[PATCH libdrm v2 00/10] Add support for low-color frame buffer formats

[Geert Uytterhoeven]

Hi Sam,

On Sun, Jul 10, 2022 at 12:40 PM Sam Ravnborg <sam at ravnborg.org> wrote:
> On Fri, Jul 08, 2022 at 08:21:30PM +0200, Geert Uytterhoeven wrote:
> > A long outstanding issue with the DRM subsystem has been the lack of
> > support for low-color displays, as used typically on older desktop
> > systems, and on small embedded displays.
> >
> > This patch series adds support for color-indexed frame buffer formats
> > with 2, 4, and 16 colors.  It has been tested on ARAnyM using a
> > work-in-progress Atari DRM driver.
> >
> > Changes compared to v1:
> >   - SMPTE color LUT accuracy,
> >   - Factor out smpte color LUT,
> >   - Restructure patches,
> >   - Improve descriptions.
> >   - Store number of colors for indexed formats,
> >   - Add SMPTE pattern support for the C1 and C2 formats.
> >
> > Please refer to [2] for related Linux DRM patches and background
> > information.
> >
> > Thanks for your comments!
> >
> > [1] "[PATCH libdrm 0/3] Add support for low-color frame buffer formats"
> >     https://lore.kernel.org/r/cover.1646683737.git.geert@linux-m68k.org
> > [2] "[PATCH v3 00/10] drm: Add support for low-color frame buffer formats"
> >     https://lore.kernel.org/r/cover.1657294931.git.geert@linux-m68k.org
> >
> > Geert Uytterhoeven (10):
> >   util: Improve SMPTE color LUT accuracy
> >   util: Factor out and optimize C8 SMPTE color LUT
> >   [RFC] drm_fourcc: Add DRM_FORMAT_C[124]
> >   util: Add support for DRM_FORMAT_C[124]
> >   util: Store number of colors for indexed formats
> >   util: Add SMPTE pattern support for C4 format
> >   util: Add SMPTE pattern support for C1 format
> >   util: Add SMPTE pattern support for C2 format
> >   modetest: Add support for DRM_FORMAT_C[124]
> >   modetest: Add SMPTE pattern support for C4 format
>
> I have browsed the patches - everything looked good.
> The parts with Floyd-Steinberg dithering did get less
> attention as I do not know it.

As a picture says more than 10000 words, I shared screenshots of
modetest showing the SMPTE pattern in C1 (monochrome FS-dithered
[1]), C2 (PenTile RG-GB FS-dithered [2]), and C4 ([3]).
And Wikipedia[4] is your friend for the algorithm ;-)

> But everything looked good and the series is:
>
> Acked-by: Sam Ravnborg <sam at ravnborg.org>

Thanks!

[1] https://drive.google.com/file/d/1waJczErrIaEKRhBCCU1ynxRG8agpo0Xx/view?usp=sharing
[2] https://drive.google.com/file/d/1g5O8XeacrjrC8rgaVENvR65YeI6QvmtO/view?usp=sharing
[3] https://drive.google.com/file/d/1VIMqz_OkjJbbFS2OCX1O8GBm4bag6y2n/view?usp=sharing
[4] https://en.wikipedia.org/wiki/Floyd%E2%80%93Steinberg_dithering

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds