The PS2Driver module provides support for PS/2 mice and keyboards on machines with the suitable hardware (e.g. RiscPC, A7000, A7000+). It uses PointerV and KeyV to report keyboard and mouse activity to the OS.
The RiscPC has one PS/2 port and one Acorn (Quadrature) mouse port, and so the usual setup is to use a PS/2 keyboard and a Quadrature mouse (driven by the Mouse module).