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/device.h>
39 #include <linux/cpu.h>
40 #include <linux/notifier.h>
41 #include <linux/uaccess.h>
42 #include <linux/gfp.h>
43 #include <linux/slab.h>
45 #include <asm/processor.h>
47 #include <asm/system.h>
49 static struct class *cpuid_class;
52 u32 eax, ebx, ecx, edx;
55 static void cpuid_smp_cpuid(void *cmd_block)
57 struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
59 cpuid_count(cmd->eax, cmd->ecx,
60 &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
63 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
66 struct inode *inode = file->f_mapping->host;
68 mutex_lock(&inode->i_mutex);
75 file->f_pos += offset;
81 mutex_unlock(&inode->i_mutex);
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);
96 return -EINVAL; /* Invalid chunk size */
98 for (; count; count -= 16) {
101 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
104 if (copy_to_user(tmp, &cmd, 16)) {
113 return bytes ? bytes : err;
116 static int cpuid_open(struct inode *inode, struct file *file)
119 struct cpuinfo_x86 *c;
121 cpu = iminor(file->f_path.dentry->d_inode);
122 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
123 return -ENXIO; /* No such CPU */
126 if (c->cpuid_level < 0)
127 return -EIO; /* CPUID not supported */
133 * File operations we support
135 static const struct file_operations cpuid_fops = {
136 .owner = THIS_MODULE,
137 .llseek = cpuid_seek,
142 static ssize_t print_cpu_modalias(struct device *dev,
143 struct device_attribute *attr,
146 int size = PAGE_SIZE;
150 n = snprintf(buf, size, "x86cpu:vendor:%04X:family:"
151 "%04X:model:%04X:feature:",
152 boot_cpu_data.x86_vendor,
154 boot_cpu_data.x86_model);
158 for (i = 0; i < NCAPINTS*32; i++) {
159 if (boot_cpu_has(i)) {
160 n = snprintf(buf, size, ",%04X", i);
162 WARN(1, "x86 features overflow page\n");
174 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
176 static __cpuinit int cpuid_device_create(int cpu)
181 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
186 err = device_create_file(dev, &dev_attr_modalias);
188 /* keep device around on error. attribute is optional. */
195 static void cpuid_device_destroy(int cpu)
197 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
200 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
201 unsigned long action,
204 unsigned int cpu = (unsigned long)hcpu;
209 err = cpuid_device_create(cpu);
211 case CPU_UP_CANCELED:
212 case CPU_UP_CANCELED_FROZEN:
214 cpuid_device_destroy(cpu);
217 return notifier_from_errno(err);
220 static struct notifier_block __refdata cpuid_class_cpu_notifier =
222 .notifier_call = cpuid_class_cpu_callback,
225 static char *cpuid_devnode(struct device *dev, umode_t *mode)
227 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
230 static int cpuid_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
232 char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
234 print_cpu_modalias(NULL, NULL, buf);
235 add_uevent_var(env, "MODALIAS=%s", buf);
241 static int __init cpuid_init(void)
246 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
247 "cpu/cpuid", &cpuid_fops)) {
248 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
253 cpuid_class = class_create(THIS_MODULE, "cpuid");
254 if (IS_ERR(cpuid_class)) {
255 err = PTR_ERR(cpuid_class);
258 cpuid_class->devnode = cpuid_devnode;
259 cpuid_class->dev_uevent = cpuid_dev_uevent;
260 for_each_online_cpu(i) {
261 err = cpuid_device_create(i);
265 register_hotcpu_notifier(&cpuid_class_cpu_notifier);
272 for_each_online_cpu(i) {
273 cpuid_device_destroy(i);
275 class_destroy(cpuid_class);
277 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
282 static void __exit cpuid_exit(void)
286 for_each_online_cpu(cpu)
287 cpuid_device_destroy(cpu);
288 class_destroy(cpuid_class);
289 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
290 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
293 module_init(cpuid_init);
294 module_exit(cpuid_exit);
296 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
297 MODULE_DESCRIPTION("x86 generic CPUID driver");
298 MODULE_LICENSE("GPL");