Re: [Bisected] [Bug #13821] Replugging USB serial converter uses new device node

Alan Stern
2009-07-27T16:18:37Z

On Mon, 27 Jul 2009, Ferenc Wagner wrote:

> > Are you certain this really is a regression? Under 2.6.30 and 2.6.27
> > the same thing happened if I unplugged a USB serial device while it was
> > in use.
>
> My original report is about unplugging the USB servial device *after*
> using it.
>
> > Can you check whether the device is still being used when you unplug
> > it? For instance, is there still a pppd process trying to communicate
> > with the device?
>
> I checked and rechecked that the pppd process is already dead by the
> time I unplug the device. However, the minor number did not increase
> if I unplugged the device without using it beforehand, as expected.
>
> > In short, it seems likely that this is not new behavior but rather the
> > way usb-serial has worked all along.
>
> I didn't experience this problem with 2.6.30: my ppp script was
> hardwired to use ttyUSB0 and it always worked. Now with 2.6.31-rc3 it
> does not, as the device node keeps changing.
>
> I'll test this with opening ttyUSB directly from the shell, instead of
> via pppd, and report back whether it makes a difference.

Another thing to check is whether this patch (not yet merged) fixes it:

http://marc.info/?l=linux-usb&m=124825571403844&w=2

Alan Stern