Re: [PATCH] drm/vkms: add support for gamma_set interface

[Simon Ser]

On Monday, August 31, 2020 3:48 PM, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> 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 support
> > > gamma" errors.
> >
> > It seems like that IGT test pixel-format is to make gamma lut like below.
> > for (i = 0; i < lut_size; i++)
> > lut[i] = (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