drivers/hwmon/hwmon.c

   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 sysfs class
  32  * @dev: the device to register
  33  *
  34  * hwmon_device_unregister() must be called when the class device is no
  35  * longer needed.
  36  *
  37  * Returns the pointer to the new struct class device.
  38  */
  39 struct class_device *hwmon_device_register(struct device *dev)
  40 {
  41         struct class_device *cdev;
  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         cdev = class_device_create(hwmon_class, NULL, MKDEV(0,0), dev,
  59                                         HWMON_ID_FORMAT, id);
  60
  61         if (IS_ERR(cdev)) {
  62                 spin_lock(&idr_lock);
  63                 idr_remove(&hwmon_idr, id);
  64                 spin_unlock(&idr_lock);
  65         }
  66
  67         return cdev;
  68 }
  69
  70 /**
  71  * hwmon_device_unregister - removes the previously registered class device
  72  *
  73  * @cdev: the class device to destroy
  74  */
  75 void hwmon_device_unregister(struct class_device *cdev)
  76 {
  77         int id;
  78
  79         if (likely(sscanf(cdev->class_id, HWMON_ID_FORMAT, &id) == 1)) {
  80                 class_device_unregister(cdev);
  81                 spin_lock(&idr_lock);
  82                 idr_remove(&hwmon_idr, id);
  83                 spin_unlock(&idr_lock);
  84         } else
  85                 dev_dbg(cdev->dev,
  86                         "hwmon_device_unregister() failed: bad class ID!\n");
  87 }
  88
  89 static int __init hwmon_init(void)
  90 {
  91         hwmon_class = class_create(THIS_MODULE, "hwmon");
  92         if (IS_ERR(hwmon_class)) {
  93                 printk(KERN_ERR "hwmon.c: couldn't create sysfs class\n");
  94                 return PTR_ERR(hwmon_class);
  95         }
  96         return 0;
  97 }
  98
  99 static void __exit hwmon_exit(void)
 100 {
 101         class_destroy(hwmon_class);
 102 }
 103
 104 module_init(hwmon_init);
 105 module_exit(hwmon_exit);
 106
 107 EXPORT_SYMBOL_GPL(hwmon_device_register);
 108 EXPORT_SYMBOL_GPL(hwmon_device_unregister);
 109
 110 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
 111 MODULE_DESCRIPTION("hardware monitoring sysfs/class support");
 112 MODULE_LICENSE("GPL");
 113