good books on writing device drivers

[Joe Gotobed x4549]

Hi,
	I'm looking for a detailed book on how to write a device driver
foir a Sun machine. I've writen for other OSs & machines (VMS/etc.)) and
I've read the Sun manuals and both Bach & McKusick's books but was looking
for something with real code.

All suggestions appreciated & if there's enough response I'd
be happy to sumarize later.
Merry Xmas!

Joe