Hi
I had a quick look at the sparc64's bus_space(9) implementation,
and could'nt figure out what kind of barriers are enforced by
bus_space_read and bus_space_write, if any.
That is, if a driver do 2 consecutive bus_space_write, are we sure that
the writes will reach the device in order ?
Also it seems the implementation is different for 32 and 64bit kernels,
so the behavior may be different.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--