device connection: Add fwnode_connection_find_match()

The fwnode_connection_find_match() function is exactly the
same as device_connection_find_match(), except it takes
struct fwnode_handle as parameter instead of struct device.
That allows locating device connections before the device
entries have been created.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1567070558-29417-7-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/devcon.c

@@ -12,9 +12,6 @@
 static DEFINE_MUTEX(devcon_lock);
 static LIST_HEAD(devcon_list);
 
-typedef void *(*devcon_match_fn_t)(struct device_connection *con, int ep,
-				   void *data);
-
 static void *
 fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 			  void *data, devcon_match_fn_t match)
@@ -60,6 +57,34 @@ fwnode_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 	return NULL;
 }
 
+/**
+ * fwnode_connection_find_match - Find connection from a device node
+ * @fwnode: Device node with the connection
+ * @con_id: Identifier for the connection
+ * @data: Data for the match function
+ * @match: Function to check and convert the connection description
+ *
+ * Find a connection with unique identifier @con_id between @fwnode and another
+ * device node. @match will be used to convert the connection description to
+ * data the caller is expecting to be returned.
+ */
+void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
+				   const char *con_id, void *data,
+				   devcon_match_fn_t match)
+{
+	void *ret;
+
+	if (!fwnode || !match)
+		return NULL;
+
+	ret = fwnode_graph_devcon_match(fwnode, con_id, data, match);
+	if (ret)
+		return ret;
+
+	return fwnode_devcon_match(fwnode, con_id, data, match);
+}
+EXPORT_SYMBOL_GPL(fwnode_connection_find_match);
+
 /**
  * device_connection_find_match - Find physical connection to a device
  * @dev: Device with the connection
@@ -83,15 +108,9 @@ void *device_connection_find_match(struct device *dev, const char *con_id,
 	if (!match)
 		return NULL;
 
-	if (fwnode) {
-		ret = fwnode_graph_devcon_match(fwnode, con_id, data, match);
-		if (ret)
-			return ret;
-
-		ret = fwnode_devcon_match(fwnode, con_id, data, match);
-		if (ret)
-			return ret;
-	}
+	ret = fwnode_connection_find_match(fwnode, con_id, data, match);
+	if (ret)
+		return ret;
 
 	mutex_lock(&devcon_lock);
 

include/linux/device.h

@@ -781,10 +781,14 @@ struct device_connection {
 	struct list_head	list;
 };
 
+typedef void *(*devcon_match_fn_t)(struct device_connection *con, int ep,
+				   void *data);
+
+void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
+				   const char *con_id, void *data,
+				   devcon_match_fn_t match);
 void *device_connection_find_match(struct device *dev, const char *con_id,
-				void *data,
-				void *(*match)(struct device_connection *con,
-					       int ep, void *data));
+				   void *data, devcon_match_fn_t match);
 
 struct device *device_connection_find(struct device *dev, const char *con_id);