Device Driver help

[NBarbieri.es at PARC-MAXC.ARPA]

I'm new at writing device drivers and need some pointers to some
documentation if it exists on the kernal device driver interfaces for
block and character devices.  Our Unix package (Unisoft+) doesn't give a
very good description of their interface mechanisms.  I called the OEM
of the system (Microbar Systems), and they say that the interfaces are
standard Unix.  Okay, then it must be documented somewhere, hopefully.
I'm looking for such things as what each function does, what it expects
for input, what it returns, etc.  (on such things as ttread().
ttwrite(), ttychars(), ttyopen(), etc.).

Any ideas?

Nick (NBarbieri.es at parc-maxc)