i have a mp8866 dual usb convertor . you can use it to attach 2 psx or ps2 controllers on one usb port. It didn't work at first with SDL but it did afterwards when i modified some of the code. so there's only basic support for it at least in SDL atm. i haven't tried it with any other program since i don't actually use my gp2x for playing games but i could test it out for you if you like. What program /game did you have in mind ?