Re: libata EH appears to be NFG up to 2.6.17 (at least).

[Tejun Heo <htejun@gmail.com>]

Hello, Mark Lord.

Mark Lord wrote:
[--snip--]
> I dunno what the new EH does (yet), but the only good way to deal with this
> is for the ATA status & error values to be read *and* saved on command 
> completion,
> and then reused by any later code that needs to do detailed sense reporting
> or other diagnostics.

Yeap, this is exactly what new EH does.  It stores TF in qc->result_tf 
on failure and EH/SCSI completion only uses the cached TF stored at the 
time of failure.

> With NCQ/TCQ, this can be tough to achieve, possibly requiring the LLDD 
> to drop to legacy mode on error, and capture the values there.  Of 
> course, by then
> it's too late to be perfect, as the host controller has probably already 
> read
> and discarded the drive status at least once.  (the PDC sata_qstor device
> is an exception there -- they save/return failed status during queuing).

With NCQ, the true TF is retrieved via log page 10.  EH retrieves it and 
stores it in qc->result_tf.  The rest is the same.

With PMP, things get more interesting though.  :-(

-- 
tejun