[libcamera-devel] [PATCH 3/3] vimc: Join pipeline if one already exists

[Helen Koike]

Hi Niklas,

Thanks for the patch (and sorry for my late reply).

On 5/17/19 10:07 PM, Niklas Söderlund wrote:
> A sensor which is running is already part of a pipeline and trying to
> start a new pipeline is not possible. This prevents two capture devices
> connected to the same sensor from running at the same time.
> 
> Instead of failing to start the second capture device allow it to join
> the already running pipeline by looking it up at the sensor. This allows
> two (or more) capture devices to independently be started and stopped
> while still being connected to the same sensor.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  drivers/media/platform/vimc/vimc-capture.c | 35 +++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
> index e7d0fc2228a6f0c1..f9eb1e327e311b4a 100644
> --- a/drivers/media/platform/vimc/vimc-capture.c
> +++ b/drivers/media/platform/vimc/vimc-capture.c
> @@ -264,16 +264,49 @@ static void vimc_cap_return_all_buffers(struct vimc_cap_device *vcap,
>  	spin_unlock(&vcap->qlock);
>  }
>  
> +static struct media_entity *vimc_cap_get_sensor(struct vimc_cap_device *vcap)
> +{
> +	struct media_entity *entity = &vcap->vdev.entity;
> +	struct media_device *mdev = entity->graph_obj.mdev;
> +	struct media_graph graph;
> +
> +	mutex_lock(&mdev->graph_mutex);
> +	if (media_graph_walk_init(&graph, mdev)) {
> +		mutex_unlock(&mdev->graph_mutex);
> +		return NULL;
> +	}
> +
> +	media_graph_walk_start(&graph, entity);
> +
> +	while ((entity = media_graph_walk_next(&graph)))
> +		if (entity->function == MEDIA_ENT_F_CAM_SENSOR)
> +			break;

I was wondering if it should search up to the sensor, or if it could just search the first entity with a pipe object, what do you think?
Like this it should work with an output device instead of a sensor.

Regards,
Helen

> +
> +	mutex_unlock(&mdev->graph_mutex);
> +
> +	media_graph_walk_cleanup(&graph);
> +
> +	return entity;
> +}
> +
>  static int vimc_cap_start_streaming(struct vb2_queue *vq, unsigned int count)
>  {
>  	struct vimc_cap_device *vcap = vb2_get_drv_priv(vq);
>  	struct media_entity *entity = &vcap->vdev.entity;
> +	struct media_pipeline *pipe = NULL;
> +	struct media_entity *sensorent;
>  	int ret;
>  
>  	vcap->sequence = 0;
>  
>  	/* Start the media pipeline */
> -	ret = media_pipeline_start(entity, &vcap->stream.pipe);
> +	sensorent = vimc_cap_get_sensor(vcap);
> +	if (sensorent && sensorent->pipe)
> +		pipe = sensorent->pipe;
> +	else
> +		pipe = &vcap->stream.pipe;
> +
> +	ret = media_pipeline_start(entity, pipe);
>  	if (ret) {
>  		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
>  		return ret;
>