drivers/base/cpu.c

/*
 * drivers/base/cpu.c - basic CPU class support
 */

#include <linux/sysdev.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/topology.h>
#include <linux/device.h>


struct sysdev_class cpu_sysdev_class = {
	set_kset_name("cpu"),
};
EXPORT_SYMBOL(cpu_sysdev_class);

#ifdef CONFIG_HOTPLUG_CPU
int __attribute__((weak)) smp_prepare_cpu (int cpu)
{
	return 0;
}

static ssize_t show_online(struct sys_device *dev, char *buf)
{
	struct cpu *cpu = container_of(dev, struct cpu, sysdev);

	return sprintf(buf, "%u\n", !!cpu_online(cpu->sysdev.id));
}

static ssize_t store_online(struct sys_device *dev, const char *buf,
			    size_t count)
{
	struct cpu *cpu = container_of(dev, struct cpu, sysdev);
	ssize_t ret;

	switch (buf[0]) {
	case '0':
		ret = cpu_down(cpu->sysdev.id);
		if (!ret)
			kobject_hotplug(&dev->kobj, KOBJ_OFFLINE);
		break;
	case '1':
		ret = smp_prepare_cpu(cpu->sysdev.id);
		if (!ret)
			ret = cpu_up(cpu->sysdev.id);
		break;
	default:
		ret = -EINVAL;
	}

	if (ret >= 0)
		ret = count;
	return ret;
}
static SYSDEV_ATTR(online, 0600, show_online, store_online);

static void __devinit register_cpu_control(struct cpu *cpu)
{
	sysdev_create_file(&cpu->sysdev, &attr_online);
}
void unregister_cpu(struct cpu *cpu, struct node *root)
{

	if (root)
		sysfs_remove_link(&root->sysdev.kobj,
				  kobject_name(&cpu->sysdev.kobj));
	sysdev_remove_file(&cpu->sysdev, &attr_online);

	sysdev_unregister(&cpu->sysdev);

	return;
}
#else /* ... !CONFIG_HOTPLUG_CPU */
static inline void register_cpu_control(struct cpu *cpu)
{
}
#endif /* CONFIG_HOTPLUG_CPU */

/*
 * register_cpu - Setup a driverfs device for a CPU.
 * @cpu - Callers can set the cpu->no_control field to 1, to indicate not to
 *		  generate a control file in sysfs for this CPU.
 * @num - CPU number to use when creating the device.
 *
 * Initialize and register the CPU device.
 */
int __devinit register_cpu(struct cpu *cpu, int num, struct node *root)
{
	int error;

	cpu->node_id = cpu_to_node(num);
	cpu->sysdev.id = num;
	cpu->sysdev.cls = &cpu_sysdev_class;

	error = sysdev_register(&cpu->sysdev);
	if (!error && root)
		error = sysfs_create_link(&root->sysdev.kobj,
					  &cpu->sysdev.kobj,
					  kobject_name(&cpu->sysdev.kobj));
	if (!error && !cpu->no_control)
		register_cpu_control(cpu);
	return error;
}



int __init cpu_dev_init(void)
{
	return sysdev_class_register(&cpu_sysdev_class);
}