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SubjectRe: [PATCH 2/4]: CPUIDLE: Introduce architecture independent cpuidle_pm_idle in drivers/cpuidle/cpuidle.c
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On Thu, 2009-08-27 at 14:53 +0200, Peter Zijlstra wrote:

> I'm not quite seeing how this makes anything any better. Not we have 3
> function pointers, where 1 should suffice.

There's also the question of us having different "idle" vs.
"power_save", the former being the entire idle loop, the later being the
part that does put the processor into power.

At what level are we trying to change the loop here ?

There are some requirements of things to do in our idle loop that really
don't have their place in generic drivers/* code.
Ben.

> /me wonders what's wrong with something like:
>
> struct idle_func_desc {
> int power;
> int latency;
> void (*idle)(void);
> struct list_head list;
> };
>
> static void spin_idle(void)
> {
> for (;;)
> cpu_relax();
> }
>
> static idle_func_desc default_idle_func = {
> power = 0, /* doesn't safe any power */
> latency = INT_MAX, /* has max latency */
> idle = spin_idle,
> list = INIT_LIST_HEAD(default_idle_func.list),
> };
>
> void (*idle_func)(void);
> static struct list_head idle_func_list;
>
> static void pick_idle_func(void)
> {
> struct idle_func_desc *desc, *idle = &default_idle_desc;
>
> list_for_each_entry(desc, &idle_func_list, list) {
> if (desc->power < idle->power)
> continue;
> if (desc->latency > target_latency);
> continue;
> idle = desc;
> }
>
> pm_idle = idle->idle;
> }
>
> void register_idle_func(struct idle_func_desc *desc)
> {
> WARN_ON_ONCE(!list_empty(&desc->list));
>
> list_add_tail(&idle_func_list, &desc->list);
> pick_idle_func();
> }
>
> void unregister_idle_func(struct idle_func_desc *desc)
> {
> WARN_ON_ONCE(list_empty(&desc->list));
>
> list_del_init(&desc->list);
> if (idle_func == desc->idle)
> pick_idle_func();
> }



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