Regarding MMC4 01g

Bmcferrin at aol.com Bmcferrin at aol.com
Mon Apr 7 15:30:36 PDT 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Bmcferrin at aol.com
*

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Hello Mr. Ito,
Neither Mode Select nor Mode Sense were specified in MMC1, MMC2, or
MMC3, so MMC4 is the first case where the statement has been made.

It is true that for several revisions, Mt Fuji has specified that DBD
shall be set to one.

With respect to the MODE SENSE command, SPC-2 states: "A disable block
descriptors (DBD) bit of zero indicates that the device server may
return zero or more block descriptors in the returned MODE SENSE data.
A DBD bit of one specifies that the device server shall not return any
block descriptors in the returned MODE SENSE data."

CASE 1: Drive supports no block descriptors
If the drive does not implement block descriptors, then the drive will
return the same information regardless of the setting of the DBD bit.
In this case, DBD may be ignored.

Case 2: Drive supports one block descriptor
Since 8020, only "Legacy SCSI" (i.e. SCSI-2) drives are permitted to
have a block descriptor.  In this case, DBD has genuine meaning.
Hoever, in the main text of MMC-4, we do not wish to address legacy
implementations.

Changes to MMC-4:
1. I need to put a sub-clause into ANNEX X - LEGACY SPECIFICATIONS to
describe the legacy case for Block Descriptors.

2. To be precise, I think that I should change the "shall ignore DBD" to
"may ignore DBD".

Kind Regards,
Bill McFerrin



Hi Bill McFerrin, how are you doing ? This is Ito of Fujitsu.
  Now, I have one comment for mmc4 document.

http://www.t10.org/new.htm
MMC4 01g MultiMedia Command Set - 4 (MMC-4) Bill McFerrin PDF (2753278)
2003/03/06 

- mmc4r01g.pdf  page240 says;
    Multi-Media Logical Units shall ignore the disable block descriptors
    (DBD) bit. Multi-Media Logical Units do not return Block
Descriptors. 

==> This is not good idea.
    I think;
    1. A lot of devices by which DBD is returned are circulating to the
market
       now. 
    2. Other OS and the application to expect BD to return exist. 
    3. There is no problem because BIOS can correctly acquire data even
if the
       device responds BD or not.

  When did you change it ? Bestway is to fix same as Mt.Fuji
documentation for it
or previous if it's possible. Please verify Fuji documentation. 
And why change it, please let me know.

Best regards,
Mike Ito(Fujitsu),

---
Masahiro Ito, Yamagata Fujitsu Limited
E-Mail:mike at yfl.fujitsu.com             
FONE:+81-237-43-7150(DID) FAX:+81-237-43-7155 






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Hello Mr. Ito,
 Neither Mode Select nor Mode Sense were specified in MMC1, MMC2, or = MMC3, so MMC4 is the first case where the statement has been made.
 
It is true that for several revisions, Mt Fuji has specified that DBD = shall be set to one.
 
With respect to the MODE SENSE command, SPC-2 states: "A disable block = descriptors (DBD) bit of zero indicates that the device server may = return zero or more block descriptors in the returned MODE SENSE = data.  A DBD bit of one specifies that the device server shall not = return any block descriptors in the returned MODE SENSE data."
 
CASE 1: Drive supports no block descriptors
 If the drive does not implement block descriptors, then the drive will = return the same information regardless of the setting of the DBD = bit.  In this case, DBD may be ignored.
 
Case 2: Drive supports one block descriptor
 Since 8020, only "Legacy SCSI" (i.e. SCSI-2) drives are permitted to = have a block descriptor.  In this case, DBD has genuine = meaning.  Hoever, in the main text of MMC-4, we do not wish to = address legacy implementations.
 
Changes to MMC-4:
 1. I need to put a sub-clause into ANNEX X - LEGACY SPECIFICATIONS to = describe the legacy case for Block Descriptors.
 
2. To be precise, I think that I should change the "shall ignore DBD" = to "may ignore DBD".
 
Kind Regards,
 Bill McFerrin
 
  Now, I have one comment for mmc4 document.
 
http://www.t10.org/new.htm
 MMC4 01g MultiMedia Command Set - 4 (MMC-4) Bill McFerrin PDF (2753278) = 2003/03/06 

- mmc4r01g.pdf  page240 says;
     Multi-Media Logical Units shall ignore the disable = block descriptors
     (DBD) bit. Multi-Media Logical Units do not return = Block Descriptors. 

=3D=3D> This is not good idea.
     I think;
     1. A lot of devices by which DBD is returned are = circulating to the market
        now. 
    2. Other OS and the application to expect BD to = return exist. 
    3. There is no problem because BIOS can correctly = acquire data even if the
        device responds BD or not.
 
  When did you change it ? Bestway is to fix same as Mt.Fuji = documentation for it
 or previous if it's possible. Please verify Fuji documentation. 
And why change it, please let me know.
 
Best regards,
 Mike Ito(Fujitsu),
 
---
 Masahiro Ito, Yamagata Fujitsu Limited
 E-Mail:mike at yfl.fujitsu.com       sp;     
FONE:+81-237-43-7150(DID) FAX:+81-237-43-7155 



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