[cardbus doesn't work on Thinkpad 600E]

John Kohl told me that he uses
  options RBUS_MIN_START="0x20000000"
on a 600E, resulting in working cardbus.

It also works on my Thinkpad 600E.  The P2CCLK stuff I described
earlier seems to be irrelevant (although setting that bit did cause
the voltage control to apparently work).  But with RBUS_MIN_START at
512M, cardbus works without setting P2CCLK.

PR 9342 should perhaps be closed.  With -current, I had no crashes
with the bad RBUS mapping (inserting a wi0 and 4 different cards
cardbus cards), so I suspect the defensive coding against garbage CIS
is now in place.  My attempts on a TP600 under 1.6-stable resulted in
cards doing nothing on insert, and I don't remember any crashes.

I filed PR kern/23388 with a patch to cardbus(4) offering a hint
about using RBUS_MIN_START.

It would be nice if RBUS could automatically determine a working range
for mapping, but I don't have any non-kludgy ideas about that. 

-- 
        Greg Troxel <gdt@ir.bbn.com>