dual port reset and mode parameters

Tom Wicklund wicklund at intellistor.com
Wed Aug 17 09:39:13 PDT 1994


I don't see an obvious answer to this in the SIP document, so I'll see
if anybody can help:

Assume a dual ported parallel SCSI device.  SCSI bus reset to one port
of the device is only supposed to reset that port, not affecting the
other port.

Also assume that this device keeps one copy of mode parameters,
operating modes, etc. for all initiators (rather than a copy per
initiator).

What happens to mode parameters, operating modes, etc. on SCSI bus
reset?

According to SIP (rev 3) section 4.2.2.1 (hard reset description in
the model), a hard reset will:

   3) Return any SCSI device operating modes to their appropriate
   initial conditions, similar to those conditions that would be found
   after a normal power-on reset.  MODE SELECT conditions shall be
   resetored to their last saved values if saved values have been
   established.  MODE SELECT conditions for which no saved values have
   been saved shall be returned to their default values.

In dual ported implementations:

   3) operating modes on the port not reset are not changed;
   4) unit attention is only generated on the reset port unless mode
   parameters affecting the port not reset are changed.

>From this it appears that a dual ported device which only has one
operating mode will leave the port which was reset in the current (not
power on) operating mode since it cannot affect the port not reset.

For mode parameters, a very literal reading would appear to require
that the port not reset revert to saved (or default) mode parameters
since it's allowed to return a UNIT ATTENTION but I can also argue
that the port which was reset should return to current mode
parameters so that the port not reset isn't affected by the reset.

There is a simlar situation for LOG parameters where one set of LOG
parameters are maintained for all initiators on both ports or for
INQUIRY parameters which might be changed by some action.

My questions from this are:

1.  Does the port being reset remain in its current operating mode (to
leave the other port unchanged) as SIP appears to state?  If so, after
a reset should the port also report "changed operating definition"
since the port is not in its power on operating definition?

2.  How should mode parameters be handled?  Go back to power on values
or leave current parameters in the port being reset?  If current
parameters are retained should the port being reset generate a "mode
parameters changed" unit attention to tell the initiator it hasn't
gone back to any power on values the initiator may be aware of?

I think some changed wording in SIP is in order, especially since
operating modes and mode parameters are handled differently, while I
think they should be handled consistently.




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