I've been considering buying a Wacom tablet for quite a while, as they make quite a few things easier, especially with photo editing. I've just had mine for a couple days, and have been using it for quite some time lately.

Now, making it work on Gentoo was a bit of a daunting task, but I've managed to make it work on my travel machine, as well as my desktop, both on Gentoo Linux but with different specifics.

I've been following the tutorial, but some things just didn't work, and some Google-fu mostly helped me out figuring out a consistent way to get such a tablet to work.

Compiling the X11 driver

First, edit /etc/make.conf, and make sure you add wacom to your INPUT_DEVICES variable, like so:

INPUT_DEVICES="evdev synaptics wacom"

Then do emerge -1va x11-base/xorg-drivers.

Compiling the kernel driver

The tablet being relatively new as of December 2011, the in-kernel driver just wouldn't pick it up. Fortunately there was another option: grabbing the input-wacom sources (and be sure to use the bamboo3 branch) and compiling those. Do a git clone or whatever you want to obtain the sources, and once you have the source tree, just do ./autogen.sh. The output looks like this:

Your wacom.ko is available under 
    /home/x0r/src/cbagwell-input-wacom-eacac38/2.6.38
If you have an USB device, you can copy the driver by:
    cp 2.6.38/wacom.ko /lib/modules/3.0.6-gentoo/kernel/drivers/input/tablet
If you have a serial device, please copy the driver by:
    cp 2.6.38/wacom_w8001.ko /lib/modules/3.0.6-gentoo/kernel/drivers/input/touchscreen

NOTE: The kernel drivers included in this package are only
tested with the X Wacom driver built from xf86-input-wacom.
 If you are running an X server version older than 1.7, 
please use the drivers provided by linuxwacom package.

Just copy the right .ko file to the right location, then do depmod -ae, and plug in your tablet. If you're getting a response, then congratulations.

X11 configuration

However, even after restarting X, I have noticed that the Synaptics driver was intercepting my tablet, something you obviously don't want. Therefore, my xorg.conf.d looks like this:

35-wacom.conf

Section "InputClass"
    Identifier "Wacom Class"
    MatchProduct "Wacom|WACOM"
    MatchDevicePath "/dev/input/event*"
    Driver "wacom"
EndSection

40-mouse.conf

Section "InputDevice"
    Identifier "Mouse0"
    Driver  "synaptics"
    Option  "Device" "/dev/input/by-path/platform-i8042-serio-1-event-mouse"
    Option  "GrabDevice" "False"
EndSection

Section "InputDevice"
    Identifier "Mouse1"
    Driver  "evdev"
    Option  "Device" "/dev/input/by-path/pci-0000:00:1a.1-usb-0:1:1.0-event-mouse"
    Option "GrabDevice" "False"
EndSection

50-evdev.conf

# Catch-all evdev loader for udev-based systems
# We don't simply match on any device since that also adds accelerometers
# and other devices that we don't really want to use. The list below
# matches everything but joysticks.

Section "InputClass"
        Identifier "evdev pointer catchall"
        MatchIsPointer "on"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
EndSection

Section "InputClass"
        Identifier "evdev keyboard catchall"
        MatchIsKeyboard "on"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
EndSection

#Section "InputClass"
#        Identifier "evdev tablet catchall"
#        MatchIsTablet "on"
#        MatchDevicePath "/dev/input/event*"
#        Driver "evdev"
#EndSection

#Section "InputClass"
#        Identifier "evdev touchscreen catchall"
#        MatchIsTouchscreen "on"
#        MatchDevicePath "/dev/input/event*"
#        Driver "evdev"
#EndSection

You'll notice that I've commented the two last sections in 50-evdev.conf. Actually, these were the ones that were causing me trouble.

Some hacks to make it work on my setup

Learn more about these in part 2.