linux-kernel - Re: [PATCH] Fix problem with cpufreq_pndemand or cpufreq

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Message-ID: <50DE3F00.70800@lwfinger.net>
Date:	Fri, 28 Dec 2012 18:53:20 -0600
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Fabio Baltieri <fabio.baltieri@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	viresh kumar <viresh.kumar@...aro.org>,
	cpufreq@...r.kernel.org, Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix problem with cpufreq_pndemand or cpufreq_conservative

On 12/28/2012 06:33 PM, Fabio Baltieri wrote:
> On Fri, Dec 28, 2012 at 05:45:54PM -0600, Larry Finger wrote:
>>> I wonder if that's avoidable?  The intention is not to create an additional
>>> module, clearly.
>>
>> It appears not to be possible. I don't know enough about to kmake to
>> understand why it is forcing a new module. Perhaps some expert knows
>> what Kconfig or Makefile magic will prevent that.
>
> kbuild is building an additional module just because the makefile is
> adding the new objects in the obj-m list directly, as in:
>
> obj-$(CONFIG_CPU_FREQ_GOV_ONDEMAND)     += cpufreq_ondemand.o cpufreq_governor.o
> obj-$(CONFIG_CPU_FREQ_GOV_CONSERVATIVE) += cpufreq_conservative.o cpufreq_governor.o
>
> To build just two modules the Makefile would have to be modified [1]
> into something into something like:
>
> obj-$(CONFIG_CPU_FREQ_GOV_ONDEMAND)     += cpufreq_ondemand_mod.o
> cpufreq_ondemand_mod-y                  := cpufreq_ondemand.o cpufreq_governor.o
> obj-$(CONFIG_CPU_FREQ_GOV_CONSERVATIVE) += cpufreq_conservative_mod.o
> cpufreq_conservative_mod-y              := cpufreq_conservative.o cpufreq_governor.o
>
> so that only two .o are added to obj-m, but that's not correct either as
> you end up with cpufreq_governor symbols exported twice.
>
> I think the only way would be to force cpufreq_governor as builtin with
> an automatic Kconfig option.
>
> Fabio
>
> 1. http://lxr.linux.no/#linux+v3.7.1/Documentation/kbuild/makefiles.txt#L191

Fabio,

Thanks for the explanation. Now I think I know how to do it.

V3 follows.

Larry


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