cpufreq 频率设置verify

新频率在被设置时需要检查是否在可用范围内.

static struct cpufreq_driver longrun_driver = {
.flags = CPUFREQ_CONST_LOOPS,
.verify = longrun_verify_policy,
.setpolicy = longrun_set_policy,
.get = longrun_get,
.init = longrun_cpu_init,
.name = “longrun”,
};

When the user decides a new policy (consisting of
“policy,governor,min,max”) shall be set, this policy must be validated
so that incompatible values can be corrected. For verifying these
values cpufreq_verify_within_limits(struct cpufreq_policy *policy,
unsigned int min_freq, unsigned int max_freq) function might be helpful.
See section 2 for details on frequency table helpers.

static inline void cpufreq_verify_within_limits(struct cpufreq_policy_data *policy,
						unsigned int min,
						unsigned int max)
{
	if (policy->min < min)
		policy->min = min;
	if (policy->max < min)
		policy->max = min;
	if (policy->min > max)
		policy->min = max;
	if (policy->max > max)
		policy->max = max;
	if (policy->min > policy->max)
		policy->min = policy->max;
	return;
}

static inline void
cpufreq_verify_within_cpu_limits(struct cpufreq_policy_data *policy)
{
	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
				     policy->cpuinfo.max_freq);
}

static int cpufreq_set_policy(struct cpufreq_policy *policy,
			      struct cpufreq_governor *new_gov,
			      unsigned int new_pol)
{
	struct cpufreq_policy_data new_data;
	struct cpufreq_governor *old_gov;
	int ret;
pr_err("+++++++ cpufreq_set_policy 1 ++++++++\n");
	memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
	new_data.freq_table = policy->freq_table;
	new_data.cpu = policy->cpu;
	/*
	 * PM QoS framework collects all the requests from users and provide us
	 * the final aggregated value here.
	 */
	new_data.min = freq_qos_read_value(&policy->constraints, FREQ_QOS_MIN);
	new_data.max = freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX);

	pr_err("setting new policy for CPU %u: %u - %u kHz\n",
		 new_data.cpu, new_data.min, new_data.max);

	/*
	 * Verify that the CPU speed can be set within these limits and make sure
	 * that min <= max.
	 */
 
	**ret = cpufreq_driver->verify(&new_data);**
	....
}