Game Input MultipleXer

I´ve read the tutorials over and over again... but still have some questions...

I understand that i have to build a dongle-ish thing to connect to the PS3 USB port?
This only have one USB outlet, how do i connect both mouse and keybord?

Or do i have to have a computer with ubuntu on, running while gaming. So the mouse and keyboard is connected to the computer. And the computer is connected with the playstation?

The latter.
Mouse, keyboard, gampads or whatever connected to PC running GIMX -> PC connected to PS3 using the adapter.