[PATCH v7 09/12] drm/bridge: auto-link panel backlight in bridge connector

[Mario Limonciello <mario.limonciello@amd.com>]

Link a panel's backlight_device to the bridge connector so
luminance-aware clients can drive it through the LUMINANCE property.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
 drivers/gpu/drm/bridge/panel.c                 | 15 +++++++++++++++
 drivers/gpu/drm/display/drm_bridge_connector.c | 11 ++++++++++-
 include/drm/drm_bridge.h                       |  1 +
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 02388a3de626e..36005e10494d3 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -233,6 +233,21 @@ bool drm_bridge_is_panel(const struct drm_bridge *bridge)
 }
 EXPORT_SYMBOL(drm_bridge_is_panel);
 
+/**
+ * drm_panel_bridge_to_panel - get the drm_panel wrapped by a panel bridge
+ * @bridge: the panel bridge
+ *
+ * Returns the &drm_panel wrapped by @bridge, or NULL if @bridge is not a
+ * panel bridge.
+ */
+struct drm_panel *drm_panel_bridge_to_panel(struct drm_bridge *bridge)
+{
+	if (!drm_bridge_is_panel(bridge))
+		return NULL;
+	return drm_bridge_to_panel_bridge(bridge)->panel;
+}
+EXPORT_SYMBOL(drm_panel_bridge_to_panel);
+
 /**
  * drm_panel_bridge_add - Creates a &drm_bridge and &drm_connector that
  * just calls the appropriate functions from &drm_panel.
diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 8b54069fa53a4..d4b4e59cea51c 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -11,7 +11,9 @@
 #include <linux/slab.h>
 
 #include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_backlight.h>
 #include <drm/drm_bridge.h>
+#include <drm/drm_panel.h>
 #include <drm/drm_bridge_connector.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_device.h>
@@ -1082,9 +1084,16 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 		connector->polled = DRM_CONNECTOR_POLL_CONNECT
 				  | DRM_CONNECTOR_POLL_DISCONNECT;
 
-	if (panel_bridge)
+	if (panel_bridge) {
+		struct drm_panel *panel;
+
 		drm_panel_bridge_set_orientation(connector, panel_bridge);
 
+		panel = drm_panel_bridge_to_panel(panel_bridge);
+		if (panel && panel->backlight)
+			drm_backlight_link(connector, panel->backlight);
+	}
+
 	if (support_hdcp && IS_REACHABLE(CONFIG_DRM_DISPLAY_HELPER) &&
 	    IS_ENABLED(CONFIG_DRM_DISPLAY_HDCP_HELPER))
 		drm_connector_attach_content_protection_property(connector, true);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 58fff047f43b6..ce1fc8695b455 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -1475,6 +1475,7 @@ void drm_bridge_hpd_notify(struct drm_bridge *bridge,
 
 #ifdef CONFIG_DRM_PANEL_BRIDGE
 bool drm_bridge_is_panel(const struct drm_bridge *bridge);
+struct drm_panel *drm_panel_bridge_to_panel(struct drm_bridge *bridge);
 struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel);
 struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
 					      u32 connector_type);
-- 
2.43.0