Subject: Re: DSSI update
To: Chuck McManis <>
From: Todd Vierling <>
List: port-vax
Date: 02/06/2001 19:51:55
On Tue, 6 Feb 2001, Chuck McManis wrote:

: #2 What is "right" ? The argument Matt proposes goes something like this:
: 	"The DSSI bus is actually just speaking the MSCP protocol so this
: 	 is just another MSCP drive, make the mscpbus attach to them."
:     This is the "protocol centric" argument. If you applied it to
: everything then you would have to also argue that SCSI controllers that
: appear on the Q-Bus should have their disks labelled sd(n) since they are
: talking the SCSI protocol. Except of course you can't do that, because you
: can't really know what protocol is being used to talk to the disk, you can
: only know what *interface* is being used.

In *NetBSD* (and no, we don't care what other DEC-supplied OS's have done in
the past), the "mscpbus" or "scsibus" or "atapibus" *is* the protocol
control layer; this can attach to a Qbus card on some VAXen, a PCI card on
other platforms, or even a USB widget on some.

So the question is:  does your "dssibus" do the MSCP protocol encapsulation
and decapsulation, or does the controller take that work away from you?  If
the former case, it should share that encap/decap code by attaching a
"mscpbus" instead.

This has nothing to do with "protocol vs. interface" -- it has entirely to
do with whether the main CPU, or the controller card, is in charge of the
protocol layer.  If you don't believe that this is standard for NetBSD, I
encourage you to look at the the "scsibus* at umass?" and
"atapibus* at umass?" USB attachments.

This argument stands for future NetBSD work in spite of the fact that some
ports (ahem, pmax) still haven't fixed their preexisting, historic SCSI
drivers to use the scsipi subsystem properly.

: yourself this question, how come every network interface that produces
: ethernet signalling levels isn't called 'eth'? Why le0, ze0, qe0, etc?

The networking subsystem is very different from the disk subsystem in
NetBSD, so this isn't really relevant.

-- Todd Vierling <>  *  Wasabi NetBSD:  Run with it.
-- NetBSD 1.5 now available on CD-ROM  --