linux-kernel - Re: [PATCH v3 5/9] vcodec: mediatek: Add Mediatek V4L2 Video Decoder Driver

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Message-ID: <8bd71dee-62ec-beba-c1d1-fc7e586d593b@xs4all.nl>
Date:	Mon, 1 Aug 2016 12:39:44 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Tiffany Lin <tiffany.lin@...iatek.com>
Cc:	Hans Verkuil <hans.verkuil@...co.com>, daniel.thompson@...aro.org,
	Rob Herring <robh+dt@...nel.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Pawel Osciak <posciak@...omium.org>,
	Eddie Huang <eddie.huang@...iatek.com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
	linux-mediatek@...ts.infradead.org, PoChun.Lin@...iatek.com
Subject: Re: [PATCH v3 5/9] vcodec: mediatek: Add Mediatek V4L2 Video Decoder
 Driver

Hi Tiffany,

On 08/01/2016 11:38 AM, Tiffany Lin wrote:
> Hi Hans,

<snip>

>>> +static int vidioc_vdec_g_selection(struct file *file, void *priv,
>>> +			struct v4l2_selection *s)
>>> +{
>>> +	struct mtk_vcodec_ctx *ctx = fh_to_ctx(priv);
>>> +
>>> +	if (V4L2_TYPE_IS_OUTPUT(s->type))
>>> +		return -EINVAL;
>>> +
>>> +	if (s->target != V4L2_SEL_TGT_CROP)
>>> +		return -EINVAL;
>>
>> How does the cropping rectangle relate to the format size? There is no s_selection,
>> so this doesn't make sense.
>>
> I want to return encoded crop information or real display region that
> display driver could know where is padding region.

Sorry, I don't understand this.

This is a decoder, so based on the bitstream it decodes to a certain width
and height. I assume that is what you refer to as coded_width and coded_height?

If so, then what is the 'real display region' and how does it relate to the
coded width/height?

This is probably a terminology issue but I need to understand this before I
can decide what should be done here.

Regards,

	Hans

> User space use s_fmt/g_fmt  to set/get coded_width and coded_height, and
> use g_crop to get real display region.
> That's why I do not add s_selection.
> 
>> Alternatively, it could be that you are really returning V4L2_SEL_TGT_COMPOSE_PADDED.
>>
> 
> V4L2_SEL_TGT_COMPOSE_PADDED means
> "The active area and all padding pixels that are inserted or modified by
> hardware."
> But I just want to return active area to user space.
> 
>>> +
>>> +	if (ctx->state < MTK_STATE_HEADER)
>>> +		return -EINVAL;
>>> +
>>> +	if ((ctx->q_data[MTK_Q_DATA_SRC].fmt->fourcc == V4L2_PIX_FMT_H264) ||
>>> +	    (ctx->q_data[MTK_Q_DATA_SRC].fmt->fourcc == V4L2_PIX_FMT_VP8) ||
>>> +	    (ctx->q_data[MTK_Q_DATA_SRC].fmt->fourcc == V4L2_PIX_FMT_VP9)) {
>>> +
>>> +		if (vdec_if_get_param(ctx, GET_PARAM_CROP_INFO, &(s->r))) {
>>> +			mtk_v4l2_debug(2,
>>> +					"[%d]Error!! Cannot get param : GET_PARAM_CROP_INFO ERR",
>>> +					ctx->id);
>>> +			s->r.left = 0;
>>> +			s->r.top = 0;
>>> +			s->r.width = ctx->picinfo.buf_w;
>>> +			s->r.height = ctx->picinfo.buf_h;
>>> +		}
>>> +		mtk_v4l2_debug(2, "Cropping info: l=%d t=%d w=%d h=%d",
>>> +				s->r.left, s->r.top, s->r.width,
>>> +				s->r.height);
>>> +	} else {
>>> +		s->r.left = 0;
>>> +		s->r.top = 0;
>>> +		s->r.width = ctx->picinfo.pic_w;
>>> +		s->r.height = ctx->picinfo.pic_h;
>>> +		mtk_v4l2_debug(2, "Cropping info: w=%d h=%d fw=%d fh=%d",
>>> +				s->r.width, s->r.height, ctx->picinfo.buf_w,
>>> +				ctx->picinfo.buf_h);
>>> +	}
>>> +	return 0;
>>> +}