USB: Add helper macro for usb_driver boilerplate

This patch introduces the module_usb_driver macro which is a convenience
macro for USB driver modules similar to module_platform_driver. It is
intended to be used by drivers which init/exit section does nothing but
register/unregister the USB driver. By using this macro it is possible
to eliminate a few lines of boilerplate code per USB driver.

Based on work done by Lars-Peter Clausen <lars@metafoo.de> for other
busses (i2c and spi).

Cc: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/usb.h

@@ -953,6 +953,18 @@ extern int usb_register_driver(struct usb_driver *, struct module *,
 
 extern void usb_deregister(struct usb_driver *);
 
+/**
+ * module_usb_driver() - Helper macro for registering a USB driver
+ * @__usb_driver: usb_driver struct
+ *
+ * Helper macro for USB drivers which do not do anything special in module
+ * init/exit. This eliminates a lot of boilerplate. Each module may only
+ * use this macro once, and calling it replaces module_init() and module_exit()
+ */
+#define module_usb_driver(__usb_driver) \
+	module_driver(__usb_driver, usb_register, \
+		       usb_deregister)
+
 extern int usb_register_device_driver(struct usb_device_driver *,
 			struct module *);
 extern void usb_deregister_device_driver(struct usb_device_driver *);