *
 * Return a pointer to the link between the two entities. If no such link
 * exists, return NULL.
 */
struct media_link *
media_entity_find_link(struct media_pad *source, struct media_pad *sink)
{
        struct media_link *link;
        unsigned int i;

        for (i = 0; i < source->entity->num_links; ++i) {
                link = &source->entity->links[i];

                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);

/**
 * media_entity_remote_source - Find the source pad at the remote end of a link
 * @pad: Sink pad at the local end of the link
 *
 * Search for a remote source pad connected to the given sink pad by iterating
 * over all links originating or terminating at that pad until an enabled link
 * is found.
 *
 * Return a pointer to the pad at the remote end of the first found enabled
 * link, or NULL if no enabled link has been found.
 */
struct media_pad *media_entity_remote_source(struct media_pad *pad)
{
        unsigned int i;

        for (i = 0; i < pad->entity->num_links; i++) {
                struct media_link *link = &pad->entity->links[i];

                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_source);