[461] in linux-scsi channel archive
Re: Generic Scsi Driver Bug Report and comments.
daemon@ATHENA.MIT.EDU (H. Peter Anvin)
Thu Aug 3 09:27:26 1995
To: submit-linux-dev-scsi@ratatosk.yggdrasil.com
From: hpa@asgard.yggdrasil.com (H. Peter Anvin)
Date: 3 Aug 1995 05:46:19 GMT
Reply-To: Peter.Anvin@linux.org (H. Peter Anvin)
Followup to: <9508021612.ZM26895@aib.com>
By author: "Eric Youngdale" <eric@aib.com>
In newsgroup: linux.dev.scsi
>
> I think the point is being missed here. The issue is not so much
> the namespace that is used, but how to map minor numbers to real devices.
> While it would be nice to be able to fix this just for the sg driver,
> I would prefer a more generic solution that works for all scsi devices
> (disks, cdroms, etc), since the same problems occur there too.
>
This is true. This would require going to a 32- or 64-bit dev_t,
however. libc-5 has the necessary hooks for changing the size of
dev_t (it includes a version number in its stat call), and with the
1.3 development kernel in full swing it is about the right time to
make such a migration.
AFAIK, the constraints to keep in mind are:
# of LUNs/ID 3 bits (can this be more on wide/xwide SCSI?)
Max # of IDs 5 bits (Extra wide SCSI = 32 IDs)
Controllers 3-4 bits
Partitions 4-6 bits
--------------
15-18 bits
Hence, going to 32 bits (16+16) *should* be enough, but there is
certainly a case worth arguing for going all the way to 64 bits. I
*presume* noone's interested in a nonsymmetric solution (e.g. 12+20).
/hpa
--
PGP public key available - finger hpa@yggdrasil.com
"The earth is but one country, and mankind its citizens." -- Baha'u'llah
