linux-kernel - Re: [PATCH v1 1/3] PM: EM: Consify two parameters of em_dev_register_perf

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Message-ID: <9a9bdf37-1462-4aca-b513-268b4f2b235c@arm.com>
Date: Thu, 6 Mar 2025 09:22:43 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v1 1/3] PM: EM: Consify two parameters of
 em_dev_register_perf_domain()



On 3/5/25 21:08, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Notice that em_dev_register_perf_domain() and the functions called by it
> do not update objects pointed to by its cb and cpus parameters, so the
> const modifier can be added to them.
> 
> This allows the return value of cpumask_of() or a pointer to a
> struct em_data_callback declared as const to be passed to
> em_dev_register_perf_domain() directly without explicit type
> casting which is rather handy.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>   include/linux/energy_model.h |    8 ++++----
>   kernel/power/energy_model.c  |   11 ++++++-----
>   2 files changed, 10 insertions(+), 9 deletions(-)
> 
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -169,8 +169,8 @@
>   int em_dev_update_perf_domain(struct device *dev,
>   			      struct em_perf_table __rcu *new_table);
>   int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
> -				struct em_data_callback *cb, cpumask_t *span,
> -				bool microwatts);
> +				const struct em_data_callback *cb,
> +				const cpumask_t *cpus, bool microwatts);
>   void em_dev_unregister_perf_domain(struct device *dev);
>   struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd);
>   void em_table_free(struct em_perf_table __rcu *table);
> @@ -346,8 +346,8 @@
>   
>   static inline
>   int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
> -				struct em_data_callback *cb, cpumask_t *span,
> -				bool microwatts)
> +				const struct em_data_callback *cb,
> +				const cpumask_t *cpus, bool microwatts)
>   {
>   	return -EINVAL;
>   }
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -231,7 +231,7 @@
>   }
>   
>   static int em_compute_costs(struct device *dev, struct em_perf_state *table,
> -			    struct em_data_callback *cb, int nr_states,
> +			    const struct em_data_callback *cb, int nr_states,
>   			    unsigned long flags)
>   {
>   	unsigned long prev_cost = ULONG_MAX;
> @@ -333,7 +333,7 @@
>   
>   static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
>   				struct em_perf_state *table,
> -				struct em_data_callback *cb,
> +				const struct em_data_callback *cb,
>   				unsigned long flags)
>   {
>   	unsigned long power, freq, prev_freq = 0;
> @@ -388,7 +388,8 @@
>   }
>   
>   static int em_create_pd(struct device *dev, int nr_states,
> -			struct em_data_callback *cb, cpumask_t *cpus,
> +			const struct em_data_callback *cb,
> +			const cpumask_t *cpus,
>   			unsigned long flags)
>   {
>   	struct em_perf_table __rcu *em_table;
> @@ -548,8 +549,8 @@
>    * Return 0 on success
>    */
>   int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
> -				struct em_data_callback *cb, cpumask_t *cpus,
> -				bool microwatts)
> +				const struct em_data_callback *cb,
> +				const cpumask_t *cpus, bool microwatts)
>   {
>   	unsigned long cap, prev_cap = 0;
>   	unsigned long flags = 0;
> 
> 
> 

LGTM,

Reviewed-by: Lukasz Luba <lukasz.luba@....com>