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

[Dan Scally]

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 at ideasonboard.com>
>> ---
>> 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;
>>   };
>>   
>>   /**