cpufreq qos

cpufreq core

static struct cpufreq_driver *cpufreq_driver;

int cpufreq_register_driver(struct cpufreq_driver *driver_data)
{
    /*
     * The cpufreq core depends heavily on the availability of device
     * structure, make sure they are available before proceeding further.
     */
    if (!get_cpu_device(0))                                                        （1）
        return -EPROBE_DEFER;
    
    if (!driver_data || !driver_data->verify || !driver_data->init ||              （2）
        !(driver_data->setpolicy || driver_data->target_index ||
            driver_data->target) ||                                                （3）
         (driver_data->setpolicy && (driver_data->target_index ||
            driver_data->target)) ||                                               （4）
         (!driver_data->get_intermediate != !driver_data->target_intermediate) ||  （5）
         (!driver_data->online != !driver_data->offline))                          （6）
        return -EINVAL;

}