drm/edid: support Microsoft extension for HMDs and specialized monitors

Add minimal support for parsing VSDBs documented in Microsoft's "EDID
extension for head-mounted and specialized monitors" [1]. The version
field and the desktop usage flag can be used to set the non_desktop
connector property.

[1] https://docs.microsoft.com/en-us/windows-hardware/drivers/display/specialized-monitors-edid-extension

Tested with HPN-36C1 and LEN-B800.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220123101653.147333-1-philipp.zabel@gmail.com

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 12893e7..271b561 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -93,6 +93,8 @@ static int oui(u8 first, u8 second, u8 third)
 /* Non desktop display (i.e. HMD) */
 #define EDID_QUIRK_NON_DESKTOP                 (1 << 12)
 
+#define MICROSOFT_IEEE_OUI     0xca125c
+
 struct detailed_mode_closure {
        struct drm_connector *connector;
        struct edid *edid;
@@ -4222,6 +4224,17 @@ static bool cea_db_is_hdmi_forum_vsdb(const u8 *db)
        return oui(db[3], db[2], db[1]) == HDMI_FORUM_IEEE_OUI;
 }
 
+static bool cea_db_is_microsoft_vsdb(const u8 *db)
+{
+       if (cea_db_tag(db) != VENDOR_BLOCK)
+               return false;
+
+       if (cea_db_payload_len(db) != 21)
+               return false;
+
+       return oui(db[3], db[2], db[1]) == MICROSOFT_IEEE_OUI;
+}
+
 static bool cea_db_is_vcdb(const u8 *db)
 {
        if (cea_db_tag(db) != USE_EXTENDED_TAG)
@@ -5149,6 +5162,25 @@ drm_parse_hdmi_vsdb_video(struct drm_connector *connector, const u8 *db)
        drm_parse_hdmi_deep_color_info(connector, db);
 }
 
+/*
+ * See EDID extension for head-mounted and specialized monitors, specified at:
+ * https://docs.microsoft.com/en-us/windows-hardware/drivers/display/specialized-monitors-edid-extension
+ */
+static void drm_parse_microsoft_vsdb(struct drm_connector *connector,
+                                    const u8 *db)
+{
+       struct drm_display_info *info = &connector->display_info;
+       u8 version = db[4];
+       bool desktop_usage = db[5] & BIT(6);
+
+       /* Version 1 and 2 for HMDs, version 3 flags desktop usage explicitly */
+       if (version == 1 || version == 2 || (version == 3 && !desktop_usage))
+               info->non_desktop = true;
+
+       drm_dbg_kms(connector->dev, "HMD or specialized display VSDB version %u: 0x%02x\n",
+                   version, db[5]);
+}
+
 static void drm_parse_cea_ext(struct drm_connector *connector,
                              const struct edid *edid)
 {
@@ -5179,6 +5211,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
                        drm_parse_hdmi_vsdb_video(connector, db);
                if (cea_db_is_hdmi_forum_vsdb(db))
                        drm_parse_hdmi_forum_vsdb(connector, db);
+               if (cea_db_is_microsoft_vsdb(db))
+                       drm_parse_microsoft_vsdb(connector, db);
                if (cea_db_is_y420cmdb(db))
                        drm_parse_y420cmdb_bitmap(connector, db);
                if (cea_db_is_vcdb(db))