Re: [PATCH][ACPI] AC/DC notifier

[Dave Airlie <airlied@gmail.com>]

On Wed, Oct 7, 2009 at 5:31 PM, Pavel Machek <pavel@ucw.cz> wrote:
> On Tue 2009-10-06 10:53:22, Tippett, Matthew wrote:
>> (Resending as text-only - sorry)
>>
>> Bringing this item back up again.
>>
>> I am not suggesting that the application of any particular policy
>> appears within the kernel or userspace or a secondary policy engine.
>> In general I am also against codifying policy within drivers.
>>
>> I am interested seeing the ACPI notifier mechanism expanded to allow
>> AC/DC state changes propagate to other kernel drivers without requiring
>> a userspace in between.
>>
>> I can continue to come up with real scenarios that would possibly
>> require kernel-to-kernel notification, but would rather focus this
>> discussion of the pure technical issues associated with adding the
>> notifier to the AC/DC ACPI subsystem.
>
> Please do. So far you did not show valid use for such notifier.
>
> (Ok, I know of one. Old amd64 notebooks had cpufreq scaling enabled,
> with battery unable to supply enough current to feed the CPU at
> highest cpufreq setting. At that point, scaling cpufreq down at unplug
> is correctness issue, and AC/DC notifier in kernel makes
> sense.)
>
> So... what do you want to use it for?

I'm not sure we have a open driver use case for this, if not I suggest
we remove it and only add it when a user is added to the kernel.

Dave.