DRM: Add support for HDMI content type

Some monitors expose a selector for the kind of content that will get
displayed, allowing them to optimise their settings for this particular
content type.

I got access to such a monitor, sadly even setting it to game mode
didn’t lower its atrocious latency, but drm_info[1] reports it to be set
correctly so hopefully it’ll work better with other monitors.

[1] https://github.com/ascent12/drm_info

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>

compositor/main.c

@@ -2024,6 +2024,7 @@ drm_backend_output_configure(struct weston_output *output,
 	char *s;
 	char *modeline = NULL;
 	char *gbm_format = NULL;
+	char *content_type = NULL;
 	char *seat = NULL;
 
 	api = weston_drm_output_get_api(output->compositor);
@@ -2080,6 +2081,12 @@ drm_backend_output_configure(struct weston_output *output,
 	api->set_gbm_format(output, gbm_format);
 	free(gbm_format);
 
+	weston_config_section_get_string(section,
+					 "content-type", &content_type, NULL);
+	if (api->set_content_type(output, content_type) < 0)
+		return -1;
+	free(content_type);
+
 	weston_config_section_get_string(section, "seat", &seat, "");
 
 	api->set_seat(output, seat);

include/libweston/backend-drm.h

@@ -93,6 +93,17 @@ struct weston_drm_output_api {
 	 * This can be set only while the output is disabled.
 	 */
 	void (*set_max_bpc)(struct weston_output *output, unsigned max_bpc);
+
+	/** The content type primarily used on the output. Valid values are:
+	 * - NULL or "no data" - No information is provided about the usage of the
+	 *   output
+	 * - "graphics"
+	 * - "photo"
+	 * - "cinema"
+	 * - "game"
+	 */
+	int (*set_content_type)(struct weston_output *output,
+				const char *content_type);
 };
 
 static inline const struct weston_drm_output_api *

libweston/backend-drm/drm-internal.h

@@ -188,6 +188,7 @@ enum wdrm_connector_property {
 	WDRM_CONNECTOR_PANEL_ORIENTATION,
 	WDRM_CONNECTOR_HDR_OUTPUT_METADATA,
 	WDRM_CONNECTOR_MAX_BPC,
+	WDRM_CONNECTOR_CONTENT_TYPE,
 	WDRM_CONNECTOR__COUNT
 };
 
@@ -220,6 +221,15 @@ enum wdrm_panel_orientation {
 	WDRM_PANEL_ORIENTATION__COUNT
 };
 
+enum wdrm_content_type {
+	WDRM_CONTENT_TYPE_NO_DATA = 0,
+	WDRM_CONTENT_TYPE_GRAPHICS,
+	WDRM_CONTENT_TYPE_PHOTO,
+	WDRM_CONTENT_TYPE_CINEMA,
+	WDRM_CONTENT_TYPE_GAME,
+	WDRM_CONTENT_TYPE__COUNT
+};
+
 /**
  * List of properties attached to DRM CRTCs
  */
@@ -587,6 +597,8 @@ struct drm_output {
 	void (*virtual_destroy)(struct weston_output *base);
 
 	submit_frame_cb virtual_submit_frame;
+
+	enum wdrm_content_type content_type;
 };
 
 void

libweston/backend-drm/drm.c

@@ -1425,6 +1425,38 @@ drm_output_set_max_bpc(struct weston_output *base, unsigned max_bpc)
 	output->max_bpc = max_bpc;
 }
 
+static const struct { const char *name; uint32_t token; } content_types[] = {
+	{ "no data",  WDRM_CONTENT_TYPE_NO_DATA },
+	{ "graphics", WDRM_CONTENT_TYPE_GRAPHICS },
+	{ "photo",    WDRM_CONTENT_TYPE_PHOTO },
+	{ "cinema",   WDRM_CONTENT_TYPE_CINEMA },
+	{ "game",     WDRM_CONTENT_TYPE_GAME },
+};
+
+static int
+drm_output_set_content_type(struct weston_output *base,
+			    const char *content_type)
+{
+	unsigned int i;
+	struct drm_output *output = to_drm_output(base);
+
+	if (content_type == NULL) {
+		output->content_type = WDRM_CONTENT_TYPE_NO_DATA;
+		return 0;
+	}
+
+	for (i = 0; i < ARRAY_LENGTH(content_types); i++)
+		if (strcmp(content_types[i].name, content_type) == 0) {
+			output->content_type = content_types[i].token;
+			return 0;
+		}
+
+	weston_log("Error: unknown content-type for output %s: \"%s\"\n",
+		   base->name, content_type);
+	output->content_type = WDRM_CONTENT_TYPE_NO_DATA;
+	return -1;
+}
+
 static int
 drm_output_init_gamma_size(struct drm_output *output)
 {
@@ -3084,6 +3116,7 @@ static const struct weston_drm_output_api api = {
 	drm_output_set_gbm_format,
 	drm_output_set_seat,
 	drm_output_set_max_bpc,
+	drm_output_set_content_type,
 };
 
 static struct drm_backend *

libweston/backend-drm/kms.c

@@ -119,6 +119,14 @@ struct drm_property_enum_info panel_orientation_enums[] = {
 	[WDRM_PANEL_ORIENTATION_RIGHT_SIDE_UP] = { .name = "Right Side Up", },
 };
 
+struct drm_property_enum_info content_type_enums[] = {
+	[WDRM_CONTENT_TYPE_NO_DATA] = { .name = "No Data", },
+	[WDRM_CONTENT_TYPE_GRAPHICS] = { .name = "Graphics", },
+	[WDRM_CONTENT_TYPE_PHOTO] = { .name = "Photo", },
+	[WDRM_CONTENT_TYPE_CINEMA] = { .name = "Cinema", },
+	[WDRM_CONTENT_TYPE_GAME] = { .name = "Game", },
+};
+
 const struct drm_property_info connector_props[] = {
 	[WDRM_CONNECTOR_EDID] = { .name = "EDID" },
 	[WDRM_CONNECTOR_DPMS] = {
@@ -147,6 +155,11 @@ const struct drm_property_info connector_props[] = {
 		.name = "HDR_OUTPUT_METADATA",
 	},
 	[WDRM_CONNECTOR_MAX_BPC] = { .name = "max bpc", },
+	[WDRM_CONNECTOR_CONTENT_TYPE] = {
+		.name = "content type",
+		.enum_values = content_type_enums,
+		.num_enum_values = WDRM_CONTENT_TYPE__COUNT,
+	},
 };
 
 const struct drm_property_info crtc_props[] = {
@@ -939,6 +952,24 @@ drm_connector_set_max_bpc(struct drm_connector *connector,
 				  WDRM_CONNECTOR_MAX_BPC, max_bpc);
 }
 
+static int
+drm_connector_set_content_type(struct drm_connector *connector,
+			       enum wdrm_content_type content_type,
+			       drmModeAtomicReq *req)
+{
+	struct drm_property_enum_info *enum_info;
+	uint64_t prop_val;
+	struct drm_property_info *props = connector->props;
+
+	if (!drm_connector_has_prop(connector, WDRM_CONNECTOR_CONTENT_TYPE))
+		return 0;
+
+	enum_info = props[WDRM_CONNECTOR_CONTENT_TYPE].enum_values;
+	prop_val = enum_info[content_type].value;
+	return connector_add_prop(req, connector,
+				  WDRM_CONNECTOR_CONTENT_TYPE, prop_val);
+}
+
 static int
 drm_output_apply_state_atomic(struct drm_output_state *state,
 			      drmModeAtomicReq *req,
@@ -992,6 +1023,8 @@ drm_output_apply_state_atomic(struct drm_output_state *state,
 	wl_list_for_each(head, &output->base.head_list, base.output_link) {
 		drm_connector_set_hdcp_property(&head->connector,
 						state->protection, req);
+		ret |= drm_connector_set_content_type(&head->connector,
+						      output->content_type, req);
 
 		if (drm_connector_has_prop(&head->connector,
 					   WDRM_CONNECTOR_HDR_OUTPUT_METADATA)) {

man/weston.ini.man

@@ -543,6 +543,10 @@ content-protection can actually be realized, only if the hardware
 (source and sink) support HDCP, and the backend has the implementation
 of content-protection protocol. Currently, HDCP is supported by drm-backend.
 .TP 7
+.BI "content-type=" content_type
+The type of the content being primarily displayed to this output. Can be "no
+data" (default), "graphics", "photo", "cinema" or "game".
+.TP 7
 .BI "app-ids=" app-id[,app_id]*
 A comma separated list of the IDs of applications to place on this output.
 These IDs should match the application IDs as set with the xdg_shell.set_app_id