linux-kernel - [PATCH v2] cpufreq: Replace pointer subtraction with iteration macros

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Message-Id: <20250923075553.45532-1-zhangzihuan@kylinos.cn>
Date: Tue, 23 Sep 2025 15:55:53 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: "Rafael J . wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>
Cc: zhenglifeng <zhenglifeng1@...wei.com>,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zihuan Zhang <zhangzihuan@...inos.cn>
Subject: [PATCH v2] cpufreq: Replace pointer subtraction with iteration macros

The cpufreq documentation suggests avoiding direct pointer subtraction
when working with entries in driver_freq_table, as it is relatively
costly. Instead, the recommended approach is to use the provided
iteration macros:

- cpufreq_for_each_valid_entry_idx()

Replace pointer subtraction in freq_table.c with the macros
cpufreq_for_each_entry_idx() and cpufreq_for_each_valid_entry_idx(), as
the index does not need initialization, avoiding unnecessary
computation. This improves code clarity and follows the established
cpufreq coding style.

No functional change intended.

Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>

V2:
 - Remove unnecessary initialization for current and remaining follow Rafael's suggestion
---
 drivers/cpufreq/freq_table.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index d5111ee56e38..408fd8fee2e3 100644
--- a/drivers/cpufreq/freq_table.c
+++ b/drivers/cpufreq/freq_table.c
@@ -33,16 +33,17 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy)
 	struct cpufreq_frequency_table *pos, *table = policy->freq_table;
 	unsigned int min_freq = ~0;
 	unsigned int max_freq = 0;
+	unsigned int i;
 	unsigned int freq;
 
-	cpufreq_for_each_valid_entry(pos, table) {
+	cpufreq_for_each_valid_entry_idx(pos, table, i) {
 		freq = pos->frequency;
 
 		if ((!cpufreq_boost_enabled() || !policy->boost_enabled)
 		    && (pos->flags & CPUFREQ_BOOST_FREQ))
 			continue;
 
-		pr_debug("table entry %u: %u kHz\n", (int)(pos - table), freq);
+		pr_debug("table entry %u: %u kHz\n", i, freq);
 		if (freq < min_freq)
 			min_freq = freq;
 		if (freq > max_freq)
@@ -126,7 +127,7 @@ int cpufreq_table_index_unsorted(struct cpufreq_policy *policy,
 	};
 	struct cpufreq_frequency_table *pos;
 	struct cpufreq_frequency_table *table = policy->freq_table;
-	unsigned int freq, diff, i = 0;
+	unsigned int freq, diff, i;
 	int index;
 
 	pr_debug("request for target %u kHz (relation: %u) for cpu %u\n",
-- 
2.25.1