Technical SCSI question

[derek@slab.slip.uiuc.edu (Derek Taubert)]

Looking through Apple's Tech. Ref. on the SCSI card, I can't figure something
out.  All of the calls involve REQUESTING a device on the SCSI bus to do some
action.  By what mechanism does a device on the bus get the host to do
something?

Example: disk is ejected from a button on the drive, icon gets dimmed.

What sequence of events (specifically around the SCSI driver level) allow this
to happen?  I'm curious, because I'm looking at some of the SCSI to E-net
converters, and I assume that their informing the host that a frame has
arrived will be of a similar nature.  At any case, it's in the other direction
that all of the calls seem to support, and I want to know how it would work.

Thanx,

Derek