Could some kind soul (perhaps he who claimed to be working on a
device driver doc) email me some generals about disabling/enabling
interrupts?  specifically: is it always best to use splXXX() or
are there other forms like "disable_intr()" (used in isa/cy.c) which
are better under some circumstances?  

how atomic are assignments?  can "a = 0" be interrupted?  how about
cp = p -> foo?  

In the com.c driver, fairly sweeping segments of code are enclosed in
spltty()/splx(); was this a quick and dirty thing, or a reasonable use?

Thanks.

-john