1 files changed, 70 insertions, 11 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 9d8f2b952004..df635afe41b7 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1342,6 +1342,7 @@ MODULE_PARM_DESC(edid_fixup,
 
 static void drm_get_displayid(struct drm_connector *connector,
 			      struct edid *edid);
+static int validate_displayid(u8 *displayid, int length, int idx);
 
 static int drm_edid_block_checksum(const u8 *raw_edid)
 {
@@ -2926,16 +2927,46 @@ static u8 *drm_find_edid_extension(const struct edid *edid, int ext_id)
 	return edid_ext;
 }
 
-static u8 *drm_find_cea_extension(const struct edid *edid)
-{
-	return drm_find_edid_extension(edid, CEA_EXT);
-}
 
 static u8 *drm_find_displayid_extension(const struct edid *edid)
 {
 	return drm_find_edid_extension(edid, DISPLAYID_EXT);
 }
 
+static u8 *drm_find_cea_extension(const struct edid *edid)
+{
+	int ret;
+	int idx = 1;
+	int length = EDID_LENGTH;
+	struct displayid_block *block;
+	u8 *cea;
+	u8 *displayid;
+
+	/* Look for a top level CEA extension block */
+	cea = drm_find_edid_extension(edid, CEA_EXT);
+	if (cea)
+		return cea;
+
+	/* CEA blocks can also be found embedded in a DisplayID block */
+	displayid = drm_find_displayid_extension(edid);
+	if (!displayid)
+		return NULL;
+
+	ret = validate_displayid(displayid, length, idx);
+	if (ret)
+		return NULL;
+
+	idx += sizeof(struct displayid_hdr);
+	for_each_displayid_db(displayid, block, idx, length) {
+		if (block->tag == DATA_BLOCK_CTA) {
+			cea = (u8 *)block;
+			break;
+		}
+	}
+
+	return cea;
+}
+
 /*
  * Calculate the alternate clock for the CEA mode
  * (60Hz vs. 59.94Hz etc.)
@@ -3659,13 +3690,38 @@ cea_revision(const u8 *cea)
 static int
 cea_db_offsets(const u8 *cea, int *start, int *end)
 {
-	/* Data block offset in CEA extension block */
-	*start = 4;
-	*end = cea[2];
-	if (*end == 0)
-		*end = 127;
-	if (*end < 4 || *end > 127)
-		return -ERANGE;
+	/* DisplayID CTA extension blocks and top-level CEA EDID
+	 * block header definitions differ in the following bytes:
+	 *   1) Byte 2 of the header specifies length differently,
+	 *   2) Byte 3 is only present in the CEA top level block.
+	 *
+	 * The different definitions for byte 2 follow.
+	 *
+	 * DisplayID CTA extension block defines byte 2 as:
+	 *   Number of payload bytes
+	 *
+	 * CEA EDID block defines byte 2 as:
+	 *   Byte number (decimal) within this block where the 18-byte
+	 *   DTDs begin. If no non-DTD data is present in this extension
+	 *   block, the value should be set to 04h (the byte after next).
+	 *   If set to 00h, there are no DTDs present in this block and
+	 *   no non-DTD data.
+	 */
+	if (cea[0] == DATA_BLOCK_CTA) {
+		*start = 3;
+		*end = *start + cea[2];
+	} else if (cea[0] == CEA_EXT) {
+		/* Data block offset in CEA extension block */
+		*start = 4;
+		*end = cea[2];
+		if (*end == 0)
+			*end = 127;
+		if (*end < 4 || *end > 127)
+			return -ERANGE;
+	} else {
+		return -ENOTSUPP;
+	}
+
 	return 0;
 }
 
@@ -5406,6 +5462,9 @@ static int drm_parse_display_id(struct drm_connector *connector,
 		case DATA_BLOCK_TYPE_1_DETAILED_TIMING:
 			/* handled in mode gathering code. */
 			break;
+		case DATA_BLOCK_CTA:
+			/* handled in the cea parser code. */
+			break;
 		default:
 			DRM_DEBUG_KMS("found DisplayID tag 0x%x, unhandled\n", block->tag);
 			break;