[linux-elitists] Simplest power management problem

James Sparenberg james@linuxrebel.org
Tue Aug 22 22:37:14 PDT 2006

On Tuesday 22 August 2006 21:42, Greg KH wrote:
> On Tue, Aug 22, 2006 at 08:52:26PM -0400, Matthew Galgoci wrote:
> > > You can easily turn off all of the above with `rmmod`, providing
> > > they've been built as modules, and you can go farther -- CPU and memory
> > > hotplug support are in newer kernels.  (If you have a dual-core machine
> > > and are feeling particularly gratuitious, you can virtually unplug a
> > > CPU.)
> >
> > Does removing a driver gurantee that the device will be left in a
> > powered off state? I remember the stone ages when this wasn't always
> > true. I've never really gone through the trouble to see if that is
> > the case today.
> No, it is still not true today.  Merely unloading the module almost
> always does not turn the device off.  So don't expect to be saving any
> power by doing this (there are a few minor exceptions, but they are the
> exception, not the rule...)
> thanks,
> greg k-h

Probably the best source of info I know of is actually in the kernel itself, 
or rather in it's docs, or rather the Documentation/power directory.  The 
best file is the tricks.txt IMHO.  


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