Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rtc: Namespace fixup
  RTC: Remove UIE emulation
  RTC: Rework RTC code to use timerqueue for events

Fix up trivial conflict in drivers/rtc/rtc-dev.c

1 files changed, 349 insertions, 225 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index a0c816238aa9..90384b9f6b2c 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -14,15 +14,11 @@
 #include <linux/rtc.h>
 #include <linux/sched.h>
 #include <linux/log2.h>
+#include <linux/workqueue.h>
 
-int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
+static 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;
-
         if (!rtc->ops)
                 err = -ENODEV;
         else if (!rtc->ops->read_time)
@@ -31,7 +27,18 @@ int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
                 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;
 }
@@ -106,188 +113,54 @@ int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
 }
 EXPORT_SYMBOL_GPL(rtc_set_mmss);
 
-static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
+int rtc_read_alarm(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);
-        }
-
+        alarm->enabled = rtc->aie_timer.enabled;
+        if (alarm->enabled)
+                alarm->time = rtc_ktime_to_tm(rtc->aie_timer.node.expires);
         mutex_unlock(&rtc->ops_lock);
-        return err;
+
+        return 0;
 }
+EXPORT_SYMBOL_GPL(rtc_read_alarm);
 
-int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
+int __rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 {
+        struct rtc_time tm;
+        long now, scheduled;
         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)
+        err = rtc_valid_tm(&alarm->time);
+        if (err)
                 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;
-                if (!alarm->enabled)
-                        return 0;
-
-                /* 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 = now.tm_mday;
-                missing = day;
-        }
-        if (alarm->time.tm_mon == -1) {
-                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) {
+        rtc_tm_to_time(&alarm->time, &scheduled);
 
-        /* 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.
+        /* 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.
          */
-        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;
+        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;
 }
-EXPORT_SYMBOL_GPL(rtc_read_alarm);
 
 int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 {
@@ -300,16 +173,18 @@ int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
         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);
-
+        if (rtc->aie_timer.enabled) {
+                rtc_timer_remove(rtc, &rtc->aie_timer);
+                rtc->aie_timer.enabled = 0;
+        }
+        rtc->aie_timer.node.expires = rtc_tm_to_ktime(alarm->time);
+        rtc->aie_timer.period = ktime_set(0, 0);
+        if (alarm->enabled) {
+                rtc->aie_timer.enabled = 1;
+                rtc_timer_enqueue(rtc, &rtc->aie_timer);
+        }
         mutex_unlock(&rtc->ops_lock);
-        return err;
+        return 0;
 }
 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 
@@ -319,6 +194,16 @@ int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
         if (err)
                 return err;
 
+        if (rtc->aie_timer.enabled != enabled) {
+                if (enabled) {
+                        rtc->aie_timer.enabled = 1;
+                        rtc_timer_enqueue(rtc, &rtc->aie_timer);
+                } else {
+                        rtc_timer_remove(rtc, &rtc->aie_timer);
+                        rtc->aie_timer.enabled = 0;
+                }
+        }
+
         if (!rtc->ops)
                 err = -ENODEV;
         else if (!rtc->ops->alarm_irq_enable)
@@ -337,52 +222,53 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
         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, enabled);
+        /* make sure we're changing state */
+        if (rtc->uie_rtctimer.enabled == enabled)
+                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);
+                rtc->uie_rtctimer.enabled = 1;
+                rtc_timer_enqueue(rtc, &rtc->uie_rtctimer);
+        } else {
+                rtc_timer_remove(rtc, &rtc->uie_rtctimer);
+                rtc->uie_rtctimer.enabled = 0;
         }
-#endif
-
-        if (!rtc->ops)
-                err = -ENODEV;
-        else if (!rtc->ops->update_irq_enable)
-                err = -EINVAL;
-        else
-                err = rtc->ops->update_irq_enable(rtc->dev.parent, enabled);
 
+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_update_irq - report RTC periodic, alarm, and/or update irqs
- * @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
+ * 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 occured (or been emulated).
+ *
+ * Triggers the registered irq_task function callback.
  */
-void rtc_update_irq(struct rtc_device *rtc,
-                unsigned long num, unsigned long events)
+static 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)) | events;
+        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);
@@ -391,6 +277,69 @@ void rtc_update_irq(struct rtc_device *rtc,
         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)
+{
+        schedule_work(&rtc->irqwork);
+}
 EXPORT_SYMBOL_GPL(rtc_update_irq);
 
 static int __rtc_match(struct device *dev, void *data)
@@ -477,18 +426,20 @@ int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled
         int err = 0;
         unsigned long flags;
 
-        if (rtc->ops->irq_set_state == NULL)
-                return -ENXIO;
-
         spin_lock_irqsave(&rtc->irq_task_lock, flags);
         if (rtc->irq_task != NULL && task == NULL)
                 err = -EBUSY;
         if (rtc->irq_task != task)
                 err = -EACCES;
-        spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
-        if (err == 0)
-                err = rtc->ops->irq_set_state(rtc->dev.parent, enabled);
+        if (enabled) {
+                ktime_t period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
+                hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
+        } else {
+                hrtimer_cancel(&rtc->pie_timer);
+        }
+        rtc->pie_enabled = enabled;
+        spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
         return err;
 }
@@ -509,21 +460,194 @@ int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
         int err = 0;
         unsigned long flags;
 
-        if (rtc->ops->irq_set_freq == NULL)
-                return -ENXIO;
-
         spin_lock_irqsave(&rtc->irq_task_lock, flags);
         if (rtc->irq_task != NULL && task == NULL)
                 err = -EBUSY;
         if (rtc->irq_task != task)
                 err = -EACCES;
-        spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
-
         if (err == 0) {
-                err = rtc->ops->irq_set_freq(rtc->dev.parent, freq);
-                if (err == 0)
-                        rtc->irq_freq = freq;
+                rtc->irq_freq = freq;
+                if (rtc->pie_enabled) {
+                        ktime_t period;
+                        hrtimer_cancel(&rtc->pie_timer);
+                        period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
+                        hrtimer_start(&rtc->pie_timer, period,
+                                        HRTIMER_MODE_REL);
+                }
         }
+        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.
+ *
+ * Must hold ops_lock for proper serialization of timerqueue
+ */
+void rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
+{
+        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);
+        }
+}
+
+/**
+ * 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.
+ *
+ * Must hold ops_lock for proper serialization of timerqueue
+ */
+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);
+
+        if (next == &timer->node) {
+                struct rtc_wkalrm alarm;
+                int err;
+                next = timerqueue_getnext(&rtc->timerqueue);
+                if (!next)
+                        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:
+        __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;
+        }
+
+        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;
+
+        timer->enabled = 1;
+        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);
+        timer->enabled = 0;
+        mutex_unlock(&rtc->ops_lock);
+        return ret;
+}
+
+