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Subject: Re: [PATCH v10 08/16] v4l: mark unordered formats
To:     Ezequiel Garcia <ezequiel@collabora.com>,
        linux-media@vger.kernel.org
Cc:     kernel@collabora.com,
        Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
        Shuah Khan <shuahkh@osg.samsung.com>,
        Pawel Osciak <pawel@osciak.com>,
        Alexandre Courbot <acourbot@chromium.org>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Brian Starkey <brian.starkey@arm.com>,
        linux-kernel@vger.kernel.org,
        Gustavo Padovan <gustavo.padovan@collabora.com>
References: <20180521165946.11778-1-ezequiel@collabora.com>
 <20180521165946.11778-9-ezequiel@collabora.com>
 <2df0ec97-9e0f-8fc3-1481-ac0a72e52e4d@xs4all.nl>
 <70b7ddaf685c2fc08dfd1caaab45bb0cc9c99a21.camel@collabora.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <db537395-836a-3f6c-0039-1f4ed957f126@xs4all.nl>
Date:   Wed, 23 May 2018 13:29:01 +0200
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On 23/05/18 12:30, Ezequiel Garcia wrote:
> On Tue, 2018-05-22 at 13:55 +0200, Hans Verkuil wrote:
>> On 21/05/18 18:59, Ezequiel Garcia wrote:
>>> From: Gustavo Padovan <gustavo.padovan@collabora.com>
>>>
>>> Now that we've introduced the V4L2_FMT_FLAG_UNORDERED flag,
>>> mark the appropriate formats.
>>>
>>> v2: Set unordered flag before calling the driver callback.
>>>
>>> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
>>> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
>>> ---
>>>  drivers/media/v4l2-core/v4l2-ioctl.c | 74 +++++++++++++++++++++++++++---------
>>>  1 file changed, 57 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> index f48c505550e0..2135ac235a96 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> @@ -1102,6 +1102,27 @@ static int v4l_enumoutput(const struct v4l2_ioctl_ops *ops,
>>>  	return ops->vidioc_enum_output(file, fh, p);
>>>  }
>>>  
>>> +static void v4l_fill_unordered_fmtdesc(struct v4l2_fmtdesc *fmt)
>>> +{
>>> +	switch (fmt->pixelformat) {
>>> +	case V4L2_PIX_FMT_MPEG:
>>> +	case V4L2_PIX_FMT_H264:
>>> +	case V4L2_PIX_FMT_H264_NO_SC:
>>> +	case V4L2_PIX_FMT_H264_MVC:
>>> +	case V4L2_PIX_FMT_H263:
>>> +	case V4L2_PIX_FMT_MPEG1:
>>> +	case V4L2_PIX_FMT_MPEG2:
>>> +	case V4L2_PIX_FMT_MPEG4:
>>> +	case V4L2_PIX_FMT_XVID:
>>> +	case V4L2_PIX_FMT_VC1_ANNEX_G:
>>> +	case V4L2_PIX_FMT_VC1_ANNEX_L:
>>> +	case V4L2_PIX_FMT_VP8:
>>> +	case V4L2_PIX_FMT_VP9:
>>> +	case V4L2_PIX_FMT_HEVC:
>>> +		fmt->flags |= V4L2_FMT_FLAG_UNORDERED;
>>
>> Please add a break here. This prevents potential future errors if new cases
>> are added below this line.
>>
> 
> Sure.
> 
>>> +	}
>>> +}
>>> +
>>>  static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
>>>  {
>>>  	const unsigned sz = sizeof(fmt->description);
>>> @@ -1310,61 +1331,80 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
>>>  
>>>  	if (descr)
>>>  		WARN_ON(strlcpy(fmt->description, descr, sz) >= sz);
>>> -	fmt->flags = flags;
>>> +	fmt->flags |= flags;
>>>  }
>>>  
>>> -static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>> -				struct file *file, void *fh, void *arg)
>>> -{
>>> -	struct v4l2_fmtdesc *p = arg;
>>> -	int ret = check_fmt(file, p->type);
>>>  
>>> -	if (ret)
>>> -		return ret;
>>> -	ret = -EINVAL;
>>> +static int __vidioc_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>> +			     struct v4l2_fmtdesc *p,
>>> +			     struct file *file, void *fh)
>>> +{
>>> +	int ret = 0;
>>>  
>>>  	switch (p->type) {
>>>  	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_vid_cap))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_vid_cap(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_vid_cap(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_vid_cap_mplane))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_vid_cap_mplane(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_vid_cap_mplane(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_VIDEO_OVERLAY:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_vid_overlay))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_vid_overlay(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_vid_overlay(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_vid_out))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_vid_out(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_vid_out(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_vid_out_mplane))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_vid_out_mplane(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_vid_out_mplane(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_SDR_CAPTURE:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_sdr_cap))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_sdr_cap(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_sdr_cap(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_SDR_OUTPUT:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_sdr_out))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_sdr_out(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_sdr_out(file, fh, p);
>>>  		break;
>>>  	case V4L2_BUF_TYPE_META_CAPTURE:
>>>  		if (unlikely(!ops->vidioc_enum_fmt_meta_cap))
>>>  			break;
>>> -		ret = ops->vidioc_enum_fmt_meta_cap(file, fh, arg);
>>> +		ret = ops->vidioc_enum_fmt_meta_cap(file, fh, p);
>>>  		break;
>>>  	}
>>> +	return ret;
>>> +}
>>> +
>>> +static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>> +				struct file *file, void *fh, void *arg)
>>> +{
>>> +	struct v4l2_fmtdesc *p = arg;
>>> +	int ret = check_fmt(file, p->type);
>>> +
>>> +	if (ret)
>>> +		return ret;
>>> +	ret = -EINVAL;
>>
>> Why set ret when it is overwritten below?
>>
> 
> Oops, seems to be some leftover code.
> 
>>> +
>>> +	ret = __vidioc_enum_fmt(ops, p, file, fh);
>>> +	if (ret)
>>> +		return ret;
>>
>> Huh? Why call the driver twice? As far as I can see you can just drop
>> these three lines above.
>>
>>
> 
> Well, because I thought this was the outcome of v9 [1]. Let me quote you:
> 
> ""
> I realized that this is a problem since this function is called *after*
> the driver. So the driver has no chance to clear this flag if it knows
> that the queue is always ordered.
> ""
> 
> So, we first call the driver to get struct v4l2_fmtdesc pixelformat field
> filled by the driver, then we call v4l_fill_unordered_fmtdesc()
> to set FLAG_UNORDERED if needed, and finally we call the driver again
> so it can clear the FLAG_UNORDERED.
> 
> Does that make sense?

Not what I meant. v4l_fill_unordered_fmtdesc() should be called first, then
the driver (which can now fiddle with the flag if it wants to) and finally
v4l_fill_fmtdesc(p) is called.

Drivers that support these compressed formats need to be checked though:
they shouldn't overwrite flags unconditionally.

Regards,

	Hans

> 
> [1] https://lkml.org/lkml/2018/5/7/349
>