[LTP] power_management: rewrite runpwtests04.sh in C

[linuxtestproject.agent@gmail.com]

Hi Jinseok,

On Wed, 8 Jul 2026, Jinseok Kim wrote:
> power_management: rewrite runpwtests04.sh in C

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

The original shell test only checked current_governor_ro and
current_driver for readability. The new test also covers
available_governors, current_governor (read), and adds a write
rejection check against current_governor. That is an extension,
not a preservation of semantics. Please update the commit message
body to reflect what is actually added.

> +static void verify_cpuidle(unsigned int i)
> +{
> +	int ret;
> +	char path[PATH_MAX];
> +	char buf[32];
> +
> +	snprintf(path, sizeof(path), "%s/%s", CPUIDLE_PATH, tcases[i].name);
> +
> +	if (tcases[i].is_writable)
> +		fd = open(path, O_RDWR);
> +	else
> +		fd = open(path, O_RDONLY);

open() is a tested subject here -- its return code drives the
TCONF/TFAIL decision. Bare syscalls that are the subject of the
test must be wrapped in TEST(), not called directly. The same
applies to read() and write() below.

> +	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);

read() is the primary subject of this test and must be wrapped in
TEST() so that TST_RET and TST_ERR are populated.

> +	if (tcases[i].is_writable) {
> +		if (write(fd, "invalid_governor", 16) < 0) {

Same for write().

> +static struct tst_test test = {
> +	.cleanup = cleanup,
> +	.needs_root = 1,

The doc comment only mentions readability. It does not explain why
root is required. Ground Rule 4 requires the reason to appear in
the /*\ ... */ block. Root is needed here for writing to
current_governor and for the save_restore of that path; please
document that.

> + * Verify that selected cpuidle sysfs files are readable.

The test also verifies that writing an invalid governor name to
current_governor is rejected with EINVAL. The description should
cover both aspects.

Verdict - Needs revision

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