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.
> For known ATA commands, this missing information can be provided by a lookup
Yes, spec'ing an enumeration rather than a bitmap helps us reserve, for
example, x00 to mean protocol decided by opcode, rather than more
> 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?
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