On 07/22/2009 11:45 PM, Tejun Heo wrote:
Shaohua Li wrote:
IIRC, not all NCQ-capable controllers support this feature... SATA 1.0
hardware may not behave properly in response, no?
It appears the AHCI spec doesn't define a HBA capability about this
feature, but I'm likely wrong as I'm not quite familar with SATA.
IIRC, AA is in the ahci spec from rev 1.0, so if controllers implement
the spec correctly, it should work. But even for ahcis, if we enable
it by default, I'm fairly sure we'll be met by a number of unpleasant
surprises. Not sure whether doing that would be worth the trouble or
not.
There's definitely a controller dependency here, as SATA 1.0 hardware
won't respond properly if this feature is turned on. Likely we need a
host flag to indicate whether the controller supports auto-activate. It
seems like AHCI shouldn't be a problem, but it's not clear if any other
controller types would support it.
As far as busted hardware not handling it properly.. well if it just
ignores the enabling then that's not a problem as things will just work
as before. There could be devices that claim support, don't ignore it
but don't handle it properly.. but realistically the only way we can
find out if that's the case is turning it on and see what breaks.
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