Re: Fwd: [PATCH #upstream-fixes 1/4] libata: fix device iteration bugs

[Mark Lord <liml@rtr.ca>]

Tejun Heo wrote:
> Mark Lord wrote:
>>> On Michael's real old ata_piix, somehow the ERR bit is set on phantom
>>> device defeating our phantom device detection logic.  We can relax
>>> phantom device condition but that increases the risk of misdetection on
>>> actual IDENTIFY errors.  Any ideas how we can nicely work around this
>>> one?
>> ..
>>
>> Mmm.. I'm way out of the loop on this now,
>> so please pardon me suggesting things known not to work, but..
>>
>> 1. Pay attention to ATA status register on this chipset?
>>   Eg. if it has BUSY, or reads 0x7f, then don't IDENTIFY?
>> 2. Check for device signature before trying IDENTIFY?
>> 3. Try a r/w test on the data register first, to see if there's
>>   really hardware attached to it?
> 
> We already do 1, 2 and 3.  The problem with phantom device is that the
> existent device on the channel replies to acesses to the other
> non-existent device and the NODEV_HINT detection is the last line of
> defense which successfully evades all the other mechanisms.  And now
> we have this controller/device combination which successfully tricks
> it too.  :-(
..

Mmm.. but he's using "really old ata_piix" hardware, as in what Intel
once called the "Triton" (or Triton II) chipset.  Which I wrote support
for in drivers/ide, way back when.. and we never had this problem.

Something weird here.