From 947d7ea6f60b5fe24d8f8b69e55e0d6e1e8855e7 Mon Sep 17 00:00:00 2001 From: Mario Limonciello Date: Wed, 20 May 2026 23:37:13 -0500 Subject: [PATCH] rtc: interface: Add rtc_read_next_alarm() to read next expiring timer Add a new function rtc_read_next_alarm() that reads the next expiring alarm from the RTC timerqueue. This is different from rtc_read_alarm(), which only reads the aie_timer. The wakealarm sysfs file programs the rtc->aie_timer, whereas the alarmtimer suspend routine programs its own timer into the RTC timerqueue. Both timers end up in the RTC's timerqueue, and the first expiring timer is what gets armed in the hardware. This new function allows code to query which alarm will actually fire next, regardless of which subsystem programmed it. This is needed by platform code that needs to program secondary timers based on the actual next wakeup time. Link: https://lore.kernel.org/all/87ed50z0le.ffs@tglx Suggested-by: Thomas Gleixner Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Mario Limonciello Link: https://patch.msgid.link/20260521043714.1022930-2-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni --- drivers/rtc/interface.c | 40 ++++++++++++++++++++++++++++++++++++++++ include/linux/rtc.h | 2 ++ 2 files changed, 42 insertions(+) diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index 1906f4884a83..7859be8f2a92 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -384,6 +384,46 @@ int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) return err; } +/** + * rtc_read_next_alarm - read the next expiring alarm + * @rtc: RTC device + * @alarm: storage for the alarm information + * + * Read the next expiring alarm from the RTC timerqueue. This returns + * the alarm that will actually fire next, which may be different from + * rtc_read_alarm() if multiple timers are queued (e.g., alarmtimer + * and wakealarm sysfs both active). + * + * Returns: 0 on success, -ENOENT if no alarm is pending, or other error. + */ +int rtc_read_next_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) +{ + struct timerqueue_node *next; + int err; + + if (!rtc || !alarm) + return -EINVAL; + + err = mutex_lock_interruptible(&rtc->ops_lock); + if (err) + return err; + + next = timerqueue_getnext(&rtc->timerqueue); + if (!next) { + err = -ENOENT; + goto unlock; + } + + memset(alarm, 0, sizeof(struct rtc_wkalrm)); + alarm->time = rtc_ktime_to_tm(next->expires); + alarm->enabled = 1; + +unlock: + mutex_unlock(&rtc->ops_lock); + return err; +} +EXPORT_SYMBOL_GPL(rtc_read_next_alarm); + int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) { int err; diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 95da051fb155..c09fc22819d0 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -190,6 +190,8 @@ extern int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm); int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm); extern int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alrm); +extern int rtc_read_next_alarm(struct rtc_device *rtc, + struct rtc_wkalrm *alrm); extern int rtc_set_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alrm); extern int rtc_initialize_alarm(struct rtc_device *rtc,