+static ssize_t show_port_number(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct usb_serial_port *port = to_usb_serial_port(dev);
+
+ return sprintf(buf, "%d\n", port->number - port->serial->minor);
+}
+
+static DEVICE_ATTR(port_number, S_IRUGO, show_port_number, NULL);
+
+static int usb_serial_device_probe(struct device *dev)