Re: community PM requirements/issues and PowerOP [Was: Re: So, what's the status on the recent patches here?]

Matthew Locke
2006-09-14T09:20:45Z

On Sep 14, 2006, at 2:12 AM, Pavel Machek wrote:

> Hi!
>
>>>> Date: Mon, 11 Sep 2006 21:36:37 +0200
>>>> From: Pavel Machek <pavel@ucw.cz>
>>>>
>>>> Kernel interface is not something to be experimented with.
>>>
>>> Disagree. How else to get it right??
>>> Try, learn, improve. That's experimentation.
>>> Linux has no "stable API nonsense" ...
>>>
>>> The point of "cathedral vs. bazaar" was that experimentation
>>> and evolution are more successful processes than "get it
>>> right the first time".
>> ---
>>
>> I think Pavel's point was that the userspace interface to
>> the kernel (at least the syscall interface) is stable (open to
>> Extension by addition of syscalls, but closed to modification
>> or deletion of existing and that any experimentation needs to
>> happen before functionality goes into the mainstream.
>
> Yes, that was my point. (And I'd add "plus you can't get around that
> by introducing interface hidden by #ifdef").
>
>> That said, I do think we probably need to add a new interface to
>> cover operating points, because some of believe that policy needs
>> to be in user space and the whole point of the OP abstraction is
>> that operating points are atomic. You can't just add knobs to
>> control more factors, because all those knobs need to be turned
>> at the same time. Setting an operating point is inherently an
>> atomic operation, not n separate operations that can be taken
>> serially.
>
> Ok, "needs to be atomic" is first real argument for OP abstraction. I
> wonder if we can get around that by delaying the transaction until
> userspace tells us it made all the changes... otoh that is going to be
> messy.
>
> But do you have some reasonable way to integrate OP with cpufreq?

Yes, it was presented in the PowerOP/cpufreq integration patches. The
cpufreq_driver layer is the natural integration point.

>
> Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures)
> http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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