linux-kernel - Re: [PATCH v3 09/14] media: platform: pxa

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Date:	Mon, 15 Aug 2016 15:26:57 +0200
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Hans Verkuil <hverkuil@...all.nl>,
	Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Jiri Kosina <trivial@...nel.org>, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org
Subject: Re: [PATCH v3 09/14] media: platform: pxa_camera: add buffer sequencing

Robert Jarzmik <robert.jarzmik@...e.fr> writes:

> Add sequence numbers to completed buffers.
>
> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
> ---
>  drivers/media/platform/soc_camera/pxa_camera.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/media/platform/soc_camera/pxa_camera.c b/drivers/media/platform/soc_camera/pxa_camera.c
> index d66443ac1f4d..8a65f126d091 100644
> --- a/drivers/media/platform/soc_camera/pxa_camera.c
> +++ b/drivers/media/platform/soc_camera/pxa_camera.c
> @@ -401,6 +402,7 @@ static void pxa_camera_start_capture(struct pxa_camera_dev *pcdev)
>  	unsigned long cicr0;
>  
>  	dev_dbg(pcdev_to_dev(pcdev), "%s\n", __func__);
> +	pcdev->buf_sequence = 0;

I'm not so sure this is the right place to reset the buffer sequence.

I've seen no documentation on the rules applicable to this sequence number:
 - should it be reset if a "start streaming" operation occurs ?
 - should it be reset if a streams stops by lack of video buffers queued ?
 - should it be reset in queue_setup() like in other drivers ?

Or should it _never_ be reset and only be a monotonic raising number ?

Cheers.

--
Robert