I found this on sourceforge
Linux SCSI Target Mode driver for Adaptec SCSI cards
http://sourceforge.net/projects/linux-scsi-tm/
Upon casual inspection, it looks like the right thing. But it's not for
the faint of heart. I have no idea if it works, but it looks right.
I think I'll fire up a box with the proper scsi card and see if I can
get it to pretend it's a disk.
-brad