linux-kernel - Re: [PATCH 3/3] [media] cobalt: Use v4l2_calc

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Date:   Thu, 30 Mar 2017 15:42:47 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Jose Abreu <Jose.Abreu@...opsys.com>, linux-media@...r.kernel.org
Cc:     Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] [media] cobalt: Use v4l2_calc_timeperframe helper

Hi Jose,

On 21/03/17 12:49, Jose Abreu wrote:
> Currently, cobalt driver always returns 60fps in g_parm.
> This patch uses the new v4l2_calc_timeperframe helper to
> calculate the time per frame value.

I can verify that g_parm works, so:

Tested-by: Hans Verkuil <hans.verkuil@...co.com>

However, the adv7604 pixelclock detection resolution is only 0.25 MHz, so it
can't tell the difference between 24 and 23.97 Hz. I can't set the new
V4L2_DV_FL_CAN_DETECT_REDUCED_FPS flag there.

It might be possible to implement this for the adv7842 receiver, I think that
that hardware is much more precise.

I would have to try this, but that will have to wait until Friday next week.

Regards,

	Hans

> 
> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: linux-media@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/media/pci/cobalt/cobalt-v4l2.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/pci/cobalt/cobalt-v4l2.c b/drivers/media/pci/cobalt/cobalt-v4l2.c
> index def4a3b..25532ae 100644
> --- a/drivers/media/pci/cobalt/cobalt-v4l2.c
> +++ b/drivers/media/pci/cobalt/cobalt-v4l2.c
> @@ -1076,10 +1076,15 @@ static int cobalt_subscribe_event(struct v4l2_fh *fh,
>  
>  static int cobalt_g_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
>  {
> +	struct cobalt_stream *s = video_drvdata(file);
> +	struct v4l2_fract fps;
> +
>  	if (a->type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
>  		return -EINVAL;
> -	a->parm.capture.timeperframe.numerator = 1;
> -	a->parm.capture.timeperframe.denominator = 60;
> +
> +	fps = v4l2_calc_timeperframe(&s->timings);
> +	a->parm.capture.timeperframe.numerator = fps.numerator;
> +	a->parm.capture.timeperframe.denominator = fps.denominator;
>  	a->parm.capture.readbuffers = 3;
>  	return 0;
>  }
>