-int hmcfgusb_send_null_frame(struct hmcfgusb_dev *usbdev);
-struct hmcfgusb_dev *hmcfgusb_init(hmcfgusb_cb_fn cb, void *data);
+int hmcfgusb_send_null_frame(struct hmcfgusb_dev *usbdev, int silent);
+struct hmcfgusb_dev *hmcfgusb_init(hmcfgusb_cb_fn cb, void *data, char *serial);