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Date:      Wed, 19 Apr 1995 09:04:06 -0400 (EDT)
From:      Peter Dufault <dufault@hda.com>
To:        julian@freefall.cdrom.com (Julian Elischer)
Cc:        fs@freefall.cdrom.com, hackers@freefall.cdrom.com, hardware@freefall.cdrom.com
Subject:   Re: [DEVFS] your opinions sought!
Message-ID:  <199504191304.JAA04622@hda.com>
In-Reply-To: <199504190519.WAA06359@freefall.cdrom.com> from "Julian Elischer" at Apr 18, 95 10:19:33 pm

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Julian Elischer writes:
> 
> I am about ready to let people hack at devfs.
> but one thing I'm not sure about:
> 
> what is a good way for the devfs to appear?
> 
> I personally favour something hierachical,
> such as:

I'd like to see an exact match of what we have now,
a typical BSD view with a different prefix:

> /devfs/rsd0a

meaning if you really wanted to you can mount devfs on dev and continue
on with no other changes.

If you want a second funky hierarchy you could create it as a
subdirectory such as:

> /devfs/devs/rdisk/pa

though I personally would be perfectly happy with the first, and if I
were making up the rules I'd say a requirement is that devfs create
something that looks just like what we have now.  I don't like the idea
of doing links to implement this; I think devfs should implement the
device file system policy so that it is uniform.

BTW: I hate mixed case but maybe others don't.

(...)

> e.g.
> /devices/scsi/b0t0l0 -> ../../disks/sd0  (?)
> or
> /devices/scsi/b0t0l0_all hardlink to /devices/sd0  (?)
> /devices/scsi/b0t0l0_P0 hardlink to /devices/sd0P0  (?)
> /devices/scsi/b0t0l0_P1Sa hardlink to /devices/sd0P1Sa  (?)

I find this sort of odd.  I'm not sure you ever care about partition
0 on the disk at B0T0L0, though you may want to access the
device at B0T0L0 for general utilities.  That is, I see a need for:

> /devfs/rsd0a

possibly AKA

> /devfs/devs/rdisk/pa

and for SCSI "device visiting" utilities (SCSICONF.EXE) possibly:

> /dev/devs/scsi/b0/t0/l0

because then you can write the utility using opendir ... etc, but
no really good reason for naming a partition of a disk accessed
via the SCSI nexus.

Aside:

At the moment only the SCSI Target device needs the encoded SCSI
nexus.  And it does need it, there is no good work around.

The support for all devices is still in there but conflicts
with the slice code.  I haven't decided if the support should be
simply removed in the general case as something that we just don't
need or kept in and made consistent with the slice code.  I
lean toward removing it.

Peter
-- 
Peter Dufault               Real Time Machine Control and Simulation
HD Associates, Inc.         Voice: 508 433 6936
dufault@hda.com             Fax:   508 433 5267



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