linux-kernel - Re: [PATCH v5 3/3] [media] s5p-mfc: Check and set 'v4l2_pix_format:field' field in try

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Date:   Wed, 22 Feb 2017 10:10:40 -0300
From:   Thibault Saunier <thibault.saunier@....samsung.com>
To:     Andrzej Hajda <a.hajda@...sung.com>, linux-kernel@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Andi Shyti <andi.shyti@...sung.com>,
        linux-media@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        linux-samsung-soc@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Inki Dae <inki.dae@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jeongtae Park <jtp.park@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Kamil Debski <kamil@...as.org>
Subject: Re: [PATCH v5 3/3] [media] s5p-mfc: Check and set
 'v4l2_pix_format:field' field in try_fmt

Hello,

On 02/22/2017 06:29 AM, Andrzej Hajda wrote:
> On 21.02.2017 20:20, Thibault Saunier wrote:
>> It is required by the standard that the field order is set by the
>> driver.
>>
>> Signed-off-by: Thibault Saunier <thibault.saunier@....samsung.com>
>>
>> ---
>>
>> Changes in v5:
>> - Just adapt the field and never error out.
>>
>> Changes in v4: None
>> Changes in v3:
>> - Do not check values in the g_fmt functions as Andrzej explained in previous review
>>
>> Changes in v2:
>> - Fix a silly build error that slipped in while rebasing the patches
>>
>>   drivers/media/platform/s5p-mfc/s5p_mfc_dec.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c b/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
>> index 0976c3e0a5ce..44ed2afe0780 100644
>> --- a/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
>> +++ b/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
>> @@ -386,6 +386,9 @@ static int vidioc_try_fmt(struct file *file, void *priv, struct v4l2_format *f)
>>   	struct v4l2_pix_format_mplane *pix_mp = &f->fmt.pix_mp;
>>   	struct s5p_mfc_fmt *fmt;
>>   
>> +	if (f->fmt.pix.field == V4L2_FIELD_ANY)
>> +		f->fmt.pix.field = V4L2_FIELD_NONE;
>> +
> In previous version the only supported field type was NONE, here you
> support everything.
> If the only supported format is none you should set 'field'
> unconditionally to NONE, nothing more.
Afaict we  support 2 things:

   1. NONE
   2. INTERLACE

Until now we were not checking what was supported or not and basically 
ignoring that info, this patch
keeps the old behaviour making sure to be compliant.

I had a doubt and was pondering doing:

``` diff

+	if (f->fmt.pix.field != V4L2_FIELD_INTERLACED)
+		f->fmt.pix.field = V4L2_FIELD_NONE;
+

```

instead, it is probably more correct, do you think it is what should be 
done here?

Regards,

Thibault

>
> Regards
> Andrzej
>
>>   	mfc_debug(2, "Type is %d\n", f->type);
>>   	if (f->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) {
>>   		fmt = find_format(f, MFC_FMT_DEC);
>