How can you Connect a Playstation Controller to a Linux Box?

killboy powerhead asks this nifty question: "I purchased a Playstation dual-shock controller clone (dual thumb joysticks!) with the express purpose of playing Robotron & Smash-TV under X-MAME. E-mail and phone requests to the "official" channels for either the interface specs or the communications protocol have yielded nothing. I've used the wiring diagram within the Linux joystick driver file to make the initial connection, but i've been unable to get a clean handshake test. I'm using an ATX motherboard, so the 3.5 volts it makes available on the parallel port should be close enough to the 3.7v expected by the controller." Can anyone help him out?