/* ----------------------------------------------------------------------- *
 *   
 *   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.
 *
 * ----------------------------------------------------------------------- */

/*
 * cpuid.c
 *
 * 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;

#ifdef CONFIG_SMP

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;

        preempt_disable();
        if (cpu == smp_processor_id()) {
                cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
        } else {
                cmd.reg = reg;
                cmd.data = data;

                smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
        }
        preempt_enable();
}
#else                           /* ! CONFIG_SMP */

static inline void do_cpuid(int cpu, u32 reg, u32 * data)
{
        cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
}

#endif                          /* ! CONFIG_SMP */

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 int cpuid_device_create(int i)
{
        int err = 0;
        struct device *dev;

        dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, i), "cpu%d",i);
        if (IS_ERR(dev))
                err = PTR_ERR(dev);
        return err;
}

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

        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                cpuid_device_create(cpu);
                break;
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
                break;
        }
        return 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) {
                device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, 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)
                device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, 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");