rspro board and mounting root from SD

[M. Warner Losh]

In message: <d763ac661002152224i7310a0d3q52bd93b64428297a at mail.gmail.com>
            Adrian Chadd <adrian.chadd at gmail.com> writes:
: Thanks, I'll just (ab)use this method of delaying the root mounting
: hackery until the umass child gets a chance to finishing probing.
: 
: A "better" solution (eg enumerating which USB children need to finish
: probing and adding them in with relevant notification) may take a bit
: more hackery than I was hoping for. Maybe slicing something hackish
: into CAM would be evil but more generic..

There is something hackish already in CAM, sadly.  kern.cam.boot_delay
looks like it defaults to '0' but you could set it to 4 I think to get
the same net-net as this patch.

I've talked through a bunch of solutions with Scott, and I think we
concluded that the right approach was for CAM to evolve a little.
As SIMs are discovered, they are added to a list of things to probe
(if their transport is polled, rather than self-discovered).  Then,
after the interrupt hooks are done, it would run through the list
polling those SIMs.  Once that's done, we'd release the hounds, errr,
I mean we'd allow mount_root to proceed.

Warner