[t13] SAT: Reminder - Teleconference Thur 8/12 9:00 AM PDT

Jeff Garzik jgarzik at pobox.com
Wed Aug 11 19:20:12 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* Jeff Garzik <jgarzik at pobox.com>
*
Curtis Stevens wrote:
>             Just a heads up, I posted a proposal (04-260.PDF) for 
> documenting how a SCSI command maps to an ATA command.

This is fantastic.  A standard method of ATA passthru is the last piece 
of the puzzle, WRT SCSI<->ATA translation, that Linux needed.  Thank you.

One problem, which appears to be easily correctable:

Any ATA passthru method must specify the command protocol:  DMA-In, 
DMA-Out, TCQ DMA-In, TCQ DMA-Out, PIO-In, PIO-Out, PIO-In-Mult, etc.

Rationale:

1) For standard ATA commands, a cumbersome (and unneeded) lookup table 
or C 'switch' statement is required to obtain the command protocol.

2) The low-level ATA driver has no idea how to execute a vendor-reserved 
ATA command without the command protocol.

My suggestion is to used the 'Reserved' byte for this data field.

The current Linux implementation of the "taskfile ioctl" (a.k.a. ATA 
passthru) includes the command protocol field.

	Jeff


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