From 7344bad7fb6daa4877a1c064b52c7d5f9182c41b Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula@intel.com>
Date: Wed, 23 Mar 2022 12:04:38 +0200
Subject: drm/edid: fix CEA extension byte #3 parsing
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: 7344bad7fb6daa4877a1c064b52c7d5f9182c41b
Patch-mainline: v5.18-rc1
References: bsc#1190786
 
Only an EDID CEA extension has byte #3, while the CTA DisplayID Data
Block does not. Don't interpret bogus data for color formats.
 
For most displays it's probably an unlikely scenario you'd have a CTA
DisplayID Data Block without a CEA extension, but they do exist.
 
Fixes: e28ad544f462 ("drm/edid: parse CEA blocks embedded in DisplayID")
Cc: <stable@vger.kernel.org>
Cc: Shawn C Lee <shawn.c.lee@intel.com>
Cc: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220323100438.1757295-1-jani.nikula@intel.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_edid.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
 
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5086,10 +5086,14 @@ static void drm_parse_cea_ext(struct drm
 
 	/* The existence of a CEA block should imply RGB support */
 	info->color_formats = DRM_COLOR_FORMAT_RGB444;
-	if (edid_ext[3] & EDID_CEA_YCRCB444)
-		info->color_formats |= DRM_COLOR_FORMAT_YCBCR444;
-	if (edid_ext[3] & EDID_CEA_YCRCB422)
-		info->color_formats |= DRM_COLOR_FORMAT_YCBCR422;
+
+	/* CTA DisplayID Data Block does not have byte #3 */
+	if (edid_ext[0] == CEA_EXT) {
+		if (edid_ext[3] & EDID_CEA_YCRCB444)
+			info->color_formats |= DRM_COLOR_FORMAT_YCBCR444;
+		if (edid_ext[3] & EDID_CEA_YCRCB422)
+			info->color_formats |= DRM_COLOR_FORMAT_YCBCR422;
+	}
 
 	if (cea_db_offsets(edid_ext, &start, &end))
 		return;