On Sat, Sep 08, 2012 at 12:14:39PM +0200, peter.sheeren@axiris.be wrote:

Hello

At the suggestion of Greg's friendly e-mail bot I'm sending my
report to this e-mail address. I hope it's the right one.

Peter

Date: Sat, 08 Sep 2012 04:21:06 +0200
From: peter.sheeren@axiris.be
To: jhovold@gmail.com, greg@kroah.com
Subject: Bug in USB FTDI SIO driver


Hello

I didn't find an easy way to file a bug report so I extracted the
source file ftdi_sio.c from the latest Linux kernel and browsed for
the e-mail addresses hence this e-mail.

I've been struggling with an annoying plug-and-play issue involving
an FT232RL-based USB device on ARM machines with Linux lately
(including Raspberry Pi and BeagleBoard). In a nutshell the
following is happening:
* I plug in the FT232RL-based USB device. /dev/ttyUSB0 is created.
* I run an application that communicate with the device via
/dev/ttyUSB0. The application sets a baudrate - this is important.
The application reads and writes data successfully.
* I unplug the USB device. /dev/ttyUSB0 remains in existence - this
is important too.

Huh?  The device node should go away, as the application was told that
the device went away, is the application somehow still keeping the
device node open?  If so, that's the issue here.

* I replug the USB device. /dev/ttyUSB0 is still there.
* I rerun the application. The application again connects with
/dev/ttyUSB0 but it fails to transfer data. So it seems.

That's because it is trying to still talk to the old device, not the new
one, which should have showed up on ttyUSB1.

What kernel version are you using here?

greg k-h