A method of polling a target for Informational Exception Condition status without issuing a Request Sense command

[Gene Milligan]

* From the SCSI Reflector, posted by:
* Gene Milligan <Gene_Milligan at notes.seagate.com>
*
Background:

The Informational Exceptions Control Mode Page (1) describes several reporting 
methods in which a target can report an informational exception condition to an 
initiator.  These reporting methods require a host to issue a Request Sense 
command and interpret sense data to determine status.  In some environments, 
issuing an unsolicited Request Sense command is not desirable.  This proposal 
provides an initiator with a method of polling a target for Informational 
Exception Condition status without issuing a Request Sense command.


This proposal is for the inclusion of an additional log page, to be known as 
the  FAILURE PREDICTION THRESHOLD EXCEEDED Status Log Page (2Fh) in SPC.  The 
FAILURE PREDICTION THRESHOLD EXCEEDED Status Log Page will contain one log 
parameter (0000h) of the format shown below.  This will allow an initiator to 
poll the target, by issuing a Log Sense command, and check for an informational 
exception condition regardless of the Reporting Method (MRIE) selected.

Proposal:

========================================================================+
   Bit  |   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
  Byte  |       |       |       |       |       |       |       |       |
========================================================================+
   0    |   (MSB)                                                       |
 -------+----             Parameter Code (0000h)                    ----+
   1    |                                                       (LSB)   |
 -------+---------------------------------------------------------------+
   2    |   X   |   X   |   X   |   0   |   0       0   |   1   |   1   |
 -------+---------------------------------------------------------------+
   3    |                   Parameter Length (2)                        |
 -------+---------------------------------------------------------------+
   4    |FAILURE PREDICTION THRESHOLD EXCEEDED ASC                      |
 -------+---------------------------------------------------------------+
   5    |FAILURE PREDICTION THRESHOLD EXCEEDED ASCQ                     |
========================================================================+

The FAILURE PREDICTION THRESHOLD EXCEEDED ASC has the same definition as the 
Additional Sense Code returned in byte 12 of Request Sense data.  

The FAILURE PREDICTION THRESHOLD EXCEEDED ASCQ has the same definition as the 
Additional Sense Code Qualifier  returned in byte 13 of Request Sense data.  
   
If either Byte 4 or Byte 5 is FFh (4) then the target is in a  test mode.  The  
test mode may be used by an initiator for software testing.