Re: [PATCH RFC] ahci: implement handoff quirk

[Tejun Heo <tj@kernel.org>]

Jeff Garzik wrote:
> Tejun Heo wrote:
>> Jeff Garzik wrote:
>>> We probably need to do this...
>>>
>>> it's not a controller requirement but a BIOS one, so in theory even an
>>> existing, deployed AHCI 1.2 platform could suddenly require BIOS/OS
>>> handoff, if a BIOS update suddenly starts doing new and weird stuff
>>> in SMI.
>>>
>>> Note that we need to do BIOS/OS handoff upon resume as well as at boot
>>> time.
>>
>> Yeah, probably.  Do you know of any system which makes use of this
>> feature?  I'm a bit uneasy about committing it without any testing.
> 
> I don't.
> 
> But the purpose of the feature is to tell BIOS to cleanup and stop using
> the hardware.  It's a dumb feature, because of compatibility realities,
> but hey, other network and SCSI drivers have been doing this sort of
> synchronization with their on-board firmwares for years.
> 
> IMO the more dangerous route is to continue loading ahci, without first
> telling the BIOS to clean up and get out of our way.

Hmmm.... yeah, I'm just worried a bit about adding a chunk of
completely untested code.  How about adding a big fat warning message
which gets triggered if the handoff thing seems to be active?

Thanks.

-- 
tejun