spibus access serialization

[Warner Losh]

On Sep 2, 2012, at 6:37 AM, Luiz Otavio O Souza wrote:

> <spibus-01.diff>

This looks good to me as is.

spibus-02.diff

This looks good as well.  There's another change mixed in (DEVMETHOD_END), but it is likely benign enough to go in with this.  If you really want, split it out, but if you don't really want, things are OK as is.

spibus-03.diff

+		mtx_sleep(sc, &sc->sc_mtx, 0, "ar71xx_spi", 0);

I'm not sure I see what wakes this up.  Am I missing something?  Same is true in all the drivers.  The rest is decent enough, but does mean we can only do acquire/release in a sleepable context.  Is that going to be OK?

Warner