Question about SCSI device drivers

[btr!!atk at decwrl.dec.com]

I'm looking for information on how to talk to a SCSI device on a Sun
system, either using one of the existing device drivers or developing one
of our own.  Does anyone have any suggestions on books to read or manuals
to look at?

Basically we want to build a device that attaches to the SCSI port of a
Sun 4 and we want to talk to it as easily as possible.

Thanks for any information.
Alex Kreis
atk at btr.com