1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index a47a24f8820d..0b14aea8ebd5 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -36,6 +36,16 @@ static int usb_serial_device_match (struct device *dev, struct device_driver *dr
         return 0;
 }
 
+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)
 {
         struct usb_serial_driver *driver;
@@ -62,6 +72,10 @@ static int usb_serial_device_probe (struct device *dev)
                         goto exit;
         }
 
+        retval = device_create_file(dev, &dev_attr_port_number);
+        if (retval)
+                goto exit;
+
         minor = port->number;
         tty_register_device (usb_serial_tty_driver, minor, dev);
         dev_info(&port->serial->dev->dev, 
@@ -84,6 +98,8 @@ static int usb_serial_device_remove (struct device *dev)
                 return -ENODEV;
         }
 
+        device_remove_file(&port->dev, &dev_attr_port_number);
+
         driver = port->serial->type;
         if (driver->port_remove) {
                 if (!try_module_get(driver->driver.owner)) {