Messages in this thread | | | Date | Fri, 18 Aug 2017 09:49:44 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH] cpufreq: Don't send callback pointer to cpufreq_add_update_util_hook() |
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On 17-08-17, 17:31, Rafael J. Wysocki wrote: > On Thursday, August 17, 2017 2:04:48 PM CEST Viresh Kumar wrote: > > The callers already have the structure (struct update_util_data) where > > the function pointer is saved by cpufreq_add_update_util_hook(). And its > > better if the callers fill it themselves, as they can do it from the > > governor->init() callback then, which is called only once per policy > > lifetime rather than doing it from governor->start which can get called > > multiple times. > > So what problem exactly is this addressing?
Its not fixing any problem really, but is rather just a cleanup patch. I had a look at include/linux/sched/cpufreq.h and got confused for a moment:
struct update_util_data { void (*func)(struct update_util_data *data, u64 time, unsigned int flags); };
void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data, void (*func)(struct update_util_data *data, u64 time, unsigned int flags));
It wasn't quite straight-forward to understand why we needed to pass both "data" and "func", while "data" should already have "func" set within it. And then I realized that cpufreq_add_update_util_hook() is actually setting that field.
Filling the pointer from the callers is probably better because: - It makes it more readable. - We have to pass one less argument and the function prototype becomes quite short. - The callers don't have to set the data->func pointer from the governor->start() callback now and can do it only once from governor->init(). ->start(), stop() callbacks can get called a lot, for example with CPU hotplug.
But yeah, its all trivial stuff. No big problem solved.
-- viresh
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