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>
44 #include <asm/processor.h>
47 static struct class *cpuid_class
;
50 u32 eax
, ebx
, ecx
, edx
;
53 static void cpuid_smp_cpuid(void *cmd_block
)
55 struct cpuid_regs
*cmd
= (struct cpuid_regs
*)cmd_block
;
57 cpuid_count(cmd
->eax
, cmd
->ecx
,
58 &cmd
->eax
, &cmd
->ebx
, &cmd
->ecx
, &cmd
->edx
);
61 static loff_t
cpuid_seek(struct file
*file
, loff_t offset
, int orig
)
64 struct inode
*inode
= file
->f_mapping
->host
;
66 mutex_lock(&inode
->i_mutex
);
73 file
->f_pos
+= offset
;
79 mutex_unlock(&inode
->i_mutex
);
83 static ssize_t
cpuid_read(struct file
*file
, char __user
*buf
,
84 size_t count
, loff_t
*ppos
)
86 char __user
*tmp
= buf
;
87 struct cpuid_regs cmd
;
88 int cpu
= iminor(file
->f_path
.dentry
->d_inode
);
94 return -EINVAL
; /* Invalid chunk size */
96 for (; count
; count
-= 16) {
99 err
= smp_call_function_single(cpu
, cpuid_smp_cpuid
, &cmd
, 1);
102 if (copy_to_user(tmp
, &cmd
, 16)) {
111 return bytes
? bytes
: err
;
114 static int cpuid_open(struct inode
*inode
, struct file
*file
)
117 struct cpuinfo_x86
*c
;
119 cpu
= iminor(file
->f_path
.dentry
->d_inode
);
120 if (cpu
>= nr_cpu_ids
|| !cpu_online(cpu
))
121 return -ENXIO
; /* No such CPU */
124 if (c
->cpuid_level
< 0)
125 return -EIO
; /* CPUID not supported */
131 * File operations we support
133 static const struct file_operations cpuid_fops
= {
134 .owner
= THIS_MODULE
,
135 .llseek
= cpuid_seek
,
140 static __cpuinit
int cpuid_device_create(int cpu
)
144 dev
= device_create(cpuid_class
, NULL
, MKDEV(CPUID_MAJOR
, cpu
), NULL
,
146 return IS_ERR(dev
) ? PTR_ERR(dev
) : 0;
149 static void cpuid_device_destroy(int cpu
)
151 device_destroy(cpuid_class
, MKDEV(CPUID_MAJOR
, cpu
));
154 static int __cpuinit
cpuid_class_cpu_callback(struct notifier_block
*nfb
,
155 unsigned long action
,
158 unsigned int cpu
= (unsigned long)hcpu
;
163 err
= cpuid_device_create(cpu
);
165 case CPU_UP_CANCELED
:
166 case CPU_UP_CANCELED_FROZEN
:
168 cpuid_device_destroy(cpu
);
171 return notifier_from_errno(err
);
174 static struct notifier_block __refdata cpuid_class_cpu_notifier
=
176 .notifier_call
= cpuid_class_cpu_callback
,
179 static char *cpuid_devnode(struct device
*dev
, umode_t
*mode
)
181 return kasprintf(GFP_KERNEL
, "cpu/%u/cpuid", MINOR(dev
->devt
));
184 static int __init
cpuid_init(void)
189 if (__register_chrdev(CPUID_MAJOR
, 0, NR_CPUS
,
190 "cpu/cpuid", &cpuid_fops
)) {
191 printk(KERN_ERR
"cpuid: unable to get major %d for cpuid\n",
196 cpuid_class
= class_create(THIS_MODULE
, "cpuid");
197 if (IS_ERR(cpuid_class
)) {
198 err
= PTR_ERR(cpuid_class
);
201 cpuid_class
->devnode
= cpuid_devnode
;
202 for_each_online_cpu(i
) {
203 err
= cpuid_device_create(i
);
207 register_hotcpu_notifier(&cpuid_class_cpu_notifier
);
214 for_each_online_cpu(i
) {
215 cpuid_device_destroy(i
);
217 class_destroy(cpuid_class
);
219 __unregister_chrdev(CPUID_MAJOR
, 0, NR_CPUS
, "cpu/cpuid");
224 static void __exit
cpuid_exit(void)
228 for_each_online_cpu(cpu
)
229 cpuid_device_destroy(cpu
);
230 class_destroy(cpuid_class
);
231 __unregister_chrdev(CPUID_MAJOR
, 0, NR_CPUS
, "cpu/cpuid");
232 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier
);
235 module_init(cpuid_init
);
236 module_exit(cpuid_exit
);
238 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
239 MODULE_DESCRIPTION("x86 generic CPUID driver");
240 MODULE_LICENSE("GPL");