Subject: Re: Drive Numbering...
To: Chris G Demetriou <Chris_G_Demetriou@BALVENIE.PDL.CS.CMU.EDU>
From: Terry Moore <firstname.lastname@example.org>
Date: 11/17/1995 19:01:32
> One of the biggest problems with pinning all devices nodes to specific
> targets is: how do you do it? in the generic kernels, do you assume
> that each bus should have its own set of (pinned) targets? (that's
> hell on device nodes, and in config files.) do you assume that you
> just have one bus? (that doesn't work on some machines.) etc.
In any event, mapping to physical target addresses, while convenient for SCSI,
is not a very useful concept for things like SSA which (while SCSI-like)
use geographical addressing. Same thing applies, I suppose for SCAM
(which Win 95 allegedly supports in order to eliminate address jumpering
on SCSI busses).
The solution people have used in the past is to have a table (in a file)
that associates the unique ID of the drive (which may have to be put
on when we do the disk label) with the system's handle (e.g., /dev/rsd0).
One might use /dev/rsdxx to indicate a physical address, and then
put magic in mount to handle this, but it may be easier to handle
this when the bus is enumerated than it is at mount time. One has
to "introduce" a drive to a system by modifying said table; but this
at least allows all the peculiarities introduced by the order of
enumeration to be hidden from the user.