System Probing with SCC lun devices

James Smart USG smart at
Fri Jan 3 13:21:38 PST 1997

* From the SCSI Reflector (scsi at, posted by:
* James Smart USG <smart at>

Hi Larry,

You don't have to be a SCC peripheral driver to send
a Report Luns command. In most cases, the probing element is
independent from the peripheral drivers (so that the appropriate
drives can thereafter attach to the appropriate device that's
known to be in existence) or each peripheral driver is told to
look at the device and see if it recognizes the device. 
As such, the probing element can pick and choose the commands
used to complete the probe.

So, using Report Luns seems reasonable to me. I do wonder if there's
a better way than trial and error to determine when it's best to
use Report Luns. The basic assumption being that Report Luns is only
present on a SCSI-3 device. If Lun 0 returns a type indicating SCSI-2
(which also means it may not indicate an SCC device type) what's the
best method to continue probing with ?

-- James

------- Begin Forwarded Message

Date: Fri,  3 Jan 97 12:19:09 PST
From: Larry Chen <larryc at>
Subject: System Probing with SCC lun devices
To: scsi at, serial_solutions at
Sender: owner-serial_solutions

* From the serial_solutions Reflector, posted by:
* Larry Chen <larryc at>
* To post to this Reflector, send email addressed to serial_solutions at

In a typical System probing methodology, the
configuration driver must probe for luns and populate
the equipment device table (edt in CAM terminology)
before any of the other peripheral device drivers are 

It has been suggested that the Report Luns command
can be issued to SCC lun to determine the
the other non-SSC lun(s) that are behind the array
controller device.

If this is the case, the SCC host driver must now be
part of the configuration driver. The SCC host driver
must issue a Report Luns command and populate the
equipment device table (edt in Cam terminology) before
any of the Non-SCC drivers are initialized (and claim
their luns).

Is this an acceptable System probing methodology for
the System folks?

Larry Chen                 Tel: 408.383.1600 (x116)
Maximum Strategy, Inc.     Fax: 408.383.1616
801 Buckeye Court       E-mail: larryc at
Milpitas, CA 95035

------- End Forwarded Message

James Smart                                            email: smart at
Alpha UNIX Systems - Digital Equipment Corp.           Phone: 603-881-2472
110 Spit Brook Road,    Nashua, NH  03060              Fax  : 603-881-2257
Disclaimer: My statements and opinions reflect my own thinking and are not
   necessarily reflective of any employer or association.

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