linux/drivers/watchdog/watchdog_core.c
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   1/*
   2 *      watchdog_core.c
   3 *
   4 *      (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5 *                                              All Rights Reserved.
   6 *
   7 *      (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
   8 *
   9 *      This source code is part of the generic code that can be used
  10 *      by all the watchdog timer drivers.
  11 *
  12 *      Based on source code of the following authors:
  13 *        Matt Domsch <Matt_Domsch@dell.com>,
  14 *        Rob Radez <rob@osinvestor.com>,
  15 *        Rusty Lynch <rusty@linux.co.intel.com>
  16 *        Satyam Sharma <satyam@infradead.org>
  17 *        Randy Dunlap <randy.dunlap@oracle.com>
  18 *
  19 *      This program is free software; you can redistribute it and/or
  20 *      modify it under the terms of the GNU General Public License
  21 *      as published by the Free Software Foundation; either version
  22 *      2 of the License, or (at your option) any later version.
  23 *
  24 *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  25 *      admit liability nor provide warranty for any of this software.
  26 *      This material is provided "AS-IS" and at no charge.
  27 */
  28
  29#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  30
  31#include <linux/module.h>       /* For EXPORT_SYMBOL/module stuff/... */
  32#include <linux/types.h>        /* For standard types */
  33#include <linux/errno.h>        /* For the -ENODEV/... values */
  34#include <linux/kernel.h>       /* For printk/panic/... */
  35#include <linux/watchdog.h>     /* For watchdog specific items */
  36#include <linux/init.h>         /* For __init/__exit/... */
  37#include <linux/idr.h>          /* For ida_* macros */
  38#include <linux/err.h>          /* For IS_ERR macros */
  39
  40#include "watchdog_core.h"      /* For watchdog_dev_register/... */
  41
  42static DEFINE_IDA(watchdog_ida);
  43static struct class *watchdog_class;
  44
  45/**
  46 * watchdog_register_device() - register a watchdog device
  47 * @wdd: watchdog device
  48 *
  49 * Register a watchdog device with the kernel so that the
  50 * watchdog timer can be accessed from userspace.
  51 *
  52 * A zero is returned on success and a negative errno code for
  53 * failure.
  54 */
  55int watchdog_register_device(struct watchdog_device *wdd)
  56{
  57        int ret, id, devno;
  58
  59        if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
  60                return -EINVAL;
  61
  62        /* Mandatory operations need to be supported */
  63        if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
  64                return -EINVAL;
  65
  66        /*
  67         * Check that we have valid min and max timeout values, if
  68         * not reset them both to 0 (=not used or unknown)
  69         */
  70        if (wdd->min_timeout > wdd->max_timeout) {
  71                pr_info("Invalid min and max timeout values, resetting to 0!\n");
  72                wdd->min_timeout = 0;
  73                wdd->max_timeout = 0;
  74        }
  75
  76        /*
  77         * Note: now that all watchdog_device data has been verified, we
  78         * will not check this anymore in other functions. If data gets
  79         * corrupted in a later stage then we expect a kernel panic!
  80         */
  81
  82        mutex_init(&wdd->lock);
  83        id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
  84        if (id < 0)
  85                return id;
  86        wdd->id = id;
  87
  88        ret = watchdog_dev_register(wdd);
  89        if (ret) {
  90                ida_simple_remove(&watchdog_ida, id);
  91                if (!(id == 0 && ret == -EBUSY))
  92                        return ret;
  93
  94                /* Retry in case a legacy watchdog module exists */
  95                id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
  96                if (id < 0)
  97                        return id;
  98                wdd->id = id;
  99
 100                ret = watchdog_dev_register(wdd);
 101                if (ret) {
 102                        ida_simple_remove(&watchdog_ida, id);
 103                        return ret;
 104                }
 105        }
 106
 107        devno = wdd->cdev.dev;
 108        wdd->dev = device_create(watchdog_class, wdd->parent, devno,
 109                                        NULL, "watchdog%d", wdd->id);
 110        if (IS_ERR(wdd->dev)) {
 111                watchdog_dev_unregister(wdd);
 112                ida_simple_remove(&watchdog_ida, id);
 113                ret = PTR_ERR(wdd->dev);
 114                return ret;
 115        }
 116
 117        return 0;
 118}
 119EXPORT_SYMBOL_GPL(watchdog_register_device);
 120
 121/**
 122 * watchdog_unregister_device() - unregister a watchdog device
 123 * @wdd: watchdog device to unregister
 124 *
 125 * Unregister a watchdog device that was previously successfully
 126 * registered with watchdog_register_device().
 127 */
 128void watchdog_unregister_device(struct watchdog_device *wdd)
 129{
 130        int ret;
 131        int devno;
 132
 133        if (wdd == NULL)
 134                return;
 135
 136        devno = wdd->cdev.dev;
 137        ret = watchdog_dev_unregister(wdd);
 138        if (ret)
 139                pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
 140        device_destroy(watchdog_class, devno);
 141        ida_simple_remove(&watchdog_ida, wdd->id);
 142        wdd->dev = NULL;
 143}
 144EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 145
 146static int __init watchdog_init(void)
 147{
 148        int err;
 149
 150        watchdog_class = class_create(THIS_MODULE, "watchdog");
 151        if (IS_ERR(watchdog_class)) {
 152                pr_err("couldn't create class\n");
 153                return PTR_ERR(watchdog_class);
 154        }
 155
 156        err = watchdog_dev_init();
 157        if (err < 0) {
 158                class_destroy(watchdog_class);
 159                return err;
 160        }
 161
 162        return 0;
 163}
 164
 165static void __exit watchdog_exit(void)
 166{
 167        watchdog_dev_exit();
 168        class_destroy(watchdog_class);
 169        ida_destroy(&watchdog_ida);
 170}
 171
 172subsys_initcall(watchdog_init);
 173module_exit(watchdog_exit);
 174
 175MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 176MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 177MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 178MODULE_LICENSE("GPL");
 179
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