USB ppbus?

[George Mitchell]

I have a USB cable that terminates in a DB25 connector.  Inside is a
Prolific Technology PL2305:
http://prolificusa.com/files/ds_pl2305I_v1.0.pdf
It probes as a ulpt.  I would love if there existed such a thing as
a uppi device.  Does it sound possible to get to such a result by
extending the ppbus code to know about USB?  Or might it be simpler
to try to add the ppi ioctls (PPIGDATA, etc.) to ulpt.c?   -- George