commit 6e74c703132a8b4af4354a5158f286dc8f2407ab
author Matt DeVillier <matt.devillier@gmail.com> Tue Jul 21 10:48:19 2026 -0500
committer Nico Huber <nico.h@gmx.de> Fri Jul 24 15:27:40 2026 +0000
tree ca76843d680a56ce9a5f5de25895d99b68185cb7
parent 6dc7843082cf50e71001c9b24850bfbc86c3a39e

hw-gfx-edid: Clamp preferred mode BPC to 8

EDID often advertises 10+ BPC while the link (or FDI) cannot carry
that at the preferred mode. Cap Mode.BPC at 8 after reading the EDID
depth field so modes stay within typical DP/HDMI/FDI bandwidth.

Tested on samsung/stumpy with a Dell UW3419 over DisplayPort.

Change-Id: I8ef4e493ded3d29be26bda851b478db7c8ad2723
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.sourcearcade.org/c/libgfxinit/+/571
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Nico Huber <nico.h@gmx.de>

common/hw-gfx-edid.adb

diff --git a/common/hw-gfx-edid.adb b/common/hw-gfx-edid.adb
index d8dba1d..57e0c7e 100644
--- a/common/hw-gfx-edid.adb
+++ b/common/hw-gfx-edid.adb
@@ -157,6 +157,11 @@
                  (Raw_EDID (INPUT) and INPUT_DIGITAL_DEPTH_MASK,
                   INPUT_DIGITAL_DEPTH_SHIFT))));
 
+      -- Clamp to 8-bit for compatibility and to conserve bandwidth
+      if Mode.BPC > 8 then
+         Mode.BPC := 8;
+      end if;
+
       -- Calculate absolute values from EDID relative values.
       Mode.H_Sync_Begin := Mode.H_Visible    + Mode.H_Sync_Begin;
       Mode.H_Sync_End   := Mode.H_Sync_Begin + Mode.H_Sync_End;