linux-kernel - Re: [PATCH v2 03/23] media: videobuf2-v4l2: Warn on holding buffers without support

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Message-ID: <Ykgq5EWX9T7q0VEZ@eze-laptop>
Date:   Sat, 2 Apr 2022 07:52:20 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Nicolas Dufresne <nicolas.dufresne@...labora.com>
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        kernel@...labora.com,
        Sebastian Fricke <sebastian.fricke@...labora.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/23] media: videobuf2-v4l2: Warn on holding buffers
 without support

On Thu, Mar 31, 2022 at 03:37:05PM -0400, Nicolas Dufresne wrote:
> From: Sebastian Fricke <sebastian.fricke@...labora.com>
> 
> Using V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF flag without specifying the
> subsystem flag VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF, results in
> silently ignoring it.
> Warn the user via a debug print when the flag is requested but ignored
> by the videobuf2 framework.
> 
> Signed-off-by: Sebastian Fricke <sebastian.fricke@...labora.com>
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>

Reviewed-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>

> ---
>  drivers/media/common/videobuf2/videobuf2-v4l2.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 6edf4508c636..812c8d1962e0 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -329,8 +329,13 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
>  		 */
>  		vbuf->flags &= ~V4L2_BUF_FLAG_TIMECODE;
>  		vbuf->field = b->field;
> -		if (!(q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF))
> +		if (!(q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)) {
> +			if (vbuf->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF)
> +				dprintk(q, 1,
> +					"Request holding buffer (%d), unsupported on output queue\n",
> +					b->index);
>  			vbuf->flags &= ~V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
> +		}
>  	} else {
>  		/* Zero any output buffer flags as this is a capture buffer */
>  		vbuf->flags &= ~V4L2_BUFFER_OUT_FLAGS;
> -- 
> 2.34.1
>