Subject: Re: The obvious inherent superiority of SVR4 device naming...
To: Ted Lemon <firstname.lastname@example.org>
From: Chris G Demetriou <Chris_G_Demetriou@LAGAVULIN.PDL.CS.CMU.EDU>
Date: 12/22/1994 04:45:49
> > p.s.: I also liked that SCSI device 5 was device 5. Always. I don't like
> > having sd0, cd0, and st0 - in fact, this confused me and made it difficult
> > for me to install, because unit 5 was sd1. ???
> This I agree with. I don't understand the motivation for the
> numbering scheme that I hear is being used in the 386 port. To me it
> seems fraught with danger. I'll probably hack it out of my kernels at
> some point. Fortunately for me, the pmax port doesn't currently
> operate this way.
one can easily make scsi disks and scsi CD-ROM's have particular
names, if you want. I don't think many people want, however.
sd0 at scsibus0 target 0 lun 0
sd1 at scsibus0 target 1 lun 0
sd2 at scsibus0 target 2 lun 0
sd3 at scsibus0 target 3 lun 0
sd4 at scsibus0 target 4 lun 0
sd5 at scsibus0 target 5 lun 0
sd6 at scsibus0 target 6 lun 0
sd7 at scsibus0 target 7 lun 0
that'll get you explicit mappings for one scsi bus, for scsi disks.
you could do the same thing with SCSI tapes, etc.
*i* would rather have control of what things are mapped to. in
particular, i like devices to start at unit zero, if it's the first
'standard' unit of tha type on the machine.
e.g. look at the SUN_LAMP config:
sd0 at scsibus? target 0 lun 0
sd1 at scsibus? target 1 lun 0
sd2 at scsibus? target 2 lun 0
sd* at scsibus? target ? lun ? # SCSI disk drives
st0 at scsibus? target 6 lun 0
st* at scsibus? target ? lun ? # SCSI tape drives
cd0 at scsibus? target 5 lun 0
cd* at scsibus? target ? lun ? # SCSI CD-ROM drives
sd0, sd1, and sd2 are (almost) explicitly named, as are st0 and cd0.
you'll note that the "scsibus" they can be on is variable; for a
while, we were trying to get the configuration happy, and trying out
various confiurations by switching the chains between two host
additional SCSI disks, tapes or CD-ROM's get added at the next
available unit number.
the point is, the autoconfigure system is the only place where the
mapping of SCSI units to device names is done, and it's completely