drm: add drm_of_encoder_active_endpoint helpers

This patch adds a helper to parse the encoder endpoint connected to the
encoder's crtc and two helpers to return its id and port id.

This can be used to determine input mux setting from endpoint or port ids.
Suggested-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/drm_of.c

@@ -149,3 +149,37 @@ int drm_of_component_probe(struct device *dev,
 	return component_master_add_with_match(dev, m_ops, match);
 }
 EXPORT_SYMBOL(drm_of_component_probe);
+
+/*
+ * drm_of_encoder_active_endpoint - return the active encoder endpoint
+ * @node: device tree node containing encoder input ports
+ * @encoder: drm_encoder
+ *
+ * Given an encoder device node and a drm_encoder with a connected crtc,
+ * parse the encoder endpoint connecting to the crtc port.
+ */
+int drm_of_encoder_active_endpoint(struct device_node *node,
+				   struct drm_encoder *encoder,
+				   struct of_endpoint *endpoint)
+{
+	struct device_node *ep;
+	struct drm_crtc *crtc = encoder->crtc;
+	struct device_node *port;
+	int ret;
+
+	if (!node || !crtc)
+		return -EINVAL;
+
+	for_each_endpoint_of_node(node, ep) {
+		port = of_graph_get_remote_port(ep);
+		of_node_put(port);
+		if (port == crtc->port) {
+			ret = of_graph_parse_endpoint(ep, endpoint);
+			of_node_put(ep);
+			return ret;
+		}
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);

include/drm/drm_of.h

 #ifndef __DRM_OF_H__
 #define __DRM_OF_H__
 
+#include <linux/of_graph.h>
+
 struct component_master_ops;
 struct device;
 struct drm_device;
+struct drm_encoder;
 struct device_node;
 
 #ifdef CONFIG_OF
@@ -12,6 +15,9 @@ extern uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 extern int drm_of_component_probe(struct device *dev,
 				  int (*compare_of)(struct device *, void *),
 				  const struct component_master_ops *m_ops);
+extern int drm_of_encoder_active_endpoint(struct device_node *node,
+					  struct drm_encoder *encoder,
+					  struct of_endpoint *endpoint);
 #else
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
@@ -26,6 +32,33 @@ drm_of_component_probe(struct device *dev,
 {
 	return -EINVAL;
 }
+
+static inline int drm_of_encoder_active_endpoint(struct device_node *node,
+						 struct drm_encoder *encoder,
+						 struct of_endpoint *endpoint)
+{
+	return -EINVAL;
+}
 #endif
 
+static inline int drm_of_encoder_active_endpoint_id(struct device_node *node,
+						    struct drm_encoder *encoder)
+{
+	struct of_endpoint endpoint;
+	int ret = drm_of_encoder_active_endpoint(node, encoder,
+						 &endpoint);
+
+	return ret ?: endpoint.id;
+}
+
+static inline int drm_of_encoder_active_port_id(struct device_node *node,
+						struct drm_encoder *encoder)
+{
+	struct of_endpoint endpoint;
+	int ret = drm_of_encoder_active_endpoint(node, encoder,
+						 &endpoint);
+
+	return ret ?: endpoint.port;
+}
+
 #endif /* __DRM_OF_H__ */