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Date:   Tue, 01 Sep 2020 08:57:37 +0000
To:     =?utf-8?Q?Ville_Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
From:   Simon Ser <contact@emersion.fr>
Cc:     Sidong Yang <realwakka@gmail.com>,
        Haneen Mohammed <hamohammed.sa@gmail.com>,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        Emil Velikov <emil.l.velikov@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        Melissa Wen <melissa.srw@gmail.com>
Reply-To: Simon Ser <contact@emersion.fr>
Subject: Re: [PATCH] drm/vkms: add support for gamma_set interface
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On Monday, August 31, 2020 3:48 PM, Ville Syrj=C3=A4l=C3=A4 <ville.syrjala@=
linux.intel.com> wrote:

> > > It doesn't seem like this IGT test's goal is to exercise support for
> > > gamma LUTs. Does the test just tries to reset the gamma LUT to linear=
?
> > > If so, I think the IGT test should be fixed to ignore "I don't suppor=
t
> > > gamma" errors.
> >
> > It seems like that IGT test pixel-format is to make gamma lut like belo=
w.
> > for (i =3D 0; i < lut_size; i++)
> > lut[i] =3D (i * 0xffff / (lut_size - 1)) & mask;
> > And set this table to drm driver. and test begins. It's the test about =
pixel
> > format. I think you're right. It's not about gamma lut.
>
> The point of the gamma LUT stuff in the pixel format test is to throw
> away a bunch of the lsbs so that the test passes when the result is
> "close enough" to the 8bpc RGB reference image. Without it we would
> never get a crc match when testing non-8bpc or YCbCr formats.

OK, that makes sense. Would it be sensible to:

- Don't set gamma if the pixel format being tested is 8bpc
- Make the test skip if the pixel format is >8bpc and gamma isn't
  supported