This engineer has done all of the clever stuff like DMA and LCD but not the keypad. He says the keypad is the most difficult as he has to write the driver from scratch since there are no examples to modify.
Do you mean using one of the PRUs to inject the 12 buttons as keypresses to the Linux Input subsystem, or what?
If you just want to do it in userspace, you can access the GPIO pins in userspace -- use the new character device interface; see examples in
tools/gpio/ in the Linux kernel sources --, and inject any keyboard events back into the Linux input subsystem using the
uinput character device. This approach works for all Linux SBCs, and has nothing BeagleBone specific.