kernel/time/alarmtimer.c

   1 /*
   2  * Alarmtimer interface
   3  *
   4  * This interface provides a timer which is similarto hrtimers,
   5  * but triggers a RTC alarm if the box is suspend.
   6  *
   7  * This interface is influenced by the Android RTC Alarm timer
   8  * interface.
   9  *
  10  * Copyright (C) 2010 IBM Corperation
  11  *
  12  * Author: John Stultz <john.stultz@linaro.org>
  13  *
  14  * This program is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License version 2 as
  16  * published by the Free Software Foundation.
  17  */
  18 #include <linux/time.h>
  19 #include <linux/hrtimer.h>
  20 #include <linux/timerqueue.h>
  21 #include <linux/rtc.h>
  22 #include <linux/alarmtimer.h>
  23 #include <linux/mutex.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/posix-timers.h>
  26 #include <linux/workqueue.h>
  27 #include <linux/freezer.h>
  28
  29 /**
  30  * struct alarm_base - Alarm timer bases
  31  * @lock:               Lock for syncrhonized access to the base
  32  * @timerqueue:         Timerqueue head managing the list of events
  33  * @timer:              hrtimer used to schedule events while running
  34  * @gettime:            Function to read the time correlating to the base
  35  * @base_clockid:       clockid for the base
  36  */
  37 static struct alarm_base {
  38         spinlock_t              lock;
  39         struct timerqueue_head  timerqueue;
  40         struct hrtimer          timer;
  41         ktime_t                 (*gettime)(void);
  42         clockid_t               base_clockid;
  43 } alarm_bases[ALARM_NUMTYPE];
  44
  45 /* freezer delta & lock used to handle clock_nanosleep triggered wakeups */
  46 static ktime_t freezer_delta;
  47 static DEFINE_SPINLOCK(freezer_delta_lock);
  48
  49 #ifdef CONFIG_RTC_CLASS
  50 /* rtc timer and device for setting alarm wakeups at suspend */
  51 static struct rtc_timer         rtctimer;
  52 static struct rtc_device        *rtcdev;
  53 static DEFINE_SPINLOCK(rtcdev_lock);
  54
  55 /**
  56  * has_wakealarm - check rtc device has wakealarm ability
  57  * @dev: current device
  58  * @name_ptr: name to be returned
  59  *
  60  * This helper function checks to see if the rtc device can wake
  61  * from suspend.
  62  */
  63 static int has_wakealarm(struct device *dev, void *name_ptr)
  64 {
  65         struct rtc_device *candidate = to_rtc_device(dev);
  66
  67         if (!candidate->ops->set_alarm)
  68                 return 0;
  69         if (!device_may_wakeup(candidate->dev.parent))
  70                 return 0;
  71
  72         *(const char **)name_ptr = dev_name(dev);
  73         return 1;
  74 }
  75
  76 /**
  77  * alarmtimer_get_rtcdev - Return selected rtcdevice
  78  *
  79  * This function returns the rtc device to use for wakealarms.
  80  * If one has not already been chosen, it checks to see if a
  81  * functional rtc device is available.
  82  */
  83 static struct rtc_device *alarmtimer_get_rtcdev(void)
  84 {
  85         struct device *dev;
  86         char *str;
  87         unsigned long flags;
  88         struct rtc_device *ret;
  89
  90         spin_lock_irqsave(&rtcdev_lock, flags);
  91         if (!rtcdev) {
  92                 /* Find an rtc device and init the rtc_timer */
  93                 dev = class_find_device(rtc_class, NULL, &str, has_wakealarm);
  94                 /* If we have a device then str is valid. See has_wakealarm() */
  95                 if (dev) {
  96                         rtcdev = rtc_class_open(str);
  97                         /*
  98                          * Drop the reference we got in class_find_device,
  99                          * rtc_open takes its own.
 100                          */
 101                         put_device(dev);
 102                         rtc_timer_init(&rtctimer, NULL, NULL);
 103                 }
 104         }
 105         ret = rtcdev;
 106         spin_unlock_irqrestore(&rtcdev_lock, flags);
 107
 108         return ret;
 109 }
 110 #else
 111 #define alarmtimer_get_rtcdev() (0)
 112 #define rtcdev (0)
 113 #endif
 114
 115
 116 /**
 117  * alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerqueue
 118  * @base: pointer to the base where the timer is being run
 119  * @alarm: pointer to alarm being enqueued.
 120  *
 121  * Adds alarm to a alarm_base timerqueue and if necessary sets
 122  * an hrtimer to run.
 123  *
 124  * Must hold base->lock when calling.
 125  */
 126 static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
 127 {
 128         timerqueue_add(&base->timerqueue, &alarm->node);
 129         if (&alarm->node == timerqueue_getnext(&base->timerqueue)) {
 130                 hrtimer_try_to_cancel(&base->timer);
 131                 hrtimer_start(&base->timer, alarm->node.expires,
 132                                 HRTIMER_MODE_ABS);
 133         }
 134 }
 135
 136 /**
 137  * alarmtimer_remove - Removes an alarm timer from an alarm_base timerqueue
 138  * @base: pointer to the base where the timer is running
 139  * @alarm: pointer to alarm being removed
 140  *
 141  * Removes alarm to a alarm_base timerqueue and if necessary sets
 142  * a new timer to run.
 143  *
 144  * Must hold base->lock when calling.
 145  */
 146 static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
 147 {
 148         struct timerqueue_node *next = timerqueue_getnext(&base->timerqueue);
 149
 150         timerqueue_del(&base->timerqueue, &alarm->node);
 151         if (next == &alarm->node) {
 152                 hrtimer_try_to_cancel(&base->timer);
 153                 next = timerqueue_getnext(&base->timerqueue);
 154                 if (!next)
 155                         return;
 156                 hrtimer_start(&base->timer, next->expires, HRTIMER_MODE_ABS);
 157         }
 158 }
 159
 160
 161 /**
 162  * alarmtimer_fired - Handles alarm hrtimer being fired.
 163  * @timer: pointer to hrtimer being run
 164  *
 165  * When a alarm timer fires, this runs through the timerqueue to
 166  * see which alarms expired, and runs those. If there are more alarm
 167  * timers queued for the future, we set the hrtimer to fire when
 168  * when the next future alarm timer expires.
 169  */
 170 static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
 171 {
 172         struct alarm_base *base = container_of(timer, struct alarm_base, timer);
 173         struct timerqueue_node *next;
 174         unsigned long flags;
 175         ktime_t now;
 176         int ret = HRTIMER_NORESTART;
 177
 178         spin_lock_irqsave(&base->lock, flags);
 179         now = base->gettime();
 180         while ((next = timerqueue_getnext(&base->timerqueue))) {
 181                 struct alarm *alarm;
 182                 ktime_t expired = next->expires;
 183
 184                 if (expired.tv64 > now.tv64)
 185                         break;
 186
 187                 alarm = container_of(next, struct alarm, node);
 188
 189                 timerqueue_del(&base->timerqueue, &alarm->node);
 190                 alarm->enabled = 0;
 191                 /* Re-add periodic timers */
 192                 if (alarm->period.tv64) {
 193                         alarm->node.expires = ktime_add(expired, alarm->period);
 194                         timerqueue_add(&base->timerqueue, &alarm->node);
 195                         alarm->enabled = 1;
 196                 }
 197                 spin_unlock_irqrestore(&base->lock, flags);
 198                 if (alarm->function)
 199                         alarm->function(alarm);
 200                 spin_lock_irqsave(&base->lock, flags);
 201         }
 202
 203         if (next) {
 204                 hrtimer_set_expires(&base->timer, next->expires);
 205                 ret = HRTIMER_RESTART;
 206         }
 207         spin_unlock_irqrestore(&base->lock, flags);
 208
 209         return ret;
 210
 211 }
 212
 213 #ifdef CONFIG_RTC_CLASS
 214 /**
 215  * alarmtimer_suspend - Suspend time callback
 216  * @dev: unused
 217  * @state: unused
 218  *
 219  * When we are going into suspend, we look through the bases
 220  * to see which is the soonest timer to expire. We then
 221  * set an rtc timer to fire that far into the future, which
 222  * will wake us from suspend.
 223  */
 224 static int alarmtimer_suspend(struct device *dev)
 225 {
 226         struct rtc_time tm;
 227         ktime_t min, now;
 228         unsigned long flags;
 229         struct rtc_device *rtc;
 230         int i;
 231
 232         spin_lock_irqsave(&freezer_delta_lock, flags);
 233         min = freezer_delta;
 234         freezer_delta = ktime_set(0, 0);
 235         spin_unlock_irqrestore(&freezer_delta_lock, flags);
 236
 237         rtc = rtcdev;
 238         /* If we have no rtcdev, just return */
 239         if (!rtc)
 240                 return 0;
 241
 242         /* Find the soonest timer to expire*/
 243         for (i = 0; i < ALARM_NUMTYPE; i++) {
 244                 struct alarm_base *base = &alarm_bases[i];
 245                 struct timerqueue_node *next;
 246                 ktime_t delta;
 247
 248                 spin_lock_irqsave(&base->lock, flags);
 249                 next = timerqueue_getnext(&base->timerqueue);
 250                 spin_unlock_irqrestore(&base->lock, flags);
 251                 if (!next)
 252                         continue;
 253                 delta = ktime_sub(next->expires, base->gettime());
 254                 if (!min.tv64 || (delta.tv64 < min.tv64))
 255                         min = delta;
 256         }
 257         if (min.tv64 == 0)
 258                 return 0;
 259
 260         /* XXX - Should we enforce a minimum sleep time? */
 261         WARN_ON(min.tv64 < NSEC_PER_SEC);
 262
 263         /* Setup an rtc timer to fire that far in the future */
 264         rtc_timer_cancel(rtc, &rtctimer);
 265         rtc_read_time(rtc, &tm);
 266         now = rtc_tm_to_ktime(tm);
 267         now = ktime_add(now, min);
 268
 269         rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
 270
 271         return 0;
 272 }
 273 #else
 274 static int alarmtimer_suspend(struct device *dev)
 275 {
 276         return 0;
 277 }
 278 #endif
 279
 280 static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
 281 {
 282         ktime_t delta;
 283         unsigned long flags;
 284         struct alarm_base *base = &alarm_bases[type];
 285
 286         delta = ktime_sub(absexp, base->gettime());
 287
 288         spin_lock_irqsave(&freezer_delta_lock, flags);
 289         if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64))
 290                 freezer_delta = delta;
 291         spin_unlock_irqrestore(&freezer_delta_lock, flags);
 292 }
 293
 294
 295 /**
 296  * alarm_init - Initialize an alarm structure
 297  * @alarm: ptr to alarm to be initialized
 298  * @type: the type of the alarm
 299  * @function: callback that is run when the alarm fires
 300  */
 301 void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
 302                 void (*function)(struct alarm *))
 303 {
 304         timerqueue_init(&alarm->node);
 305         alarm->period = ktime_set(0, 0);
 306         alarm->function = function;
 307         alarm->type = type;
 308         alarm->enabled = 0;
 309 }
 310
 311 /**
 312  * alarm_start - Sets an alarm to fire
 313  * @alarm: ptr to alarm to set
 314  * @start: time to run the alarm
 315  * @period: period at which the alarm will recur
 316  */
 317 void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period)
 318 {
 319         struct alarm_base *base = &alarm_bases[alarm->type];
 320         unsigned long flags;
 321
 322         spin_lock_irqsave(&base->lock, flags);
 323         if (alarm->enabled)
 324                 alarmtimer_remove(base, alarm);
 325         alarm->node.expires = start;
 326         alarm->period = period;
 327         alarmtimer_enqueue(base, alarm);
 328         alarm->enabled = 1;
 329         spin_unlock_irqrestore(&base->lock, flags);
 330 }
 331
 332 /**
 333  * alarm_cancel - Tries to cancel an alarm timer
 334  * @alarm: ptr to alarm to be canceled
 335  */
 336 void alarm_cancel(struct alarm *alarm)
 337 {
 338         struct alarm_base *base = &alarm_bases[alarm->type];
 339         unsigned long flags;
 340
 341         spin_lock_irqsave(&base->lock, flags);
 342         if (alarm->enabled)
 343                 alarmtimer_remove(base, alarm);
 344         alarm->enabled = 0;
 345         spin_unlock_irqrestore(&base->lock, flags);
 346 }
 347
 348
 349 /**
 350  * clock2alarm - helper that converts from clockid to alarmtypes
 351  * @clockid: clockid.
 352  */
 353 static enum alarmtimer_type clock2alarm(clockid_t clockid)
 354 {
 355         if (clockid == CLOCK_REALTIME_ALARM)
 356                 return ALARM_REALTIME;
 357         if (clockid == CLOCK_BOOTTIME_ALARM)
 358                 return ALARM_BOOTTIME;
 359         return -1;
 360 }
 361
 362 /**
 363  * alarm_handle_timer - Callback for posix timers
 364  * @alarm: alarm that fired
 365  *
 366  * Posix timer callback for expired alarm timers.
 367  */
 368 static void alarm_handle_timer(struct alarm *alarm)
 369 {
 370         struct k_itimer *ptr = container_of(alarm, struct k_itimer,
 371                                                 it.alarmtimer);
 372         if (posix_timer_event(ptr, 0) != 0)
 373                 ptr->it_overrun++;
 374 }
 375
 376 /**
 377  * alarm_clock_getres - posix getres interface
 378  * @which_clock: clockid
 379  * @tp: timespec to fill
 380  *
 381  * Returns the granularity of underlying alarm base clock
 382  */
 383 static int alarm_clock_getres(const clockid_t which_clock, struct timespec *tp)
 384 {
 385         clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;
 386
 387         if (!alarmtimer_get_rtcdev())
 388                 return -ENOTSUPP;
 389
 390         return hrtimer_get_res(baseid, tp);
 391 }
 392
 393 /**
 394  * alarm_clock_get - posix clock_get interface
 395  * @which_clock: clockid
 396  * @tp: timespec to fill.
 397  *
 398  * Provides the underlying alarm base time.
 399  */
 400 static int alarm_clock_get(clockid_t which_clock, struct timespec *tp)
 401 {
 402         struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
 403
 404         if (!alarmtimer_get_rtcdev())
 405                 return -ENOTSUPP;
 406
 407         *tp = ktime_to_timespec(base->gettime());
 408         return 0;
 409 }
 410
 411 /**
 412  * alarm_timer_create - posix timer_create interface
 413  * @new_timer: k_itimer pointer to manage
 414  *
 415  * Initializes the k_itimer structure.
 416  */
 417 static int alarm_timer_create(struct k_itimer *new_timer)
 418 {
 419         enum  alarmtimer_type type;
 420         struct alarm_base *base;
 421
 422         if (!alarmtimer_get_rtcdev())
 423                 return -ENOTSUPP;
 424
 425         if (!capable(CAP_WAKE_ALARM))
 426                 return -EPERM;
 427
 428         type = clock2alarm(new_timer->it_clock);
 429         base = &alarm_bases[type];
 430         alarm_init(&new_timer->it.alarmtimer, type, alarm_handle_timer);
 431         return 0;
 432 }
 433
 434 /**
 435  * alarm_timer_get - posix timer_get interface
 436  * @new_timer: k_itimer pointer
 437  * @cur_setting: itimerspec data to fill
 438  *
 439  * Copies the itimerspec data out from the k_itimer
 440  */
 441 static void alarm_timer_get(struct k_itimer *timr,
 442                                 struct itimerspec *cur_setting)
 443 {
 444         memset(cur_setting, 0, sizeof(struct itimerspec));
 445
 446         cur_setting->it_interval =
 447                         ktime_to_timespec(timr->it.alarmtimer.period);
 448         cur_setting->it_value =
 449                         ktime_to_timespec(timr->it.alarmtimer.node.expires);
 450         return;
 451 }
 452
 453 /**
 454  * alarm_timer_del - posix timer_del interface
 455  * @timr: k_itimer pointer to be deleted
 456  *
 457  * Cancels any programmed alarms for the given timer.
 458  */
 459 static int alarm_timer_del(struct k_itimer *timr)
 460 {
 461         if (!rtcdev)
 462                 return -ENOTSUPP;
 463
 464         alarm_cancel(&timr->it.alarmtimer);
 465         return 0;
 466 }
 467
 468 /**
 469  * alarm_timer_set - posix timer_set interface
 470  * @timr: k_itimer pointer to be deleted
 471  * @flags: timer flags
 472  * @new_setting: itimerspec to be used
 473  * @old_setting: itimerspec being replaced
 474  *
 475  * Sets the timer to new_setting, and starts the timer.
 476  */
 477 static int alarm_timer_set(struct k_itimer *timr, int flags,
 478                                 struct itimerspec *new_setting,
 479                                 struct itimerspec *old_setting)
 480 {
 481         if (!rtcdev)
 482                 return -ENOTSUPP;
 483
 484         /*
 485          * XXX HACK! Currently we can DOS a system if the interval
 486          * period on alarmtimers is too small. Cap the interval here
 487          * to 100us and solve this properly in a future patch! -jstultz
 488          */
 489         if ((new_setting->it_interval.tv_sec == 0) &&
 490                         (new_setting->it_interval.tv_nsec < 100000))
 491                 new_setting->it_interval.tv_nsec = 100000;
 492
 493         if (old_setting)
 494                 alarm_timer_get(timr, old_setting);
 495
 496         /* If the timer was already set, cancel it */
 497         alarm_cancel(&timr->it.alarmtimer);
 498
 499         /* start the timer */
 500         alarm_start(&timr->it.alarmtimer,
 501                         timespec_to_ktime(new_setting->it_value),
 502                         timespec_to_ktime(new_setting->it_interval));
 503         return 0;
 504 }
 505
 506 /**
 507  * alarmtimer_nsleep_wakeup - Wakeup function for alarm_timer_nsleep
 508  * @alarm: ptr to alarm that fired
 509  *
 510  * Wakes up the task that set the alarmtimer
 511  */
 512 static void alarmtimer_nsleep_wakeup(struct alarm *alarm)
 513 {
 514         struct task_struct *task = (struct task_struct *)alarm->data;
 515
 516         alarm->data = NULL;
 517         if (task)
 518                 wake_up_process(task);
 519 }
 520
 521 /**
 522  * alarmtimer_do_nsleep - Internal alarmtimer nsleep implementation
 523  * @alarm: ptr to alarmtimer
 524  * @absexp: absolute expiration time
 525  *
 526  * Sets the alarm timer and sleeps until it is fired or interrupted.
 527  */
 528 static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp)
 529 {
 530         alarm->data = (void *)current;
 531         do {
 532                 set_current_state(TASK_INTERRUPTIBLE);
 533                 alarm_start(alarm, absexp, ktime_set(0, 0));
 534                 if (likely(alarm->data))
 535                         schedule();
 536
 537                 alarm_cancel(alarm);
 538         } while (alarm->data && !signal_pending(current));
 539
 540         __set_current_state(TASK_RUNNING);
 541
 542         return (alarm->data == NULL);
 543 }
 544
 545
 546 /**
 547  * update_rmtp - Update remaining timespec value
 548  * @exp: expiration time
 549  * @type: timer type
 550  * @rmtp: user pointer to remaining timepsec value
 551  *
 552  * Helper function that fills in rmtp value with time between
 553  * now and the exp value
 554  */
 555 static int update_rmtp(ktime_t exp, enum  alarmtimer_type type,
 556                         struct timespec __user *rmtp)
 557 {
 558         struct timespec rmt;
 559         ktime_t rem;
 560
 561         rem = ktime_sub(exp, alarm_bases[type].gettime());
 562
 563         if (rem.tv64 <= 0)
 564                 return 0;
 565         rmt = ktime_to_timespec(rem);
 566
 567         if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
 568                 return -EFAULT;
 569
 570         return 1;
 571
 572 }
 573
 574 /**
 575  * alarm_timer_nsleep_restart - restartblock alarmtimer nsleep
 576  * @restart: ptr to restart block
 577  *
 578  * Handles restarted clock_nanosleep calls
 579  */
 580 static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
 581 {
 582         enum  alarmtimer_type type = restart->nanosleep.clockid;
 583         ktime_t exp;
 584         struct timespec __user  *rmtp;
 585         struct alarm alarm;
 586         int ret = 0;
 587
 588         exp.tv64 = restart->nanosleep.expires;
 589         alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
 590
 591         if (alarmtimer_do_nsleep(&alarm, exp))
 592                 goto out;
 593
 594         if (freezing(current))
 595                 alarmtimer_freezerset(exp, type);
 596
 597         rmtp = restart->nanosleep.rmtp;
 598         if (rmtp) {
 599                 ret = update_rmtp(exp, type, rmtp);
 600                 if (ret <= 0)
 601                         goto out;
 602         }
 603
 604
 605         /* The other values in restart are already filled in */
 606         ret = -ERESTART_RESTARTBLOCK;
 607 out:
 608         return ret;
 609 }
 610
 611 /**
 612  * alarm_timer_nsleep - alarmtimer nanosleep
 613  * @which_clock: clockid
 614  * @flags: determins abstime or relative
 615  * @tsreq: requested sleep time (abs or rel)
 616  * @rmtp: remaining sleep time saved
 617  *
 618  * Handles clock_nanosleep calls against _ALARM clockids
 619  */
 620 static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
 621                      struct timespec *tsreq, struct timespec __user *rmtp)
 622 {
 623         enum  alarmtimer_type type = clock2alarm(which_clock);
 624         struct alarm alarm;
 625         ktime_t exp;
 626         int ret = 0;
 627         struct restart_block *restart;
 628
 629         if (!alarmtimer_get_rtcdev())
 630                 return -ENOTSUPP;
 631
 632         if (!capable(CAP_WAKE_ALARM))
 633                 return -EPERM;
 634
 635         alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
 636
 637         exp = timespec_to_ktime(*tsreq);
 638         /* Convert (if necessary) to absolute time */
 639         if (flags != TIMER_ABSTIME) {
 640                 ktime_t now = alarm_bases[type].gettime();
 641                 exp = ktime_add(now, exp);
 642         }
 643
 644         if (alarmtimer_do_nsleep(&alarm, exp))
 645                 goto out;
 646
 647         if (freezing(current))
 648                 alarmtimer_freezerset(exp, type);
 649
 650         /* abs timers don't set remaining time or restart */
 651         if (flags == TIMER_ABSTIME) {
 652                 ret = -ERESTARTNOHAND;
 653                 goto out;
 654         }
 655
 656         if (rmtp) {
 657                 ret = update_rmtp(exp, type, rmtp);
 658                 if (ret <= 0)
 659                         goto out;
 660         }
 661
 662         restart = &current_thread_info()->restart_block;
 663         restart->fn = alarm_timer_nsleep_restart;
 664         restart->nanosleep.clockid = type;
 665         restart->nanosleep.expires = exp.tv64;
 666         restart->nanosleep.rmtp = rmtp;
 667         ret = -ERESTART_RESTARTBLOCK;
 668
 669 out:
 670         return ret;
 671 }
 672
 673
 674 /* Suspend hook structures */
 675 static const struct dev_pm_ops alarmtimer_pm_ops = {
 676         .suspend = alarmtimer_suspend,
 677 };
 678
 679 static struct platform_driver alarmtimer_driver = {
 680         .driver = {
 681                 .name = "alarmtimer",
 682                 .pm = &alarmtimer_pm_ops,
 683         }
 684 };
 685
 686 /**
 687  * alarmtimer_init - Initialize alarm timer code
 688  *
 689  * This function initializes the alarm bases and registers
 690  * the posix clock ids.
 691  */
 692 static int __init alarmtimer_init(void)
 693 {
 694         int error = 0;
 695         int i;
 696         struct k_clock alarm_clock = {
 697                 .clock_getres   = alarm_clock_getres,
 698                 .clock_get      = alarm_clock_get,
 699                 .timer_create   = alarm_timer_create,
 700                 .timer_set      = alarm_timer_set,
 701                 .timer_del      = alarm_timer_del,
 702                 .timer_get      = alarm_timer_get,
 703                 .nsleep         = alarm_timer_nsleep,
 704         };
 705
 706         posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
 707         posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);
 708
 709         /* Initialize alarm bases */
 710         alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
 711         alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
 712         alarm_bases[ALARM_BOOTTIME].base_clockid = CLOCK_BOOTTIME;
 713         alarm_bases[ALARM_BOOTTIME].gettime = &ktime_get_boottime;
 714         for (i = 0; i < ALARM_NUMTYPE; i++) {
 715                 timerqueue_init_head(&alarm_bases[i].timerqueue);
 716                 spin_lock_init(&alarm_bases[i].lock);
 717                 hrtimer_init(&alarm_bases[i].timer,
 718                                 alarm_bases[i].base_clockid,
 719                                 HRTIMER_MODE_ABS);
 720                 alarm_bases[i].timer.function = alarmtimer_fired;
 721         }
 722         error = platform_driver_register(&alarmtimer_driver);
 723         platform_device_register_simple("alarmtimer", -1, NULL, 0);
 724
 725         return error;
 726 }
 727 device_initcall(alarmtimer_init);
 728