Subject: Re: power management and idle detection on non-x86
To: Jared D. McNeill <email@example.com>
From: Michael Lorenz <firstname.lastname@example.org>
Date: 05/07/2006 20:26:25
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>> I've been working to get some sort of power management into my
>> sparcbook for a while now and apart from powerhooks in many device
>> drivers there are a few other things missing.
>> First, we need a way to know when the machine is idle so we can dim
>> backlight at some point, or fall asleep. What I'd like to have is a
>> bunch of 'idle timers' - just write the current timestamp into a more
>> or less global variable whenever the mouse is moved, some key is
>> pressed etc., probably keep different counters for different devices.
>> With this we could detect 'idleness' by just comparing these
>> variables to current time, if enough of them differ by some
>> predefined value we can take actions. On PCs this is probably handled
>> by the APM BIOS but on macppc or sparc we don't have anything like
>> that so we need our own.
> wscons seems like the ideal place to handle this.
Yeah, it's getting all the relevant input anyway.
> Low level hw drivers should be able to register callbacks for certain
> actions ("dim/standby/suspend display", etc).
Agreed, so far pnozz and tctrl talk to each other in a not exactly
generic way ( since tctrl controls the backlight but pnozz needs to
support the ioctl for it ) Maybe something similar to powerhooks? Hmm,
Cherry wanted to extend the powerhooks interface.
> Now, policy needs to be set in userland.
Of course. But it shouldn't depend on something like X and it should
probably work reasonably without userland intervention.
> Also, if you sleep, you want to notify powerd that you want to go to
> sleep so it can run its sleep scripts before powering off -- don't do
> this directly from the kernel.
Of course. So we can power down / reconfigure / reconnect network
interfaces and such.
> Also, x86 is interested in this for ACPI. I'd be willing to work with
> you on this.
Yeah, wants to know when we're going to sleep / wake up so it can do
its voodoo with the graphics chip(s). I think something like that is in
place already but probably linux-specific.
>> So, before I'm wasting my time inventing the wheel the 5th time - do
>> we have something like this somewhere in the kernel? Should it be
>> integrated with powerd? What about powerd vs. apmd? Their scopes seem
>> to overlap quite a bit.
> apmd is dead; the future is powerd.
Ok, that's what my sparcbook is running.
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