I've just checked in a set of changes to the `sbc' driver.  If you are
using this in the "standard" mode, that is, without using flags on the
sbc0 line in your config file, you will not notice any difference.

The new meanings of the flags are as follows:

0x1	PDMA		Use polled pseudo-DMA mode (default: on)
0x2	INTR		Use interrupt-driven pseudo-DMA mode (default: off)
0x4	RESELECT	Enable disconnect/reselect (default: off)

You can enable any of these behaviors by adding the values together and
putting the result in the config file on the sbc driver line:

	sbc0 at obio? flags 0x7   # ..but read note on the INTR flag below

Unfortunately, there is no way to turn off the polled PDMA mode without
using DDB, kgdb, or recompiling the kernel.

A word to the wise:  there are problems in the current interrupt handlers
that make the INTR flag virtually useless.  Unless you place little value
on your data or are willing to hack on the driver and the interrupt code,
I specifically recommend that you _not_ enable this flag.  Note that
without INTR enabled, the RESELECT flag has no meaning. 

--scott