Subject: Re: [v8 PATCH 2/8]: cpuidle: implement a list based approach to register a set of idle routines.

From: Arun R Bharadwaj <[email-masked]>
Date: Thu, 15 Oct 2009 11:36:52 +0530

* Andi Kleen <[email-masked]> [2009-10-14 09:18:38]:

> > How about something like this..
> > If the arch does not enable CONFIG_CPU_IDLE, the cpuidle_idle_call
> > which is called from cpu_idle() should call default_idle without
> > involving the registering cpuidle steps. This should prevent bloating
> > up of the kernel for archs which dont want to use cpuidle.
> 
> On x86 some people want small kernel too, so selecting it on a architecture
> granuality is not good. Also you can make it default, you just need
> to slim it down first.
> 

No, I dont mean selecting it on an architecture granularity.

At compile time, if CONFIG_CPU_IDLE is disabled, the arch can redefine
cpuidle_idle_call. For e.g. in arch/x86/kernel/process.c

#ifndef CONFIG_CPU_IDLE
void cpuidle_idle_call(void)
{
	if (local_idle)
		local_idle();
	else
		default_idle();
}
#endif

where local_idle points to the idle routine selected using
select_idle_routine() which can be poll, mwait, c1e.

So this way, we still preserve the exact same functionality as before
and we also remove the ugly pm_idle exported function pointer and we
avoid unnecessary code bloat for platforms who do not want to use
cpuidle.

--arun