On 9/1/22 00:54, Damien Le Moal wrote:
On 8/31/22 22:30, Peter Fröhlich wrote:
Sorry for spamming replies and quoting myself.
On Wed, Aug 31, 2022 at 12:21 PM Peter Fröhlich
<peter.hans.froehlich@xxxxxxxxx> wrote:
On Wed, Aug 31, 2022 at 9:48 AM Damien Le Moal
<damien.lemoal@xxxxxxxxxxxxxxxxxx> wrote:
On 8/31/22 16:15, Hannes Reinecke wrote:
Oh, of course :-)
That was when doing SMR support for libata.
I dimly remember that some pre-spec drives had been using the DRDY bit
to signal an unaligned write. Which never made it into the spec, but the
decoding stayed.
Any idea where the other bits come from ? Except for bit 5 (device fault),
I do not see anything else in the specs that mandate these definitions...
I have since discovered the "SCSI to ATA" specification which has two
tables about mapping ATA errors to SCSI errors. Among those I was able
to find an "unaligned write" case as well, but I cannot properly parse
the rest of the two tables yet. They are in sections 11.6 and 11.7 of
that document.
So I've re-read everything I can get my hands on and from what I can
tell the overall "flow" of ata_to_sense_error() is not what the
specifications would imply. For example we look at BSY on entry and
then say "ah, it's set, then let's ignore the error field" when the
specification (the way I read it) instead says "BSY is transport
dependent, so we say nothing about it here; but check the error bit in
status, if it is set, interpret the error field, otherwise there's
nothing for you in the error field". Of course I am a complete noob
when it comes to this ATA/SATA/SCSI/AHCI stuff, so please divide by at
least two. Sorry if this adds more confusion on top.
I had a quick look at the specs again. I already spotted an error: when
the status device fault bit is set, the sense should be HARDWARE ERROR /
INTERNAL TARGET FAILURE and not ABORTED COMMAND / 0x47 like now. That is
according to SAT-5. But looking at ACS-5, sections 6 and 7.1.6, there are
*a lot* of cases that need to be taken care of. It looks like the
sense_table does that, but need to cross check.
As for the stat_table, except for the first buggy entry as mentioned
above, I have no clue where these come from. SAT only defines the HARDWARE
ERROR / INTERNAL TARGET FAILURE for when the status field device fault bit
is set. Need to dig further, but I am afraid this code may be due to years
of supporting drives returning weird errors that got mapped to sensible
sense codes instead of a pure implementation of the specs...
I need to spend some quality time with ACS and SAT documents to sort out
this one... And lots of coffee too probably :)
And, to make matters ever more complicated, the error and status bits
changed over time. And even the SAT translation changed between versions.
So there really is no clear "that's the way to go" style of thing; if we
want to be correct we would need to evaluate the ATA version for that
device, and have different translation tables depending on the version.
Not sure if it's worth it, though; in the end it's just an error
description which will get changed. Commands will be aborted in either
case, so the net result is close to zero :-)
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
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