Subject: Re: Dynamic SCSI ids (was: A possible way of handling...)
To: Johan Danielsson <>
From: Chris G. Demetriou <>
List: tech-kern
Date: 03/28/1997 23:41:14
> "Chris G. Demetriou" <> writes:
> > And, because your opinion does not necessarily match that of others,
> > the existing system gives you the flexibility to configure it
> > _either_ way, or some strange in-between way, if you see fit.
> For specific disks, yes. How do I make it *always* use the `right'
> naming?

Huh?  What do you mean?

You could configure something like:

sd0	at scsibus0 target 0
sd1	at scsibus0 target 1
sd2	at scsibus0 target 2
sd3	at scsibus0 target 3
sd4	at scsibus0 target 4
sd5	at scsibus0 target 5
sd6	at scsibus0 target 6
sd7	at scsibus0 target 7
sd8	at scsibus1 target 0
[ ... ]

until you were blue in the face.  You could then wire all SCSI
controllers you might ever want in your system to scsibus units, etc.

It is quite possible to 'nail down' just about any configuration you
want, even if you specify 'nailed down' unit numbers for many, many
devices that you'll never have connected to your system.

Because of the variation and type of SCSI bus configurations, it's
completely unreasonable to try to hard code this in the GENERIC
kernels.  It makes little sense to a user to have 'their SCSI bus', on
their only controller, be scsibus15, because that's how it happened to
be wired down in the config files.  (Remember, unless you wire down
busses to controllers, and controllers to their busses, you still have
the potential to lose!)  It also makes no sense that their only SCSI
disk, at ID 0 of that bus, is then sd120 (or sd240, if you're leaving
room for 16 targets on each bus).

And this doesn't even account for leaving plenty of unit numbers for
non-zero LUNs.

In a nutshell, I think trying to make generic kernels 'hardwire' all
of the SCSI devices ridiculous, for this reason.  It is quite
practical to do it for specific systems, and even for 'generic'
kernels if you're willing to deal with the requisite config file hair,
but it's not worth it for most people to go to the extreme of wanting
everything wired down.