From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
The media_pipeline_start() function has two purposes: it constructs a
pipeline by recording the entities that are part of it, gathered from a
graph walk, and validate the media links. The pipeline pointer is stored
in the media_entity structure as part of this process, and the entity's
stream count is increased, to record that the entity is streaming.
When multiple video nodes are present in a pipeline,
media_pipeline_start() is typically called on all of them, with the same
pipeline pointer. This is taken into account in media_pipeline_start()
by skipping validation for entities that are already part of the
pipeline, while returning an error if an entity is part of a different
pipeline.
It turns out that this process is overly complicated. When
media_pipeline_start() is called for the first time, it constructs the
full pipeline, adding all entities and validating all the links.
Subsequent calls to media_pipeline_start() are then nearly no-ops, they
only increase the stream count on the pipeline and on all entities.
The media_entity stream_count field is used for two purposes: checking
if the entity is streaming, and detecting when a call to
media_pipeline_stop() balances needs to reset the entity pipe pointer to
NULL. The former can easily be replaced by a check of the pipe pointer.
Simplify media_pipeline_start() by avoiding the pipeline walk on all
calls but the first one, and drop the media_entity stream_count field.
media_pipeline_stop() is updated accordingly.
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
drivers/media/mc/mc-entity.c | 52 +++++++++++++++---------------------
include/media/media-entity.h | 11 +++-----
2 files changed, 26 insertions(+), 37 deletions(-)
diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
index f83e043f0f3b..8ab0913d8d82 100644
--- a/drivers/media/mc/mc-entity.c
+++ b/drivers/media/mc/mc-entity.c
@@ -396,20 +396,21 @@ __must_check int __media_pipeline_start(struct media_entity *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;
+ if (pipe->streaming_count) {
+ pipe->streaming_count++;
+ return 0;
}
+ ret = media_graph_walk_init(&pipe->graph, mdev);
+ if (ret)
+ return ret;
+
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,
@@ -418,12 +419,12 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
goto error;
}
- entity->pipe = pipe;
-
/* Already streaming --- no need to check. */
- if (entity->stream_count > 1)
+ if (entity->pipe)
continue;
+ entity->pipe = pipe;
+
if (!entity->ops || !entity->ops->link_validate)
continue;
@@ -479,6 +480,8 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
}
}
+ pipe->streaming_count++;
+
return 0;
error:
@@ -489,24 +492,17 @@ __must_check int __media_pipeline_start(struct media_entity *entity,
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;
- }
+ entity_err->pipe = NULL;
/*
- * We haven't increased stream_count further than this
- * so we quit here.
+ * We haven't started entities 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);
+ media_graph_walk_cleanup(graph);
return ret;
}
@@ -537,19 +533,15 @@ void __media_pipeline_stop(struct media_entity *entity)
if (WARN_ON(!pipe))
return;
+ if (--pipe->streaming_count)
+ 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;
- }
- }
+ while ((entity = media_graph_walk_next(graph)))
+ entity->pipe = NULL;
- if (!--pipe->streaming_count)
- media_graph_walk_cleanup(graph);
+ media_graph_walk_cleanup(graph);
}
EXPORT_SYMBOL_GPL(__media_pipeline_stop);
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 8546f13c42a9..e3c4fd1e3623 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -268,7 +268,6 @@ enum media_entity_type {
* @pads: Pads array with the size defined by @num_pads.
* @links: List of data links.
* @ops: Entity operations.
- * @stream_count: Stream count for the entity.
* @use_count: Use count for the entity.
* @pipe: Pipeline this entity belongs to.
* @info: Union with devnode information. Kept just for backward
@@ -283,10 +282,9 @@ enum media_entity_type {
*
* .. note::
*
- * @stream_count and @use_count reference counts must never be
- * negative, but are signed integers on purpose: a simple ``WARN_ON(<0)``
- * check can be used to detect reference count bugs that would make them
- * negative.
+ * The @use_count reference count must never be negative, but is a signed
+ * integer on purpose: a simple ``WARN_ON(<0)`` check can be used to detect
+ * reference count bugs that would make it negative.
*/
struct media_entity {
struct media_gobj graph_obj; /* must be first field in struct */
@@ -305,7 +303,6 @@ struct media_entity {
const struct media_entity_operations *ops;
- int stream_count;
int use_count;
struct media_pipeline *pipe;
@@ -867,7 +864,7 @@ struct media_pad *media_entity_remote_pad(const struct media_pad *pad);
*/
static inline bool media_entity_is_streaming(const struct media_entity *entity)
{
- return entity->stream_count > 0;
+ return entity->pipe != NULL;
}
/**
--
Regards,
Laurent Pinchart
