drivers/base/cpu.c

   1 /*
   2  * drivers/base/cpu.c - basic CPU class support
   3  */
   4
   5 #include <linux/sysdev.h>
   6 #include <linux/module.h>
   7 #include <linux/init.h>
   8 #include <linux/cpu.h>
   9 #include <linux/topology.h>
  10 #include <linux/device.h>
  11
  12 #include "base.h"
  13
  14 struct sysdev_class cpu_sysdev_class = {
  15         set_kset_name("cpu"),
  16 };
  17 EXPORT_SYMBOL(cpu_sysdev_class);
  18
  19 static struct sys_device *cpu_sys_devices[NR_CPUS];
  20
  21 #ifdef CONFIG_HOTPLUG_CPU
  22 int __attribute__((weak)) smp_prepare_cpu (int cpu)
  23 {
  24         return 0;
  25 }
  26
  27 static ssize_t show_online(struct sys_device *dev, char *buf)
  28 {
  29         struct cpu *cpu = container_of(dev, struct cpu, sysdev);
  30
  31         return sprintf(buf, "%u\n", !!cpu_online(cpu->sysdev.id));
  32 }
  33
  34 static ssize_t store_online(struct sys_device *dev, const char *buf,
  35                             size_t count)
  36 {
  37         struct cpu *cpu = container_of(dev, struct cpu, sysdev);
  38         ssize_t ret;
  39
  40         switch (buf[0]) {
  41         case '0':
  42                 ret = cpu_down(cpu->sysdev.id);
  43                 if (!ret)
  44                         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
  45                 break;
  46         case '1':
  47                 ret = smp_prepare_cpu(cpu->sysdev.id);
  48                 if (!ret)
  49                         ret = cpu_up(cpu->sysdev.id);
  50                 if (!ret)
  51                         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
  52                 break;
  53         default:
  54                 ret = -EINVAL;
  55         }
  56
  57         if (ret >= 0)
  58                 ret = count;
  59         return ret;
  60 }
  61 static SYSDEV_ATTR(online, 0600, show_online, store_online);
  62
  63 static void __devinit register_cpu_control(struct cpu *cpu)
  64 {
  65         sysdev_create_file(&cpu->sysdev, &attr_online);
  66 }
  67 void unregister_cpu(struct cpu *cpu, struct node *root)
  68 {
  69         int logical_cpu = cpu->sysdev.id;
  70
  71         if (root)
  72                 sysfs_remove_link(&root->sysdev.kobj,
  73                                   kobject_name(&cpu->sysdev.kobj));
  74         sysdev_remove_file(&cpu->sysdev, &attr_online);
  75
  76         sysdev_unregister(&cpu->sysdev);
  77         cpu_sys_devices[logical_cpu] = NULL;
  78         return;
  79 }
  80 #else /* ... !CONFIG_HOTPLUG_CPU */
  81 static inline void register_cpu_control(struct cpu *cpu)
  82 {
  83 }
  84 #endif /* CONFIG_HOTPLUG_CPU */
  85
  86 #ifdef CONFIG_KEXEC
  87 #include <linux/kexec.h>
  88
  89 static ssize_t show_crash_notes(struct sys_device *dev, char *buf)
  90 {
  91         struct cpu *cpu = container_of(dev, struct cpu, sysdev);
  92         ssize_t rc;
  93         unsigned long long addr;
  94         int cpunum;
  95
  96         cpunum = cpu->sysdev.id;
  97
  98         /*
  99          * Might be reading other cpu's data based on which cpu read thread
 100          * has been scheduled. But cpu data (memory) is allocated once during
 101          * boot up and this data does not change there after. Hence this
 102          * operation should be safe. No locking required.
 103          */
 104         addr = __pa(per_cpu_ptr(crash_notes, cpunum));
 105         rc = sprintf(buf, "%Lx\n", addr);
 106         return rc;
 107 }
 108 static SYSDEV_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 109 #endif
 110
 111 /*
 112  * register_cpu - Setup a driverfs device for a CPU.
 113  * @cpu - Callers can set the cpu->no_control field to 1, to indicate not to
 114  *                generate a control file in sysfs for this CPU.
 115  * @num - CPU number to use when creating the device.
 116  *
 117  * Initialize and register the CPU device.
 118  */
 119 int __devinit register_cpu(struct cpu *cpu, int num, struct node *root)
 120 {
 121         int error;
 122
 123         cpu->node_id = cpu_to_node(num);
 124         cpu->sysdev.id = num;
 125         cpu->sysdev.cls = &cpu_sysdev_class;
 126
 127         error = sysdev_register(&cpu->sysdev);
 128         if (!error && root)
 129                 error = sysfs_create_link(&root->sysdev.kobj,
 130                                           &cpu->sysdev.kobj,
 131                                           kobject_name(&cpu->sysdev.kobj));
 132         if (!error && !cpu->no_control)
 133                 register_cpu_control(cpu);
 134         if (!error)
 135                 cpu_sys_devices[num] = &cpu->sysdev;
 136
 137 #ifdef CONFIG_KEXEC
 138         if (!error)
 139                 error = sysdev_create_file(&cpu->sysdev, &attr_crash_notes);
 140 #endif
 141         return error;
 142 }
 143
 144 struct sys_device *get_cpu_sysdev(int cpu)
 145 {
 146         if (cpu < NR_CPUS)
 147                 return cpu_sys_devices[cpu];
 148         else
 149                 return NULL;
 150 }
 151 EXPORT_SYMBOL_GPL(get_cpu_sysdev);
 152
 153 int __init cpu_dev_init(void)
 154 {
 155         return sysdev_class_register(&cpu_sysdev_class);
 156 }