Wacom Touchscreen of a Toshiba M750 not detected properly?

[miyamoto moesasji]

I'm working on getting FreeBSD Stable (svn rev 235652, AMD64) running
to my satisfaction on a Toshiba M750. The challenge is that it
contains a builtin Wacom touchscreen. People report it working under
Linux using the linuxwacom driver also present in ports. Unfortunately
I fail to get it working under FreeBSD and find no reports on the web
of anyone that succeeded for FreeBSD. I have the impression that it is
related to the kernel not detecting it properly, which is why I ask
the question on the Stable mailing list. My apologies if it should
have gone elsewhere. Below a short summary of what I did in trying to
get this to work.

I've installed the x11-drivers/input-wacom port and enabled it by
using wacom_enable in /etc/rc.conf. Upon a reboot I get the message
that /boot/modules/uwacom.ko can not be loaded in dmesg. This is
correct as this file doesn't exist, but it highlights the problem as
this driver is only needed for Wacom tablets connected through USB.
Yet this is a builtin tablet which is connected by a serial
connection. There is no other mention of anything wacom related in
dmesg -a. Enabling webcamd which is often mentioned for USB connect
tablets as being important makes no difference. Moreover building
x11-drivers/input-wacom with the USB flag set also doesn't build the
driver.

I then explored further using devinfo -v, which indeed shows the
presence of the tablet giving the following message:

unknown pnpinfo _HID=WACF009 _UID=0 at handle=\_SB_.PCI0.FNC0.TBLT

This according to the inputwacom wiki is indeed the device I'm trying
to get working, see
http://sourceforge.net/apps/mediawiki/linuxwacom/index.php?title=Device_IDs
but it doesn't appear in dmesg at all.

If I grep through the FreeBSD source I only find a mention of the
older Wacom Tablet generation (WACF004 in this case) in the serial
driver files, i.e. /sys/dev/uart/uart_acpi.c

Unfortunately that is the point at which I am completely stuck as I
don't directly see how I can ensure that the Wacom Tablet is picked up
correctly, so any suggestion how to proceed would be highly
appreciated. Note that it might simply be that I don't understand how
I should enable the appropriate serial connection?.