98-115r0 - Sundry Minor Enhancements for SPC-2

ROWEBER at acm.org ROWEBER at acm.org
Fri Jan 30 13:46:13 PST 1998

* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* ROWEBER at acm.org
Date:	 30 January, 1998
To:	 T10 Membership
From:	 Ralph Weber, X3T10 Alternate member from Symbios Logic
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, of data that results from an insufficient allocation 
   length value, unless the description of the data-in buffer format 
   specifically states otherwise in this or some other standard."

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 36 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 by that device server, target, or device, then 
   the device server shall return CHECK CONDITION status with the sense key 
   set to ILLEGAL REQUEST and an additional sense code of INVALID COMMAND 

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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