I've been having an interesting experience getting sym53c8xx_2 working
on ppc64 now that highio is in place.  Of course ppc64 doesn't need
highio, and it does set blk_nohighio = 1 in setup_arch().  So the
sym53c8xx driver works.

However, sym53c8xx_2 fails because after calling scsi_register() in its
attach it blindly slams highmem_io on (in sym_glue.c).  Is this
correct?  It seems to me that it should just leave it alone since
scsi_register already handled that.

I might be misunderstanding something here.  Is there anything else a
64-bit arch must do for highio?  I found we also weren't setting max_pfn
which seemed bad...though maybe irrelevant.

The trivial patch to fix it is attached, but I haven't tested it on a
system that supports highio.

-todd