Re: [PATCH v6 01/18] media: mc-entity: Record number of video devices in a pipeline

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Hi Laurent

On 30/07/2024 16:09, Laurent Pinchart wrote:
Hi Dan,

Thank you for the patch.

On Tue, Jul 09, 2024 at 02:28:49PM +0100, Daniel Scally wrote:
Record the number of video devices in a pipeline so that we can track
in a central location how many need to be started before drivers must
actually begin streaming.

Signed-off-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
---
Changes in v6:

	- New patch. This is intended to support Sakari's requirement for the
	  driver not to start streaming before all of the video devices have
	  called streamon(). This was the cleanest way I could think to acheive
	  the goal, and lets us just check for start_count == required_count
	  before streaming.
This violates the abstraction layers a bit, the MC code isn't supposed
to handle video devices like that.

What you can instead do is to use media_pipeline_for_each_entity() in
your driver when starting the pipeline to iterate over all entities, and
count the video devices there.


That'll do! Thanks for the suggestion.


  drivers/media/mc/mc-entity.c | 5 +++++
  include/media/media-entity.h | 2 ++
  2 files changed, 7 insertions(+)

diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
index 96dd0f6ccd0d..1e8186b13b55 100644
--- a/drivers/media/mc/mc-entity.c
+++ b/drivers/media/mc/mc-entity.c
@@ -596,6 +596,9 @@ static int media_pipeline_add_pad(struct media_pipeline *pipe,
list_add_tail(&ppad->list, &pipe->pads); + if (pad->entity->obj_type == MEDIA_ENTITY_TYPE_VIDEO_DEVICE)
+		pipe->required_count++;
+
  	dev_dbg(pad->graph_obj.mdev->dev,
  		"media pipeline: added pad '%s':%u\n",
  		pad->entity->name, pad->index);
@@ -713,6 +716,8 @@ static void media_pipeline_cleanup(struct media_pipeline *pipe)
  		list_del(&ppad->list);
  		kfree(ppad);
  	}
+
+	pipe->required_count = 0;
  }
static int media_pipeline_populate(struct media_pipeline *pipe,
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 0393b23129eb..ab84458b40dc 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -104,12 +104,14 @@ struct media_graph {
   * @mdev:		The media device the pipeline is part of
   * @pads:		List of media_pipeline_pad
   * @start_count:	Media pipeline start - stop count
+ * @required_count:	Number of starts required to be "running"
   */
  struct media_pipeline {
  	bool allocated;
  	struct media_device *mdev;
  	struct list_head pads;
  	int start_count;
+	int required_count;
  };
/**




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