Instead, print a diagnostic and return. (Some drivers do this already.)
Also, normalize the diagnostic message, and fix some places where the
printfs were getting ugly.
(currently only CD-ROM drives on i386). The sys/dev/scsipi system provides 2
busses to which devices can attach (scsibus and atapibus). This needed to
change some include files and structure names in the low level scsi drivers.
thorpej