Re: USB PORT assignment

[Gordon Farquharson <gordonfarquharson@gmail.com>]

Hi Doug

On Fri, Jun 5, 2009 at 15:40, Mr Doug -<dsc3507@yahoo.com> wrote:

> When I connect a USB to serial adapter on my NSLU2 Debian system all is well... it assigns ttyUSB0.  But if I disconnect the cable and then reconnect it assigns the next port - ttyUSB1 and so on going up.
>
> Is this normal? I tried deleting the /dev/ttyUSBx  files but it still assigns the next port. Is there a way to delete a port so it can be reassigned? I know rebooting would solve the problem but I do not want to do that every time.

I've seen this behaviour before, but I've never investigated why it
happens. udev should be handling the assignment of device names, so
that may be a place to start looking for clues. You may be able to add
a udev rule like

SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", SYMLINK+="my_USB_serial_device_name"

to create a device node /dev/my_USB_serial_device_name which you could
use each time. I have not tested this idea.

To get some information that you may need to create an appropriate
udev rule, try:

$ sudo udevadm monitor

and insert and remove the USB to serial adapter a few times. If you
are not familiar with udev rules (they can be a pain), have a look at

http://reactivated.net/writing_udev_rules.html

I hope that this information helps.

Gordon

-- 
Gordon Farquharson
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