Commit ce0d9325 authored by Roman Kagan's avatar Roman Kagan Committed by Greg Kroah-Hartman
Browse files

usb-serial: show port number in sysfs

Some usb-serial devices (e.g. certain Edgeport models) have more than
one serial port on the same USB device/interface.

Currently the only way to distinguish these ports in userspace is by
their minor device number: the driver makes them consecutive and in
stable order.

However, for the purpose of stable naming with udev this is
insufficient: when udev handles the ADD event for one of the ports it
doesn't know what minor number the other one has.

To make stable naming easier, export the port number via sysfs.
Signed-off-by: default avatarRoman Kagan <>
Signed-off-by: default avatarDmitry Guryanov <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent fdf99c9e
......@@ -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);
......@@ -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)) {
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment