[LAU] GPIO to alsa

Hello, Having some bare keyboards and raspberry-sortof boards, I'd be interested in connecting both of them without using a midi interface, but only the available GPIO pins available on the board. This is as well to save external components and as a programming exercise. After searching for information, nothing revelant was found, except a experimental python script to read gpio and using the mididings library to output messages. Is there a existing project which would scan rows/colums of a keyboard from the designated(configured) gpios, and throw midi message to an alsa midi port ? Would such a program better be a kernel module or a userland program ? Thanks for your advice Raphaël