It lets you use PS/2 drivers on modern systems.
This is tgwbd's ACPIPS2Nub, except it:
- builds correctly on modern 64-bit systems
- does not require a PS/2 mouse for your PS/2 keyboard to work :p
PS/2 drivers expect to see a ps2controller, and to use predefined interrupts. Neither of these hold on ACPI-based systems.
This:
- finds the PS/2 devices from PNP identifiers
- provides a fake ps2controller device that maps the legacy interrupts.