device property: Introduce fwnode_find_reference()

In most cases the references that the drivers look for don't
have any arguments. This introduces a wrapper function for
fwnode_property_get_reference_args() that looks for
references by using only the name and index.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: Heikki Krogerus

drivers/base/property.c

@@ -484,6 +484,30 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 }
 EXPORT_SYMBOL_GPL(fwnode_property_get_reference_args);
 
+/**
+ * fwnode_find_reference - Find named reference to a fwnode_handle
+ * @fwnode: Firmware node where to look for the reference
+ * @name: The name of the reference
+ * @index: Index of the reference
+ *
+ * @index can be used when the named reference holds a table of references.
+ *
+ * Returns pointer to the reference fwnode, or ERR_PTR. Caller is responsible to
+ * call fwnode_handle_put() on the returned fwnode pointer.
+ */
+struct fwnode_handle *fwnode_find_reference(const struct fwnode_handle *fwnode,
+					    const char *name,
+					    unsigned int index)
+{
+	struct fwnode_reference_args args;
+	int ret;
+
+	ret = fwnode_property_get_reference_args(fwnode, name, NULL, 0, index,
+						 &args);
+	return ret ? ERR_PTR(ret) : args.fwnode;
+}
+EXPORT_SYMBOL_GPL(fwnode_find_reference);
+
 /**
  * device_remove_properties - Remove properties from a device object.
  * @dev: Device whose properties to remove.

include/linux/property.h

@@ -79,6 +79,10 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 				       unsigned int nargs, unsigned int index,
 				       struct fwnode_reference_args *args);
 
+struct fwnode_handle *fwnode_find_reference(const struct fwnode_handle *fwnode,
+					    const char *name,
+					    unsigned int index);
+
 struct fwnode_handle *fwnode_get_parent(const struct fwnode_handle *fwnode);
 struct fwnode_handle *fwnode_get_next_parent(
 	struct fwnode_handle *fwnode);