[PATCH v11 08/12] drm/bridge_connector: add luminance support

["Mario Limonciello (AMD)" <superm1@kernel.org>]

From: Mario Limonciello <mario.limonciello@amd.com>

Discover the last bridge in a chain that owns brightness control, attach
its relative luminance range to the connector, and forward atomic
luminance updates to it.

Do not infer panel luminance support from a terminal panel bridge. Panels
still have direct consumers, so their connector integration must remain
explicit.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v11:
 * Drop .disable_luminance, it clobbered the bridge's saved level; the
   bridge disable path already turns the panel off
 * Fix checkpatch line length
v10:
 * Split bridge connector integration into a separate patch
 * Do not special-case panels in the generic bridge connector
---
 drivers/gpu/drm/display/drm_bridge_connector.c | 39 ++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 2202e60444449..18927fed83732 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -125,6 +125,13 @@ struct drm_bridge_connector {
 	 */
 	struct drm_bridge *bridge_hdmi_cec;
 
+	/**
+	 * @bridge_luminance:
+	 *
+	 * The last bridge in the chain that controls panel luminance.
+	 */
+	struct drm_bridge *bridge_luminance;
+
 	/**
 	 * @hdmi_funcs:
 	 *
@@ -421,6 +428,17 @@ static int drm_bridge_connector_atomic_check(struct drm_connector *connector,
 	return 0;
 }
 
+static void
+drm_bridge_connector_set_luminance(const struct drm_connector_state *conn_state)
+{
+	struct drm_bridge_connector *bridge_connector =
+		to_drm_bridge_connector(conn_state->connector);
+	struct drm_bridge *bridge = bridge_connector->bridge_luminance;
+
+	if (bridge)
+		bridge->funcs->set_luminance(bridge, conn_state->luminance);
+}
+
 static const struct drm_connector_helper_funcs drm_bridge_connector_helper_funcs = {
 	.get_modes = drm_bridge_connector_get_modes,
 	.detect_ctx = drm_bridge_connector_detect_ctx,
@@ -429,6 +447,7 @@ static const struct drm_connector_helper_funcs drm_bridge_connector_helper_funcs
 	.enable_hpd = drm_bridge_connector_enable_hpd,
 	.disable_hpd = drm_bridge_connector_disable_hpd,
 	.atomic_check = drm_bridge_connector_atomic_check,
+	.set_luminance = drm_bridge_connector_set_luminance,
 };
 
 static enum drm_mode_status
@@ -835,6 +854,7 @@ static void drm_bridge_connector_put_bridges(struct drm_device *dev, void *data)
 	drm_bridge_put(bridge_connector->bridge_hdmi_audio);
 	drm_bridge_put(bridge_connector->bridge_dp_audio);
 	drm_bridge_put(bridge_connector->bridge_hdmi_cec);
+	drm_bridge_put(bridge_connector->bridge_luminance);
 }
 
 /**
@@ -918,6 +938,13 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 			drm_bridge_put(bridge_connector->bridge_detect);
 			bridge_connector->bridge_detect = drm_bridge_get(bridge);
 		}
+		if (bridge->ops & DRM_BRIDGE_OP_LUMINANCE) {
+			if (!bridge->funcs->set_luminance)
+				return ERR_PTR(-EINVAL);
+
+			drm_bridge_put(bridge_connector->bridge_luminance);
+			bridge_connector->bridge_luminance = drm_bridge_get(bridge);
+		}
 		if (bridge->ops & DRM_BRIDGE_OP_HDMI) {
 			if (bridge_connector->bridge_hdmi)
 				return ERR_PTR(-EBUSY);
@@ -1144,6 +1171,18 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 	if (panel_bridge)
 		drm_panel_bridge_set_orientation(connector, panel_bridge);
 
+	if (IS_ENABLED(CONFIG_DRM_LUMINANCE) &&
+	    bridge_connector->bridge_luminance &&
+	    !connector->luminance_property) {
+		struct drm_bridge *bridge = bridge_connector->bridge_luminance;
+
+		ret = drm_connector_attach_luminance_property(connector, 0,
+							      bridge->luminance_max,
+							      bridge->luminance);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
 	if (support_hdcp && IS_REACHABLE(CONFIG_DRM_DISPLAY_HELPER) &&
 	    IS_ENABLED(CONFIG_DRM_DISPLAY_HDCP_HELPER))
 		drm_connector_attach_content_protection_property(connector, true);

-- 
2.53.0