arch/um/drivers/harddog_kern.c

   1 /* UML hardware watchdog, shamelessly stolen from:
   2  *
   3  *      SoftDog 0.05:   A Software Watchdog Device
   4  *
   5  *      (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
   6  *                              http://www.redhat.com
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  *
  13  *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
  14  *      warranty for any of this software. This material is provided
  15  *      "AS-IS" and at no charge.
  16  *
  17  *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
  18  *
  19  *      Software only watchdog driver. Unlike its big brother the WDT501P
  20  *      driver this won't always recover a failed machine.
  21  *
  22  *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
  23  *      Modularised.
  24  *      Added soft_margin; use upon insmod to change the timer delay.
  25  *      NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
  26  *          minors.
  27  *
  28  *  19980911 Alan Cox
  29  *      Made SMP safe for 2.3.x
  30  *
  31  *  20011127 Joel Becker (jlbec@evilplan.org>
  32  *      Added soft_noboot; Allows testing the softdog trigger without
  33  *      requiring a recompile.
  34  *      Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
  35  */
  36
  37 #include <linux/module.h>
  38 #include <linux/config.h>
  39 #include <linux/types.h>
  40 #include <linux/kernel.h>
  41 #include <linux/fs.h>
  42 #include <linux/mm.h>
  43 #include <linux/miscdevice.h>
  44 #include <linux/watchdog.h>
  45 #include <linux/reboot.h>
  46 #include <linux/smp_lock.h>
  47 #include <linux/init.h>
  48 #include <asm/uaccess.h>
  49 #include "helper.h"
  50 #include "mconsole.h"
  51
  52 MODULE_LICENSE("GPL");
  53
  54 /* Locked by the BKL in harddog_open and harddog_release */
  55 static int timer_alive;
  56 static int harddog_in_fd = -1;
  57 static int harddog_out_fd = -1;
  58
  59 /*
  60  *      Allow only one person to hold it open
  61  */
  62
  63 extern int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
  64
  65 static int harddog_open(struct inode *inode, struct file *file)
  66 {
  67         int err;
  68         char *sock = NULL;
  69
  70         lock_kernel();
  71         if(timer_alive)
  72                 return -EBUSY;
  73 #ifdef CONFIG_HARDDOG_NOWAYOUT
  74         __module_get(THIS_MODULE);
  75 #endif
  76
  77 #ifdef CONFIG_MCONSOLE
  78         sock = mconsole_notify_socket();
  79 #endif
  80         err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
  81         if(err) return(err);
  82
  83         timer_alive = 1;
  84         unlock_kernel();
  85         return nonseekable_open(inode, file);
  86 }
  87
  88 extern void stop_watchdog(int in_fd, int out_fd);
  89
  90 static int harddog_release(struct inode *inode, struct file *file)
  91 {
  92         /*
  93          *      Shut off the timer.
  94          */
  95         lock_kernel();
  96
  97         stop_watchdog(harddog_in_fd, harddog_out_fd);
  98         harddog_in_fd = -1;
  99         harddog_out_fd = -1;
 100
 101         timer_alive=0;
 102         unlock_kernel();
 103         return 0;
 104 }
 105
 106 extern int ping_watchdog(int fd);
 107
 108 static ssize_t harddog_write(struct file *file, const char *data, size_t len,
 109                              loff_t *ppos)
 110 {
 111         /*
 112          *      Refresh the timer.
 113          */
 114         if(len)
 115                 return(ping_watchdog(harddog_out_fd));
 116         return 0;
 117 }
 118
 119 static int harddog_ioctl(struct inode *inode, struct file *file,
 120                          unsigned int cmd, unsigned long arg)
 121 {
 122         static struct watchdog_info ident = {
 123                 WDIOC_SETTIMEOUT,
 124                 0,
 125                 "UML Hardware Watchdog"
 126         };
 127         switch (cmd) {
 128                 default:
 129                         return -ENOTTY;
 130                 case WDIOC_GETSUPPORT:
 131                         if(copy_to_user((struct harddog_info *)arg, &ident,
 132                                         sizeof(ident)))
 133                                 return -EFAULT;
 134                         return 0;
 135                 case WDIOC_GETSTATUS:
 136                 case WDIOC_GETBOOTSTATUS:
 137                         return put_user(0,(int *)arg);
 138                 case WDIOC_KEEPALIVE:
 139                         return(ping_watchdog(harddog_out_fd));
 140         }
 141 }
 142
 143 static struct file_operations harddog_fops = {
 144         .owner          = THIS_MODULE,
 145         .write          = harddog_write,
 146         .ioctl          = harddog_ioctl,
 147         .open           = harddog_open,
 148         .release        = harddog_release,
 149 };
 150
 151 static struct miscdevice harddog_miscdev = {
 152         .minor          = WATCHDOG_MINOR,
 153         .name           = "watchdog",
 154         .fops           = &harddog_fops,
 155 };
 156
 157 static char banner[] __initdata = KERN_INFO "UML Watchdog Timer\n";
 158
 159 static int __init harddog_init(void)
 160 {
 161         int ret;
 162
 163         ret = misc_register(&harddog_miscdev);
 164
 165         if (ret)
 166                 return ret;
 167
 168         printk(banner);
 169
 170         return(0);
 171 }
 172
 173 static void __exit harddog_exit(void)
 174 {
 175         misc_deregister(&harddog_miscdev);
 176 }
 177
 178 module_init(harddog_init);
 179 module_exit(harddog_exit);
 180
 181 /*
 182  * Overrides for Emacs so that we follow Linus's tabbing style.
 183  * Emacs will notice this stuff at the end of the file and automatically
 184  * adjust the settings for this buffer only.  This must remain at the end
 185  * of the file.
 186  * ---------------------------------------------------------------------------
 187  * Local variables:
 188  * c-file-style: "linux"
 189  * End:
 190  */