linux-kernel - Re: [PATCH] cpufreq: Change link order of x86 cpufreq modules

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Date:	Thu, 19 Feb 2009 13:03:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	alan-jenkins@...fmail.co.uk
Cc:	Matthew Garrett <mjg59@...f.ucam.org>, davej@...emonkey.org.uk,
	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org
Subject: Re: [PATCH] cpufreq: Change link order of x86 cpufreq modules

* Alan Jenkins <sourcejedi.lkml@...glemail.com> wrote:

> On 2/18/09, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * Matthew Garrett <mjg59@...f.ucam.org> wrote:
> >
> >> On Wed, Feb 18, 2009 at 07:31:37PM +0100, Ingo Molnar wrote:
> >>
> >> > Nice fix! Where does this information come from? Distro module
> >> > ordering magic? It's rather non-trivial.
> >>
> >> Pretty much. p4-clockmod is never the preferred option because
> >> it does no voltage scaling. speedstep-centrino is now almost
> >> entirely functionally replaced with acpi-cpufreq. The
> >> powernow-k8 issue was a personal communication from davej.
> >
> > I'm wondering whether that priority order should/could be
> > expressed in the module space too - so that distros wouldnt have
> > to replicate this. This is really a piece of information the
> > kernel is best at maintaining.
> 
> The latest development version of module-init-tools (in the 
> git tree) is designed to preserve the kernel link order when 
> resolving builtin aliases.  If you have two modules which 
> provide the alias "pci:123", they will be loaded in the same 
> order as if they were builtin drivers.

very nifty ...

> It should work if all the cpufreq drivers provide an alias 
> "cpufreq-driver" and userspace just does "modprobe 
> cpufreq-driver". You just need to be sure none of the cpufreq 
> drivers provide *other* aliases which cause them to be loaded 
> earlier, by udev or some other bootscript.

yeah. Nice.

	Ingo
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