The relevant section is this :
#xorg
x11-drivers/xf86-input-evdev ~x86
x11-drivers/xf86-input-joystick ~x86
x11-drivers/xf86-input-keyboard ~x86
x11-drivers/xf86-input-mouse ~x86
x11-base/xorg-server ~x86
im sure if you emerge it that new entries will have to be made.
l
totally boring desktop .. notice i use two k buttons .. one in traditional the other in the newer form on the right of the left screen. it's shorter to hit if you got one near the middle regardless of initial location on screen