text: /*
   * RTC subsystem, interface functions
   *
   * Copyright (C) 2005 Tower Technologies
   * Author: Alessandro Zummo <a.zummo@towertech.it>
   *
   * based on arch/arm/common/rtctime.c
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
  */
  
  #include <linux/rtc.h>
  #include <linux/sched.h>
  #include <linux/module.h>
  #include <linux/log2.h>
  #include <linux/workqueue.h>
  
  static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
  static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
  
  static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
  {
  	int err;
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (!rtc->ops->read_time)
  		err = -EINVAL;
  	else {
  		memset(tm, 0, sizeof(struct rtc_time));
  		err = rtc->ops->read_time(rtc->dev.parent, tm);
  	}
  	return err;
  }
  
  int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
  {
  	int err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	err = __rtc_read_time(rtc, tm);
  	mutex_unlock(&rtc->ops_lock);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_read_time);
  
  int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
  {
  	int err;
  
  	err = rtc_valid_tm(tm);
  	if (err != 0)
  		return err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (rtc->ops->set_time)
  		err = rtc->ops->set_time(rtc->dev.parent, tm);
  	else if (rtc->ops->set_mmss) {
  		unsigned long secs;
  		err = rtc_tm_to_time(tm, &secs);
  		if (err == 0)
  			err = rtc->ops->set_mmss(rtc->dev.parent, secs);
  	} else
  		err = -EINVAL;
  
  	mutex_unlock(&rtc->ops_lock);
  	/* A timer might have just expired */
  	schedule_work(&rtc->irqwork);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_set_time);
  
  int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
  {
  	int err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (rtc->ops->set_mmss)
  		err = rtc->ops->set_mmss(rtc->dev.parent, secs);
  	else if (rtc->ops->read_time && rtc->ops->set_time) {
  		struct rtc_time new, old;
  
  		err = rtc->ops->read_time(rtc->dev.parent, &old);
  		if (err == 0) {
  			rtc_time_to_tm(secs, &new);
  
  			/*
  			 * avoid writing when we're going to change the day of
  			 * the month. We will retry in the next minute. This
  			 * basically means that if the RTC must not drift
  			 * by more than 1 minute in 11 minutes.
  			 */
  			if (!((old.tm_hour == 23 && old.tm_min == 59) ||
  				(new.tm_hour == 23 && new.tm_min == 59)))
  				err = rtc->ops->set_time(rtc->dev.parent,
  						&new);
  		}
  	}
  	else
  		err = -EINVAL;
  
  	mutex_unlock(&rtc->ops_lock);
  	/* A timer might have just expired */
  	schedule_work(&rtc->irqwork);
  
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_set_mmss);
  
  static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  	int err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	if (rtc->ops == NULL)
  		err = -ENODEV;
  	else if (!rtc->ops->read_alarm)
  		err = -EINVAL;
  	else {
  		memset(alarm, 0, sizeof(struct rtc_wkalrm));
  		err = rtc->ops->read_alarm(rtc->dev.parent, alarm);
  	}
  
  	mutex_unlock(&rtc->ops_lock);
  	return err;
  }
  
  int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  	int err;
  	struct rtc_time before, now;
  	int first_time = 1;
  	unsigned long t_now, t_alm;
  	enum { none, day, month, year } missing = none;
  	unsigned days;
  
  	/* The lower level RTC driver may return -1 in some fields,
  	 * creating invalid alarm->time values, for reasons like:
  	 *
  	 *   - The hardware may not be capable of filling them in;
  	 *     many alarms match only on time-of-day fields, not
  	 *     day/month/year calendar data.
  	 *
  	 *   - Some hardware uses illegal values as "wildcard" match
  	 *     values, which non-Linux firmware (like a BIOS) may try
  	 *     to set up as e.g. "alarm 15 minutes after each hour".
  	 *     Linux uses only oneshot alarms.
  	 *
  	 * When we see that here, we deal with it by using values from
  	 * a current RTC timestamp for any missing (-1) values.  The
  	 * RTC driver prevents "periodic alarm" modes.
  	 *
  	 * But this can be racey, because some fields of the RTC timestamp
  	 * may have wrapped in the interval since we read the RTC alarm,
  	 * which would lead to us inserting inconsistent values in place
  	 * of the -1 fields.
  	 *
  	 * Reading the alarm and timestamp in the reverse sequence
  	 * would have the same race condition, and not solve the issue.
  	 *
  	 * So, we must first read the RTC timestamp,
  	 * then read the RTC alarm value,
  	 * and then read a second RTC timestamp.
  	 *
  	 * If any fields of the second timestamp have changed
  	 * when compared with the first timestamp, then we know
  	 * our timestamp may be inconsistent with that used by
  	 * the low-level rtc_read_alarm_internal() function.
  	 *
  	 * So, when the two timestamps disagree, we just loop and do
  	 * the process again to get a fully consistent set of values.
  	 *
  	 * This could all instead be done in the lower level driver,
  	 * but since more than one lower level RTC implementation needs it,
  	 * then it's probably best best to do it here instead of there..
  	 */
  
  	/* Get the "before" timestamp */
  	err = rtc_read_time(rtc, &before);
  	if (err < 0)
  		return err;
  	do {
  		if (!first_time)
  			memcpy(&before, &now, sizeof(struct rtc_time));
  		first_time = 0;
  
  		/* get the RTC alarm values, which may be incomplete */
  		err = rtc_read_alarm_internal(rtc, alarm);
  		if (err)
  			return err;
  
  		/* full-function RTCs won't have such missing fields */
  		if (rtc_valid_tm(&alarm->time) == 0)
  			return 0;
  
  		/* get the "after" timestamp, to detect wrapped fields */
  		err = rtc_read_time(rtc, &now);
  		if (err < 0)
  			return err;
  
  		/* note that tm_sec is a "don't care" value here: */
  	} while (   before.tm_min   != now.tm_min
  		 || before.tm_hour  != now.tm_hour
  		 || before.tm_mon   != now.tm_mon
  		 || before.tm_year  != now.tm_year);
  
  	/* Fill in the missing alarm fields using the timestamp; we
  	 * know there's at least one since alarm->time is invalid.
  	 */
  	if (alarm->time.tm_sec == -1)
  		alarm->time.tm_sec = now.tm_sec;
  	if (alarm->time.tm_min == -1)
  		alarm->time.tm_min = now.tm_min;
  	if (alarm->time.tm_hour == -1)
  		alarm->time.tm_hour = now.tm_hour;
  
  	/* For simplicity, only support date rollover for now */
  	if (alarm->time.tm_mday < 1 || alarm->time.tm_mday > 31) {
  		alarm->time.tm_mday = now.tm_mday;
  		missing = day;
  	}
  	if ((unsigned)alarm->time.tm_mon >= 12) {
  		alarm->time.tm_mon = now.tm_mon;
  		if (missing == none)
  			missing = month;
  	}
  	if (alarm->time.tm_year == -1) {
  		alarm->time.tm_year = now.tm_year;
  		if (missing == none)
  			missing = year;
  	}
  
  	/* with luck, no rollover is needed */
  	rtc_tm_to_time(&now, &t_now);
  	rtc_tm_to_time(&alarm->time, &t_alm);
  	if (t_now < t_alm)
  		goto done;
  
  	switch (missing) {
  
  	/* 24 hour rollover ... if it's now 10am Monday, an alarm that
  	 * that will trigger at 5am will do so at 5am Tuesday, which
  	 * could also be in the next month or year.  This is a common
  	 * case, especially for PCs.
  	 */
  	case day:
  		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day");
  		t_alm += 24 * 60 * 60;
  		rtc_time_to_tm(t_alm, &alarm->time);
  		break;
  
  	/* Month rollover ... if it's the 31th, an alarm on the 3rd will
  	 * be next month.  An alarm matching on the 30th, 29th, or 28th
  	 * may end up in the month after that!  Many newer PCs support
  	 * this type of alarm.
  	 */
  	case month:
  		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month");
  		do {
  			if (alarm->time.tm_mon < 11)
  				alarm->time.tm_mon++;
  			else {
  				alarm->time.tm_mon = 0;
  				alarm->time.tm_year++;
  			}
  			days = rtc_month_days(alarm->time.tm_mon,
  					alarm->time.tm_year);
  		} while (days < alarm->time.tm_mday);
  		break;
  
  	/* Year rollover ... easy except for leap years! */
  	case year:
  		dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year");
  		do {
  			alarm->time.tm_year++;
  		} while (rtc_valid_tm(&alarm->time) != 0);
  		break;
  
  	default:
  		dev_warn(&rtc->dev, "alarm rollover not handled\n");
  	}
  
  done:
  	return 0;
  }
  
  int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  #ifdef RTC_LEGACY_ALARM_IMPL
  	return __rtc_read_alarm(rtc, alarm);
  #else	
  	int err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  	if (rtc->ops == NULL)
  		err = -ENODEV;
  	else if (!rtc->ops->read_alarm)
  		err = -EINVAL;
  	else {
  		memset(alarm, 0, sizeof(struct rtc_wkalrm));
  		alarm->enabled = rtc->aie_timer.enabled;
  		alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
  	}
  	mutex_unlock(&rtc->ops_lock);
  
  	return err;
  #endif
  }
  EXPORT_SYMBOL_GPL(rtc_read_alarm);
  
  static int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  #ifdef RTC_LEGACY_ALARM_IMPL
  	WARN(1, "__rtc_set_alarm() is not supported!!\n");
  	return -EPERM;
  #else	
  	struct rtc_time tm;
  	long now, scheduled;
  	int err;
  
  	err = rtc_valid_tm(&alarm->time);
  	if (err)
  		return err;
  	rtc_tm_to_time(&alarm->time, &scheduled);
  
  	/* Make sure we're not setting alarms in the past */
  	err = __rtc_read_time(rtc, &tm);
  	rtc_tm_to_time(&tm, &now);
  	if (scheduled <= now)
  		return -ETIME;
  	/*
  	 * XXX - We just checked to make sure the alarm time is not
  	 * in the past, but there is still a race window where if
  	 * the is alarm set for the next second and the second ticks
  	 * over right here, before we set the alarm.
  	 */
  
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (!rtc->ops->set_alarm)
  		err = -EINVAL;
  	else
  		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
  
  	return err;
  #endif
  }
  
  int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  	int err;
  
  	err = rtc_valid_tm(&alarm->time);
  	if (err != 0)
  		return err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  #ifdef RTC_LEGACY_ALARM_IMPL
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (!rtc->ops->set_alarm)
  		err = -EINVAL;
  	else
  		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
  #else
  
  	if (rtc->aie_timer.enabled) {
  		rtc_timer_remove(rtc, &rtc->aie_timer);
  	}
  	rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
  	rtc->aie_timer.period = ktime_set(0, 0);
  	if (alarm->enabled) {
  		err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
  	}
  #endif
  	mutex_unlock(&rtc->ops_lock);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_set_alarm);
  
  int rtc_set_alarm_poweron(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  	int err;
  
  	err = rtc_valid_tm(&alarm->time);
  	if (err != 0)
  		return err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  		
  	if (!rtc->ops)
  		err = -ENODEV;
  	else if (!rtc->ops->set_alarm)
  		err = -EINVAL;
  	else
  		err = rtc->ops->set_alarm(rtc->dev.parent, alarm);
  	
  	mutex_unlock(&rtc->ops_lock);
  	return err;	
  }
  EXPORT_SYMBOL_GPL(rtc_set_alarm_poweron);
  
  /* Called once per device from rtc_device_register */
  int rtc_initialize_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
  {
  #ifdef RTC_LEGACY_ALARM_IMPL
  			return 0;
  #else
  	int err;
  	struct rtc_time now;
  
  	err = rtc_valid_tm(&alarm->time);
  	if (err != 0)
  		return err;
  
  	err = rtc_read_time(rtc, &now);
  	if (err)
  		return err;
  
  	err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
  	rtc->aie_timer.period = ktime_set(0, 0);
  
  	/* Alarm has to be enabled & in the futrure for us to enqueue it */
  	if (alarm->enabled && (rtc_tm_to_ktime(now).tv64 <
  			 rtc->aie_timer.node.expires.tv64)) {
  
  		rtc->aie_timer.enabled = 1;
  		timerqueue_add(&rtc->timerqueue, &rtc->aie_timer.node);
  	}
  	mutex_unlock(&rtc->ops_lock);
  	return err;
  #endif
  }
  EXPORT_SYMBOL_GPL(rtc_initialize_alarm);
  
  
  
  int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
  {
  	int err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  	if (rtc->aie_timer.enabled != enabled) {
  		if (enabled)
  			err = rtc_timer_enqueue(rtc, &rtc->aie_timer);
  		else
  			rtc_timer_remove(rtc, &rtc->aie_timer);
  	}
  
  	if (err)
  		/* nothing */;
  	else if (!rtc->ops)
  		err = -ENODEV;
  	else if (!rtc->ops->alarm_irq_enable)
  		err = -EINVAL;
  	else
  		err = rtc->ops->alarm_irq_enable(rtc->dev.parent, enabled);
  
  	mutex_unlock(&rtc->ops_lock);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_alarm_irq_enable);
  
  int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
  {
  	int err = mutex_lock_interruptible(&rtc->ops_lock);
  	if (err)
  		return err;
  
  #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
  	if (enabled == 0 && rtc->uie_irq_active) {
  		mutex_unlock(&rtc->ops_lock);
  		return rtc_dev_update_irq_enable_emul(rtc, 0);
  	}
  #endif
  	/* make sure we're changing state */
  	if (rtc->uie_rtctimer.enabled == enabled)
  		goto out;
  
  	if (rtc->uie_unsupported) {
  		err = -EINVAL;
  		goto out;
  	}
  
  	if (enabled) {
  		struct rtc_time tm;
  		ktime_t now, onesec;
  
  		__rtc_read_time(rtc, &tm);
  		onesec = ktime_set(1, 0);
  		now = rtc_tm_to_ktime(tm);
  		rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
  		rtc->uie_rtctimer.period = ktime_set(1, 0);
  		err = rtc_timer_enqueue(rtc, &rtc->uie_rtctimer);
  	} else
  		rtc_timer_remove(rtc, &rtc->uie_rtctimer);
  
  out:
  	mutex_unlock(&rtc->ops_lock);
  #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
  	/*
  	 * Enable emulation if the driver did not provide
  	 * the update_irq_enable function pointer or if returned
  	 * -EINVAL to signal that it has been configured without
  	 * interrupts or that are not available at the moment.
  	 */
  	if (err == -EINVAL)
  		err = rtc_dev_update_irq_enable_emul(rtc, enabled);
  #endif
  	return err;
  
  }
  EXPORT_SYMBOL_GPL(rtc_update_irq_enable);
  
  
  /**
   * rtc_handle_legacy_irq - AIE, UIE and PIE event hook
   * @rtc: pointer to the rtc device
   *
   * This function is called when an AIE, UIE or PIE mode interrupt
   * has occurred (or been emulated).
   *
   * Triggers the registered irq_task function callback.
   */
  void rtc_handle_legacy_irq(struct rtc_device *rtc, int num, int mode)
  {
  	unsigned long flags;
  
  	/* mark one irq of the appropriate mode */
  	spin_lock_irqsave(&rtc->irq_lock, flags);
  	rtc->irq_data = (rtc->irq_data + (num << 8)) | (RTC_IRQF|mode);
  	spin_unlock_irqrestore(&rtc->irq_lock, flags);
  
  	/* call the task func */
  	spin_lock_irqsave(&rtc->irq_task_lock, flags);
  	if (rtc->irq_task)
  		rtc->irq_task->func(rtc->irq_task->private_data);
  	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
  
  	wake_up_interruptible(&rtc->irq_queue);
  	kill_fasync(&rtc->async_queue, SIGIO, POLL_IN);
  }
  
  
  /**
   * rtc_aie_update_irq - AIE mode rtctimer hook
   * @private: pointer to the rtc_device
   *
   * This functions is called when the aie_timer expires.
   */
  void rtc_aie_update_irq(void *private)
  {
  	struct rtc_device *rtc = (struct rtc_device *)private;
  	rtc_handle_legacy_irq(rtc, 1, RTC_AF);
  }
  
  
  /**
   * rtc_uie_update_irq - UIE mode rtctimer hook
   * @private: pointer to the rtc_device
   *
   * This functions is called when the uie_timer expires.
   */
  void rtc_uie_update_irq(void *private)
  {
  	struct rtc_device *rtc = (struct rtc_device *)private;
  	rtc_handle_legacy_irq(rtc, 1,  RTC_UF);
  }
  
  
  /**
   * rtc_pie_update_irq - PIE mode hrtimer hook
   * @timer: pointer to the pie mode hrtimer
   *
   * This function is used to emulate PIE mode interrupts
   * using an hrtimer. This function is called when the periodic
   * hrtimer expires.
   */
  enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer)
  {
  	struct rtc_device *rtc;
  	ktime_t period;
  	int count;
  	rtc = container_of(timer, struct rtc_device, pie_timer);
  
  	period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
  	count = hrtimer_forward_now(timer, period);
  
  	rtc_handle_legacy_irq(rtc, count, RTC_PF);
  
  	return HRTIMER_RESTART;
  }
  
  /**
   * rtc_update_irq - Triggered when a RTC interrupt occurs.
   * @rtc: the rtc device
   * @num: how many irqs are being reported (usually one)
   * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
   * Context: any
   */
  void rtc_update_irq(struct rtc_device *rtc,
  		unsigned long num, unsigned long events)
  {
  	pm_stay_awake(rtc->dev.parent);
  	schedule_work(&rtc->irqwork);
  }
  EXPORT_SYMBOL_GPL(rtc_update_irq);
  
  static int __rtc_match(struct device *dev, const void *data)
  {
  	const char *name = data;
  
  	if (strcmp(dev_name(dev), name) == 0)
  		return 1;
  	return 0;
  }
  
  struct rtc_device *rtc_class_open(const char *name)
  {
  	struct device *dev;
  	struct rtc_device *rtc = NULL;
  
  	dev = class_find_device(rtc_class, NULL, name, __rtc_match);
  	if (dev)
  		rtc = to_rtc_device(dev);
  
  	if (rtc) {
  		if (!try_module_get(rtc->owner)) {
  			put_device(dev);
  			rtc = NULL;
  		}
  	}
  
  	return rtc;
  }
  EXPORT_SYMBOL_GPL(rtc_class_open);
  
  void rtc_class_close(struct rtc_device *rtc)
  {
  	module_put(rtc->owner);
  	put_device(&rtc->dev);
  }
  EXPORT_SYMBOL_GPL(rtc_class_close);
  
  int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
  {
  	int retval = -EBUSY;
  
  	if (task == NULL || task->func == NULL)
  		return -EINVAL;
  
  	/* Cannot register while the char dev is in use */
  	if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
  		return -EBUSY;
  
  	spin_lock_irq(&rtc->irq_task_lock);
  	if (rtc->irq_task == NULL) {
  		rtc->irq_task = task;
  		retval = 0;
  	}
  	spin_unlock_irq(&rtc->irq_task_lock);
  
  	clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
  
  	return retval;
  }
  EXPORT_SYMBOL_GPL(rtc_irq_register);
  
  void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
  {
  	spin_lock_irq(&rtc->irq_task_lock);
  	if (rtc->irq_task == task)
  		rtc->irq_task = NULL;
  	spin_unlock_irq(&rtc->irq_task_lock);
  }
  EXPORT_SYMBOL_GPL(rtc_irq_unregister);
  
  static int rtc_update_hrtimer(struct rtc_device *rtc, int enabled)
  {
  	/*
  	 * We always cancel the timer here first, because otherwise
  	 * we could run into BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
  	 * when we manage to start the timer before the callback
  	 * returns HRTIMER_RESTART.
  	 *
  	 * We cannot use hrtimer_cancel() here as a running callback
  	 * could be blocked on rtc->irq_task_lock and hrtimer_cancel()
  	 * would spin forever.
  	 */
  	if (hrtimer_try_to_cancel(&rtc->pie_timer) < 0)
  		return -1;
  
  	if (enabled) {
  		ktime_t period = ktime_set(0, NSEC_PER_SEC / rtc->irq_freq);
  
  		hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
  	}
  	return 0;
  }
  
  /**
   * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
   * @rtc: the rtc device
   * @task: currently registered with rtc_irq_register()
   * @enabled: true to enable periodic IRQs
   * Context: any
   *
   * Note that rtc_irq_set_freq() should previously have been used to
   * specify the desired frequency of periodic IRQ task->func() callbacks.
   */
  int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled)
  {
  	int err = 0;
  	unsigned long flags;
  
  retry:
  	spin_lock_irqsave(&rtc->irq_task_lock, flags);
  	if (rtc->irq_task != NULL && task == NULL)
  		err = -EBUSY;
  	if (rtc->irq_task != task)
  		err = -EACCES;
  	if (!err) {
  		if (rtc_update_hrtimer(rtc, enabled) < 0) {
  			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
  			cpu_relax();
  			goto retry;
  		}
  		rtc->pie_enabled = enabled;
  	}
  	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_irq_set_state);
  
  /**
   * rtc_irq_set_freq - set 2^N Hz periodic IRQ frequency for IRQ
   * @rtc: the rtc device
   * @task: currently registered with rtc_irq_register()
   * @freq: positive frequency with which task->func() will be called
   * Context: any
   *
   * Note that rtc_irq_set_state() is used to enable or disable the
   * periodic IRQs.
   */
  int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
  {
  	int err = 0;
  	unsigned long flags;
  
  	if (freq <= 0 || freq > RTC_MAX_FREQ)
  		return -EINVAL;
  retry:
  	spin_lock_irqsave(&rtc->irq_task_lock, flags);
  	if (rtc->irq_task != NULL && task == NULL)
  		err = -EBUSY;
  	if (rtc->irq_task != task)
  		err = -EACCES;
  	if (!err) {
  		rtc->irq_freq = freq;
  		if (rtc->pie_enabled && rtc_update_hrtimer(rtc, 1) < 0) {
  			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
  			cpu_relax();
  			goto retry;
  		}
  	}
  	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rtc_irq_set_freq);
  
  /**
   * rtc_timer_enqueue - Adds a rtc_timer to the rtc_device timerqueue
   * @rtc rtc device
   * @timer timer being added.
   *
   * Enqueues a timer onto the rtc devices timerqueue and sets
   * the next alarm event appropriately.
   *
   * Sets the enabled bit on the added timer.
   *
   * Must hold ops_lock for proper serialization of timerqueue
   */
  static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
  {
  	timer->enabled = 1;
  	timerqueue_add(&rtc->timerqueue, &timer->node);
  	if (&timer->node == timerqueue_getnext(&rtc->timerqueue)) {
  		struct rtc_wkalrm alarm;
  		int err;
  		alarm.time = rtc_ktime_to_tm(timer->node.expires);
  		alarm.enabled = 1;
  		err = __rtc_set_alarm(rtc, &alarm);
  		if (err == -ETIME)
  			schedule_work(&rtc->irqwork);
  		else if (err) {
  			timerqueue_del(&rtc->timerqueue, &timer->node);
  			timer->enabled = 0;
  			return err;
  		}
  	}
  	return 0;
  }
  
  static void rtc_alarm_disable(struct rtc_device *rtc)
  {
  	if (!rtc->ops || !rtc->ops->alarm_irq_enable)
  		return;
  
  	rtc->ops->alarm_irq_enable(rtc->dev.parent, false);
  }
  
  /**
   * rtc_timer_remove - Removes a rtc_timer from the rtc_device timerqueue
   * @rtc rtc device
   * @timer timer being removed.
   *
   * Removes a timer onto the rtc devices timerqueue and sets
   * the next alarm event appropriately.
   *
   * Clears the enabled bit on the removed timer.
   *
   * Must hold ops_lock for proper serialization of timerqueue
   */
  static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer)
  {
  	struct timerqueue_node *next = timerqueue_getnext(&rtc->timerqueue);
  	timerqueue_del(&rtc->timerqueue, &timer->node);
  	timer->enabled = 0;
  	if (next == &timer->node) {
  		struct rtc_wkalrm alarm;
  		int err;
  		next = timerqueue_getnext(&rtc->timerqueue);
  		if (!next) {
  			rtc_alarm_disable(rtc);
  			return;
  		}
  		alarm.time = rtc_ktime_to_tm(next->expires);
  		alarm.enabled = 1;
  		err = __rtc_set_alarm(rtc, &alarm);
  		if (err == -ETIME)
  			schedule_work(&rtc->irqwork);
  	}
  }
  
  /**
   * rtc_timer_do_work - Expires rtc timers
   * @rtc rtc device
   * @timer timer being removed.
   *
   * Expires rtc timers. Reprograms next alarm event if needed.
   * Called via worktask.
   *
   * Serializes access to timerqueue via ops_lock mutex
   */
  void rtc_timer_do_work(struct work_struct *work)
  {
  	struct rtc_timer *timer;
  	struct timerqueue_node *next;
  	ktime_t now;
  	struct rtc_time tm;
  
  	struct rtc_device *rtc =
  		container_of(work, struct rtc_device, irqwork);
  
  	mutex_lock(&rtc->ops_lock);
  again:
  	pm_relax(rtc->dev.parent);
  	__rtc_read_time(rtc, &tm);
  	now = rtc_tm_to_ktime(tm);
  	while ((next = timerqueue_getnext(&rtc->timerqueue))) {
  		if (next->expires.tv64 > now.tv64)
  			break;
  
  		/* expire timer */
  		timer = container_of(next, struct rtc_timer, node);
  		timerqueue_del(&rtc->timerqueue, &timer->node);
  		timer->enabled = 0;
  		if (timer->task.func)
  			timer->task.func(timer->task.private_data);
  
  		/* Re-add/fwd periodic timers */
  		if (ktime_to_ns(timer->period)) {
  			timer->node.expires = ktime_add(timer->node.expires,
  							timer->period);
  			timer->enabled = 1;
  			timerqueue_add(&rtc->timerqueue, &timer->node);
  		}
  	}
  
  	/* Set next alarm */
  	if (next) {
  		struct rtc_wkalrm alarm;
  		int err;
  		alarm.time = rtc_ktime_to_tm(next->expires);
  		alarm.enabled = 1;
  		err = __rtc_set_alarm(rtc, &alarm);
  		if (err == -ETIME)
  			goto again;
  	} else
  		rtc_alarm_disable(rtc);
  
  	mutex_unlock(&rtc->ops_lock);
  }
  
  
  /* rtc_timer_init - Initializes an rtc_timer
   * @timer: timer to be intiialized
   * @f: function pointer to be called when timer fires
   * @data: private data passed to function pointer
   *
   * Kernel interface to initializing an rtc_timer.
   */
  void rtc_timer_init(struct rtc_timer *timer, void (*f)(void* p), void* data)
  {
  	timerqueue_init(&timer->node);
  	timer->enabled = 0;
  	timer->task.func = f;
  	timer->task.private_data = data;
  }
  
  /* rtc_timer_start - Sets an rtc_timer to fire in the future
   * @ rtc: rtc device to be used
   * @ timer: timer being set
   * @ expires: time at which to expire the timer
   * @ period: period that the timer will recur
   *
   * Kernel interface to set an rtc_timer
   */
  int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer* timer,
  			ktime_t expires, ktime_t period)
  {
  	int ret = 0;
  	mutex_lock(&rtc->ops_lock);
  	if (timer->enabled)
  		rtc_timer_remove(rtc, timer);
  
  	timer->node.expires = expires;
  	timer->period = period;
  
  	ret = rtc_timer_enqueue(rtc, timer);
  
  	mutex_unlock(&rtc->ops_lock);
  	return ret;
  }
  
  /* rtc_timer_cancel - Stops an rtc_timer
   * @ rtc: rtc device to be used
   * @ timer: timer being set
   *
   * Kernel interface to cancel an rtc_timer
   */
  int rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer* timer)
  {
  	int ret = 0;
  	mutex_lock(&rtc->ops_lock);
  	if (timer->enabled)
  		rtc_timer_remove(rtc, timer);
  	mutex_unlock(&rtc->ops_lock);
  	return ret;
  }
  
  
  