Virtualization - Apr 2021 - [PATCH v4 0/9] drm: Support simple-framebuffer devices and firmware fbs

Hi,
> > > Patches 4 to 8 add the simpledrm driver. It's build on simple
DRM helpers
> > > and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB
framebuffers. During
> > 
> > .... if support for 8-bit frame buffers would be added?
> 
> Is that 8-bit greyscale or 8-bit indexed with 256 entry palette? Former
> shouldn't be a big thing, but the latter is only really supported by
the
> overall drm ecosystem in theory. Most userspace assumes that xrgb8888
> works, and we keep that illusion up by emulating it in kernel for hw which
> just doesn't support it. But reformatting xrgb8888 to c8 is tricky at
> best.
Well.  cirrus converts xrgb8888 on the fly to rgb888 or rgb565
(depending on display resolution).  We could pull off the same trick
here and convert to rgb332 (assuming we can program the palette with the
color cube needed for that).  Wouldn't look pretty, but would probably
work better than expecting userspace know what color palettes are in
2021 ...

take care,
  Gerd

Hi Gerd,

On Tue, Apr 20, 2021 at 11:22 AM Gerd Hoffmann <kraxel at redhat.com>
wrote:
> > > > Patches 4 to 8 add the simpledrm driver. It's build on
simple DRM helpers
> > > > and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB
framebuffers. During
> > >
> > > .... if support for 8-bit frame buffers would be added?
> >
> > Is that 8-bit greyscale or 8-bit indexed with 256 entry palette?
Former
> > shouldn't be a big thing, but the latter is only really supported
by the
> > overall drm ecosystem in theory. Most userspace assumes that xrgb8888
> > works, and we keep that illusion up by emulating it in kernel for hw
which
> > just doesn't support it. But reformatting xrgb8888 to c8 is tricky
at
> > best.
>
> Well.  cirrus converts xrgb8888 on the fly to rgb888 or rgb565
> (depending on display resolution).  We could pull off the same trick
> here and convert to rgb332 (assuming we can program the palette with the
> color cube needed for that).  Wouldn't look pretty, but would probably
> work better than expecting userspace know what color palettes are in
> 2021 ...
Yeah, I already had a similar idea for Amiga HAM ;-)

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