drm/edid: Add flag to drm_display_info to identify HDMI sinks

The drm_display_info structure contains many fields related to HDMI
sinks, but none that identifies if a sink compliant with CEA-861 (EDID)
shall be treated as an HDMI sink or a DVI sink. Add such a flag, and
populate it according to section 8.3.3 ("DVI/HDMI Device
Discrimination") of the HDMI v1.3 specification.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226112514.12455-4-laurent.pinchart@ideasonboard.com

Documentation/gpu/todo.rst

@@ -407,6 +407,20 @@ Contact: Daniel Vetter
 
 Level: Intermediate
 
+Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi
+---------------------------------------------------------------
+
+Once EDID is parsed, the monitor HDMI support information is available through
+drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to
+retrieve the same information, which is less efficient.
+
+Audit each individual driver calling drm_detect_hdmi_monitor() and switch to
+drm_display_info.is_hdmi if applicable.
+
+Contact: Laurent Pinchart, respective driver maintainers
+
+Level: Intermediate
+
 Core refactorings
 =================
 

drivers/gpu/drm/drm_edid.c

@@ -4647,6 +4647,9 @@ EXPORT_SYMBOL(drm_av_sync_delay);
  *
  * Parse the CEA extension according to CEA-861-B.
  *
+ * Drivers that have added the modes parsed from EDID to drm_display_info
+ * should use &drm_display_info.is_hdmi instead of calling this function.
+ *
  * Return: True if the monitor is HDMI, false if not or unknown.
  */
 bool drm_detect_hdmi_monitor(struct edid *edid)
@@ -4881,6 +4884,8 @@ drm_parse_hdmi_vsdb_video(struct drm_connector *connector, const u8 *db)
 	struct drm_display_info *info = &connector->display_info;
 	u8 len = cea_db_payload_len(db);
 
+	info->is_hdmi = true;
+
 	if (len >= 6)
 		info->dvi_dual = db[6] & 1;
 	if (len >= 7)
@@ -4949,6 +4954,7 @@ drm_reset_display_info(struct drm_connector *connector)
 	info->cea_rev = 0;
 	info->max_tmds_clock = 0;
 	info->dvi_dual = false;
+	info->is_hdmi = false;
 	info->has_hdmi_infoframe = false;
 	info->rgb_quant_range_selectable = false;
 	memset(&info->hdmi, 0, sizeof(info->hdmi));

include/drm/drm_connector.h

@@ -434,6 +434,14 @@ struct drm_display_info {
 	 */
 	bool dvi_dual;
 
+	/**
+	 * @is_hdmi: True if the sink is an HDMI device.
+	 *
+	 * This field shall be used instead of calling
+	 * drm_detect_hdmi_monitor() when possible.
+	 */
+	bool is_hdmi;
+
 	/**
 	 * @has_hdmi_infoframe: Does the sink support the HDMI infoframe?
 	 */