linux-kernel - Re: [PATCH v5 05/10] PM: EM: Add an iterator and accessor for the performance domain

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Message-ID: <e700f9bc-d77e-43a1-9e7d-f53764d57ca6@arm.com>
Date: Tue, 14 Oct 2025 09:45:31 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: Changwoo Min <changwoo@...lia.com>
Cc: christian.loehle@....com, tj@...nel.org, pavel@...nel.org,
 len.brown@...el.com, rafael@...nel.org, kernel-dev@...lia.com,
 linux-pm@...r.kernel.org, sched-ext@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/10] PM: EM: Add an iterator and accessor for the
 performance domain



On 10/14/25 01:10, Changwoo Min wrote:
> Add an iterator function (for_each_em_perf_domain) that iterates all the
> performance domains in the global list. A passed callback function (cb) is
> called for each performance domain.
> 
> Additionally, add a lookup function (em_perf_domain_get_by_id) that
> searches for a performance domain by matching the ID in the global list.
> 
> Signed-off-by: Changwoo Min <changwoo@...lia.com>
> ---
>   kernel/power/em_netlink.h   | 14 ++++++++++++++
>   kernel/power/energy_model.c | 36 ++++++++++++++++++++++++++++++++++++
>   2 files changed, 50 insertions(+)
> 
> diff --git a/kernel/power/em_netlink.h b/kernel/power/em_netlink.h
> index acd186c92d6b..8114b018c73b 100644
> --- a/kernel/power/em_netlink.h
> +++ b/kernel/power/em_netlink.h
> @@ -10,7 +10,21 @@
>   #define _EM_NETLINK_H
>   
>   #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_NET)
> +int for_each_em_perf_domain(int (*cb)(struct em_perf_domain*, void *),
> +			    void *data);
> +struct em_perf_domain *em_perf_domain_get_by_id(int id);
>   #else
> +static inline
> +int for_each_em_perf_domain(int (*cb)(struct em_perf_domain*, void *),
> +			    void *data)
> +{
> +	return -EINVAL;
> +}
> +static inline
> +struct em_perf_domain *em_perf_domain_get_by_id(int id)
> +{
> +	return NULL;
> +}
>   #endif
>   
>   #endif /* _EM_NETLINK_H */
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index 756debf5406a..43a243f9cfa2 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -17,6 +17,8 @@
>   #include <linux/sched/topology.h>
>   #include <linux/slab.h>
>   
> +#include "em_netlink.h"
> +
>   /*
>    * Mutex serializing the registrations of performance domains and letting
>    * callbacks defined by drivers sleep.
> @@ -998,3 +1000,37 @@ void em_rebuild_sched_domains(void)
>   	 */
>   	schedule_work(&rebuild_sd_work);
>   }
> +
> +int for_each_em_perf_domain(int (*cb)(struct em_perf_domain*, void *),
> +			    void *data)
> +{
> +	struct em_perf_domain *pd;
> +
> +	lockdep_assert_not_held(&em_pd_mutex);
> +	guard(mutex)(&em_pd_list_mutex);
> +
> +	list_for_each_entry(pd, &em_pd_list, node) {
> +		int ret;
> +
> +		ret = cb(pd, data);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +struct em_perf_domain *em_perf_domain_get_by_id(int id)
> +{
> +	struct em_perf_domain *pd;
> +
> +	lockdep_assert_not_held(&em_pd_mutex);
> +	guard(mutex)(&em_pd_list_mutex);
> +
> +	list_for_each_entry(pd, &em_pd_list, node) {
> +		if (pd->id == id)
> +			return pd;
> +	}
> +
> +	return NULL;
> +}



LGTM,

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