linux-kernel - [PATCH v5 3/7] drm/edid: MSO should only be used for non-eDP displays

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251017162736.45368-4-iam@lach.pw>
Date: Fri, 17 Oct 2025 18:27:32 +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 3/7] drm/edid: MSO should only be used for non-eDP displays

As per DisplayID v2.1a spec:
If Offset 06h[2:0] is programmed to 001b (External DisplayPort), this field shallbe cleared to 00b (Not supported).

Ref: https://lore.kernel.org/lkml/3abc1087618c822e5676e67a3ec2e64e506dc5ec@intel.com/
Signed-off-by: Yaroslav Bolyukin <iam@...h.pw>
---
 drivers/gpu/drm/drm_displayid_internal.h |  4 +++
 drivers/gpu/drm/drm_edid.c               | 36 +++++++++++++++---------
 2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
index 957dd0619f5c..cf02647b41b4 100644
--- a/drivers/gpu/drm/drm_displayid_internal.h
+++ b/drivers/gpu/drm/drm_displayid_internal.h
@@ -142,9 +142,13 @@ struct displayid_formula_timing_block {
 	struct displayid_formula_timings_9 timings[];
 } __packed;
 
+#define DISPLAYID_VESA_DP_TYPE		GENMASK(2, 0)
 #define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)
 #define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)
 
+#define DISPLAYID_VESA_DP_TYPE_EDP	0
+#define DISPLAYID_VESA_DP_TYPE_DP	1
+
 struct displayid_vesa_vendor_specific_block {
 	struct displayid_block base;
 	u8 oui[3];
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 725ae5f9d160..13df2854617c 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -6530,6 +6530,7 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
 	struct displayid_vesa_vendor_specific_block *vesa =
 		(struct displayid_vesa_vendor_specific_block *)block;
 	struct drm_display_info *info = &connector->display_info;
+	int dp_type;
 
 	if (block->num_bytes < 3) {
 		drm_dbg_kms(connector->dev,
@@ -6548,20 +6549,29 @@ static void drm_parse_vesa_specific_block(struct drm_connector *connector,
 		return;
 	}
 
-	switch (FIELD_GET(DISPLAYID_VESA_MSO_MODE, vesa->mso)) {
-	default:
-		drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] Reserved MSO mode value\n",
+	dp_type = FIELD_GET(DISPLAYID_VESA_DP_TYPE, vesa->data_structure_type);
+	if (dp_type > 1) {
+		drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] Reserved dp type value\n",
 			    connector->base.id, connector->name);
-		fallthrough;
-	case 0:
-		info->mso_stream_count = 0;
-		break;
-	case 1:
-		info->mso_stream_count = 2; /* 2 or 4 links */
-		break;
-	case 2:
-		info->mso_stream_count = 4; /* 4 links */
-		break;
+	}
+
+	/* MSO is not supported for eDP */
+	if (dp_type != DISPLAYID_VESA_DP_TYPE_EDP) {
+		switch (FIELD_GET(DISPLAYID_VESA_MSO_MODE, vesa->mso)) {
+		default:
+			drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] Reserved MSO mode value\n",
+				    connector->base.id, connector->name);
+			fallthrough;
+		case 0:
+			info->mso_stream_count = 0;
+			break;
+		case 1:
+			info->mso_stream_count = 2; /* 2 or 4 links */
+			break;
+		case 2:
+			info->mso_stream_count = 4; /* 4 links */
+			break;
+		}
 	}
 
 	if (info->mso_stream_count) {
-- 
2.51.0