linux-kernel - [PATCH v2] cpupower: Implement powercap_set

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Message-ID: <20250520094345.97200-1-suchitkarunakaran@gmail.com>
Date: Tue, 20 May 2025 15:13:45 +0530
From: Suchit Karunakaran <suchitkarunakaran@...il.com>
To: trenn@...e.com,
	shuah@...nel.org,
	jwyatt@...hat.com,
	jkacur@...hat.com,
	linux-pm@...r.kernel.org
Cc: linux-kernel-mentees@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Suchit Karunakaran <suchitkarunakaran@...il.com>
Subject: [PATCH v2] cpupower: Implement powercap_set_enabled()

The powercap_set_enabled() function previously returned a dummy value
and was marked with a TODO comment to implement it. This patch implements the 
function by writing the desired mode (0 or 1) to /sys/class/powercap/intel-rapl/enabled

Signed-off-by: Suchit Karunakaran <suchitkarunakaran@...il.com>
---
 tools/power/cpupower/lib/powercap.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/tools/power/cpupower/lib/powercap.c b/tools/power/cpupower/lib/powercap.c
index 94a0c69e55ef..7947b9809239 100644
--- a/tools/power/cpupower/lib/powercap.c
+++ b/tools/power/cpupower/lib/powercap.c
@@ -70,6 +70,22 @@ static int sysfs_get_enabled(char *path, int *mode)
 	return ret;
 }
 
+static int sysfs_set_enabled(const char *path, int mode)
+{
+	int fd;
+	char buf[2] = { mode ? '1' : '0', '\n' };
+	ssize_t ret;
+
+	fd = open(path, O_WRONLY);
+	if (fd == -1)
+		return -1;
+
+	ret = write(fd, buf, sizeof(buf));
+	close(fd);
+
+	return ret == sizeof(buf) ? 0 : -1;
+}
+
 int powercap_get_enabled(int *mode)
 {
 	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP "/intel-rapl/enabled";
@@ -77,12 +93,10 @@ int powercap_get_enabled(int *mode)
 	return sysfs_get_enabled(path, mode);
 }
 
-/*
- * TODO: implement function. Returns dummy 0 for now.
- */
 int powercap_set_enabled(int mode)
 {
-	return 0;
+	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP "/intel-rapl/enabled";
+	return sysfs_set_enabled(path, mode);
 }
 
 /*
-- 
2.49.0