linux/drivers/watchdog/watchdog_dev.c
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   1/*
   2 *      watchdog_dev.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 *
  10 *      This source code is part of the generic code that can be used
  11 *      by all the watchdog timer drivers.
  12 *
  13 *      This part of the generic code takes care of the following
  14 *      misc device: /dev/watchdog.
  15 *
  16 *      Based on source code of the following authors:
  17 *        Matt Domsch <Matt_Domsch@dell.com>,
  18 *        Rob Radez <rob@osinvestor.com>,
  19 *        Rusty Lynch <rusty@linux.co.intel.com>
  20 *        Satyam Sharma <satyam@infradead.org>
  21 *        Randy Dunlap <randy.dunlap@oracle.com>
  22 *
  23 *      This program is free software; you can redistribute it and/or
  24 *      modify it under the terms of the GNU General Public License
  25 *      as published by the Free Software Foundation; either version
  26 *      2 of the License, or (at your option) any later version.
  27 *
  28 *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  29 *      admit liability nor provide warranty for any of this software.
  30 *      This material is provided "AS-IS" and at no charge.
  31 */
  32
  33#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  34
  35#include <linux/module.h>       /* For module stuff/... */
  36#include <linux/types.h>        /* For standard types (like size_t) */
  37#include <linux/errno.h>        /* For the -ENODEV/... values */
  38#include <linux/kernel.h>       /* For printk/panic/... */
  39#include <linux/fs.h>           /* For file operations */
  40#include <linux/watchdog.h>     /* For watchdog specific items */
  41#include <linux/miscdevice.h>   /* For handling misc devices */
  42#include <linux/init.h>         /* For __init/__exit/... */
  43#include <linux/uaccess.h>      /* For copy_to_user/put_user/... */
  44
  45#include "watchdog_core.h"
  46
  47/* the dev_t structure to store the dynamically allocated watchdog devices */
  48static dev_t watchdog_devt;
  49/* the watchdog device behind /dev/watchdog */
  50static struct watchdog_device *old_wdd;
  51
  52/*
  53 *      watchdog_ping: ping the watchdog.
  54 *      @wddev: the watchdog device to ping
  55 *
  56 *      If the watchdog has no own ping operation then it needs to be
  57 *      restarted via the start operation. This wrapper function does
  58 *      exactly that.
  59 *      We only ping when the watchdog device is running.
  60 */
  61
  62static int watchdog_ping(struct watchdog_device *wddev)
  63{
  64        int err = 0;
  65
  66        mutex_lock(&wddev->lock);
  67
  68        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
  69                err = -ENODEV;
  70                goto out_ping;
  71        }
  72
  73        if (!watchdog_active(wddev))
  74                goto out_ping;
  75
  76        if (wddev->ops->ping)
  77                err = wddev->ops->ping(wddev);  /* ping the watchdog */
  78        else
  79                err = wddev->ops->start(wddev); /* restart watchdog */
  80
  81out_ping:
  82        mutex_unlock(&wddev->lock);
  83        return err;
  84}
  85
  86/*
  87 *      watchdog_start: wrapper to start the watchdog.
  88 *      @wddev: the watchdog device to start
  89 *
  90 *      Start the watchdog if it is not active and mark it active.
  91 *      This function returns zero on success or a negative errno code for
  92 *      failure.
  93 */
  94
  95static int watchdog_start(struct watchdog_device *wddev)
  96{
  97        int err = 0;
  98
  99        mutex_lock(&wddev->lock);
 100
 101        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 102                err = -ENODEV;
 103                goto out_start;
 104        }
 105
 106        if (watchdog_active(wddev))
 107                goto out_start;
 108
 109        err = wddev->ops->start(wddev);
 110        if (err == 0)
 111                set_bit(WDOG_ACTIVE, &wddev->status);
 112
 113out_start:
 114        mutex_unlock(&wddev->lock);
 115        return err;
 116}
 117
 118/*
 119 *      watchdog_stop: wrapper to stop the watchdog.
 120 *      @wddev: the watchdog device to stop
 121 *
 122 *      Stop the watchdog if it is still active and unmark it active.
 123 *      This function returns zero on success or a negative errno code for
 124 *      failure.
 125 *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 126 */
 127
 128static int watchdog_stop(struct watchdog_device *wddev)
 129{
 130        int err = 0;
 131
 132        mutex_lock(&wddev->lock);
 133
 134        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 135                err = -ENODEV;
 136                goto out_stop;
 137        }
 138
 139        if (!watchdog_active(wddev))
 140                goto out_stop;
 141
 142        if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
 143                dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n");
 144                err = -EBUSY;
 145                goto out_stop;
 146        }
 147
 148        err = wddev->ops->stop(wddev);
 149        if (err == 0)
 150                clear_bit(WDOG_ACTIVE, &wddev->status);
 151
 152out_stop:
 153        mutex_unlock(&wddev->lock);
 154        return err;
 155}
 156
 157/*
 158 *      watchdog_get_status: wrapper to get the watchdog status
 159 *      @wddev: the watchdog device to get the status from
 160 *      @status: the status of the watchdog device
 161 *
 162 *      Get the watchdog's status flags.
 163 */
 164
 165static int watchdog_get_status(struct watchdog_device *wddev,
 166                                                        unsigned int *status)
 167{
 168        int err = 0;
 169
 170        *status = 0;
 171        if (!wddev->ops->status)
 172                return -EOPNOTSUPP;
 173
 174        mutex_lock(&wddev->lock);
 175
 176        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 177                err = -ENODEV;
 178                goto out_status;
 179        }
 180
 181        *status = wddev->ops->status(wddev);
 182
 183out_status:
 184        mutex_unlock(&wddev->lock);
 185        return err;
 186}
 187
 188/*
 189 *      watchdog_set_timeout: set the watchdog timer timeout
 190 *      @wddev: the watchdog device to set the timeout for
 191 *      @timeout: timeout to set in seconds
 192 */
 193
 194static int watchdog_set_timeout(struct watchdog_device *wddev,
 195                                                        unsigned int timeout)
 196{
 197        int err;
 198
 199        if ((wddev->ops->set_timeout == NULL) ||
 200            !(wddev->info->options & WDIOF_SETTIMEOUT))
 201                return -EOPNOTSUPP;
 202
 203        if ((wddev->max_timeout != 0) &&
 204            (timeout < wddev->min_timeout || timeout > wddev->max_timeout))
 205                return -EINVAL;
 206
 207        mutex_lock(&wddev->lock);
 208
 209        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 210                err = -ENODEV;
 211                goto out_timeout;
 212        }
 213
 214        err = wddev->ops->set_timeout(wddev, timeout);
 215
 216out_timeout:
 217        mutex_unlock(&wddev->lock);
 218        return err;
 219}
 220
 221/*
 222 *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 223 *      @wddev: the watchdog device to get the remaining time from
 224 *      @timeleft: the time that's left
 225 *
 226 *      Get the time before a watchdog will reboot (if not pinged).
 227 */
 228
 229static int watchdog_get_timeleft(struct watchdog_device *wddev,
 230                                                        unsigned int *timeleft)
 231{
 232        int err = 0;
 233
 234        *timeleft = 0;
 235        if (!wddev->ops->get_timeleft)
 236                return -EOPNOTSUPP;
 237
 238        mutex_lock(&wddev->lock);
 239
 240        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 241                err = -ENODEV;
 242                goto out_timeleft;
 243        }
 244
 245        *timeleft = wddev->ops->get_timeleft(wddev);
 246
 247out_timeleft:
 248        mutex_unlock(&wddev->lock);
 249        return err;
 250}
 251
 252/*
 253 *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 254 *      @wddev: the watchdog device to do the ioctl on
 255 *      @cmd: watchdog command
 256 *      @arg: argument pointer
 257 */
 258
 259static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd,
 260                                                        unsigned long arg)
 261{
 262        int err;
 263
 264        if (!wddev->ops->ioctl)
 265                return -ENOIOCTLCMD;
 266
 267        mutex_lock(&wddev->lock);
 268
 269        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 270                err = -ENODEV;
 271                goto out_ioctl;
 272        }
 273
 274        err = wddev->ops->ioctl(wddev, cmd, arg);
 275
 276out_ioctl:
 277        mutex_unlock(&wddev->lock);
 278        return err;
 279}
 280
 281/*
 282 *      watchdog_write: writes to the watchdog.
 283 *      @file: file from VFS
 284 *      @data: user address of data
 285 *      @len: length of data
 286 *      @ppos: pointer to the file offset
 287 *
 288 *      A write to a watchdog device is defined as a keepalive ping.
 289 *      Writing the magic 'V' sequence allows the next close to turn
 290 *      off the watchdog (if 'nowayout' is not set).
 291 */
 292
 293static ssize_t watchdog_write(struct file *file, const char __user *data,
 294                                                size_t len, loff_t *ppos)
 295{
 296        struct watchdog_device *wdd = file->private_data;
 297        size_t i;
 298        char c;
 299
 300        if (len == 0)
 301                return 0;
 302
 303        /*
 304         * Note: just in case someone wrote the magic character
 305         * five months ago...
 306         */
 307        clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 308
 309        /* scan to see whether or not we got the magic character */
 310        for (i = 0; i != len; i++) {
 311                if (get_user(c, data + i))
 312                        return -EFAULT;
 313                if (c == 'V')
 314                        set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 315        }
 316
 317        /* someone wrote to us, so we send the watchdog a keepalive ping */
 318        watchdog_ping(wdd);
 319
 320        return len;
 321}
 322
 323/*
 324 *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 325 *      @file: file handle to the device
 326 *      @cmd: watchdog command
 327 *      @arg: argument pointer
 328 *
 329 *      The watchdog API defines a common set of functions for all watchdogs
 330 *      according to their available features.
 331 */
 332
 333static long watchdog_ioctl(struct file *file, unsigned int cmd,
 334                                                        unsigned long arg)
 335{
 336        struct watchdog_device *wdd = file->private_data;
 337        void __user *argp = (void __user *)arg;
 338        int __user *p = argp;
 339        unsigned int val;
 340        int err;
 341
 342        err = watchdog_ioctl_op(wdd, cmd, arg);
 343        if (err != -ENOIOCTLCMD)
 344                return err;
 345
 346        switch (cmd) {
 347        case WDIOC_GETSUPPORT:
 348                return copy_to_user(argp, wdd->info,
 349                        sizeof(struct watchdog_info)) ? -EFAULT : 0;
 350        case WDIOC_GETSTATUS:
 351                err = watchdog_get_status(wdd, &val);
 352                if (err == -ENODEV)
 353                        return err;
 354                return put_user(val, p);
 355        case WDIOC_GETBOOTSTATUS:
 356                return put_user(wdd->bootstatus, p);
 357        case WDIOC_SETOPTIONS:
 358                if (get_user(val, p))
 359                        return -EFAULT;
 360                if (val & WDIOS_DISABLECARD) {
 361                        err = watchdog_stop(wdd);
 362                        if (err < 0)
 363                                return err;
 364                }
 365                if (val & WDIOS_ENABLECARD) {
 366                        err = watchdog_start(wdd);
 367                        if (err < 0)
 368                                return err;
 369                }
 370                return 0;
 371        case WDIOC_KEEPALIVE:
 372                if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
 373                        return -EOPNOTSUPP;
 374                watchdog_ping(wdd);
 375                return 0;
 376        case WDIOC_SETTIMEOUT:
 377                if (get_user(val, p))
 378                        return -EFAULT;
 379                err = watchdog_set_timeout(wdd, val);
 380                if (err < 0)
 381                        return err;
 382                /* If the watchdog is active then we send a keepalive ping
 383                 * to make sure that the watchdog keep's running (and if
 384                 * possible that it takes the new timeout) */
 385                watchdog_ping(wdd);
 386                /* Fall */
 387        case WDIOC_GETTIMEOUT:
 388                /* timeout == 0 means that we don't know the timeout */
 389                if (wdd->timeout == 0)
 390                        return -EOPNOTSUPP;
 391                return put_user(wdd->timeout, p);
 392        case WDIOC_GETTIMELEFT:
 393                err = watchdog_get_timeleft(wdd, &val);
 394                if (err)
 395                        return err;
 396                return put_user(val, p);
 397        default:
 398                return -ENOTTY;
 399        }
 400}
 401
 402/*
 403 *      watchdog_open: open the /dev/watchdog* devices.
 404 *      @inode: inode of device
 405 *      @file: file handle to device
 406 *
 407 *      When the /dev/watchdog* device gets opened, we start the watchdog.
 408 *      Watch out: the /dev/watchdog device is single open, so we make sure
 409 *      it can only be opened once.
 410 */
 411
 412static int watchdog_open(struct inode *inode, struct file *file)
 413{
 414        int err = -EBUSY;
 415        struct watchdog_device *wdd;
 416
 417        /* Get the corresponding watchdog device */
 418        if (imajor(inode) == MISC_MAJOR)
 419                wdd = old_wdd;
 420        else
 421                wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
 422
 423        /* the watchdog is single open! */
 424        if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
 425                return -EBUSY;
 426
 427        /*
 428         * If the /dev/watchdog device is open, we don't want the module
 429         * to be unloaded.
 430         */
 431        if (!try_module_get(wdd->ops->owner))
 432                goto out;
 433
 434        err = watchdog_start(wdd);
 435        if (err < 0)
 436                goto out_mod;
 437
 438        file->private_data = wdd;
 439
 440        if (wdd->ops->ref)
 441                wdd->ops->ref(wdd);
 442
 443        /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 444        return nonseekable_open(inode, file);
 445
 446out_mod:
 447        module_put(wdd->ops->owner);
 448out:
 449        clear_bit(WDOG_DEV_OPEN, &wdd->status);
 450        return err;
 451}
 452
 453/*
 454 *      watchdog_release: release the watchdog device.
 455 *      @inode: inode of device
 456 *      @file: file handle to device
 457 *
 458 *      This is the code for when /dev/watchdog gets closed. We will only
 459 *      stop the watchdog when we have received the magic char (and nowayout
 460 *      was not set), else the watchdog will keep running.
 461 */
 462
 463static int watchdog_release(struct inode *inode, struct file *file)
 464{
 465        struct watchdog_device *wdd = file->private_data;
 466        int err = -EBUSY;
 467
 468        /*
 469         * We only stop the watchdog if we received the magic character
 470         * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 471         * watchdog_stop will fail.
 472         */
 473        if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
 474            !(wdd->info->options & WDIOF_MAGICCLOSE))
 475                err = watchdog_stop(wdd);
 476
 477        /* If the watchdog was not stopped, send a keepalive ping */
 478        if (err < 0) {
 479                mutex_lock(&wdd->lock);
 480                if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
 481                        dev_crit(wdd->dev, "watchdog did not stop!\n");
 482                mutex_unlock(&wdd->lock);
 483                watchdog_ping(wdd);
 484        }
 485
 486        /* Allow the owner module to be unloaded again */
 487        module_put(wdd->ops->owner);
 488
 489        /* make sure that /dev/watchdog can be re-opened */
 490        clear_bit(WDOG_DEV_OPEN, &wdd->status);
 491
 492        /* Note wdd may be gone after this, do not use after this! */
 493        if (wdd->ops->unref)
 494                wdd->ops->unref(wdd);
 495
 496        return 0;
 497}
 498
 499static const struct file_operations watchdog_fops = {
 500        .owner          = THIS_MODULE,
 501        .write          = watchdog_write,
 502        .unlocked_ioctl = watchdog_ioctl,
 503        .open           = watchdog_open,
 504        .release        = watchdog_release,
 505};
 506
 507static struct miscdevice watchdog_miscdev = {
 508        .minor          = WATCHDOG_MINOR,
 509        .name           = "watchdog",
 510        .fops           = &watchdog_fops,
 511};
 512
 513/*
 514 *      watchdog_dev_register: register a watchdog device
 515 *      @watchdog: watchdog device
 516 *
 517 *      Register a watchdog device including handling the legacy
 518 *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 519 *      thus we set it up like that.
 520 */
 521
 522int watchdog_dev_register(struct watchdog_device *watchdog)
 523{
 524        int err, devno;
 525
 526        if (watchdog->id == 0) {
 527                watchdog_miscdev.parent = watchdog->parent;
 528                err = misc_register(&watchdog_miscdev);
 529                if (err != 0) {
 530                        pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
 531                                watchdog->info->identity, WATCHDOG_MINOR, err);
 532                        if (err == -EBUSY)
 533                                pr_err("%s: a legacy watchdog module is probably present.\n",
 534                                        watchdog->info->identity);
 535                        return err;
 536                }
 537                old_wdd = watchdog;
 538        }
 539
 540        /* Fill in the data structures */
 541        devno = MKDEV(MAJOR(watchdog_devt), watchdog->id);
 542        cdev_init(&watchdog->cdev, &watchdog_fops);
 543        watchdog->cdev.owner = watchdog->ops->owner;
 544
 545        /* Add the device */
 546        err  = cdev_add(&watchdog->cdev, devno, 1);
 547        if (err) {
 548                pr_err("watchdog%d unable to add device %d:%d\n",
 549                        watchdog->id,  MAJOR(watchdog_devt), watchdog->id);
 550                if (watchdog->id == 0) {
 551                        misc_deregister(&watchdog_miscdev);
 552                        old_wdd = NULL;
 553                }
 554        }
 555        return err;
 556}
 557
 558/*
 559 *      watchdog_dev_unregister: unregister a watchdog device
 560 *      @watchdog: watchdog device
 561 *
 562 *      Unregister the watchdog and if needed the legacy /dev/watchdog device.
 563 */
 564
 565int watchdog_dev_unregister(struct watchdog_device *watchdog)
 566{
 567        mutex_lock(&watchdog->lock);
 568        set_bit(WDOG_UNREGISTERED, &watchdog->status);
 569        mutex_unlock(&watchdog->lock);
 570
 571        cdev_del(&watchdog->cdev);
 572        if (watchdog->id == 0) {
 573                misc_deregister(&watchdog_miscdev);
 574                old_wdd = NULL;
 575        }
 576        return 0;
 577}
 578
 579/*
 580 *      watchdog_dev_init: init dev part of watchdog core
 581 *
 582 *      Allocate a range of chardev nodes to use for watchdog devices
 583 */
 584
 585int __init watchdog_dev_init(void)
 586{
 587        int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
 588        if (err < 0)
 589                pr_err("watchdog: unable to allocate char dev region\n");
 590        return err;
 591}
 592
 593/*
 594 *      watchdog_dev_exit: exit dev part of watchdog core
 595 *
 596 *      Release the range of chardev nodes used for watchdog devices
 597 */
 598
 599void __exit watchdog_dev_exit(void)
 600{
 601        unregister_chrdev_region(watchdog_devt, MAX_DOGS);
 602}
 603
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