linux-kernel - Re: [PATCH v4 3/5] media: uvcvideo: Split uvc_stop

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Message-ID: <04e10cfa-f1b1-4327-b0ca-c66f8450d42f@xs4all.nl>
Date: Tue, 17 Jun 2025 11:27:44 +0200
From: Hans Verkuil <hverkuil@...all.nl>
To: Ricardo Ribalda <ribalda@...omium.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Hans de Goede <hdegoede@...hat.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 Hans de Goede <hansg@...nel.org>
Subject: Re: [PATCH v4 3/5] media: uvcvideo: Split uvc_stop_streaming()

On 16/06/2025 17:24, Ricardo Ribalda wrote:
> uvc_stop_streaming() is used for meta and video nodes. Split the function
> in two to avoid confusion.
> 
> Use this opportunity to rename uvc_start_streaming() to
> uvc_start_streaming_video(), as it is only called by the video nodes.
> 
> Reviewed-by: Hans de Goede <hansg@...nel.org>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_queue.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
> index 8f9737ac729546683ca48f5e71ce3dfacbae2926..3f357c2d48cfd258c26f0342007d1d12f1e01007 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -167,7 +167,7 @@ static void uvc_buffer_finish(struct vb2_buffer *vb)
>  		uvc_video_clock_update(stream, vbuf, buf);
>  }
>  
> -static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
> +static int uvc_start_streaming_video(struct vb2_queue *vq, unsigned int count)
>  {
>  	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
>  	struct uvc_streaming *stream = uvc_queue_to_stream(queue);
> @@ -186,14 +186,22 @@ static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	return ret;
>  }
>  
> -static void uvc_stop_streaming(struct vb2_queue *vq)
> +static void uvc_stop_streaming_video(struct vb2_queue *vq)
>  {
>  	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
>  
>  	lockdep_assert_irqs_enabled();
>  
> -	if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
> -		uvc_video_stop_streaming(uvc_queue_to_stream(queue));
> +	uvc_video_stop_streaming(uvc_queue_to_stream(queue));
> +
> +	uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
> +}
> +
> +static void uvc_stop_streaming_meta(struct vb2_queue *vq)
> +{
> +	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> +
> +	lockdep_assert_irqs_enabled();
>  
>  	uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
>  }
> @@ -203,15 +211,15 @@ static const struct vb2_ops uvc_queue_qops = {
>  	.buf_prepare = uvc_buffer_prepare,
>  	.buf_queue = uvc_buffer_queue,
>  	.buf_finish = uvc_buffer_finish,
> -	.start_streaming = uvc_start_streaming,
> -	.stop_streaming = uvc_stop_streaming,
> +	.start_streaming = uvc_start_streaming_video,
> +	.stop_streaming = uvc_stop_streaming_video,
>  };
>  
>  static const struct vb2_ops uvc_meta_queue_qops = {
>  	.queue_setup = uvc_queue_setup,
>  	.buf_prepare = uvc_buffer_prepare,
>  	.buf_queue = uvc_buffer_queue,
> -	.stop_streaming = uvc_stop_streaming,
> +	.stop_streaming = uvc_stop_streaming_meta,
>  };

I think there should be a comment stating that the metadata stream
expects that video is streaming, it does not start streaming by itself.

Something like:

	/*
	 * .start_streaming is not provided here. Metadata relies on
	 * video streaming being active. If video isn't streaming, then
	 * no metadata will arrive either.
	 */

It's unexpected that there is no start_streaming for metadata, so a
comment wouldn't hurt.

Otherwise this looks fine, so:

Reviewed-by: Hans Verkuil <hverkuil@...all.nl>

Regards,

	Hans

>  
>  int uvc_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type)
>