[media] media: Pipelines and media streams

Drivers often need to associate pipeline objects to entities, and to
take stream state into account when configuring entities and links. The
pipeline API helps drivers manage that information.

When starting streaming, drivers call media_entity_pipeline_start(). The
function marks all entities connected to the given entity through
enabled links, either directly or indirectly, as streaming. Similarly,
when stopping the stream, drivers call media_entity_pipeline_stop().

The media_entity_pipeline_start() function takes a pointer to a media
pipeline and stores it in every entity in the graph. Drivers should
embed the media_pipeline structure in higher-level pipeline structures
and can then access the pipeline through the media_entity structure.

Link configuration will fail with -EBUSY by default if either end of the
link is a streaming entity, unless the link is marked with the
MEDIA_LNK_FL_DYNAMIC flag.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/media.h b/include/linux/media.h
index 7c69913c0ad2..7ed23b43f43b 100644
--- a/include/linux/media.h
+++ b/include/linux/media.h
@@ -106,6 +106,7 @@ struct media_pad_desc {
 
 #define MEDIA_LNK_FL_ENABLED            (1 << 0)
 #define MEDIA_LNK_FL_IMMUTABLE          (1 << 1)
+#define MEDIA_LNK_FL_DYNAMIC            (1 << 2)
 
 struct media_link_desc {
         struct media_pad_desc source;
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index d889dcc67d0d..cd8bca63a502 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -26,6 +26,9 @@
 #include <linux/list.h>
 #include <linux/media.h>
 
+struct media_pipeline {
+};
+
 struct media_link {
         struct media_pad *source;       /* Source pad */
         struct media_pad *sink;         /* Sink pad  */
@@ -71,8 +74,11 @@ struct media_entity {
          * purpose: a simple WARN_ON(<0) check can be used to detect reference
          * count bugs that would make them negative.
          */
+        int stream_count;               /* Stream count for the entity. */
         int use_count;                  /* Use count for the entity. */
 
+        struct media_pipeline *pipe;    /* Pipeline this entity belongs to. */
+
         union {
                 /* Node specifications */
                 struct {
@@ -118,6 +124,7 @@ struct media_entity_graph {
 int media_entity_init(struct media_entity *entity, u16 num_pads,
                 struct media_pad *pads, u16 extra_links);
 void media_entity_cleanup(struct media_entity *entity);
+
 int media_entity_create_link(struct media_entity *source, u16 source_pad,
                 struct media_entity *sink, u16 sink_pad, u32 flags);
 int __media_entity_setup_link(struct media_link *link, u32 flags);
@@ -133,6 +140,9 @@ void media_entity_graph_walk_start(struct media_entity_graph *graph,
                 struct media_entity *entity);
 struct media_entity *
 media_entity_graph_walk_next(struct media_entity_graph *graph);
+void media_entity_pipeline_start(struct media_entity *entity,
+                struct media_pipeline *pipe);
+void media_entity_pipeline_stop(struct media_entity *entity);
 
 #define media_entity_call(entity, operation, args...)                   \
         (((entity)->ops && (entity)->ops->operation) ?                  \