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>
#include <linux/node.h>

#include "base.h"

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

static struct sys_device *cpu_sys_devices[NR_CPUS];

#ifdef CONFIG_HOTPLUG_CPU
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_uevent(&dev->kobj, KOBJ_OFFLINE);
		break;
	case '1':
		ret = cpu_up(cpu->sysdev.id);
		if (!ret)
			kobject_uevent(&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)
{
	int logical_cpu = cpu->sysdev.id;

	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

	sysdev_remove_file(&cpu->sysdev, &attr_online);

	sysdev_unregister(&cpu->sysdev);
	cpu_sys_devices[logical_cpu] = NULL;
	return;
}
#else /* ... !CONFIG_HOTPLUG_CPU */
static inline void register_cpu_control(struct cpu *cpu)
{
}
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_KEXEC
#include <linux/kexec.h>

static ssize_t show_crash_notes(struct sys_device *dev, char *buf)
{
	struct cpu *cpu = container_of(dev, struct cpu, sysdev);
	ssize_t rc;
	unsigned long long addr;
	int cpunum;

	cpunum = cpu->sysdev.id;

	/*
	 * Might be reading other cpu's data based on which cpu read thread
	 * has been scheduled. But cpu data (memory) is allocated once during
	 * boot up and this data does not change there after. Hence this
	 * operation should be safe. No locking required.
	 */
	addr = __pa(per_cpu_ptr(crash_notes, cpunum));
	rc = sprintf(buf, "%Lx\n", addr);
	return rc;
}
static SYSDEV_ATTR(crash_notes, 0400, show_crash_notes, NULL);
#endif

/*
 * 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)
{
	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 && !cpu->no_control)
		register_cpu_control(cpu);
	if (!error)
		cpu_sys_devices[num] = &cpu->sysdev;
	if (!error)
		register_cpu_under_node(num, cpu_to_node(num));

#ifdef CONFIG_KEXEC
	if (!error)
		error = sysdev_create_file(&cpu->sysdev, &attr_crash_notes);
#endif
	return error;
}

struct sys_device *get_cpu_sysdev(unsigned cpu)
{
	if (cpu < NR_CPUS)
		return cpu_sys_devices[cpu];
	else
		return NULL;
}
EXPORT_SYMBOL_GPL(get_cpu_sysdev);

int __init cpu_dev_init(void)
{
	int err;

	err = sysdev_class_register(&cpu_sysdev_class);
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
	if (!err)
		err = sched_create_sysfs_power_savings_entries(&cpu_sysdev_class);
#endif

	return err;
}