[PATCH 3/9] drm/connector: Add drm_connector_find_by_fwnode() function

[Hans de Goede <hdegoede@redhat.com>]

Add a function which allows other subsystems to find a connector
based on a fwnode.

This will be used by the USB-Type-C code to be able to find the DP
connector to which to send hotplug events received by a Type-C port in
DP-alternate-mode.

Note this function is defined in drivers/gpu/drm/drm_sysfs.c because it
needs access to the drm_sysfs_device_connector device_type struct.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/drm_sysfs.c | 38 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h |  1 +
 2 files changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index c1d3e2b843b7..ca71c46fad78 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -520,3 +520,41 @@ void drm_class_device_unregister(struct device *dev)
 	return device_unregister(dev);
 }
 EXPORT_SYMBOL_GPL(drm_class_device_unregister);
+
+/**
+ * drm_connector_find_by_fwnode - Find a connector based on the associated fwnode
+ * @fwnode: fwnode for which to find the matching drm_connector
+ *
+ * This functions looks up a drm_connector based on its associated fwnode. When
+ * a connector is found a reference to the connector is returned. The caller must
+ * call drm_connector_put() to release this reference when it is done with the
+ * connector.
+ *
+ * Returns: A reference to the found connector or NULL if no matching connector was found
+ */
+struct drm_connector *drm_connector_find_by_fwnode(struct fwnode_handle *fwnode)
+{
+	struct drm_connector *connector, *found = NULL;
+	struct class_dev_iter iter;
+	struct device *dev;
+
+	if (!fwnode)
+		return NULL;
+
+	class_dev_iter_init(&iter, drm_class, NULL, &drm_sysfs_device_connector);
+	while ((dev = class_dev_iter_next(&iter))) {
+		connector = to_drm_connector(dev);
+
+		if ((connector->fwnode == fwnode) ||
+		    (connector->fwnode && connector->fwnode->secondary == fwnode)) {
+			drm_connector_get(connector);
+			found = connector;
+			break;
+		}
+
+	}
+	class_dev_iter_exit(&iter);
+
+	return found;
+}
+EXPORT_SYMBOL(drm_connector_find_by_fwnode);
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index d20bfd7576ed..1e5d154d1f4a 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1696,6 +1696,7 @@ drm_connector_is_unregistered(struct drm_connector *connector)
 		DRM_CONNECTOR_UNREGISTERED;
 }
 
+struct drm_connector *drm_connector_find_by_fwnode(struct fwnode_handle *fwnode);
 const char *drm_get_connector_type_name(unsigned int connector_type);
 const char *drm_get_connector_status_name(enum drm_connector_status status);
 const char *drm_get_subpixel_order_name(enum subpixel_order order);
-- 
2.31.1