DPO bit in sample CDB

Gerry Houlder gerry.houlder at seagate.com
Mon Aug 29 14:15:20 PDT 2011


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1108291_f.htm">HTML-formatted message</a>

You have a valid point. All of the other similar tables get around the issue
by calling these bits "miscellaneous CDB information" or even "service
action (if required)" for those bit positions. It seems that table 17 could
(or even should) use the same technique.
On Wed, Aug 24, 2011 at 12:39 PM, Kevin D Butt <kdbutt at us.ibm.com> wrote:
> All,
>
> I stumbled onto bits in the type variable length CDB for long LBA 32-byte
> commands that are not defined.
> I sent the following note to Ralph:
> In SPC-4r31, Table 17 -Typical variable length CDB for long LBA 32-byte
> commands in byte 10 bit 4 there is a DPO field and in bit 3 there is a FUA
> field.  There is no description for what these fields mean.  I can search
> for FUA and find it being used in multiple places.
> When I search for DPO I cannot find a single instance.
>
> His response was that he suspects they are from SBC-3.
> Indeed, I can find them defined in SBC-3.
>
> The problem I still have, however, is that they are shown in Table 17 -
> Typical variable length CDB for long LBA 32-byte commands but there is not
> definition of what the bits mean.  While I don't like that the bits aren't
> described for the table, the FUA didn't bother me too much, because I could
> find it in a search of SPC-4.  However, not being able to find the DPO bit
> in SPC-4 left me lost and confused.  What should be done to remove that
> confusion?  Should there be a reference to the bits and where they can be
> found or should the offending bits be replaced with "device type specific
> info"?
>
> Thanks,
>
> Kevin D. Butt
> SCSI & Fibre Channel Architect, Tape Firmware
> Data Protection & Retention
> MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
> Tel: 520-799-5280
> Fax: 520-799-2723 (T/L:321)
> Email address: kdbutt at us.ibm.com
> http://www-03.ibm.com/servers/storage/



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