Re: [RFC] mode pages for ATA/ATAPI devices via libata

[Douglas Gilbert <dougg@torque.net>]

Doug Maxey wrote:
> On Fri, 13 May 2005 15:19:39 +1000, Douglas Gilbert wrote:
> 
>>Doug Maxey wrote:
>>
>>>ahem, the neural pathways are not just worn, they have become ruts. =) 
>>>
>>>s/mode/vpd/.
>>>
>>>On Wed, 11 May 2005 13:01:25 CDT, Doug Maxey wrote:
>>>
>>>
>>>>Howdy,
>>>>
>>>>When a ATA/ATAPI device is attached via libata, what should the handling 
>>>>be for mode pages that do not exist in the device?
>>>>
>>>>Assuming the page being asked for is 0x83, should libata fake up the
>>>>page from the IDENTIFY (PACKET) DEVICE data?  Or should it just respond
>>>>there is no page 0x83 as it does now in INQUIRY?  Likewise for 0x80?
>>
>>Doug,
>>For ATAPI, the packet interface is almost always
>>carrying a SCSI command set (exceptions anybody??),
> 
> 
> call it 95% SCSI, and I will agree.
> 
> 
>>typically MMC (for CD/DVD drives). Recent SPC-3 drafts
>>(to which MMC-4,5 should comply) have made the device
>>identification VPD page (0x83) mandatory. I haven't
>>seen any compliance yet (or for that matter a drive that
>>implements feature 0x108: LU serial number).
> 
> 
> I have recently been looking at the specs for a rebranded Panasonic
> Slimline DVD/RAM/+R/+RW drive.  The EVPD bit on the inquiry page is marked
> as optional, but returns CHECK CONDITION if set, and you get a 5/24/00
> back. :-/  So even if the device had the pages, we can't get to them.
> Nowhere in the device spec is there an indication they even exist.

Getting compliance via the SAM/SPC/device_type_command_set
route takes a long time. So I'm happy to report that
recent SAS 1.1 drafts (soon to be set in stone) have a new
section telling firmware engineers exactly what they
"shall" support in the device identification VPD page.

> Of the few ATAPI drive specs I have seen, this seems to be the standard 
> behavior.  The data (serial number, anyway), is ostensibly available 
> from the IDENTIFY DEVICE data.  However, the bytes available are 
> invariably smashed to a sequence of 0x20.
> 
> Lastly, looking at a recent version of MtFuji 6.08, support for the EVPD bit
> is optional.  I just suspect it's one of those things that is interpreted
> as a MUST NOT implement in the cost conscious manufacturing environment. 
> Nor are there any references to VPD data other than the Standard 
> INQUIRY data.
> 
> 
>>For ATA, work is being done on a SCSI-ATA Translation
>>draft standard see:
>>http://www.t10.org/ftp/t10/drafts/sat/sat-r03.pdf
>>section 8.1.3.3 .
>>
> 
> 
> Ah yes, the other 90% of ATA.  But that is just for disks.

Probably true yet the SAT draft has a "14 Translation for
ATAPI devices" section.

> The optical drive vendors seem to pretty closely follow
> ftp://ftp.avc-pioneer.com/Mtfuji_6/Spec/Fuji6r08.pdf

Thanks, I'll look at this document.

BTW I know that the libata implementers are keeping a
close eye on SAT.

Doug Gilbert