RESERVE(6)/RELEASE(6) should be optional.

[scheible at vnet.ibm.com]

* From the SCSI Reflector, posted by:
* scheible at VNET.IBM.COM
*
   This note is copied to the SSA, SCSI and serial concerns reflectors.  Sorry
for any duplication.
------------------------------------------------------------------------------

BACKGROUND
----------
   I propose a change to the "mandatory-ness" of the RESERVE(6) and
RELEASE(6) commands.  Third party reserve/release is considered
mandatory, but with the 3 bit device address does not work well with
anything but narrow (parallel) SCSI.  FCP/SBP/S3P/wide SCSI cannot
fully implement these commands with only a 3 bit third party copy
address.  RESERVE(10) and RELEASE(10) fix this problem (8 byte addr).

   SPC states that some fields within RESERVE(6) and RELEASE(6) are
mandatory, but the commands themselves are "device type specific".
I think that it is wrong to make commands that only work with some
transport layer(s) device type specific.  They should be either
"transport layer specific" or "optional".  If they are optional, then
the device type standards cannot make them mandatory.

   I found this when attempting SCSI-3 compliance with SSA-S3P using
SPC and SBC.  I have a proposal and a question as shown below.


PROPOSAL
--------
   Make RESERVE(6) and RELEASE(6) optional.  This affects the following
standards (not an exhaustive list).

SPC rev 9, table 5 - 1) Make RESERVE(6) and RELEASE(6) optional.
SBC rev 2, table 1 - 1) Make RESERVE(6) and RELEASE(6) optional.
SSC rev 6, table 9 - 1) Rename RESERVE UNIT to RESERVE(6).
                     2) Rename RELEASE UNIT to RELEASE(6).
                     3) Make RESERVE(6) and RELEASE(6) optional.
                     4) Add RESERVE(10) and RELEASE(10) as mandatory.
SGC rev 0, table 1 - 1) Rename RESERVE UNIT to RESERVE(6).
                     2) Rename RELEASE UNIT to RELEASE(6).
                     3) Make RESERVE(6) and RELEASE(6) optional.
                     4) Add RESERVE(10) and RELEASE(10) as mandatory.
SMC rev 5, table 2 - 1) Add RESERVE(10) and RELEASE(10) as optional.
                     2) Rename RESERVE as RESERVE(6).
                     3) Rename RELEASE as RELEASE(6).
MMC rev 4, table 4 - 1) Add RESERVE(10) and RELEASE(10) as mandatory.
                     2) Rename RESERVE as RESERVE(6)
                     3) Rename RELEASE as RELEASE(6)
SCC rev 6, NO CHANGE


QUESTION
--------
   What does SPC mean when it says that a command is "device type
specific" but fields are mandatory?  If a device type standard lists
the command as optional, does it violate SPC's requirement for mandatory
support of fields?  If SPC means that a mandatory field is only
required if a command is implemented, then it should state so clearly
(sorry if it does and I missed it).

Thanks,
John Scheible
scheible at vnet.ibm.com