[t13] T10/04-262r0

Pat LaVarre p.lavarre at IEEE.org
Thu Aug 12 15:41:34 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* Pat LaVarre <p.lavarre at ieee.org>
*
> A single byte, command protocol, can provide all this information and 
> more.  With command protocol byte, your CDB is "future proof":  you 
> don't need to specify additional bit flags for DMA, PIO Mult, TCQ, NCQ, 
> etc. ...
> ...
> In the implementation of the low-level driver, all this information is 
> required, and all this information is independent of transport.

Yes.

> For known ATA commands, this missing information can be provided by a lookup 
> table.

Yes, spec'ing an enumeration rather than a bitmap helps us reserve, for
example, x00 to mean protocol decided by opcode, rather than more
explicitly specified.

> For unknown (vendor reserved) commands, this information must be 
> specified by the client app _somewhere_, since the low-level driver 
> cannot know it.

So how do we answer Nathan M's question - how do SATA/ PATA bridges
transport vendor-specific ATA commands today?

> PIO versus PIO-Mult versus ATAPI PIO
> DMA versus TCQ DMA versus NCQ DMA versus ATAPI DMA

Do bridges assume all vendor-specific protocol is PIO?

Pat LaVarre


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