[LTP] cpufreq.c: add new test for cpufreq sysfs interface validation

[linuxtestproject.agent@gmail.com]

Hi Piotr,

On Thu, 11 Jun 2026 13:42:20 +0200, Piotr Kubaj wrote:
> cpufreq.c: add new test for cpufreq sysfs interface validation

> +		if (cpuinfo_max_freq < scaling_max_freq) {
> +			tst_res(TINFO, "cpuinfo_max_freq: %ld", cpuinfo_max_freq);
> +			tst_res(TINFO, "scaling_max_freq: %ld", scaling_max_freq);
> +			tst_res(TFAIL, "Failure setting %s", path);
> +		} else {
> +			tst_res(TPASS, "Successfully set up %s", path);
> +		}

The frequency write-back checks throughout run() use one-directional
comparisons. Here the test writes cpuinfo_max_freq to scaling_max_freq
and reads it back, but only fails when the read value is *higher*
than what was written. If the kernel rounded the value *down* (or the
write silently failed to a lower value), the test would still report
TPASS with "Successfully set up".

The same pattern applies to the scaling_min_freq checks further down,
which only fail when the read value is *lower* than what was written.

Since the purpose of these checks is to validate that exact boundary
values can be written, would it not be more correct to use != instead
of < / > here?

> +		if (cpuinfo_max_freq < scaling_min_freq) {

Same issue: only catches upward deviations.

> +		if (cpuinfo_min_freq > scaling_min_freq) {

Same issue: only catches downward deviations.

> +		if (cpuinfo_min_freq > scaling_max_freq) {

Same issue: only catches downward deviations.

Verdict: Needs revision

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