[PATCH libdrm v2 01/10] util: Improve SMPTE color LUT accuracy

[Sam Ravnborg]

Hi Geert,

On Sun, Jul 10, 2022 at 01:04:23PM +0200, Geert Uytterhoeven wrote:
> Hi Sam,
> 
> On Sun, Jul 10, 2022 at 12:31 PM Sam Ravnborg <sam at ravnborg.org> wrote:
> > On Fri, Jul 08, 2022 at 08:21:31PM +0200, Geert Uytterhoeven wrote:
> > > Fill in the LSB when converting color components from 8-bit to 16-bit.
> > >
> > > Signed-off-by: Geert Uytterhoeven <geert at linux-m68k.org>
> > > ---
> > > v2:
> > >   - New.
> > > ---
> > >  tests/util/pattern.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tests/util/pattern.c b/tests/util/pattern.c
> > > index 178aee8341a38920..3753ebc1eeae6c9a 100644
> > > --- a/tests/util/pattern.c
> > > +++ b/tests/util/pattern.c
> > > @@ -646,9 +646,9 @@ void util_smpte_c8_gamma(unsigned size, struct drm_color_lut *lut)
> > >       memset(lut, 0, size * sizeof(struct drm_color_lut));
> > >
> > >  #define FILL_COLOR(idx, r, g, b) \
> > > -     lut[idx].red = (r) << 8; \
> > > -     lut[idx].green = (g) << 8; \
> > > -     lut[idx].blue = (b) << 8
> > > +     lut[idx].red = (r) * 0x101; \
> >
> >         (lut[idx].red = (r) << 8) | 1;
> >
> > had IMO been easier to read.
> 
> I guess you mean "| (r)" instead of "| 1"?
Well, I meant what I wrote but it is obviously wrong.

So yes
	lut[idx].red = (r) << 8 | (r);

is the equivalent of multiplying with 0x101.

Whatever works, but if you update this patch, then please update the
later patch where the multiply with 0x101 is also used.

	Sam