Ultrix device driver question

[Allan G. Weber]

I have a MicroVAX-II (Ultrix 2.2) system that I am considering updating to
Ultrix 3.1 or whatever is the latest version.  My problem is that the
system has two non-DEC device drivers for handling some laboratory
peripherals.  For one I only have an object file and it was written by a
vendor who has since decided to not support Unix systems any more.  The
other driver is for a DRV11W and I have sources to it.  Both drivers had to
be changed when we went from Ultrix 1.2 to 2.2.  Does anybody know if the
rules for writing drivers changed again between version 2.2 and 3.x?  If
so, I could use some advise on how to make the one I have sources for
compatible with Ultrix 3.x.  By the way, is there any Ultrix document on
writing device drivers?  I've seen a similar document for VMS, but I've
never seen one for Ultrix.

Thank you.

Allan Weber
University of Southern California
Signal and Image Processing Institute
weber%brand at usc.edu