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 (watchdog_timeout_invalid(wddev, timeout))
 204                return -EINVAL;
 205
 206        mutex_lock(&wddev->lock);
 207
 208        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 209                err = -ENODEV;
 210                goto out_timeout;
 211        }
 212
 213        err = wddev->ops->set_timeout(wddev, timeout);
 214
 215out_timeout:
 216        mutex_unlock(&wddev->lock);
 217        return err;
 218}
 219
 220/*
 221 *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 222 *      @wddev: the watchdog device to get the remaining time from
 223 *      @timeleft: the time that's left
 224 *
 225 *      Get the time before a watchdog will reboot (if not pinged).
 226 */
 227
 228static int watchdog_get_timeleft(struct watchdog_device *wddev,
 229                                                        unsigned int *timeleft)
 230{
 231        int err = 0;
 232
 233        *timeleft = 0;
 234        if (!wddev->ops->get_timeleft)
 235                return -EOPNOTSUPP;
 236
 237        mutex_lock(&wddev->lock);
 238
 239        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 240                err = -ENODEV;
 241                goto out_timeleft;
 242        }
 243
 244        *timeleft = wddev->ops->get_timeleft(wddev);
 245
 246out_timeleft:
 247        mutex_unlock(&wddev->lock);
 248        return err;
 249}
 250
 251/*
 252 *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 253 *      @wddev: the watchdog device to do the ioctl on
 254 *      @cmd: watchdog command
 255 *      @arg: argument pointer
 256 */
 257
 258static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd,
 259                                                        unsigned long arg)
 260{
 261        int err;
 262
 263        if (!wddev->ops->ioctl)
 264                return -ENOIOCTLCMD;
 265
 266        mutex_lock(&wddev->lock);
 267
 268        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
 269                err = -ENODEV;
 270                goto out_ioctl;
 271        }
 272
 273        err = wddev->ops->ioctl(wddev, cmd, arg);
 274
 275out_ioctl:
 276        mutex_unlock(&wddev->lock);
 277        return err;
 278}
 279
 280/*
 281 *      watchdog_write: writes to the watchdog.
 282 *      @file: file from VFS
 283 *      @data: user address of data
 284 *      @len: length of data
 285 *      @ppos: pointer to the file offset
 286 *
 287 *      A write to a watchdog device is defined as a keepalive ping.
 288 *      Writing the magic 'V' sequence allows the next close to turn
 289 *      off the watchdog (if 'nowayout' is not set).
 290 */
 291
 292static ssize_t watchdog_write(struct file *file, const char __user *data,
 293                                                size_t len, loff_t *ppos)
 294{
 295        struct watchdog_device *wdd = file->private_data;
 296        size_t i;
 297        char c;
 298
 299        if (len == 0)
 300                return 0;
 301
 302        /*
 303         * Note: just in case someone wrote the magic character
 304         * five months ago...
 305         */
 306        clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 307
 308        /* scan to see whether or not we got the magic character */
 309        for (i = 0; i != len; i++) {
 310                if (get_user(c, data + i))
 311                        return -EFAULT;
 312                if (c == 'V')
 313                        set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
 314        }
 315
 316        /* someone wrote to us, so we send the watchdog a keepalive ping */
 317        watchdog_ping(wdd);
 318
 319        return len;
 320}
 321
 322/*
 323 *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 324 *      @file: file handle to the device
 325 *      @cmd: watchdog command
 326 *      @arg: argument pointer
 327 *
 328 *      The watchdog API defines a common set of functions for all watchdogs
 329 *      according to their available features.
 330 */
 331
 332static long watchdog_ioctl(struct file *file, unsigned int cmd,
 333                                                        unsigned long arg)
 334{
 335        struct watchdog_device *wdd = file->private_data;
 336        void __user *argp = (void __user *)arg;
 337        int __user *p = argp;
 338        unsigned int val;
 339        int err;
 340
 341        err = watchdog_ioctl_op(wdd, cmd, arg);
 342        if (err != -ENOIOCTLCMD)
 343                return err;
 344
 345        switch (cmd) {
 346        case WDIOC_GETSUPPORT:
 347                return copy_to_user(argp, wdd->info,
 348                        sizeof(struct watchdog_info)) ? -EFAULT : 0;
 349        case WDIOC_GETSTATUS:
 350                err = watchdog_get_status(wdd, &val);
 351                if (err == -ENODEV)
 352                        return err;
 353                return put_user(val, p);
 354        case WDIOC_GETBOOTSTATUS:
 355                return put_user(wdd->bootstatus, p);
 356        case WDIOC_SETOPTIONS:
 357                if (get_user(val, p))
 358                        return -EFAULT;
 359                if (val & WDIOS_DISABLECARD) {
 360                        err = watchdog_stop(wdd);
 361                        if (err < 0)
 362                                return err;
 363                }
 364                if (val & WDIOS_ENABLECARD) {
 365                        err = watchdog_start(wdd);
 366                        if (err < 0)
 367                                return err;
 368                }
 369                return 0;
 370        case WDIOC_KEEPALIVE:
 371                if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
 372                        return -EOPNOTSUPP;
 373                watchdog_ping(wdd);
 374                return 0;
 375        case WDIOC_SETTIMEOUT:
 376                if (get_user(val, p))
 377                        return -EFAULT;
 378                err = watchdog_set_timeout(wdd, val);
 379                if (err < 0)
 380                        return err;
 381                /* If the watchdog is active then we send a keepalive ping
 382                 * to make sure that the watchdog keep's running (and if
 383                 * possible that it takes the new timeout) */
 384                watchdog_ping(wdd);
 385                /* Fall */
 386        case WDIOC_GETTIMEOUT:
 387                /* timeout == 0 means that we don't know the timeout */
 388                if (wdd->timeout == 0)
 389                        return -EOPNOTSUPP;
 390                return put_user(wdd->timeout, p);
 391        case WDIOC_GETTIMELEFT:
 392                err = watchdog_get_timeleft(wdd, &val);
 393                if (err)
 394                        return err;
 395                return put_user(val, p);
 396        default:
 397                return -ENOTTY;
 398        }
 399}
 400
 401/*
 402 *      watchdog_open: open the /dev/watchdog* devices.
 403 *      @inode: inode of device
 404 *      @file: file handle to device
 405 *
 406 *      When the /dev/watchdog* device gets opened, we start the watchdog.
 407 *      Watch out: the /dev/watchdog device is single open, so we make sure
 408 *      it can only be opened once.
 409 */
 410
 411static int watchdog_open(struct inode *inode, struct file *file)
 412{
 413        int err = -EBUSY;
 414        struct watchdog_device *wdd;
 415
 416        /* Get the corresponding watchdog device */
 417        if (imajor(inode) == MISC_MAJOR)
 418                wdd = old_wdd;
 419        else
 420                wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
 421
 422        /* the watchdog is single open! */
 423        if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
 424                return -EBUSY;
 425
 426        /*
 427         * If the /dev/watchdog device is open, we don't want the module
 428         * to be unloaded.
 429         */
 430        if (!try_module_get(wdd->ops->owner))
 431                goto out;
 432
 433        err = watchdog_start(wdd);
 434        if (err < 0)
 435                goto out_mod;
 436
 437        file->private_data = wdd;
 438
 439        if (wdd->ops->ref)
 440                wdd->ops->ref(wdd);
 441
 442        /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 443        return nonseekable_open(inode, file);
 444
 445out_mod:
 446        module_put(wdd->ops->owner);
 447out:
 448        clear_bit(WDOG_DEV_OPEN, &wdd->status);
 449        return err;
 450}
 451
 452/*
 453 *      watchdog_release: release the watchdog device.
 454 *      @inode: inode of device
 455 *      @file: file handle to device
 456 *
 457 *      This is the code for when /dev/watchdog gets closed. We will only
 458 *      stop the watchdog when we have received the magic char (and nowayout
 459 *      was not set), else the watchdog will keep running.
 460 */
 461
 462static int watchdog_release(struct inode *inode, struct file *file)
 463{
 464        struct watchdog_device *wdd = file->private_data;
 465        int err = -EBUSY;
 466
 467        /*
 468         * We only stop the watchdog if we received the magic character
 469         * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 470         * watchdog_stop will fail.
 471         */
 472        if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
 473            !(wdd->info->options & WDIOF_MAGICCLOSE))
 474                err = watchdog_stop(wdd);
 475
 476        /* If the watchdog was not stopped, send a keepalive ping */
 477        if (err < 0) {
 478                mutex_lock(&wdd->lock);
 479                if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
 480                        dev_crit(wdd->dev, "watchdog did not stop!\n");
 481                mutex_unlock(&wdd->lock);
 482                watchdog_ping(wdd);
 483        }
 484
 485        /* Allow the owner module to be unloaded again */
 486        module_put(wdd->ops->owner);
 487
 488        /* make sure that /dev/watchdog can be re-opened */
 489        clear_bit(WDOG_DEV_OPEN, &wdd->status);
 490
 491        /* Note wdd may be gone after this, do not use after this! */
 492        if (wdd->ops->unref)
 493                wdd->ops->unref(wdd);
 494
 495        return 0;
 496}
 497
 498static const struct file_operations watchdog_fops = {
 499        .owner          = THIS_MODULE,
 500        .write          = watchdog_write,
 501        .unlocked_ioctl = watchdog_ioctl,
 502        .open           = watchdog_open,
 503        .release        = watchdog_release,
 504};
 505
 506static struct miscdevice watchdog_miscdev = {
 507        .minor          = WATCHDOG_MINOR,
 508        .name           = "watchdog",
 509        .fops           = &watchdog_fops,
 510};
 511
 512/*
 513 *      watchdog_dev_register: register a watchdog device
 514 *      @watchdog: watchdog device
 515 *
 516 *      Register a watchdog device including handling the legacy
 517 *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 518 *      thus we set it up like that.
 519 */
 520
 521int watchdog_dev_register(struct watchdog_device *watchdog)
 522{
 523        int err, devno;
 524
 525        if (watchdog->id == 0) {
 526                old_wdd = watchdog;
 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                        old_wdd = NULL;
 536                        return err;
 537                }
 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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