mask x7F of byte 1 of Inquiry, by any other name
roweber at IEEE.org
Thu Feb 15 17:01:03 PST 2007
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The change cited below was made during Letter Ballot processing
on SPC sometime between January 1996 (rev 9) and May 1996 (rev 9b).
The change appears to have been viewed as editorial, perhaps
based on the following agreement vis a vis SPC rev 7 (Dec 1995):
"Remove all references to SCSI-1 and CCS. Make code values that
represent SCSI-1 and CCS reserved for historical uses."
I cannot find any mention of the change in the SPC Letter Ballot
comments resolution document:
Since the bits have been reserved for over ten years and (as of
this writing) represent one-third of the 21 reserved bits in the
Inquiry data prior to the version descriptors, I would resist
attempts to change their definition based on what is basically
a SCSI-1 usage.
N.B., SCSI-2 defined the bits as follows: "The device-type modifier
field was defined in SCSI-1 to permit vendor-specific qualification
codes of the device type. This field is retained for compatibility
with SCSI-1. Targets that do not support this field should return
a value of zero."
I interpret this to mean that the bits were essentially obsolete
in SCSI-2. Surely, bits that have been in practice obsolete for
over 17 years (SCSI-2 went to Public Review in 1989) can be recycled
to reserved (or in this case left reserved).
All the best,
plavarre at lexar.com wrote:
> Why is "Reserved" our Spc-4 name for mask x7F of byte 1 of Inquiry,
> rather than "Obsolete"?
> Over time, the names I see we gave this field include:
> "Device-Type Qualifier" in T10 S1-r17b.txt
> "Device-type modifier" in T10 S2-r10l.pdf and
> "Reserved" in Spc-r11a.pdf and other T10 Spc since then
> Anybody know why?
> Curiously yours, thanks in advance,
> P.S. I haven't yet checked the other prominent redefinitions of
> Inquiry (T10 Mmc Scsi, Sff Scsi, Ufi Scsi, etc).
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