98-115r1 - Sundry Minor Enhancements for SPC-2

ROWEBER at acm.org ROWEBER at acm.org
Tue Feb 10 15:25:42 PST 1998

* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* ROWEBER at acm.org
Date:	 10 February, 1998
To:	 T10 Membership
From:	 Ralph Weber, T10 Alternate member from Symbios, Inc.
Subject: Sundry Minor Enhancements for SPC-2

During the past several months various suggestions have been made for minor 
enhancements in SPC-2.  These proposals are complied here for consideration 
by T10.

1) Add the following before the last sentence in clause 4.2.4:

   "If the information being transferred to the data-in buffer includes fields 
   containing counts of the number of bytes in some or all of the data, the 
   contents of these fields shall not be altered to reflect the truncation, 
   if any, that results from an insufficient allocation length value, unless 
   the standard that describes the data-in buffer format specifically states 

It has been noted that most command descriptions include wording with effects 
similar to what is proposed above.  However, some command descriptions are 
silent on this subject and adding the proposed wording in clause 4.2.4 (the 
description of the allocation length CDB field) will cover all cases.

2) In the process of resolving an issue regarding field pointer bytes sense-key 
specific data in the standard sense data (see 97-187), the working group 
produced the following statement of its position regarding multi-byte fields:

   a) A multi-byte field is a defined field in a CDB or parameter list whose 
      length exceeds one byte; and
   b) The contents of the sense-key specific data for the ILLEGAL REQUEST sense 
      key is not specified by SCSI-2 when the error occurs in a reserved field.

The following should be added at the end of the third paragraph after Table 63 
in clause 7.20.1 to embody the committee's position in SPC-2:

    "If a field whose length exceeds one byte is reserved, it shall be treated 
    as a multiple-byte field.  If several consecutive bytes are individually 
    reserved, each shall be treated as a single-byte field."

3) It has been noted that no SCSI standard contains the requirement that 
invalid operation codes result in a CHECK CONDITION status.  To address this 
omission, the following wording should be added at the end of the second 
paragraph in clause 4.2:

    "If a device server receives a CDB containing an operation code that is 
    invalid or not supported, it shall return CHECK CONDITION status with the 
    sense key set to ILLEGAL REQUEST and an additional sense code of INVALID 

4) The SPC recommendations for  virtual units regarding the contents of the 
device identification VPD page have been overtaken by events, specifically the 
IEEE Tutorial for SCSI use of IEEE company_id (also available as T10/97-101r2).
Unless or until an IEEE document number than can be referenced from an ANSI 
standard becomes known to T10, note 53 (the first note in clause 8.4.3) should 
be removed from SPC-2.

5) The description of the Identification descriptor field in the device 
identification VPD page has been rendered incorrect by the addition of the 
Association field.  The second paragraph before Table 112 in clause 8.4.3 
should be replaced with:

    "Each Identification descriptor (see table 111) contains information 
    identifying the logical unit, physical device, or access path used by 
    the command and returned parameter data.  The Association field indicates 
    the entity that the Identification descriptor describes.  If a physical 
    or logical device returns an Identification descriptor with  the 
    Association field set to 0h, it shall return the same descriptor when 
    it is accessed through any other path."
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