[LTP] [PATCH v7] power_management: rewrite runpwtests04.sh in C

[Jinseok Kim <always.starving0@gmail.com>]

As part of the ongoing effort to reduce shell-based tests in LTP,
rewrite the cpuidle sysfs smoke test in C using the modern LTP test API.

The new implementation preserves the original test semantics while
removing shell dependencies.

Signed-off-by: Jinseok Kim <always.starving0@gmail.com>
---
Changes in v7:
- Replace the array-based test with dedicated helper functions.
- Use TST_EXP_FAIL2() for the invalid governor test.
- Clarify the test description.
- Link to v6: https://lore.kernel.org/ltp/20260707150920.6489-1-always.starving0@gmail.com

Changes in v6:
- Expand test coverage to include 4 core cpuidle sysfs ABIs.
- Add verification of read() system call return values (bytes read).
- Add negative testing for 'current_governor' to verify EINVAL return value.
- Replace manual access() check with LTP .save_restore.
- Link to v5: https://lore.kernel.org/ltp/20260612171415.988-1-always.starving0@gmail.com

Changes in v5:
- Remove runpwtests04.sh
- Link to v4: https://lore.kernel.org/ltp/20260612122045.14962-1-always.starving0@gmail.com

Changes in v4:
- Fix patch application failure reported by CI.
- Link to v3: https://lore.kernel.org/ltp/20260611145911.3752-1-always.starving0@gmail.com

Changes in v3:
- Replace SAFE_OPEN() with open() to convert ENOENT to TCONF.
- Add a cleanup function.
- Link to v2: https://lore.kernel.org/ltp/20260524154221.2064-1-always.starving0@gmail.com

Changes in v2:
- Update runtest entry
- Clarify commit message
- Link to v1: https://lore.kernel.org/ltp/20260516200015.12689-1-always.starving0@gmail.com
---
 runtest/power_management_tests                |   2 +-
 testcases/kernel/power_management/.gitignore  |   1 +
 testcases/kernel/power_management/cpuidle01.c | 107 ++++++++++++++++++
 .../kernel/power_management/runpwtests04.sh   |  58 ----------
 4 files changed, 109 insertions(+), 59 deletions(-)
 create mode 100644 testcases/kernel/power_management/cpuidle01.c
 delete mode 100755 testcases/kernel/power_management/runpwtests04.sh

diff --git a/runtest/power_management_tests b/runtest/power_management_tests
index 4da57ee72..0f2656b52 100644
--- a/runtest/power_management_tests
+++ b/runtest/power_management_tests
@@ -1,5 +1,5 @@
 #POWER_MANAGEMENT
 high_freq_hwp_cap_cppc high_freq_hwp_cap_cppc
+cpuidle01 cpuidle01
 runpwtests03 runpwtests03.sh
-runpwtests04 runpwtests04.sh
 runpwtests06 runpwtests06.sh
diff --git a/testcases/kernel/power_management/.gitignore b/testcases/kernel/power_management/.gitignore
index 03f0c83e4..e237df1c8 100644
--- a/testcases/kernel/power_management/.gitignore
+++ b/testcases/kernel/power_management/.gitignore
@@ -1 +1,2 @@
 high_freq_hwp_cap_cppc
+cpuidle01
diff --git a/testcases/kernel/power_management/cpuidle01.c b/testcases/kernel/power_management/cpuidle01.c
new file mode 100644
index 000000000..abbf507a0
--- /dev/null
+++ b/testcases/kernel/power_management/cpuidle01.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2026 Jinseok Kim <always.starving0@gmail.com>
+ */
+
+/*\
+ * Basic cpuidle sysfs smoke test.
+ *
+ * Verify that selected cpuidle sysfs files are readable and contain
+ * non-empty values. Also verify that current_governor rejects an
+ * invalid governor.
+ *
+ * Root privileges are required to write to current_governor and to save
+ * and restore its original value.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "tst_test.h"
+
+#define CPUIDLE_PATH "/sys/devices/system/cpu/cpuidle"
+#define AVAILABLE_GOVERNORS CPUIDLE_PATH "/available_governors"
+#define CURRENT_DRIVER CPUIDLE_PATH "/current_driver"
+#define CURRENT_GOVERNOR CPUIDLE_PATH "/current_governor"
+#define CURRENT_GOVERNOR_RO CPUIDLE_PATH "/current_governor_ro"
+
+static void verify_readable(const char *path)
+{
+	int ret;
+	char buf[32];
+
+	int fd = open(path, O_RDONLY);
+
+	if (fd < 0) {
+		if (errno == ENOENT)
+			tst_res(TCONF, "%s is not available", path);
+		else
+			tst_res(TFAIL | TERRNO, "open(%s) failed", path);
+		return;
+	}
+
+	ret = read(fd, buf, sizeof(buf));
+
+	if (ret < 0)
+		tst_res(TFAIL | TERRNO, "%s read() failed", path);
+	else if (ret == 0)
+		tst_res(TFAIL, "%s read() returned 0", path);
+	else
+		tst_res(TPASS, "%s read() successfully", path);
+
+	SAFE_CLOSE(fd);
+}
+
+static void check_available_governors(void)
+{
+	verify_readable(AVAILABLE_GOVERNORS);
+}
+
+static void check_current_driver(void)
+{
+	verify_readable(CURRENT_DRIVER);
+}
+
+static void check_current_governor_ro(void)
+{
+	verify_readable(CURRENT_GOVERNOR_RO);
+}
+
+static void check_current_governor(void)
+{
+	int fd;
+
+	verify_readable(CURRENT_GOVERNOR);
+
+	fd = open(CURRENT_GOVERNOR, O_WRONLY);
+
+	if (fd < 0) {
+		if (errno == ENOENT)
+			tst_res(TCONF, "%s is not available", CURRENT_GOVERNOR);
+		else
+			tst_res(TFAIL | TERRNO, "open(%s) failed", CURRENT_GOVERNOR);
+		return;
+	}
+
+	TST_EXP_FAIL2(write(fd, "invalid_governor", 16), EINVAL);
+
+	SAFE_CLOSE(fd);
+}
+
+static void run(void)
+{
+	check_available_governors();
+	check_current_driver();
+	check_current_governor();
+	check_current_governor_ro();
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.needs_root = 1,
+	.save_restore = (const struct tst_path_val[]) {
+		{ CPUIDLE_PATH "/current_governor", NULL, TST_SR_TCONF },
+		{}
+	},
+};
diff --git a/testcases/kernel/power_management/runpwtests04.sh b/testcases/kernel/power_management/runpwtests04.sh
deleted file mode 100755
index 6565320d2..000000000
--- a/testcases/kernel/power_management/runpwtests04.sh
+++ /dev/null
@@ -1,58 +0,0 @@
-#! /bin/sh
-#
-# Copyright (c) International Business Machines  Corp., 2001
-# Author: Nageswara R Sastry <nasastry@in.ibm.com>
-#
-# This program is free software;  you can redistribute it and#or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-# for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program;  if not, write to the Free Software Foundation,
-# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
-#
-
-export TCID="Power_Management04"
-export TST_TOTAL=1
-
-. test.sh
-. pm_include.sh
-
-check_cpuidle_sysfs_files() {
-	RC=0
-	if [ -d /sys/devices/system/cpu/cpuidle ] ; then
-		for files in current_governor_ro current_driver
-		do
-			cat /sys/devices/system/cpu/cpuidle/${files} \
-				>/dev/null 2>&1
-			if [ $? -ne 0 ] ; then
-				echo "${0}: FAIL: cat ${files}"
-				RC=1
-			fi
-		done
-	fi
-	if [ ${RC} -eq 0 ] ; then
-		echo "${0}: PASS: Checking cpu idle sysfs files"
-	else
-		echo "${0}: FAIL: Checking cpu idle sysfs files"
-	fi
-	return $RC
-}
-
-# Checking test environment
-check_arch
-
-# Checking cpuidle sysfs interface files
-if check_cpuidle_sysfs_files ; then
-	tst_resm TPASS "CPUIDLE sysfs tests passed"
-else
-    tst_resm TFAIL "CPUIDLE sysfs tests failed"
-fi
-
-tst_exit
--
2.43.0

-- 
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