/* * 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_CPUint __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);		if (!ret)			kobject_hotplug(&dev->kobj, KOBJ_ONLINE);		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);}