99-229r0 - Restricting Mode Page Code Usage

Ralph Weber ralphoweber at CompuServe.COM
Sat Aug 21 06:07:36 PDT 1999

* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <ralphoweber at compuserve.com>
A proposal for consideration at the September meetings has
been placed on the T10 FTP site as:

< ftp://ftp.t10.org/t10/document.99/99-229r0.pdf >

The text of the proposal is as follows:

Doc:  T10/99-229r0
Date: 15 August 1999
To:   T10 Technical Committee
From: Ralph Weber, LSI Logic Alternate Member of T10
Subj: Restricting Mode Page Code Usage

As of SPC-2 revision 11, only three mode page codes are available for
assignment to new uses that involve all device types (15h, 16h, and
17h).  Recently, the SSC ad hoc assigned the previously unused code
0Fh to a tape-only function.  This action was unnecessary because
codes 03h, 04h, 05h, 06h, 07h, 08h, 0Bh, 0Ch, 0Eh, 1Bh, 1Dh, 1Eh, or
1Fh could have been used with equal effect.

To reduce the possibility of an ad hoc unnecessarily assigning an
unused mode page code, the Description column for codes 15h, 16h and
17h should be changed from blank to "Restricted [3]" and the
following footnote should be added:

    "[3] Assignment of a restricted mode page code requires prior
    approval from the T10 plenary meeting.  Approval from a T10 ad
    hoc meeting is not sufficient.  T10 reserves the right to
    reassign any uses of these restricted mode page codes that come
    to its attention without having received prior explicit

Without the change, it is possible that a T10 ad hoc could assign all
three of the currently unused codes in a draft standard.  Should that
happen, T10 will have no escape code value to use in defining a
mechanism that provides from more mode page codes than are currently

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