Hi Daniel,
On Fri, Jan 21, 2022 at 9:55 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
> Just to clarify, since we had lots of smaller and bigger
> misunderstandings in the thread thus far: DRM_FORMAT_RGB332 exists, so
> drm support that already. The fbdev emulation doesn't yet, but all
> that's needed for that is filling out the code to remap the drm
> description to the fbdev format description for this case. Plus
> testing it all works ofc with fbcon and whatelse. Note that RGB332 is
> a bit more work than e.g. C4, since atm fbdev still uses only bpp to
> identify formats, so would need to be switch over to drm_fourcc first
> before adding anything which aliases with something existing (we have
> C8 already wired up).
I doubt that RGB332 would be a bit more work than C4, as RGB332 is still
8 bpp, while C4 is less. To support C4, all DRM code that cannot
handle format->cpp[0] < 1 or drm_format_info_block_width() > 1 has to be
fixed first.
On the plus side, I finally got my proof-of-concept Atari DRM driver
working with fbcon on ARAnyM. Mapping /dev/fb0 from userspace doesn't
work (fbtest SEGVs while reading from the mapped frame buffer). I don't
know yet if this is a general issue without deferred I/O in v5.17-rc1,
or a bug in the m68k MM code...
So far it supports C8 only, but I hope to tackle C4 and monochrome soon.
Whether the end result will be usable on real hardware is still to be
seen, but at least I hope to get some DRM code written...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
