[PATCH 1/3] RFT: drm/pl111: Support grayscale

[Daniel Vetter]

On Tue, Jul 23, 2019 at 7:25 PM Adam Jackson <ajax at redhat.com> wrote:
>
> On Tue, 2019-07-23 at 15:37 +0200, Linus Walleij wrote:
> > Migrating the TI nspire calculators to use the PL111 driver for
> > framebuffer requires grayscale support for the elder panel
> > which uses 8bit grayscale only.
> >
> > DRM does not support 8bit grayscale framebuffers in memory,
> > but by defining the bus format to be MEDIA_BUS_FMT_Y8_1X8 we
> > can get the hardware to turn on a grayscaling feature and
> > convert the RGB framebuffer to grayscale for us.
>
> What's wrong with DRM_FORMAT_R8? Yes the hardware is not really
> "redscale", but it's still a single color channel and there's not
> really any ambiguity.

Yeah, I think with a comment or an aliasing #define to _Y8 (or both)
this is good to go.

You probably still want to expose the rgb format since too much
userspace just assumes that xrgb8888 works. Same reason why the
tinydrm drivers do the sw conversion.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch