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cpuid.c

/* ----------------------------------------------------------------------- *
 *   
 *   Copyright 2000 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
 *   USA; either version 2 of the License, or (at your option) any later
 *   version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * x86 CPUID access device
 *
 * This device is accessed by lseek() to the appropriate CPUID level
 * and then read in chunks of 16 bytes.  A larger size means multiple
 * reads of consecutive levels.
 *
 * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
 * an SMP box will direct the access to CPU %d.
 */

#include <linux/module.h>

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/smp.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/notifier.h>

#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/uaccess.h>
#include <asm/system.h>

static struct class *cpuid_class;

struct cpuid_command {
      u32 reg;
      u32 *data;
};

static void cpuid_smp_cpuid(void *cmd_block)
{
      struct cpuid_command *cmd = (struct cpuid_command *)cmd_block;

      cpuid(cmd->reg, &cmd->data[0], &cmd->data[1], &cmd->data[2],
                  &cmd->data[3]);
}

static inline void do_cpuid(int cpu, u32 reg, u32 * data)
{
      struct cpuid_command cmd;

      cmd.reg = reg;
      cmd.data = data;

      smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
}

static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
{
      loff_t ret;

      lock_kernel();

      switch (orig) {
      case 0:
            file->f_pos = offset;
            ret = file->f_pos;
            break;
      case 1:
            file->f_pos += offset;
            ret = file->f_pos;
            break;
      default:
            ret = -EINVAL;
      }

      unlock_kernel();
      return ret;
}

static ssize_t cpuid_read(struct file *file, char __user *buf,
                    size_t count, loff_t * ppos)
{
      char __user *tmp = buf;
      u32 data[4];
      u32 reg = *ppos;
      int cpu = iminor(file->f_path.dentry->d_inode);

      if (count % 16)
            return -EINVAL;   /* Invalid chunk size */

      for (; count; count -= 16) {
            do_cpuid(cpu, reg, data);
            if (copy_to_user(tmp, &data, 16))
                  return -EFAULT;
            tmp += 16;
            *ppos = reg++;
      }

      return tmp - buf;
}

static int cpuid_open(struct inode *inode, struct file *file)
{
      unsigned int cpu = iminor(file->f_path.dentry->d_inode);
      struct cpuinfo_x86 *c = &cpu_data(cpu);

      if (cpu >= NR_CPUS || !cpu_online(cpu))
            return -ENXIO;    /* No such CPU */
      if (c->cpuid_level < 0)
            return -EIO;      /* CPUID not supported */

      return 0;
}

/*
 * File operations we support
 */
static const struct file_operations cpuid_fops = {
      .owner = THIS_MODULE,
      .llseek = cpuid_seek,
      .read = cpuid_read,
      .open = cpuid_open,
};

static __cpuinit int cpuid_device_create(int cpu)
{
      struct device *dev;

      dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu),
                      "cpu%d", cpu);
      return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}

static void cpuid_device_destroy(int cpu)
{
      device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
}

static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
                                    unsigned long action,
                                    void *hcpu)
{
      unsigned int cpu = (unsigned long)hcpu;
      int err = 0;

      switch (action) {
      case CPU_UP_PREPARE:
      case CPU_UP_PREPARE_FROZEN:
            err = cpuid_device_create(cpu);
            break;
      case CPU_UP_CANCELED:
      case CPU_UP_CANCELED_FROZEN:
      case CPU_DEAD:
      case CPU_DEAD_FROZEN:
            cpuid_device_destroy(cpu);
            break;
      }
      return err ? NOTIFY_BAD : NOTIFY_OK;
}

static struct notifier_block __cpuinitdata cpuid_class_cpu_notifier =
{
      .notifier_call = cpuid_class_cpu_callback,
};

static int __init cpuid_init(void)
{
      int i, err = 0;
      i = 0;

      if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
            printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
                   CPUID_MAJOR);
            err = -EBUSY;
            goto out;
      }
      cpuid_class = class_create(THIS_MODULE, "cpuid");
      if (IS_ERR(cpuid_class)) {
            err = PTR_ERR(cpuid_class);
            goto out_chrdev;
      }
      for_each_online_cpu(i) {
            err = cpuid_device_create(i);
            if (err != 0) 
                  goto out_class;
      }
      register_hotcpu_notifier(&cpuid_class_cpu_notifier);

      err = 0;
      goto out;

out_class:
      i = 0;
      for_each_online_cpu(i) {
            cpuid_device_destroy(i);
      }
      class_destroy(cpuid_class);
out_chrdev:
      unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");    
out:
      return err;
}

static void __exit cpuid_exit(void)
{
      int cpu = 0;

      for_each_online_cpu(cpu)
            cpuid_device_destroy(cpu);
      class_destroy(cpuid_class);
      unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
      unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
}

module_init(cpuid_init);
module_exit(cpuid_exit);

MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
MODULE_DESCRIPTION("x86 generic CPUID driver");
MODULE_LICENSE("GPL");

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