SAM-3 proposal: ... Sense Data sizes

Pat LaVarre LAVARRE at
Mon Oct 28 08:19:36 PST 2002

* From the T10 Reflector (t10 at, posted by:
* "Pat LaVarre" <LAVARRE at>
Can you easily elaborate?
In a place like:
the redundancy between .SenseInfoLength and chars[SenseInfoOffset + 7] exists in part because the host controls how in/accurate the .SenseInfoLength is and the target controls how in/accurate the chars[SenseInfoOffset + 7] is.
Apps then compete over whom to trust most when.
Only recently did I learn, for example, that a zeroed additionalLength in op x03 RequestSense data meant (xE - (7 + 1)) for the simulated Cd drives of a Connectix Virtual PC, until this year or so.  AFAIK, Microsoft is still shipping zeroed additionalLength in op x12 Inquiry data (meaning x24 - (4 + 1)).
Given that such inconsistencies exist in some places, I'm curious to understand why we would not want to provide a way to forward them faithfully.
Curiously yours in truly breathtaking ignorance, Pat LaVarre

	-----Original Message----- 
	From: Ralph Weber [mailto:ralphoweber at] 
	Sent: Tue 10/22/2002 3:04 PM 
	To: t10 at 
	Cc: Elliott, Robert (Server Storage) 
	Subject: Re: SAM-3 proposal: ... Data-In and Sense Data sizes

	1) There is no need for a Sense Data Size parameter because
	   the Sense Data format is self-defining with respect to
	   the number of sense data bytes present (see the ADDITIONAL
	   SENSE LENGTH field at fixed position byte 7 of the
	   Descriptor Sense Data Format). Adding a Sense Data Size
	   parameter only introduces new forms of inconsistent
	   (so might say erroneous) responses targets can generate.

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