"Rafael J. Wysocki" [off-list ref] writes:
[..]

If I understand you correctly, you want to have an iterface for specifying
min and max frequencies from user space.  I can understand that.  At least
I can see some use cases for that.

Now, the question is if using the PM QoS framework is the right way to do
that.

quoted

The change to cpufreq core just adds two read-only files to be able to
inspect user_policy.min/max in addition to the currently enforced
policy->min/max. Yes - there has been the possibility of using the sysfs
min for setting a frequency floor but this is problematic when there are
multiple clients. You'd need some kind of arbitration and book keeping
to set/restore the minimum. And PM QoS provides exactly this mechanism.

Just as I suspected. :-)

OK, so what's your anticipated usage model of this?

We've been experimenting with hooking the frequency boost to e.g. touch
screen UI events and application launch. I believe there are also some
specific applications that would want to either set a frequency floor or
ceiling in some situations.

quoted

I think the kernel needs to be extended to handle more PM constraints
and PM QoS is the closest thing I know for this kind of
functionality. However, I'm open to suggestions about alternative
approaches. I think we need e.g. more than just min/max "reduction
operators". Ideas, anyone?

I first need to know who those multiple clients are going to be.

Thanks,
Rafael

For the touch screen UI, the boost could be implemented as a kernel
module hooked with suitable event filter to the input event
stream. Another possibility is the UI framework in user space. Some
specific user space applications would also be clients.

	--Antti