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

[Alan Jenkins]

On 2/18/09, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Matthew Garrett <mjg59@xxxxxxxxxxxxx> 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.

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.

Alan
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