drm/fb-helper: Add support for DRM_FORMAT_C[124]
Add support for color-indexed frame buffer formats with two, four, and
sixteen colors to the DRM framebuffer helper functions:
1. Add support for 1, 2, and 4 bits per pixel to the damage helper,
2. For color-indexed modes, the length of the color bitfields must be
set to the color depth, else the logo code may pick a logo with too
many colors. Drop the incorrect DAC width comment, which
originates from the i915 driver.
3. Accept C[124] modes when validating or filling in struct
fb_var_screeninfo, and use the correct number of bits per pixel.
4. Set the visual to FB_VISUAL_PSEUDOCOLOR for all color-indexed
modes.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/db3e80b445df661ff0cd7e698507a8d24a4c867e.1657294931.git.geert@linux-m68k.org