drivers/watchdog/watchdog_pretimeout.c

   1 /*
   2  * Copyright (C) 2015-2016 Mentor Graphics
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  */
  10
  11 #include <linux/list.h>
  12 #include <linux/slab.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/string.h>
  15 #include <linux/watchdog.h>
  16
  17 #include "watchdog_pretimeout.h"
  18
  19 /* Default watchdog pretimeout governor */
  20 static struct watchdog_governor *default_gov;
  21
  22 /* The spinlock protects default_gov, wdd->gov and pretimeout_list */
  23 static DEFINE_SPINLOCK(pretimeout_lock);
  24
  25 /* List of watchdog devices, which can generate a pretimeout event */
  26 static LIST_HEAD(pretimeout_list);
  27
  28 struct watchdog_pretimeout {
  29         struct watchdog_device          *wdd;
  30         struct list_head                entry;
  31 };
  32
  33 /* The mutex protects governor list and serializes external interfaces */
  34 static DEFINE_MUTEX(governor_lock);
  35
  36 /* List of the registered watchdog pretimeout governors */
  37 static LIST_HEAD(governor_list);
  38
  39 struct governor_priv {
  40         struct watchdog_governor        *gov;
  41         struct list_head                entry;
  42 };
  43
  44 static struct governor_priv *find_governor_by_name(const char *gov_name)
  45 {
  46         struct governor_priv *priv;
  47
  48         list_for_each_entry(priv, &governor_list, entry)
  49                 if (sysfs_streq(gov_name, priv->gov->name))
  50                         return priv;
  51
  52         return NULL;
  53 }
  54
  55 int watchdog_pretimeout_available_governors_get(char *buf)
  56 {
  57         struct governor_priv *priv;
  58         int count = 0;
  59
  60         mutex_lock(&governor_lock);
  61
  62         list_for_each_entry(priv, &governor_list, entry)
  63                 count += sprintf(buf + count, "%s\n", priv->gov->name);
  64
  65         mutex_unlock(&governor_lock);
  66
  67         return count;
  68 }
  69
  70 int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)
  71 {
  72         int count = 0;
  73
  74         spin_lock_irq(&pretimeout_lock);
  75         if (wdd->gov)
  76                 count = sprintf(buf, "%s\n", wdd->gov->name);
  77         spin_unlock_irq(&pretimeout_lock);
  78
  79         return count;
  80 }
  81
  82 int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
  83                                      const char *buf)
  84 {
  85         struct governor_priv *priv;
  86
  87         mutex_lock(&governor_lock);
  88
  89         priv = find_governor_by_name(buf);
  90         if (!priv) {
  91                 mutex_unlock(&governor_lock);
  92                 return -EINVAL;
  93         }
  94
  95         spin_lock_irq(&pretimeout_lock);
  96         wdd->gov = priv->gov;
  97         spin_unlock_irq(&pretimeout_lock);
  98
  99         mutex_unlock(&governor_lock);
 100
 101         return 0;
 102 }
 103
 104 void watchdog_notify_pretimeout(struct watchdog_device *wdd)
 105 {
 106         unsigned long flags;
 107
 108         spin_lock_irqsave(&pretimeout_lock, flags);
 109         if (!wdd->gov) {
 110                 spin_unlock_irqrestore(&pretimeout_lock, flags);
 111                 return;
 112         }
 113
 114         wdd->gov->pretimeout(wdd);
 115         spin_unlock_irqrestore(&pretimeout_lock, flags);
 116 }
 117 EXPORT_SYMBOL_GPL(watchdog_notify_pretimeout);
 118
 119 int watchdog_register_governor(struct watchdog_governor *gov)
 120 {
 121         struct watchdog_pretimeout *p;
 122         struct governor_priv *priv;
 123
 124         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 125         if (!priv)
 126                 return -ENOMEM;
 127
 128         mutex_lock(&governor_lock);
 129
 130         if (find_governor_by_name(gov->name)) {
 131                 mutex_unlock(&governor_lock);
 132                 kfree(priv);
 133                 return -EBUSY;
 134         }
 135
 136         priv->gov = gov;
 137         list_add(&priv->entry, &governor_list);
 138
 139         if (!strncmp(gov->name, WATCHDOG_PRETIMEOUT_DEFAULT_GOV,
 140                      WATCHDOG_GOV_NAME_MAXLEN)) {
 141                 spin_lock_irq(&pretimeout_lock);
 142                 default_gov = gov;
 143
 144                 list_for_each_entry(p, &pretimeout_list, entry)
 145                         if (!p->wdd->gov)
 146                                 p->wdd->gov = default_gov;
 147                 spin_unlock_irq(&pretimeout_lock);
 148         }
 149
 150         mutex_unlock(&governor_lock);
 151
 152         return 0;
 153 }
 154 EXPORT_SYMBOL(watchdog_register_governor);
 155
 156 void watchdog_unregister_governor(struct watchdog_governor *gov)
 157 {
 158         struct watchdog_pretimeout *p;
 159         struct governor_priv *priv, *t;
 160
 161         mutex_lock(&governor_lock);
 162
 163         list_for_each_entry_safe(priv, t, &governor_list, entry) {
 164                 if (priv->gov == gov) {
 165                         list_del(&priv->entry);
 166                         kfree(priv);
 167                         break;
 168                 }
 169         }
 170
 171         spin_lock_irq(&pretimeout_lock);
 172         list_for_each_entry(p, &pretimeout_list, entry)
 173                 if (p->wdd->gov == gov)
 174                         p->wdd->gov = default_gov;
 175         spin_unlock_irq(&pretimeout_lock);
 176
 177         mutex_unlock(&governor_lock);
 178 }
 179 EXPORT_SYMBOL(watchdog_unregister_governor);
 180
 181 int watchdog_register_pretimeout(struct watchdog_device *wdd)
 182 {
 183         struct watchdog_pretimeout *p;
 184
 185         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 186                 return 0;
 187
 188         p = kzalloc(sizeof(*p), GFP_KERNEL);
 189         if (!p)
 190                 return -ENOMEM;
 191
 192         spin_lock_irq(&pretimeout_lock);
 193         list_add(&p->entry, &pretimeout_list);
 194         p->wdd = wdd;
 195         wdd->gov = default_gov;
 196         spin_unlock_irq(&pretimeout_lock);
 197
 198         return 0;
 199 }
 200
 201 void watchdog_unregister_pretimeout(struct watchdog_device *wdd)
 202 {
 203         struct watchdog_pretimeout *p, *t;
 204
 205         if (!(wdd->info->options & WDIOF_PRETIMEOUT))
 206                 return;
 207
 208         spin_lock_irq(&pretimeout_lock);
 209         wdd->gov = NULL;
 210
 211         list_for_each_entry_safe(p, t, &pretimeout_list, entry) {
 212                 if (p->wdd == wdd) {
 213                         list_del(&p->entry);
 214                         break;
 215                 }
 216         }
 217         spin_unlock_irq(&pretimeout_lock);
 218
 219         kfree(p);
 220 }