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

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Date:   Fri, 31 Mar 2017 09:59:57 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        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 Hans,


On 30-03-2017 14:42, Hans Verkuil wrote:
> 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.

Thanks! Yes, maybe its better to test with a different receiver,
if it has more precision then its great. Let me know if you need
any help :)

Best regards,
Jose Miguel Abreu

>
> 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;
>>  }
>>