[PATCH 02/10] drm/bridge: Add a function to abstract away panels

[Maxime Ripard <maxime@cerno.tech>]

Display drivers so far need to have a lot of boilerplate to first
retrieve either the panel or bridge that they are connected to using
drm_of_find_panel_or_bridge(), and then either deal with each with ad-hoc
functions or create a drm panel bridge through drm_panel_bridge_add.

In order to reduce the boilerplate and hopefully create a path of least
resistance towards using the DRM panel bridge layer, let's create the
function devm_drm_of_get_next to reduce that boilerplate.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/drm_bridge.c | 62 +++++++++++++++++++++++++++++++++---
 drivers/gpu/drm/drm_of.c     |  3 ++
 include/drm/drm_bridge.h     |  2 ++
 3 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 044acd07c153..aef8c9f4fb9f 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -24,10 +24,12 @@
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/of_graph.h>
 
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_encoder.h>
+#include <drm/drm_panel.h>
 
 #include "drm_crtc_internal.h"
 
@@ -50,10 +52,8 @@
  *
  * Display drivers are responsible for linking encoders with the first bridge
  * in the chains. This is done by acquiring the appropriate bridge with
- * of_drm_find_bridge() or drm_of_find_panel_or_bridge(), or creating it for a
- * panel with drm_panel_bridge_add_typed() (or the managed version
- * devm_drm_panel_bridge_add_typed()). Once acquired, the bridge shall be
- * attached to the encoder with a call to drm_bridge_attach().
+ * drm_of_get_next(). Once acquired, the bridge shall be attached to the
+ * encoder with a call to drm_bridge_attach().
  *
  * Bridges are responsible for linking themselves with the next bridge in the
  * chain, if any. This is done the same way as for encoders, with the call to
@@ -1223,6 +1223,60 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np)
 	return NULL;
 }
 EXPORT_SYMBOL(of_drm_find_bridge);
+
+/**
+ * devm_drm_of_get_next - Return next bridge in the chain
+ * @dev: device to tie the bridge lifetime to
+ * @np: device tree node containing encoder output ports
+ * @port: port in the device tree node
+ * @endpoint: endpoint in the device tree node
+ *
+ * Given a DT node's port and endpoint number, finds the connected node
+ * and returns the associated bridge if any, or creates and returns a
+ * drm panel bridge instance if a panel is connected.
+ *
+ * Returns a pointer to the bridge if successful, or an error pointer
+ * otherwise.
+ */
+struct drm_bridge *devm_drm_of_get_next(struct device *dev,
+					struct device_node *np,
+					unsigned int port,
+					unsigned int endpoint)
+{
+	struct device_node *remote;
+	struct drm_bridge *bridge;
+	struct drm_panel *panel;
+
+	/*
+	 * of_graph_get_remote_node() produces a noisy error message if port
+	 * node isn't found and the absence of the port is a legit case here,
+	 * so at first we silently check whether graph presents in the
+	 * device-tree node.
+	 */
+	if (!of_graph_is_present(np))
+		return ERR_PTR(-ENODEV);
+
+	remote = of_graph_get_remote_node(np, port, endpoint);
+	if (!remote)
+		return ERR_PTR(-ENODEV);
+
+	bridge = of_drm_find_bridge(remote);
+	if (bridge) {
+		of_node_put(remote);
+		return bridge;
+	}
+
+	panel = of_drm_find_panel(remote);
+	if (IS_ERR(panel)) {
+		of_node_put(remote);
+		return ERR_CAST(panel);
+	}
+
+	of_node_put(remote);
+
+	return devm_drm_panel_bridge_add(dev, panel);
+}
+EXPORT_SYMBOL(devm_drm_of_get_next);
 #endif
 
 MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@samsung.com>");
diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 997b8827fed2..bbbdc4d17ac9 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -231,6 +231,9 @@ EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
  * return either the associated struct drm_panel or drm_bridge device. Either
  * @panel or @bridge must not be NULL.
  *
+ * This function is deprecated and should not be used in new drivers. Use
+ * drm_of_get_next() instead.
+ *
  * Returns zero if successful, or one of the standard error codes if it fails.
  */
 int drm_of_find_panel_or_bridge(const struct device_node *np,
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 46bdfa48c413..e16fafc6f37d 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -911,6 +911,8 @@ struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
 struct drm_bridge *devm_drm_panel_bridge_add_typed(struct device *dev,
 						   struct drm_panel *panel,
 						   u32 connector_type);
+struct drm_bridge *devm_drm_of_get_next(struct device *dev, struct device_node *node,
+					unsigned int port, unsigned int endpoint);
 struct drm_connector *drm_panel_bridge_connector(struct drm_bridge *bridge);
 #endif
 
-- 
2.31.1