[Intel-gfx] [PATCH 1/4] drm: Fix color LUT rounding

[Borah, Chaitanya Kumar]

Hello Ville,

> -----Original Message-----
> From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjälä
> Sent: Tuesday, October 31, 2023 9:37 PM
> To: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 1/4] drm: Fix color LUT rounding
> 
> On Tue, Oct 31, 2023 at 11:15:35AM +0200, Jani Nikula wrote:
> > On Fri, 13 Oct 2023, Ville Syrjala <ville.syrjala at linux.intel.com> wrote:
> > > entrirely. But perhaps a better idea would be to follow the OpenGL
> > > int<->float conversion rules, in which case we get the following
> > > results:
> >
> > Do you have a pointer to the rules handy, I couldn't find it. :(
> 
> Eg. '2.3.5 Fixed-Point Data Conversions' in GL 4.6 spec. The section number
> probably changes depending on which version of the spec you look at.
> 

This section particularly talks about conversion of normalized fixed point  to floating point numbers and vice versa.
Pardon my limited knowledge on the topic but aren't we just doing a scaling factor conversion(Q0.16 -> Q0.8) in these patches?

I could not draw a direct relation between the formulas in the section[1] and what we are doing here.(but it could be just me!)

Regards

Chaitanya

[1] https://registry.khronos.org/OpenGL/specs/gl/glspec46.core.pdf '2.3.5 Fixed-Point Data Conversions'

> >
> > Might also add the reference to the commit message and/or comment.
> >
> > BR,
> > Jani.
> >
> > --
> > Jani Nikula, Intel
> 
> --
> Ville Syrjälä
> Intel