On Mon, Jan 17, 2022 at 02:29:47PM +0100, Geert Uytterhoeven wrote:
> Hi Gerd,
>
> On Mon, Jan 17, 2022 at 1:57 PM Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
> > > b) to include new drivers (for old hardware) if they arrive (probably happens rarely but there can be).
> > > I know of at least one driver which won't be able to support DRM....
> >
> > Hmm? I seriously doubt that. There is always the option to use a
> > shadow framebuffer, then convert from standard drm formats to whatever
> > esoteric pixel format your hardware expects.
> >
> > Been there, done that. Have a look at the cirrus driver. The physical
> > hardware was designed in the early 90-ies, almost 30 years ago. These
> > days it exists in virtual form only (qemu emulates it). Thanks to the
> > drm driver it runs wayland just fine even though it has a bunch of
> > constrains dictated by the hardware design.
>
> The Cirrus DRM driver supports TrueColor (RGB565/888 and ARGB8888)
> modes only. The Cirrus fbdev driver also supports mochrome and 256
> color modes.
>
> There exist some DRM drivers that do support DRM_FORMAT_C8, but none of
> the "tiny" ones do. Same for DRM_FORMAT_RGB{332,233}.
Adding that to the cirrus driver shouldn't be hard. I'm wondering
whenever there are any userspace apps which would actually use that
though.
take care,
Gerd
