__func__, result);
 }
 
+static void metrousb_write_int_callback(struct urb *urb)
+{
+       struct usb_serial_port *port = urb->context;
+
+       dev_warn(&port->dev, "%s not implemented yet.\n",
+               __func__);
+}
+
 static void metrousb_cleanup(struct usb_serial_port *port)
 {
        dev_dbg(&port->dev, "%s\n", __func__);
        .open                   = metrousb_open,
        .close                  = metrousb_cleanup,
        .read_int_callback      = metrousb_read_int_callback,
+       .write_int_callback     = metrousb_write_int_callback,
        .attach                 = metrousb_startup,
        .release                = metrousb_shutdown,
        .throttle               = metrousb_throttle,