I've trying to get my Wacom serial tablet on my Thinkpad x61 to work on Windows XP under VirtualBox for some time now.
post, I was able to install a COM port under Windows. It's shown as COM3, since I'm using and IRQ of 5 and an I/O Port of 0x200.
When I run VirtualBox, it seems to see the port:
Gwendolyn:/home/corey# lsof /dev/ttyS0
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
Xorg 9306 root 11u CHR 4,64 1514 /dev/ttyS0
VirtualBo 9608 corey 37u CHR 4,64 1514 /dev/ttyS0
That line beginning with VirtualBox doesn't show up when VirtualBox is off. I took out the relevant lines in my xorg.conf in case the Linux host and Windows can't use the serial device simultaneously, so now Xorg doesn't show up when I run lsof.
Like I said, I've gotten the COM3 port to show up in Windows' Device Manager. But there's nothing that indicates that there's something (my tablet) connected to the COM port. I installed the tablet drivers from Wacom's website, but the program doesn't recognize any devices.
EDIT: I'm running Debian testing on 2.6.26-1-amd64