linux-kernel - [PATCH v5 2/7] drm/edid: prepare for VESA vendor-specific data block extension

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Message-ID: <20251017162736.45368-3-iam@lach.pw>
Date: Fri, 17 Oct 2025 18:27:31 +0200
From: Yaroslav Bolyukin <iam@...h.pw>
To: Ville Syrjälä <ville.syrjala@...ux.intel.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Harry Wentland <harry.wentland@....com>,
	Leo Li <sunpeng.li@....com>,
	Rodrigo Siqueira <siqueira@...lia.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	Wayne Lin <Wayne.Lin@....com>,
	amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Yaroslav Bolyukin <iam@...h.pw>
Subject: [PATCH v5 2/7] drm/edid: prepare for VESA vendor-specific data block extension

Current VESA vendor-specific block parsing expects real block size to be
the same as the defined struct size, use real offsets in conditionals
instead to add struct fields in future commits.

Signed-off-by: Yaroslav Bolyukin <iam@...h.pw>
---
 drivers/gpu/drm/drm_edid.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 4fcde52291ce..725ae5f9d160 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -6541,7 +6541,7 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
 	if (oui(vesa->oui[0], vesa->oui[1], vesa->oui[2]) != VESA_IEEE_OUI)
 		return;
 
-	if (sizeof(*vesa) != sizeof(*block) + block->num_bytes) {
+	if (block->num_bytes < 5) {
 		drm_dbg_kms(connector->dev,
 			    "[CONNECTOR:%d:%s] Unexpected VESA vendor block size\n",
 			    connector->base.id, connector->name);
@@ -6564,24 +6564,20 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
 		break;
 	}
 
-	if (!info->mso_stream_count) {
-		info->mso_pixel_overlap = 0;
-		return;
-	}
-
-	info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
-	if (info->mso_pixel_overlap > 8) {
+	if (info->mso_stream_count) {
+		info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
+		if (info->mso_pixel_overlap > 8) {
+			drm_dbg_kms(connector->dev,
+				    "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
+				    connector->base.id, connector->name,
+				    info->mso_pixel_overlap);
+			info->mso_pixel_overlap = 8;
+		}
 		drm_dbg_kms(connector->dev,
-			    "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
+			    "[CONNECTOR:%d:%s] MSO stream count %u, pixel overlap %u\n",
 			    connector->base.id, connector->name,
-			    info->mso_pixel_overlap);
-		info->mso_pixel_overlap = 8;
+			    info->mso_stream_count, info->mso_pixel_overlap);
 	}
-
-	drm_dbg_kms(connector->dev,
-		    "[CONNECTOR:%d:%s] MSO stream count %u, pixel overlap %u\n",
-		    connector->base.id, connector->name,
-		    info->mso_stream_count, info->mso_pixel_overlap);
 }
 
 static void drm_update_vesa_specific_block(struct drm_connector *connector,
-- 
2.51.0