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
;
49 static void cpuid_smp_cpuid(void *cmd_block
)
51 struct cpuid_regs
*cmd
= (struct cpuid_regs
*)cmd_block
;
53 cpuid_count(cmd
->eax
, cmd
->ecx
,
54 &cmd
->eax
, &cmd
->ebx
, &cmd
->ecx
, &cmd
->edx
);
57 static ssize_t
cpuid_read(struct file
*file
, char __user
*buf
,
58 size_t count
, loff_t
*ppos
)
60 char __user
*tmp
= buf
;
61 struct cpuid_regs cmd
;
62 int cpu
= iminor(file_inode(file
));
68 return -EINVAL
; /* Invalid chunk size */
70 for (; count
; count
-= 16) {
73 err
= smp_call_function_single(cpu
, cpuid_smp_cpuid
, &cmd
, 1);
76 if (copy_to_user(tmp
, &cmd
, 16)) {
85 return bytes
? bytes
: err
;
88 static int cpuid_open(struct inode
*inode
, struct file
*file
)
91 struct cpuinfo_x86
*c
;
93 cpu
= iminor(file_inode(file
));
94 if (cpu
>= nr_cpu_ids
|| !cpu_online(cpu
))
95 return -ENXIO
; /* No such CPU */
98 if (c
->cpuid_level
< 0)
99 return -EIO
; /* CPUID not supported */
105 * File operations we support
107 static const struct file_operations cpuid_fops
= {
108 .owner
= THIS_MODULE
,
109 .llseek
= no_seek_end_llseek
,
114 static int cpuid_device_create(int cpu
)
118 dev
= device_create(cpuid_class
, NULL
, MKDEV(CPUID_MAJOR
, cpu
), NULL
,
120 return PTR_ERR_OR_ZERO(dev
);
123 static void cpuid_device_destroy(int cpu
)
125 device_destroy(cpuid_class
, MKDEV(CPUID_MAJOR
, cpu
));
128 static int cpuid_class_cpu_callback(struct notifier_block
*nfb
,
129 unsigned long action
, void *hcpu
)
131 unsigned int cpu
= (unsigned long)hcpu
;
136 err
= cpuid_device_create(cpu
);
138 case CPU_UP_CANCELED
:
139 case CPU_UP_CANCELED_FROZEN
:
141 cpuid_device_destroy(cpu
);
144 return notifier_from_errno(err
);
147 static struct notifier_block cpuid_class_cpu_notifier
=
149 .notifier_call
= cpuid_class_cpu_callback
,
152 static char *cpuid_devnode(struct device
*dev
, umode_t
*mode
)
154 return kasprintf(GFP_KERNEL
, "cpu/%u/cpuid", MINOR(dev
->devt
));
157 static int __init
cpuid_init(void)
162 if (__register_chrdev(CPUID_MAJOR
, 0, NR_CPUS
,
163 "cpu/cpuid", &cpuid_fops
)) {
164 printk(KERN_ERR
"cpuid: unable to get major %d for cpuid\n",
169 cpuid_class
= class_create(THIS_MODULE
, "cpuid");
170 if (IS_ERR(cpuid_class
)) {
171 err
= PTR_ERR(cpuid_class
);
174 cpuid_class
->devnode
= cpuid_devnode
;
176 cpu_notifier_register_begin();
177 for_each_online_cpu(i
) {
178 err
= cpuid_device_create(i
);
182 __register_hotcpu_notifier(&cpuid_class_cpu_notifier
);
183 cpu_notifier_register_done();
190 for_each_online_cpu(i
) {
191 cpuid_device_destroy(i
);
193 cpu_notifier_register_done();
194 class_destroy(cpuid_class
);
196 __unregister_chrdev(CPUID_MAJOR
, 0, NR_CPUS
, "cpu/cpuid");
201 static void __exit
cpuid_exit(void)
205 cpu_notifier_register_begin();
206 for_each_online_cpu(cpu
)
207 cpuid_device_destroy(cpu
);
208 class_destroy(cpuid_class
);
209 __unregister_chrdev(CPUID_MAJOR
, 0, NR_CPUS
, "cpu/cpuid");
210 __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier
);
211 cpu_notifier_register_done();
214 module_init(cpuid_init
);
215 module_exit(cpuid_exit
);
217 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
218 MODULE_DESCRIPTION("x86 generic CPUID driver");
219 MODULE_LICENSE("GPL");