Indigo2 parallel port

Hello !

I would like to use my indigo2's parallel port for printing under
GNU/Linux, but according to some e-mails from the archive (Mar. 2002), the indigo2 parallel port has no existing driver yet.
So I would like to write one.

Sadly, the only information I have about SGI parallel port hardware is
the name of the chip: "PI1". I could not manage to find anything with google :/

I would appreciate it very much if someone could point me to a place
with SGI hardware specifications (parallel port asic state machine, registers mapping, etc...)

Thank you !

Vincent