usb: roles: Add usb_role_switch_find_by_fwnode()

Simple wrapper function that searches USB role switches with
class_find_device_by_fwnode().

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20191008122600.22340-2-heikki.krogerus@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/roles/class.c

@@ -175,6 +175,27 @@ void usb_role_switch_put(struct usb_role_switch *sw)
 }
 EXPORT_SYMBOL_GPL(usb_role_switch_put);
 
+/**
+ * usb_role_switch_find_by_fwnode - Find USB role switch with its fwnode
+ * @fwnode: fwnode of the USB Role Switch
+ *
+ * Finds and returns role switch with @fwnode. The reference count for the
+ * found switch is incremented.
+ */
+struct usb_role_switch *
+usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode)
+{
+	struct device *dev;
+
+	if (!fwnode)
+		return NULL;
+
+	dev = class_find_device_by_fwnode(role_class, fwnode);
+
+	return dev ? to_role_switch(dev) : NULL;
+}
+EXPORT_SYMBOL_GPL(usb_role_switch_find_by_fwnode);
+
 static umode_t
 usb_role_switch_is_visible(struct kobject *kobj, struct attribute *attr, int n)
 {

include/linux/usb/role.h

@@ -50,6 +50,9 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev);
 struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *node);
 void usb_role_switch_put(struct usb_role_switch *sw);
 
+struct usb_role_switch *
+usb_role_switch_find_by_fwnode(const struct fwnode_handle *fwnode);
+
 struct usb_role_switch *
 usb_role_switch_register(struct device *parent,
 			 const struct usb_role_switch_desc *desc);