[LTP] [PATCH v4] power_management: rewrite runpwtests04.sh in C

[Jinseok Kim]

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 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/pwtests01.c | 67 +++++++++++++++++++
 3 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 testcases/kernel/power_management/pwtests01.c

diff --git a/runtest/power_management_tests b/runtest/power_management_tests
index 4da57ee72..7a31cde36 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
+pwtests01 pwtests01
 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..e07cda0c5 100644
--- a/testcases/kernel/power_management/.gitignore
+++ b/testcases/kernel/power_management/.gitignore
@@ -1 +1,2 @@
 high_freq_hwp_cap_cppc
+pwtests01
diff --git a/testcases/kernel/power_management/pwtests01.c b/testcases/kernel/power_management/pwtests01.c
new file mode 100644
index 000000000..ae4ed0651
--- /dev/null
+++ b/testcases/kernel/power_management/pwtests01.c
@@ -0,0 +1,67 @@
+// 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.
+ */
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "tst_test.h"
+
+#define CPUIDLE_PATH "/sys/devices/system/cpu/cpuidle"
+
+static struct tcase {
+	const char *name;
+} tcases[] = {
+	{ "current_governor_ro" },
+	{ "current_driver" },
+};
+
+static int fd = -1;
+
+static void verify_cpuidle(unsigned int i)
+{
+	char path[PATH_MAX];
+	char buf[32];
+
+	snprintf(path, sizeof(path), "%s/%s", CPUIDLE_PATH, tcases[i].name);
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		if (errno == ENOENT)
+			tst_res(TCONF, "%s not available", path);
+		else
+			tst_res(TFAIL | TERRNO, "open(%s) failed", path);
+		return;
+	}
+
+	SAFE_READ(0, fd, buf, sizeof(buf));
+	SAFE_CLOSE(fd);
+
+	tst_res(TPASS, "%s read successfully", path);
+}
+
+static void setup(void)
+{
+	if (access(CPUIDLE_PATH, R_OK))
+		tst_brk(TCONF, "%s is not available", CPUIDLE_PATH);
+}
+
+static void cleanup(void)
+{
+	if (fd != -1)
+		SAFE_CLOSE(fd);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.tcnt = ARRAY_SIZE(tcases),
+	.test = verify_cpuidle,
+};
--
2.43.0