Re: [PATCH v9 11/11] media: i2c: ov7670: Fully set mbus frame fmt

[jacopo mondi]

Hello again,

On Tue, Feb 20, 2018 at 09:58:57AM +0100, jacopo mondi wrote:
> Hi Laurent,
>
> On Mon, Feb 19, 2018 at 09:19:32PM +0200, Laurent Pinchart wrote:
> > Hi Jacopo,
> >
> > Thank you for the patch.
> >
> > On Monday, 19 February 2018 18:59:44 EET Jacopo Mondi wrote:
> > > The sensor driver sets mbus format colorspace information and sizes,
> > > but not ycbcr encoding, quantization and xfer function. When supplied
> > > with an badly initialized mbus frame format structure, those fields
> > > need to be set explicitly not to leave them uninitialized. This is
> > > tested by v4l2-compliance, which supplies a mbus format description
> > > structure and checks for all fields to be properly set.
> > >
> > > Without this commit, v4l2-compliance fails when testing formats with:
> > > fail: v4l2-test-formats.cpp(335): ycbcr_enc >= 0xff
> > >
> > > Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> > > ---
> > >  drivers/media/i2c/ov7670.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/media/i2c/ov7670.c b/drivers/media/i2c/ov7670.c
> > > index 25b26d4..61c472e 100644
> > > --- a/drivers/media/i2c/ov7670.c
> > > +++ b/drivers/media/i2c/ov7670.c
> > > @@ -996,6 +996,10 @@ static int ov7670_try_fmt_internal(struct v4l2_subdev
> > > *sd, fmt->height = wsize->height;
> > >  	fmt->colorspace = ov7670_formats[index].colorspace;
> >
> > On a side note, if I'm not mistaken the colorspace field is set to SRGB for
> > all entries. Shouldn't you hardcode it here and remove the field ?
> >
> > > +	fmt->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
> > > +	fmt->quantization = V4L2_QUANTIZATION_DEFAULT;
> > > +	fmt->xfer_func = V4L2_XFER_FUNC_DEFAULT;
> >
> > How about setting the values explicitly instead of relying on defaults ? That
> > would be V4L2_YCBCR_ENC_601, V4L2_QUANTIZATION_LIM_RANGE and
> > V4L2_XFER_FUNC_SRGB. And could you then check a captured frame to see if the
> > sensor outputs limited or full range ?
> >
>
> This actually makes me wonder if those informations (ycbcb_enc,
> quantization and xfer_func) shouldn't actually be part of the
> supported format list... I blindly added those default fields in the
> try_fmt function, but I doubt they applies to all supported formats.
>
> Eg. the sensor supports YUYV as well as 2 RGB encodings (RGB444 and
> RGB 565) and 1 raw format (BGGR). I now have a question here:
>
> 1) ycbcr_enc transforms non-linear R'G'B' to Y'CbCr: does this
> applies to RGB and raw formats? I don't think so, and what value is
> the correct one for the ycbcr_enc field in this case? I assume
> xfer_func and quantization applies to all formats instead..
>

What if I repropose this as separate patch not part of the CEU series
in order not to hold back v10 (which I hope will be the last CEU
iteration)?

> Thanks
>    j
>
> > >  	info->format = *fmt;
> > >
> > >  	return 0;
> >
> > --
> > Regards,
> >
> > Laurent Pinchart
> >