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/smp_lock.h>
37 #include <linux/major.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)
65 struct inode *inode = file->f_mapping->host;
67 mutex_lock(&inode->i_mutex);
74 file->f_pos += offset;
80 mutex_unlock(&inode->i_mutex);
84 static ssize_t cpuid_read(struct file *file, char __user *buf,
85 size_t count, loff_t * ppos)
87 char __user *tmp = buf;
88 struct cpuid_regs cmd;
89 int cpu = iminor(file->f_path.dentry->d_inode);
93 return -EINVAL; /* Invalid chunk size */
95 for (; count; count -= 16) {
98 smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
99 if (copy_to_user(tmp, &cmd, 16))
108 static int cpuid_open(struct inode *inode, struct file *file)
111 struct cpuinfo_x86 *c;
116 cpu = iminor(file->f_path.dentry->d_inode);
117 if (cpu >= NR_CPUS || !cpu_online(cpu)) {
118 ret = -ENXIO; /* No such CPU */
122 if (c->cpuid_level < 0)
123 ret = -EIO; /* CPUID not supported */
130 * File operations we support
132 static const struct file_operations cpuid_fops = {
133 .owner = THIS_MODULE,
134 .llseek = cpuid_seek,
139 static __cpuinit int cpuid_device_create(int cpu)
143 dev = device_create_drvdata(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu),
145 return IS_ERR(dev) ? PTR_ERR(dev) : 0;
148 static void cpuid_device_destroy(int cpu)
150 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
153 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
154 unsigned long action,
157 unsigned int cpu = (unsigned long)hcpu;
162 err = cpuid_device_create(cpu);
164 case CPU_UP_CANCELED:
165 case CPU_UP_CANCELED_FROZEN:
167 cpuid_device_destroy(cpu);
170 return err ? NOTIFY_BAD : NOTIFY_OK;
173 static struct notifier_block __refdata cpuid_class_cpu_notifier =
175 .notifier_call = cpuid_class_cpu_callback,
178 static int __init cpuid_init(void)
183 if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
184 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
189 cpuid_class = class_create(THIS_MODULE, "cpuid");
190 if (IS_ERR(cpuid_class)) {
191 err = PTR_ERR(cpuid_class);
194 for_each_online_cpu(i) {
195 err = cpuid_device_create(i);
199 register_hotcpu_notifier(&cpuid_class_cpu_notifier);
206 for_each_online_cpu(i) {
207 cpuid_device_destroy(i);
209 class_destroy(cpuid_class);
211 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
216 static void __exit cpuid_exit(void)
220 for_each_online_cpu(cpu)
221 cpuid_device_destroy(cpu);
222 class_destroy(cpuid_class);
223 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
224 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
227 module_init(cpuid_init);
228 module_exit(cpuid_exit);
230 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
231 MODULE_DESCRIPTION("x86 generic CPUID driver");
232 MODULE_LICENSE("GPL");