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
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