int cpufreq_register_driver()

in cpufreq.c [2778:2869]

• 68 lines of code
• 22 McCabe index (conditional complexity)

int cpufreq_register_driver(struct cpufreq_driver *driver_data)
{
	unsigned long flags;
	int ret;

	if (cpufreq_disabled())
		return -ENODEV;

	/*
	 * The cpufreq core depends heavily on the availability of device
	 * structure, make sure they are available before proceeding further.
	 */
	if (!get_cpu_device(0))
		return -EPROBE_DEFER;

	if (!driver_data || !driver_data->verify || !driver_data->init ||
	    !(driver_data->setpolicy || driver_data->target_index ||
		    driver_data->target) ||
	     (driver_data->setpolicy && (driver_data->target_index ||
		    driver_data->target)) ||
	     (!driver_data->get_intermediate != !driver_data->target_intermediate) ||
	     (!driver_data->online != !driver_data->offline))
		return -EINVAL;

	pr_debug("trying to register driver %s\n", driver_data->name);

	/* Protect against concurrent CPU online/offline. */
	cpus_read_lock();

	write_lock_irqsave(&cpufreq_driver_lock, flags);
	if (cpufreq_driver) {
		write_unlock_irqrestore(&cpufreq_driver_lock, flags);
		ret = -EEXIST;
		goto out;
	}
	cpufreq_driver = driver_data;
	write_unlock_irqrestore(&cpufreq_driver_lock, flags);

	/*
	 * Mark support for the scheduler's frequency invariance engine for
	 * drivers that implement target(), target_index() or fast_switch().
	 */
	if (!cpufreq_driver->setpolicy) {
		static_branch_enable_cpuslocked(&cpufreq_freq_invariance);
		pr_debug("supports frequency invariance");
	}

	if (driver_data->setpolicy)
		driver_data->flags |= CPUFREQ_CONST_LOOPS;

	if (cpufreq_boost_supported()) {
		ret = create_boost_sysfs_file();
		if (ret)
			goto err_null_driver;
	}

	ret = subsys_interface_register(&cpufreq_interface);
	if (ret)
		goto err_boost_unreg;

	if (unlikely(list_empty(&cpufreq_policy_list))) {
		/* if all ->init() calls failed, unregister */
		ret = -ENODEV;
		pr_debug("%s: No CPU initialized for driver %s\n", __func__,
			 driver_data->name);
		goto err_if_unreg;
	}

	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
						   "cpufreq:online",
						   cpuhp_cpufreq_online,
						   cpuhp_cpufreq_offline);
	if (ret < 0)
		goto err_if_unreg;
	hp_online = ret;
	ret = 0;

	pr_debug("driver %s up and running\n", driver_data->name);
	goto out;

err_if_unreg:
	subsys_interface_unregister(&cpufreq_interface);
err_boost_unreg:
	remove_boost_sysfs_file();
err_null_driver:
	write_lock_irqsave(&cpufreq_driver_lock, flags);
	cpufreq_driver = NULL;
	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
out:
	cpus_read_unlock();
	return ret;
}