xref: /openbmc/linux/drivers/hwmon/hwmon.c (revision a1e58bbd)
1 /*
2     hwmon.c - part of lm_sensors, Linux kernel modules for hardware monitoring
3 
4     This file defines the sysfs class "hwmon", for use by sensors drivers.
5 
6     Copyright (C) 2005 Mark M. Hoffman <mhoffman@lightlink.com>
7 
8     This program is free software; you can redistribute it and/or modify
9     it under the terms of the GNU General Public License as published by
10     the Free Software Foundation; version 2 of the License.
11 */
12 
13 #include <linux/module.h>
14 #include <linux/device.h>
15 #include <linux/err.h>
16 #include <linux/kdev_t.h>
17 #include <linux/idr.h>
18 #include <linux/hwmon.h>
19 #include <linux/gfp.h>
20 #include <linux/spinlock.h>
21 
22 #define HWMON_ID_PREFIX "hwmon"
23 #define HWMON_ID_FORMAT HWMON_ID_PREFIX "%d"
24 
25 static struct class *hwmon_class;
26 
27 static DEFINE_IDR(hwmon_idr);
28 static DEFINE_SPINLOCK(idr_lock);
29 
30 /**
31  * hwmon_device_register - register w/ hwmon
32  * @dev: the device to register
33  *
34  * hwmon_device_unregister() must be called when the device is no
35  * longer needed.
36  *
37  * Returns the pointer to the new device.
38  */
39 struct device *hwmon_device_register(struct device *dev)
40 {
41 	struct device *hwdev;
42 	int id, err;
43 
44 again:
45 	if (unlikely(idr_pre_get(&hwmon_idr, GFP_KERNEL) == 0))
46 		return ERR_PTR(-ENOMEM);
47 
48 	spin_lock(&idr_lock);
49 	err = idr_get_new(&hwmon_idr, NULL, &id);
50 	spin_unlock(&idr_lock);
51 
52 	if (unlikely(err == -EAGAIN))
53 		goto again;
54 	else if (unlikely(err))
55 		return ERR_PTR(err);
56 
57 	id = id & MAX_ID_MASK;
58 	hwdev = device_create(hwmon_class, dev, MKDEV(0,0), HWMON_ID_FORMAT, id);
59 
60 	if (IS_ERR(hwdev)) {
61 		spin_lock(&idr_lock);
62 		idr_remove(&hwmon_idr, id);
63 		spin_unlock(&idr_lock);
64 	}
65 
66 	return hwdev;
67 }
68 
69 /**
70  * hwmon_device_unregister - removes the previously registered class device
71  *
72  * @dev: the class device to destroy
73  */
74 void hwmon_device_unregister(struct device *dev)
75 {
76 	int id;
77 
78 	if (likely(sscanf(dev->bus_id, HWMON_ID_FORMAT, &id) == 1)) {
79 		device_unregister(dev);
80 		spin_lock(&idr_lock);
81 		idr_remove(&hwmon_idr, id);
82 		spin_unlock(&idr_lock);
83 	} else
84 		dev_dbg(dev->parent,
85 			"hwmon_device_unregister() failed: bad class ID!\n");
86 }
87 
88 static int __init hwmon_init(void)
89 {
90 	hwmon_class = class_create(THIS_MODULE, "hwmon");
91 	if (IS_ERR(hwmon_class)) {
92 		printk(KERN_ERR "hwmon.c: couldn't create sysfs class\n");
93 		return PTR_ERR(hwmon_class);
94 	}
95 	return 0;
96 }
97 
98 static void __exit hwmon_exit(void)
99 {
100 	class_destroy(hwmon_class);
101 }
102 
103 subsys_initcall(hwmon_init);
104 module_exit(hwmon_exit);
105 
106 EXPORT_SYMBOL_GPL(hwmon_device_register);
107 EXPORT_SYMBOL_GPL(hwmon_device_unregister);
108 
109 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
110 MODULE_DESCRIPTION("hardware monitoring sysfs/class support");
111 MODULE_LICENSE("GPL");
112 
113