edid: Add helper function to calculate bits-per-pixel dependent values

Coreboot and most payloads support three basic pixel widths for the
framebuffer. It assumes 32 by default, but several chipsets need to
override that value with whatever else they're supporting. Our struct
edid contains multiple convenience values that are directly derived from
this (and other properties), so changing the bits per pixel always
requires recalculating all those dependents in the chipset code. This
patch provides a small convenience wrapper that can be used to
consistently update the whole struct edid with a new pixel width
instead, so we no longer need to duplicate those calculations
everywhere.

BUG=None
TEST=Booted Oak in all three pixel widths (which it conveniently all
supports), confirmed that images looked good.

Change-Id: I5376dd4e28cf107ac2fba1dc418f5e1c5a2e2de6
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/14158
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/include/edid.h b/src/include/edid.h
index d3cab17f497d..f46c7619354b 100644
--- a/src/include/edid.h
+++ b/src/include/edid.h
@@ -93,6 +93,7 @@ struct edid {
 
 /* Defined in src/lib/edid.c */
 int decode_edid(unsigned char *edid, int size, struct edid *out);
+void edid_set_framebuffer_bits_per_pixel(struct edid *edid, int fb_bpp);
 void set_vbe_mode_info_valid(struct edid *edid, uintptr_t fb_addr);
 int set_display_mode(struct edid *edid, enum edid_modes mode);