I do this question, cause I'm working in a USB stack in kernel mode in my free time.
I got stuck with USB transfers in UHCI module, altough the drivers detect when a new USB device is connected and disconnected.
The PCI host controller is detected, I'm using VIA VT6212 in a Fuel R14000.
Had to do some weird things, cause the Irix drivers developers manual does not cover some interesting functionalities, needed for a USB stack, like communication from one modules to another.
However, things seems to work, except DMA transfers from PCI Host Controller to DMA memory. (well, the UHCI transfers get stuck, no errors signals from host controller received... just a sudden stop in communication). I think it has something to do with the DMA management and transfers from the PCI controller, some Irix specific stuff....
Does anybody would like to check things? I'll send code under request.