[t13] T10/04-262r0

Curtis Stevens curtis.stevens at wdc.com
Thu Aug 12 16:54:06 PDT 2004

* From the T10 Reflector (t10 at t10.org), posted by:
* "Curtis Stevens" <curtis.stevens at wdc.com>

	One thing to keep in mind is that we do not want the bridge to look
at the command code or any other register.  We want SCSI to be a blind
tunnel to the ATA device.  The bridge should not look at the command code,
sector count, or any other part of the register set.  This is what makes it
work for standard and vendor specific commands.  It also makes it so new
commands can be implemented without changing the bridge.  This is why length
is also important.

	FYI: we are using SCT (See T13 project 1701) for our vendor specific
stuff.  This tunnels through standard ATA commands and side-steps the VS
issues in SATA-PATA bridges.

Curtis E. Stevens
20511 Lake Forest Dr.  #C 214-D
Lake Forest, Ca. 92630
Phone: 949-672-7933
Cell: 949-307-5050
E-Mail: Curtis.Stevens at wdc.com

 -----Original Message-----
From: 	Jeff Garzik [mailto:jgarzik at pobox.com] 
Sent:	Thursday, August 12, 2004 4:15 PM
To:	Curtis Stevens
Cc:	t10 at t10.org; Forum at t13.org
Subject:	Re: [t13] T10/04-262r0

Jeff Garzik wrote:
> Curtis Stevens wrote:
>> I also do not believe the transport can be separated from the CDB because
>> this has the transfer length in addition to the direction.  While I could
>> place the protocol field in the CDB, there is no room for the length.  
>> The
>> ATA host also needs this information to properly complete a PIO transfer.
>> For DMA transfers, this information may also be necessary for buffer size
>> allocation, although some implementations could do it without buffers.
> Er, huh?
> Every ATA read/write command specifies transfer length and data 
> direction already.  No need to store or derive that information elsewhere.

Ah, for vendor-reserved commands, yes it would need specification.


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