Re: [PATCH v2 3/4] media: qcom: camss: always stop the pipeline in stop_streaming

[Loic Poulain]

On Mon, Nov 9, 2026 at 12:26 PM Allan Siriani <allan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> video_stop_streaming() walks the pipeline upstream and calls
> .s_stream(0) on every subdev. It gives up on the first non-zero return,
> without stopping the media pipeline and without returning the queued
> buffers to vb2.
>
> A subdev without .s_stream() returns -ENOIOCTLCMD. video_start_streaming()
> already ignores that, but video_stop_streaming() does not, so with such a
> subdev in the pipeline, e.g. the pixel array entity of the MT9M114 sensor
> driver, every stream off:
>
> - triggers the vb2 WARN about buffers still owned by the driver,
> - leaves the pipeline started, so the next VIDIOC_STREAMON and
>   "media-ctl -r" fail with -EBUSY.
>
> Treat -ENOIOCTLCMD as success, as at stream on, and only log real
> errors, then always stop the pipeline and flush the buffers: a
> .stop_streaming() callback cannot fail and must give back all buffers.
>
> Fixes: 89013969e232 ("media: camss: sm8250: Pipeline starting and stopping for multiple virtual channels")
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
> Signed-off-by: Allan Siriani <allan@xxxxxxxxxxxxxxxxxxx>

Reviewed-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>

> ---
>  drivers/media/platform/qcom/camss/camss-video.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/qcom/camss/camss-video.c b/drivers/media/platform/qcom/camss/camss-video.c
> index 5de6ff5ec..8341666f9 100644
> --- a/drivers/media/platform/qcom/camss/camss-video.c
> +++ b/drivers/media/platform/qcom/camss/camss-video.c
> @@ -313,12 +313,16 @@ static void video_stop_streaming(struct vb2_queue *q)
>                 entity = pad->entity;
>                 subdev = media_entity_to_v4l2_subdev(entity);
>
> +               /*
> +                * Subdevs without .s_stream(), such as a sensor pixel array
> +                * entity, return -ENOIOCTLCMD, as at stream on. On a real error
> +                * keep going: the pipeline must be stopped and the buffers
> +                * returned to vb2 in any case.
> +                */
>                 ret = v4l2_subdev_call(subdev, video, s_stream, 0);
> -
> -               if (ret) {
> -                       dev_err(video->camss->dev, "Video pipeline stop failed: %d\n", ret);
> -                       return;
> -               }
> +               if (ret && ret != -ENOIOCTLCMD)
> +                       dev_err(video->camss->dev,
> +                               "Failed to stop %s: %d\n", entity->name, ret);
>         }
>
>         video_device_pipeline_stop(vdev);
> --
> 2.43.0
>