drm/edid: parse the DisplayID v2.0 VESA vendor block for MSO

The VESA Organization Vendor-Specific Data Block, defined in VESA
DisplayID Standard v2.0, specifies the eDP Multi-SST Operation (MSO)
stream count and segment pixel overlap.

DisplayID v1.3 has Appendix B: DisplayID as an EDID Extension,
describing how DisplayID sections may be embedded in EDID extension
blocks. DisplayID v2.0 does not have such a section, perhaps implying
that DisplayID v2.0 data should not be included in EDID extensions, but
rather in a "pure" DisplayID structure at its own DDC address pair
A4h/A5h, as described in VESA E-DDC Standard v1.3 chapter 3.

However, in practice, displays out in the field have embedded DisplayID
v2.0 data blocks in EDID extensions, including, in particular, some eDP
MSO displays, where a pure DisplayID structure is not available at all.

Parse the MSO data from the DisplayID data block. Do it as part of
drm_add_display_info(), extending it to parse also DisplayID data to
avoid requiring extra calls to update the information.

v2: Check for VESA OUI (Ville)

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/73ca2887e7b37880690f5c9ba4594c9cd1170669.1630419362.git.jani.nikula@intel.com

1 files changed, 13 insertions, 0 deletions

diff --git a/include/drm/drm_displayid.h b/include/drm/drm_displayid.h
index 79771091771a..7ffbd9f7bfc7 100644
--- a/include/drm/drm_displayid.h
+++ b/include/drm/drm_displayid.h
@@ -23,9 +23,12 @@
 #define DRM_DISPLAYID_H
 
 #include <linux/types.h>
+#include <linux/bits.h>
 
 struct edid;
 
+#define VESA_IEEE_OUI				0x3a0292
+
 /* DisplayID Structure versions */
 #define DISPLAY_ID_STRUCTURE_VER_12		0x12
 #define DISPLAY_ID_STRUCTURE_VER_20		0x20
@@ -126,6 +129,16 @@ struct displayid_detailed_timing_block {
 	struct displayid_detailed_timings_1 timings[];
 };
 
+#define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)
+#define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)
+
+struct displayid_vesa_vendor_specific_block {
+	struct displayid_block base;
+	u8 oui[3];
+	u8 data_structure_type;
+	u8 mso;
+} __packed;
+
 /* DisplayID iteration */
 struct displayid_iter {
 	const struct edid *edid;