kgdb debug with ttyUSB0 instead of ttyS0

[Oliver Graute]

Hello list,

i'am using a null modem cable with two usb to serial converts on both
ends between my develop and my target machine. The connection is fine.
On both machines the serial interface is /dev/ttyUSB0 for this connection.

On the target machine I try to enable kgdboc

echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc

but only got:

echo write error: No such device

if I try:

echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc

is not complaining. Some ideas why ttyUSB0 can't be used with kgdb? 

Best regards,

Oliver