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

	if (((old_priv.flags & ASYNC_SPD_MASK) !=
	     (priv->flags & ASYNC_SPD_MASK)) ||
	    (((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST) &&
	     (old_priv.custom_divisor != priv->custom_divisor))) {
		change_speed(tty, port);

Function change_speed() is called only when the baudrate  
(custom_divisor) has changed but after a USB replug this assumption is  
wrong. Also note that /dev/ttyUSB0 remains in existence on the system  
under test. If it were up to me, I'd always send the baudrate setting  
over the USB bus nomatter whether the baudrate (supposedly) has  
changed or not.

We don't do that because if you gratuitously send speed changes that have
no effect the hardware seems to reset its configuration and you lose
characters, something a lot of software doesn't expect.

If you think that if check is the problem can you replace it with an
unconditional call to change_speed(tty, port) and the re-test. That will
confirm if it is the cause.

If it is then we can think about fixing it somehow.

Alan