*BSD News Article 96549


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From: wpaul@ctr.columbia.edu (Bill Paul)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: strange message from SCSI ahc driver at boot
Date: 30 May 1997 19:04:27 GMT
Organization: Columbia University Center for Telecommunications Research
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Daring to challenge the will of the almighty Leviam00se, Jose M. Alcaide
(jose@we.lc.ehu.es) had the courage to say:

: J.C. Archambeau wrote:
: > 
: > Did you try disabling wide negotiation for SCSI ID 5 from SCSISelect?
: > Some narrow devices complain if the adapter attempts wide negotiation
: > and you get strange results.  Your Seagate may be functioning in wide
: > mode and the error message is applicable to your CD-ROM drive.
: > Another option would be to examine the mode parameters for SCSI ID 0
: > from EZ-SCSI or FreeBSD's SCSI utility; man scsi from your shell
: > prompt, and see how the device is configured.
: > 

: I have received the following message from Ron Bolin
: <rlb@mindspring.com>:

: :This is normal. I have the same similar system. It just means that the
: :CD is 8 bit. Boot using -v option and you will see 16 bit for the disk.

: Sure. Booting with -v showed that transfers with the HD are 16-bit
: wide. Anyway, I would like to know what "ahc:0:A:5" means. At least,
: it's a somewhat confusing message.

It means target 5 on channel A of controller ahc0. The ahc driver supports
certain Adaptec cards that have two channels: one internal (you attach
devices with a 50-pin ribbon cable) and one external (there's a 50-pin
mini SCSI2 'D' connector on the part of the card that sticks out the
back of the computer). Each channel is a seperate SCSI bus that can
support up to 7 SCSI devices. In effect, it is like having two SCSI
host adapter cards in one package. The 'A' violates the BSD device ID
convention to a certain extent since normally controllers/busses/devices
are numbered rather than lettered. Probably the Adaptec documentation
refers to the busses as channel A and channel B, so the driver author
used that nomenclature in the debug and probe messages.

Anyway: the driver is written to support both single channel and dual
channel adapters, so the probe/debug messages contain a channel identifier
in addition to the other information so that there's no ambiguity about
what device the message refers to.

The fact that your particular card may have only one channel doesn't
invalidate the use of the notation: you have just one bus called channel A,
whereas prople with the dual channel cards will have channel A and
channel B.

In FreeBSD-current, some of the printf()s in the SCSI subsystem were
changed so that now you see messages like:

scbus0 at ahc0 bus 0
sd0 at scbus0 target 5 lun 0
sd0: <foo bar baz>
scbus1 at ahc0 bus 1
sd1 at scbus0 target 1 lun 0
sd1: <foo bar baz>

This makes a little more sense to some people. This is also the notation
used to 'hard wire' SCSI devices in the kernel config file. Note however
that the ahc driver itself was not changed, and it is the ahc driver that
generates the 'ahc:0:A:5' identifier.

-Bill

--
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-Bill Paul            (212) 854-6020 | System Manager, Master of Unix-Fu
Work:         wpaul@ctr.columbia.edu | Center for Telecommunications Research
Home:  wpaul@skynet.ctr.columbia.edu | Columbia University, New York City
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