Does anyone have a suggestion as to the best place to quickly learn about
how NetBSD device drivers work and how to begin adding a new driver?  I'm
comfortable with C as far as writing smallish userland type programs, but
know absolutely nothing about kernel programming.  I flipped through a few
books (in particular the design of 4.4 BSD book), but nothing jumped out
at me as the place to start.  My interest is so I can start work on
porting over a preliminary FreeBSD driver for a isa card I have.  I've
heard talk of "bus_space"?  Any pointers to the correct part of some
manual for info on that?  

Thanks much for any pointers

Dan