linux-kernel - [PATCH for 6.19 3/4] PM: EM: Change cpus' type from string to u64 array in the EM YNL spec

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Message-ID: <20251225040104.982704-4-changwoo@igalia.com>
Date: Thu, 25 Dec 2025 13:01:03 +0900
From: Changwoo Min <changwoo@...lia.com>
To: lukasz.luba@....com,
	rafael@...nel.org,
	donald.hunter@...il.com,
	kuba@...nel.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	horms@...nel.org,
	lenb@...nel.org,
	pavel@...nel.org,
	changwoo@...lia.com
Cc: kernel-dev@...lia.com,
	linux-pm@...r.kernel.org,
	netdev@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH for 6.19 3/4] PM: EM: Change cpus' type from string to u64 array in the EM YNL spec

Previously, the cpus attribute was a string format which was a "%*pb"
stringification of a bitmap. That is not very consumable for a UAPI,
so let’s change it to an u64 array of CPU ids.

Suggested-by: Donald Hunter <donald.hunter@...il.com>
Signed-off-by: Changwoo Min <changwoo@...lia.com>
---
 .../netlink/specs/dev-energymodel.yaml        |  3 ++-
 kernel/power/em_netlink.c                     | 22 +++++++++----------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/Documentation/netlink/specs/dev-energymodel.yaml b/Documentation/netlink/specs/dev-energymodel.yaml
index cbc4bc38f23c..af8b8f72f722 100644
--- a/Documentation/netlink/specs/dev-energymodel.yaml
+++ b/Documentation/netlink/specs/dev-energymodel.yaml
@@ -73,7 +73,8 @@ attribute-sets:
         enum: perf-domain-flags
       -
         name: cpus
-        type: string
+        type: u64
+        multi-attr: true
         doc: >-
           CPUs that belong to this performance domain.
   -
diff --git a/kernel/power/em_netlink.c b/kernel/power/em_netlink.c
index 6f6238c465bb..b6edb018c65a 100644
--- a/kernel/power/em_netlink.c
+++ b/kernel/power/em_netlink.c
@@ -17,17 +17,14 @@
 #include "em_netlink.h"
 #include "em_netlink_autogen.h"
 
-#define DEV_ENERGYMODEL_A_PERF_DOMAIN_CPUS_LEN		256
-
 /*************************** Command encoding ********************************/
 static int __em_nl_get_pd_size(struct em_perf_domain *pd, void *data)
 {
-	char cpus_buf[DEV_ENERGYMODEL_A_PERF_DOMAIN_CPUS_LEN];
+	int nr_cpus, msg_sz, cpus_sz;
 	int *tot_msg_sz = data;
-	int msg_sz, cpus_sz;
 
-	cpus_sz = snprintf(cpus_buf, sizeof(cpus_buf), "%*pb",
-			   cpumask_pr_args(to_cpumask(pd->cpus)));
+	nr_cpus = cpumask_weight(to_cpumask(pd->cpus));
+	cpus_sz = nla_total_size_64bit(sizeof(u64)) * nr_cpus;
 
 	msg_sz = nla_total_size(0) +
 		 /* DEV_ENERGYMODEL_A_PERF_DOMAINS_PERF_DOMAIN */
@@ -44,9 +41,10 @@ static int __em_nl_get_pd_size(struct em_perf_domain *pd, void *data)
 
 static int __em_nl_get_pd(struct em_perf_domain *pd, void *data)
 {
-	char cpus_buf[DEV_ENERGYMODEL_A_PERF_DOMAIN_CPUS_LEN];
 	struct sk_buff *msg = data;
+	struct cpumask *cpumask;
 	struct nlattr *entry;
+	int cpu;
 
 	entry = nla_nest_start(msg,
 			       DEV_ENERGYMODEL_A_PERF_DOMAINS_PERF_DOMAIN);
@@ -61,10 +59,12 @@ static int __em_nl_get_pd(struct em_perf_domain *pd, void *data)
 			      pd->flags, DEV_ENERGYMODEL_A_PERF_DOMAIN_PAD))
 		goto out_cancel_nest;
 
-	snprintf(cpus_buf, sizeof(cpus_buf), "%*pb",
-		 cpumask_pr_args(to_cpumask(pd->cpus)));
-	if (nla_put_string(msg, DEV_ENERGYMODEL_A_PERF_DOMAIN_CPUS, cpus_buf))
-		goto out_cancel_nest;
+	cpumask = to_cpumask(pd->cpus);
+	for_each_cpu(cpu, cpumask) {
+		if (nla_put_u64_64bit(msg, DEV_ENERGYMODEL_A_PERF_DOMAIN_CPUS,
+				      cpu, DEV_ENERGYMODEL_A_PERF_DOMAIN_PAD))
+			goto out_cancel_nest;
+	}
 
 	nla_nest_end(msg, entry);
 
-- 
2.52.0