1 /* ----------------------------------------------------------------------- *
3 * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
8 * USA; either version 2 of the License, or (at your option) any later
9 * version; incorporated herein by reference.
11 * ----------------------------------------------------------------------- */
14 * x86 CPUID access device
16 * This device is accessed by lseek() to the appropriate CPUID level
17 * and then read in chunks of 16 bytes. A larger size means multiple
18 * reads of consecutive levels.
20 * The lower 32 bits of the file position is used as the incoming %eax,
21 * and the upper 32 bits of the file position as the incoming %ecx,
22 * the latter intended for "counting" eax levels like eax=4.
24 * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
25 * an SMP box will direct the access to CPU %d.
28 #include <linux/module.h>
30 #include <linux/types.h>
31 #include <linux/errno.h>
32 #include <linux/fcntl.h>
33 #include <linux/init.h>
34 #include <linux/poll.h>
35 #include <linux/smp.h>
36 #include <linux/major.h>
38 #include <linux/smp_lock.h>
39 #include <linux/device.h>
40 #include <linux/cpu.h>
41 #include <linux/notifier.h>
43 #include <asm/processor.h>
45 #include <asm/uaccess.h>
46 #include <asm/system.h>
48 static struct class *cpuid_class;
51 u32 eax, ebx, ecx, edx;
54 static void cpuid_smp_cpuid(void *cmd_block)
56 struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
58 cpuid_count(cmd->eax, cmd->ecx,
59 &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
62 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
74 file->f_pos += offset;
85 static ssize_t cpuid_read(struct file *file, char __user *buf,
86 size_t count, loff_t * ppos)
88 char __user *tmp = buf;
89 struct cpuid_regs cmd;
90 int cpu = iminor(file->f_path.dentry->d_inode);
94 return -EINVAL; /* Invalid chunk size */
96 for (; count; count -= 16) {
99 smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
100 if (copy_to_user(tmp, &cmd, 16))
109 static int cpuid_open(struct inode *inode, struct file *file)
111 unsigned int cpu = iminor(file->f_path.dentry->d_inode);
112 struct cpuinfo_x86 *c = &cpu_data(cpu);
114 if (cpu >= NR_CPUS || !cpu_online(cpu))
115 return -ENXIO; /* No such CPU */
116 if (c->cpuid_level < 0)
117 return -EIO; /* CPUID not supported */
123 * File operations we support
125 static const struct file_operations cpuid_fops = {
126 .owner = THIS_MODULE,
127 .llseek = cpuid_seek,
132 static __cpuinit int cpuid_device_create(int cpu)
136 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu),
138 return IS_ERR(dev) ? PTR_ERR(dev) : 0;
141 static void cpuid_device_destroy(int cpu)
143 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
146 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
147 unsigned long action,
150 unsigned int cpu = (unsigned long)hcpu;
155 err = cpuid_device_create(cpu);
157 case CPU_UP_CANCELED:
159 cpuid_device_destroy(cpu);
161 case CPU_UP_CANCELED_FROZEN:
162 destroy_suspended_device(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
165 return err ? NOTIFY_BAD : NOTIFY_OK;
168 static struct notifier_block __refdata cpuid_class_cpu_notifier =
170 .notifier_call = cpuid_class_cpu_callback,
173 static int __init cpuid_init(void)
178 if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
179 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
184 cpuid_class = class_create(THIS_MODULE, "cpuid");
185 if (IS_ERR(cpuid_class)) {
186 err = PTR_ERR(cpuid_class);
189 for_each_online_cpu(i) {
190 err = cpuid_device_create(i);
194 register_hotcpu_notifier(&cpuid_class_cpu_notifier);
201 for_each_online_cpu(i) {
202 cpuid_device_destroy(i);
204 class_destroy(cpuid_class);
206 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
211 static void __exit cpuid_exit(void)
215 for_each_online_cpu(cpu)
216 cpuid_device_destroy(cpu);
217 class_destroy(cpuid_class);
218 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
219 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
222 module_init(cpuid_init);
223 module_exit(cpuid_exit);
225 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
226 MODULE_DESCRIPTION("x86 generic CPUID driver");
227 MODULE_LICENSE("GPL");