AER and UA interlock

Elliott, Robert Robert.Elliott at COMPAQ.com
Tue Nov 27 15:51:44 PST 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at compaq.com>
*
The Control mode page defines how asynchronous event reporting (AER) is
enabled for three kinds of events: 
a) ready unit attentions (initialization complete)
b) other unit attentions (all other kinds of UAs)
c) deferred errors

It says that AER is used <instead of> creating a unit attention
condition for the first two cases.  Taken literally, if the event is
reported via AER, a unit attention condition is not established.

This did not matter before the UA interlock proposal (00-359r7, sam2r21,
spc3r2).
That proposal mentions interlocking unit attentions that are reported
with AERs.
However, the SPC-3 wording means no UA condition exists to be reported
(see below).  I suggest changing SPC-3 to indicate that unit attentions
are created for cases a) and b) - getting rid of the "instead of"
wording.

Also, although deferred errors don't generate UAs, should they also be
covered by the UA interlock feature?


SAM-2 revision 21 section 5.8.5
===============================
If a logical unit reports a unit attention condition with
autosense (see 5.8.4.3) or with an asynchronous event 
report (see 5.8.4.2) and the UA_INTLCK_CTRL field in the 
Control mode page contains 00b (see SPC-3), then the logical 
unit shall clear the reported unit attention condition for that 
initiator on the logical unit. If the UA_INTLCK_CTRL field in 
the Control mode page contains 10b or 11b, the logical unit 
shall not clear unit attention conditions reported with
autosense or an asynchronous event report.


SPC-3 revision 2 section 8.3.6
==============================
A ready AER permission (RAERP) bit of one specifies that the device
server may issue an asynchronous event report upon completing its
initialization sequence <instead of generating a unit attention
condition>. A RAERP bit of zero specifies that the device server shall
not issue an asynchronous event report upon  completing its
initialization sequence.

NOTE 49 - If the device server's default value for the RAERP bit is one
and it does not implement saved parameters or include a hardware switch,
then it may be impossible to disable the initialization sequence
asynchronous event
reporting.

A unit attention AER permission (UAAERP) bit of one specifies that the
device server may issue an asynchronous event report <instead of
creating a unit attention condition> upon detecting a unit attention
condition event, other than
upon completing an initialization sequence. A UAAERP bit of zero
specifies that the device server shall not issue an asynchronous event
reporting _instead of creating a unit attention condition_.

An error AER permission (EAERP) bit of one specifies that the device
server may issue an asynchronous event report upon detecting a deferred
error condition instead of waiting to report the deferred error on the
next command. An EAERP bit of zero specifies that the device server
shall not report deferred error  conditions via an asynchronous event
reporting.

---
Rob Elliott, Compaq Server Storage
Robert.Elliott at compaq.com

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