[PATCH v6 1/7] drm/bridge: aux-hpd-bridge: Add drm_dev_has_dp_hpd_bridge()

[Chaoyi Chen <kernel@airkyi.com>]

From: Chaoyi Chen <chaoyi.chen@rock-chips.com>

Add a new API to check whether a DisplayPort HPD bridge has already
been registered. This helps avoid duplicate registration of the same
HPD bridge, although the current framework allows doing so.

Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
---
 drivers/gpu/drm/bridge/aux-hpd-bridge.c | 42 ++++++++++++++++++++++++-
 include/drm/bridge/aux-bridge.h         |  6 ++++
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
index f02a38a2638a..a56c88eba005 100644
--- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
@@ -12,6 +12,8 @@
 #include <drm/drm_bridge.h>
 #include <drm/bridge/aux-bridge.h>
 
+#define DRM_AUX_HPD_BRIDGE_NAME	"dp_hpd_bridge"
+
 static DEFINE_IDA(drm_aux_hpd_bridge_ida);
 
 struct drm_aux_hpd_bridge_data {
@@ -36,6 +38,44 @@ static void drm_aux_hpd_bridge_free_adev(void *_adev)
 	auxiliary_device_uninit(_adev);
 }
 
+static int hpd_bridge_match(struct device *dev, const void *data)
+{
+	const struct device_node *np = data;
+	struct auxiliary_device *adev;
+
+	if (!dev_is_auxiliary(dev))
+		return 0;
+
+	adev = to_auxiliary_dev(dev);
+	if (strcmp(adev->name, DRM_AUX_HPD_BRIDGE_NAME))
+		return 0;
+
+	return adev->dev.platform_data == np;
+}
+
+/**
+ * drm_dev_has_dp_hpd_bridge - check whether a HPD DisplayPort bridge is registered
+ * @parent: device instance providing this bridge
+ * @np: device node pointer corresponding to this bridge instance
+ *
+ * Walk the children of @parent and check whether a HPD DisplayPort bridge for
+ * the given @np has already been registered via devm_drm_dp_hpd_bridge_add().
+ *
+ * Return: true if a HPD bridge for @parent / @np already exists, false otherwise
+ */
+bool drm_dev_has_dp_hpd_bridge(struct device *parent, struct device_node *np)
+{
+	struct device *child;
+
+	child = device_find_child(parent, np, hpd_bridge_match);
+	if (child) {
+		put_device(child);
+		return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(drm_dev_has_dp_hpd_bridge);
+
 /**
  * devm_drm_dp_hpd_bridge_alloc - allocate a HPD DisplayPort bridge
  * @parent: device instance providing this bridge
@@ -63,7 +103,7 @@ struct auxiliary_device *devm_drm_dp_hpd_bridge_alloc(struct device *parent, str
 	}
 
 	adev->id = ret;
-	adev->name = "dp_hpd_bridge";
+	adev->name = DRM_AUX_HPD_BRIDGE_NAME;
 	adev->dev.parent = parent;
 	adev->dev.release = drm_aux_hpd_bridge_release;
 	adev->dev.platform_data = of_node_get(np);
diff --git a/include/drm/bridge/aux-bridge.h b/include/drm/bridge/aux-bridge.h
index c2f5a855512f..cca07a8e2d45 100644
--- a/include/drm/bridge/aux-bridge.h
+++ b/include/drm/bridge/aux-bridge.h
@@ -25,6 +25,7 @@ struct auxiliary_device *devm_drm_dp_hpd_bridge_alloc(struct device *parent, str
 int devm_drm_dp_hpd_bridge_add(struct device *dev, struct auxiliary_device *adev);
 struct device *drm_dp_hpd_bridge_register(struct device *parent,
 					  struct device_node *np);
+bool drm_dev_has_dp_hpd_bridge(struct device *parent, struct device_node *np);
 void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status);
 #else
 static inline struct auxiliary_device *devm_drm_dp_hpd_bridge_alloc(struct device *parent,
@@ -44,6 +45,11 @@ static inline struct device *drm_dp_hpd_bridge_register(struct device *parent,
 	return NULL;
 }
 
+static inline bool drm_dev_has_dp_hpd_bridge(struct device *parent, struct device_node *np)
+{
+	return false;
+}
+
 static inline void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
 {
 }
-- 
2.53.0


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