[t13] SCSI ATA f/w revision bytes how many

Pat LaVarre p.lavarre at IEEE.org
Tue May 25 13:30:11 PDT 2004

* From the T10 Reflector (t10 at t10.org), posted by:
* Pat LaVarre <p.lavarre at ieee.org>
> The only thing I care about is the 16-byte CDB limit currently in 
> Linux...

If we take advantage of the extra four bytes there, we will not design 
a solution usable by the max-12-CDB-byte connections, in particular 
normal PATAPI, that also wish to give ATA pass thru to hosts that think 
they support only SCSI pass thru.  Those people will therefore push to 
revisit this issue, yet again.

>> ... a sequence of four:
>> 1) a command out command, promising data in or data out next
>> 2) a data out command
>> 3) a data in command
>> 4) a status in command.
>> That's how SCSI over USB works.
> For some definition of "works" :)

I see the ":)".  Apologies in advance for me not understanding it.

I agree, SCSI over USB, like all SCSI, never more than mostly works.

I agree, SCSI over USB does inflict two theoretically unnecessary 
turnaround overheads.  Before fetching data in and status in, the host 
has to wait for the device to ack command and data out.  Before sending 
more command and data out, the host has to wait for the device to 
finish supplying data in and status in.

Pat LaVarre

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