Re: System hangs when using USB 3.0 HD with on Ubuntu

Alan Stern
2010-04-21T16:10:01Z

On Wed, 21 Apr 2010, Luben Tuikov wrote:

> The Sector Count field in the ATA PASS-THROUGH (12) or (16) CDB
> should be set appropriately by the Application Client as the neither
> the SAT bridge nor the SATA transport will interpret the ATA Command
> byte. Thus, for IDENTIFY (PACKET) DEVICE the Application Client
> should set it to 1.
>
> Why do you say that 1 is the appropriate value? In the ATA-5 spec
> (which is the most recent version I have) Sector Count is listed as
> "na" for IDENTIFY DEVICE, which means that the content of that field is
> not applicable to this particular command. Hence the value shouldn't
> matter.
>
> It is needed by the transport protocol(s).

I don't understand; can you explain more fully? Which transport
protocol(s) need to use the Sector Count? The USB transport protocol
doesn't; it encodes the transfer length in a wrapper. The bridge chip
should interpret the wrapper instead of looking inside the SAT command.

Alan Stern