drivers/rtc/interface.c

   1 /*
   2  * RTC subsystem, interface functions
   3  *
   4  * Copyright (C) 2005 Tower Technologies
   5  * Author: Alessandro Zummo <a.zummo@towertech.it>
   6  *
   7  * based on arch/arm/common/rtctime.c
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12 */
  13
  14 #include <linux/rtc.h>
  15 #include <linux/sched.h>
  16 #include <linux/log2.h>
  17 #include <linux/workqueue.h>
  18
  19 static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
  20 static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
  21
  22 static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
  23 {
  24         int err;
  25         if (!rtc->ops)
  26                 err = -ENODEV;
  27         else if (!rtc->ops->read_time)
  28                 err = -EINVAL;
  29         else {
  30                 memset(tm, 0, sizeof(struct rtc_time));
  31                 err = rtc->ops->read_time(rtc->dev.parent, tm);
  32         }
  33         return err;
  34 }
  35
  36 int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
  37 {
  38         int err;
  39
  40         err = mutex_lock_interruptible(&rtc->ops_lock);
  41         if (err)
  42                 return err;
  43
  44         err = __rtc_read_time(rtc, tm);
  45         mutex_unlock(&rtc->ops_lock);
  46         return err;
  47 }
  48 EXPORT_SYMBOL_GPL(rtc_read_time);
  49
  50 int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
  51 {
  52         int err;
  53
  54         err = rtc_valid_tm(tm);
  55         if (err != 0)
  56                 return err;
  57
  58         err = mutex_lock_interruptible(&rtc->ops_lock);
  59         if (err)
  60                 return err;
  61
  62         if (!rtc->ops)
  63                 err = -ENODEV;
  64         else if (rtc->ops->set_time)
  65                 err = rtc->ops->set_time(rtc->dev.parent, tm);
  66         else if (rtc->ops->set_mmss) {
  67                 unsigned long secs;
  68                 err = rtc_tm_to_time(tm, &secs);
  69                 if (err == 0)
  70                         err = rtc->ops->set_mmss(rtc->dev.parent, secs);
  71         } else
  72                 err = -EINVAL;
  73
  74         mutex_unlock(&rtc->ops_lock);
  75         return err;
  76 }
  77 EXPORT_SYMBOL_GPL(rtc_set_time);
  78
  79 int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
  80 {
  81         int err;
  82
  83         err = mutex_lock_interruptible(&rtc->ops_lock);
  84         if (err)
  85                 return err;
  86
  87         if (!rtc->ops)
  88                 err = -ENODEV;
  89         else if (rtc->ops->set_mmss)
  90                 err = rtc->ops->set_mmss(rtc->dev.parent, secs);
  91         else if (rtc->ops->read_time && rtc->ops->set_time) {
  92                 struct rtc_time new, old;
  93
  94                 err = rtc->ops->read_time(rtc->dev.parent, &old);
  95                 if (err == 0) {
  96                         rtc_time_to_tm(secs, &new);
  97
  98                         /*
  99                          * avoid writing when we're going to change the day of
 100                          * the month. We will retry in the next minute. This
 101                          * basically means that if the RTC must not drift
 102                          * by more than 1 minute in 11 minutes.
 103                          */
 104                         if (!((old.tm_hour == 23 && old.tm_min == 59) ||
 105                                 (new.tm_hour == 23 && new.tm_min == 59)))
 106                                 err = rtc->ops->set_time(rtc->dev.parent,
 107                                                 &new);
 108                 }
 109         }
 110         else
 111                 err = -EINVAL;
 112
 113         mutex_unlock(&rtc->ops_lock);
 114
 115         return err;
 116 }
 117 EXPORT_SYMBOL_GPL(rtc_set_mmss);
 118
 119 int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 120 {
 121         int err;
 122
 123         err = mutex_lock_interruptible(&rtc->ops_lock);
 124         if (err)
 125                 return err;
 126         if (rtc->ops == NULL)
 127                 err = -ENODEV;
 128         else if (!rtc->ops->read_alarm)
 129                 err = -EINVAL;
 130         else {
 131                 memset(alarm, 0, sizeof(struct rtc_wkalrm));
 132                 alarm->enabled = rtc->aie_timer.enabled;
 133                 alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
 134         }
 135         mutex_unlock(&rtc->ops_lock);
 136
 137         return err;
 138 }
 139 EXPORT_SYMBOL_GPL(rtc_read_alarm);
 140
 141 int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 142 {
 143         struct rtc_time tm;
 144         long now, scheduled;
 145         int err;
 146
 147         err = rtc_valid_tm(&alarm->time);
 148         if (err)
 149                 return err;
 150         rtc_tm_to_time(&alarm->time, &scheduled);
 151
 152         /* Make sure we're not setting alarms in the past */
 153         err = __rtc_read_time(rtc, &tm);
 154         rtc_tm_to_time(&tm, &now);
 155         if (scheduled <= now)
 156                 return -ETIME;
 157         /*
 158          * XXX - We just checked to make sure the alarm time is not
 159          * in the past, but there is still a race window where if
 160          * the is alarm set for the next second and the second ticks
 161          * over right here, before we set the alarm.
 162          */
 163
 164         if (!rtc->ops)
 165                 err = -ENODEV;
 166         else if (!rtc->ops->set_alarm)
 167                 err = -EINVAL;
 168         else
 169                 err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
 170
 171         return err;
 172 }
 173
 174 int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 175 {
 176         int err;
 177
 178         err = rtc_valid_tm(&alarm->time);
 179         if (err != 0)
 180                 return err;
 181
 182         err = mutex_lock_interruptible(&rtc->ops_lock);
 183         if (err)
 184                 return err;
 185         if (rtc->aie_timer.enabled) {
 186                 rtc_timer_remove(rtc, &rtc->aie_timer);
 187         }
 188         rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
 189         rtc->aie_timer.period = ktime_set(0, 0);
 190         if (alarm->enabled) {
 191                 err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
 192         }
 193         mutex_unlock(&rtc->ops_lock);
 194         return err;
 195 }
 196 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 197
 198 int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 199 {
 200         int err = mutex_lock_interruptible(&rtc->ops_lock);
 201         if (err)
 202                 return err;
 203
 204         if (rtc->aie_timer.enabled != enabled) {
 205                 if (enabled)
 206                         err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
 207                 else
 208                         rtc_timer_remove(rtc, &rtc->aie_timer);
 209         }
 210
 211         if (err)
 212                 /* nothing */;
 213         else if (!rtc->ops)
 214                 err = -ENODEV;
 215         else if (!rtc->ops->alarm_irq_enable)
 216                 err = -EINVAL;
 217         else
 218                 err = rtc->ops->alarm_irq_enable(rtc->dev.parent, enabled);
 219
 220         mutex_unlock(&rtc->ops_lock);
 221         return err;
 222 }
 223 EXPORT_SYMBOL_GPL(rtc_alarm_irq_enable);
 224
 225 int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
 226 {
 227         int err = mutex_lock_interruptible(&rtc->ops_lock);
 228         if (err)
 229                 return err;
 230
 231 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 232         if (enabled == 0 && rtc->uie_irq_active) {
 233                 mutex_unlock(&rtc->ops_lock);
 234                 return rtc_dev_update_irq_enable_emul(rtc, 0);
 235         }
 236 #endif
 237         /* make sure we're changing state */
 238         if (rtc->uie_rtctimer.enabled == enabled)
 239                 goto out;
 240
 241         if (enabled) {
 242                 struct rtc_time tm;
 243                 ktime_t now, onesec;
 244
 245                 __rtc_read_time(rtc, &tm);
 246                 onesec = ktime_set(1, 0);
 247                 now = rtc_tm_to_ktime(tm);
 248                 rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
 249                 rtc->uie_rtctimer.period = ktime_set(1, 0);
 250                 err = rtc_timer_enqueue(rtc, &rtc->uie_rtctimer);
 251         } else
 252                 rtc_timer_remove(rtc, &rtc->uie_rtctimer);
 253
 254 out:
 255         mutex_unlock(&rtc->ops_lock);
 256 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
 257         /*
 258          * Enable emulation if the driver did not provide
 259          * the update_irq_enable function pointer or if returned
 260          * -EINVAL to signal that it has been configured without
 261          * interrupts or that are not available at the moment.
 262          */
 263         if (err == -EINVAL)
 264                 err = rtc_dev_update_irq_enable_emul(rtc, enabled);
 265 #endif
 266         return err;
 267
 268 }
 269 EXPORT_SYMBOL_GPL(rtc_update_irq_enable);
 270
 271
 272 /**
 273  * rtc_handle_legacy_irq - AIE, UIE and PIE event hook
 274  * @rtc: pointer to the rtc device
 275  *
 276  * This function is called when an AIE, UIE or PIE mode interrupt
 277  * has occured (or been emulated).
 278  *
 279  * Triggers the registered irq_task function callback.
 280  */
 281 void rtc_handle_legacy_irq(struct rtc_device *rtc, int num, int mode)
 282 {
 283         unsigned long flags;
 284
 285         /* mark one irq of the appropriate mode */
 286         spin_lock_irqsave(&rtc->irq_lock, flags);
 287         rtc->irq_data = (rtc->irq_data + (num << 8)) | (RTC_IRQF|mode);
 288         spin_unlock_irqrestore(&rtc->irq_lock, flags);
 289
 290         /* call the task func */
 291         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 292         if (rtc->irq_task)
 293                 rtc->irq_task->func(rtc->irq_task->private_data);
 294         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 295
 296         wake_up_interruptible(&rtc->irq_queue);
 297         kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
 298 }
 299
 300
 301 /**
 302  * rtc_aie_update_irq - AIE mode rtctimer hook
 303  * @private: pointer to the rtc_device
 304  *
 305  * This functions is called when the aie_timer expires.
 306  */
 307 void rtc_aie_update_irq(void *private)
 308 {
 309         struct rtc_device *rtc = (struct rtc_device *)private;
 310         rtc_handle_legacy_irq(rtc, 1, RTC_AF);
 311 }
 312
 313
 314 /**
 315  * rtc_uie_update_irq - UIE mode rtctimer hook
 316  * @private: pointer to the rtc_device
 317  *
 318  * This functions is called when the uie_timer expires.
 319  */
 320 void rtc_uie_update_irq(void *private)
 321 {
 322         struct rtc_device *rtc = (struct rtc_device *)private;
 323         rtc_handle_legacy_irq(rtc, 1,  RTC_UF);
 324 }
 325
 326
 327 /**
 328  * rtc_pie_update_irq - PIE mode hrtimer hook
 329  * @timer: pointer to the pie mode hrtimer
 330  *
 331  * This function is used to emulate PIE mode interrupts
 332  * using an hrtimer. This function is called when the periodic
 333  * hrtimer expires.
 334  */
 335 enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer)
 336 {
 337         struct rtc_device *rtc;
 338         ktime_t period;
 339         int count;
 340         rtc = container_of(timer, struct rtc_device, pie_timer);
 341
 342         period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
 343         count = hrtimer_forward_now(timer, period);
 344
 345         rtc_handle_legacy_irq(rtc, count, RTC_PF);
 346
 347         return HRTIMER_RESTART;
 348 }
 349
 350 /**
 351  * rtc_update_irq - Triggered when a RTC interrupt occurs.
 352  * @rtc: the rtc device
 353  * @num: how many irqs are being reported (usually one)
 354  * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
 355  * Context: any
 356  */
 357 void rtc_update_irq(struct rtc_device *rtc,
 358                 unsigned long num, unsigned long events)
 359 {
 360         schedule_work(&rtc->irqwork);
 361 }
 362 EXPORT_SYMBOL_GPL(rtc_update_irq);
 363
 364 static int __rtc_match(struct device *dev, void *data)
 365 {
 366         char *name = (char *)data;
 367
 368         if (strcmp(dev_name(dev), name) == 0)
 369                 return 1;
 370         return 0;
 371 }
 372
 373 struct rtc_device *rtc_class_open(char *name)
 374 {
 375         struct device *dev;
 376         struct rtc_device *rtc = NULL;
 377
 378         dev = class_find_device(rtc_class, NULL, name, __rtc_match);
 379         if (dev)
 380                 rtc = to_rtc_device(dev);
 381
 382         if (rtc) {
 383                 if (!try_module_get(rtc->owner)) {
 384                         put_device(dev);
 385                         rtc = NULL;
 386                 }
 387         }
 388
 389         return rtc;
 390 }
 391 EXPORT_SYMBOL_GPL(rtc_class_open);
 392
 393 void rtc_class_close(struct rtc_device *rtc)
 394 {
 395         module_put(rtc->owner);
 396         put_device(&rtc->dev);
 397 }
 398 EXPORT_SYMBOL_GPL(rtc_class_close);
 399
 400 int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
 401 {
 402         int retval = -EBUSY;
 403
 404         if (task == NULL || task->func == NULL)
 405                 return -EINVAL;
 406
 407         /* Cannot register while the char dev is in use */
 408         if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
 409                 return -EBUSY;
 410
 411         spin_lock_irq(&rtc->irq_task_lock);
 412         if (rtc->irq_task == NULL) {
 413                 rtc->irq_task = task;
 414                 retval = 0;
 415         }
 416         spin_unlock_irq(&rtc->irq_task_lock);
 417
 418         clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
 419
 420         return retval;
 421 }
 422 EXPORT_SYMBOL_GPL(rtc_irq_register);
 423
 424 void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
 425 {
 426         spin_lock_irq(&rtc->irq_task_lock);
 427         if (rtc->irq_task == task)
 428                 rtc->irq_task = NULL;
 429         spin_unlock_irq(&rtc->irq_task_lock);
 430 }
 431 EXPORT_SYMBOL_GPL(rtc_irq_unregister);
 432
 433 /**
 434  * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
 435  * @rtc: the rtc device
 436  * @task: currently registered with rtc_irq_register()
 437  * @enabled: true to enable periodic IRQs
 438  * Context: any
 439  *
 440  * Note that rtc_irq_set_freq() should previously have been used to
 441  * specify the desired frequency of periodic IRQ task->func() callbacks.
 442  */
 443 int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled)
 444 {
 445         int err = 0;
 446         unsigned long flags;
 447
 448         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 449         if (rtc->irq_task != NULL && task == NULL)
 450                 err = -EBUSY;
 451         if (rtc->irq_task != task)
 452                 err = -EACCES;
 453
 454         if (enabled) {
 455                 ktime_t period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
 456                 hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
 457         } else {
 458                 hrtimer_cancel(&rtc->pie_timer);
 459         }
 460         rtc->pie_enabled = enabled;
 461         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 462
 463         return err;
 464 }
 465 EXPORT_SYMBOL_GPL(rtc_irq_set_state);
 466
 467 /**
 468  * rtc_irq_set_freq - set 2^N Hz periodic IRQ frequency for IRQ
 469  * @rtc: the rtc device
 470  * @task: currently registered with rtc_irq_register()
 471  * @freq: positive frequency with which task->func() will be called
 472  * Context: any
 473  *
 474  * Note that rtc_irq_set_state() is used to enable or disable the
 475  * periodic IRQs.
 476  */
 477 int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
 478 {
 479         int err = 0;
 480         unsigned long flags;
 481
 482         if (freq <= 0)
 483                 return -EINVAL;
 484
 485         spin_lock_irqsave(&rtc->irq_task_lock, flags);
 486         if (rtc->irq_task != NULL && task == NULL)
 487                 err = -EBUSY;
 488         if (rtc->irq_task != task)
 489                 err = -EACCES;
 490         if (err == 0) {
 491                 rtc->irq_freq = freq;
 492                 if (rtc->pie_enabled) {
 493                         ktime_t period;
 494                         hrtimer_cancel(&rtc->pie_timer);
 495                         period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
 496                         hrtimer_start(&rtc->pie_timer, period,
 497                                         HRTIMER_MODE_REL);
 498                 }
 499         }
 500         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 501         return err;
 502 }
 503 EXPORT_SYMBOL_GPL(rtc_irq_set_freq);
 504
 505 /**
 506  * rtc_timer_enqueue - Adds a rtc_timer to the rtc_device timerqueue
 507  * @rtc rtc device
 508  * @timer timer being added.
 509  *
 510  * Enqueues a timer onto the rtc devices timerqueue and sets
 511  * the next alarm event appropriately.
 512  *
 513  * Sets the enabled bit on the added timer.
 514  *
 515  * Must hold ops_lock for proper serialization of timerqueue
 516  */
 517 static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
 518 {
 519         timer->enabled = 1;
 520         timerqueue_add(&rtc->timerqueue, &timer->node);
 521         if (&timer->node == timerqueue_getnext(&rtc->timerqueue)) {
 522                 struct rtc_wkalrm alarm;
 523                 int err;
 524                 alarm.time = rtc_ktime_to_tm(timer->node.expires);
 525                 alarm.enabled = 1;
 526                 err = __rtc_set_alarm(rtc, &alarm);
 527                 if (err == -ETIME)
 528                         schedule_work(&rtc->irqwork);
 529                 else if (err) {
 530                         timerqueue_del(&rtc->timerqueue, &timer->node);
 531                         timer->enabled = 0;
 532                         return err;
 533                 }
 534         }
 535         return 0;
 536 }
 537
 538 /**
 539  * rtc_timer_remove - Removes a rtc_timer from the rtc_device timerqueue
 540  * @rtc rtc device
 541  * @timer timer being removed.
 542  *
 543  * Removes a timer onto the rtc devices timerqueue and sets
 544  * the next alarm event appropriately.
 545  *
 546  * Clears the enabled bit on the removed timer.
 547  *
 548  * Must hold ops_lock for proper serialization of timerqueue
 549  */
 550 static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
 551 {
 552         struct timerqueue_node *next = timerqueue_getnext(&rtc->timerqueue);
 553         timerqueue_del(&rtc->timerqueue, &timer->node);
 554         timer->enabled = 0;
 555         if (next == &timer->node) {
 556                 struct rtc_wkalrm alarm;
 557                 int err;
 558                 next = timerqueue_getnext(&rtc->timerqueue);
 559                 if (!next)
 560                         return;
 561                 alarm.time = rtc_ktime_to_tm(next->expires);
 562                 alarm.enabled = 1;
 563                 err = __rtc_set_alarm(rtc, &alarm);
 564                 if (err == -ETIME)
 565                         schedule_work(&rtc->irqwork);
 566         }
 567 }
 568
 569 /**
 570  * rtc_timer_do_work - Expires rtc timers
 571  * @rtc rtc device
 572  * @timer timer being removed.
 573  *
 574  * Expires rtc timers. Reprograms next alarm event if needed.
 575  * Called via worktask.
 576  *
 577  * Serializes access to timerqueue via ops_lock mutex
 578  */
 579 void rtc_timer_do_work(struct work_struct *work)
 580 {
 581         struct rtc_timer *timer;
 582         struct timerqueue_node *next;
 583         ktime_t now;
 584         struct rtc_time tm;
 585
 586         struct rtc_device *rtc =
 587                 container_of(work, struct rtc_device, irqwork);
 588
 589         mutex_lock(&rtc->ops_lock);
 590 again:
 591         __rtc_read_time(rtc, &tm);
 592         now = rtc_tm_to_ktime(tm);
 593         while ((next = timerqueue_getnext(&rtc->timerqueue))) {
 594                 if (next->expires.tv64 > now.tv64)
 595                         break;
 596
 597                 /* expire timer */
 598                 timer = container_of(next, struct rtc_timer, node);
 599                 timerqueue_del(&rtc->timerqueue, &timer->node);
 600                 timer->enabled = 0;
 601                 if (timer->task.func)
 602                         timer->task.func(timer->task.private_data);
 603
 604                 /* Re-add/fwd periodic timers */
 605                 if (ktime_to_ns(timer->period)) {
 606                         timer->node.expires = ktime_add(timer->node.expires,
 607                                                         timer->period);
 608                         timer->enabled = 1;
 609                         timerqueue_add(&rtc->timerqueue, &timer->node);
 610                 }
 611         }
 612
 613         /* Set next alarm */
 614         if (next) {
 615                 struct rtc_wkalrm alarm;
 616                 int err;
 617                 alarm.time = rtc_ktime_to_tm(next->expires);
 618                 alarm.enabled = 1;
 619                 err = __rtc_set_alarm(rtc, &alarm);
 620                 if (err == -ETIME)
 621                         goto again;
 622         }
 623
 624         mutex_unlock(&rtc->ops_lock);
 625 }
 626
 627
 628 /* rtc_timer_init - Initializes an rtc_timer
 629  * @timer: timer to be intiialized
 630  * @f: function pointer to be called when timer fires
 631  * @data: private data passed to function pointer
 632  *
 633  * Kernel interface to initializing an rtc_timer.
 634  */
 635 void rtc_timer_init(struct rtc_timer *timer, void (*f)(void* p), void* data)
 636 {
 637         timerqueue_init(&timer->node);
 638         timer->enabled = 0;
 639         timer->task.func = f;
 640         timer->task.private_data = data;
 641 }
 642
 643 /* rtc_timer_start - Sets an rtc_timer to fire in the future
 644  * @ rtc: rtc device to be used
 645  * @ timer: timer being set
 646  * @ expires: time at which to expire the timer
 647  * @ period: period that the timer will recur
 648  *
 649  * Kernel interface to set an rtc_timer
 650  */
 651 int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer* timer,
 652                         ktime_t expires, ktime_t period)
 653 {
 654         int ret = 0;
 655         mutex_lock(&rtc->ops_lock);
 656         if (timer->enabled)
 657                 rtc_timer_remove(rtc, timer);
 658
 659         timer->node.expires = expires;
 660         timer->period = period;
 661
 662         ret = rtc_timer_enqueue(rtc, timer);
 663
 664         mutex_unlock(&rtc->ops_lock);
 665         return ret;
 666 }
 667
 668 /* rtc_timer_cancel - Stops an rtc_timer
 669  * @ rtc: rtc device to be used
 670  * @ timer: timer being set
 671  *
 672  * Kernel interface to cancel an rtc_timer
 673  */
 674 int rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer* timer)
 675 {
 676         int ret = 0;
 677         mutex_lock(&rtc->ops_lock);
 678         if (timer->enabled)
 679                 rtc_timer_remove(rtc, timer);
 680         mutex_unlock(&rtc->ops_lock);
 681         return ret;
 682 }
 683
 684