Additional important comment on SES
bob.snively at Eng.Sun.COM
Thu Oct 31 13:37:22 PST 1996
* From the SCSI Reflector (scsi at symbios.com), posted by:
* bob.snively at Eng.Sun.COM (Bob Snively)
Jay Elrod of Seagate has pointed out some discrepancies between
SFF-8067 and SES revision 7.0 with respect to the behavior of
a disk drive providing interface services for an enclosure services
process. I hope I am paraphrasing our teleconference correctly when I
SFF-8067 is woefully out of date, only mentioning 4 of the
pages defined for SES.
This should be brought into compliance. I agree.
This requires an update of SFF-8067.
As presently worded, there is a strong implication in SFF-8067
that the disk drive should consider direction of transfer for each
page and provide check conditions for each page. Jay points out
that this may be unknowable by a disk drive as future revisions
to SES occur.
Jay suggests that the disk drive simply pass through the requests.
For SEND DIAGNOSTIC commands that were invalid or of an invalid
length, the enclosure services processor would be required to
deposit the arriving stream of bits in the bit bucket. An
INVOP condition would be established for later presentation.
For RECEIVE DIAGNOSTIC RESULTS commands that were invalid or
of an invalid length, the enclosure services processor would
be required to create a page header that indicated an additional
data length of zero and the drive would be required to
deal with this by posting back just the received page header.
Again, an INVOP condition would be established for later
presentation by the enclosure services device. I agree.
Note that enclosure services devices do not have any of these
problems and would simply generate an appropriate check
condition when such invalid requests were made.
This requires clarification of both SFF-8067 and may require
a few additional words in selected paragraphs of SES.
As presently worded, all unused pages are reserved for general
SCSI use. Jay strongly recommends that all the pages 1-F
be reserved for enclosure services functions. That way, he
can create a drive that simply passes any of these pages
through for the enclosure services device to throw away or
use. Any new pages introduced into SES or SES-2 would not
require the drives to be modified, but could be simply
passed on through to the enclosure services device (at least
until we had more than 15 pages defined). While such
expansion is not likely at any time soon, his point is valid
and these "spare pins" should be provided. Any pages not
valid would be treated as in B.
The clarification of SFF-8067 would include this change as
an extension to B above.
Small wording changes might be required to section 4.1.5 of SES.
Section 6.1 would have new lines installed in the diagnostic
page code table for reserved enclosure services pages.
This would include pages 08-0F. In addition, the reverse
directions for single-direction pages would be clearly
labeled as reserved. The text would be modified to indicate
how those additional pages were to be handled, probably
referencing the modified section 4.1.5.
I believe that these should be added to the technical corrections of
SES, as extensions to the following problem numbers:
SU.21 (referencing section 4.1.5, clarifying INVOP)
SU.18/29 (referencing section 4.1.1 and 4.1.2, clarifying model)
SU.131 (referencing 6.1.7, but corrected in section 4.1.6)
SY.43 (referencing the reserved values in the diagnostic page codes)
but documented as separate comments identified during the
editorial process for convenience.
Is that okay with everybody?
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