[tip: timers/core] rtc: Add API function to return alarm time bound by hardware limit

["tip-bot2 for Guenter Roeck" <tip-bot2@linutronix.de>]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     a0fddaa0b5a587cc8d185f8802fe7e48493c43ed
Gitweb:        https://git.kernel.org/tip/a0fddaa0b5a587cc8d185f8802fe7e48493c43ed
Author:        Guenter Roeck <linux@roeck-us.net>
AuthorDate:    Fri, 15 Sep 2023 08:22:37 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 09 Oct 2023 15:03:28 +02:00

rtc: Add API function to return alarm time bound by hardware limit

Add rtc_bound_alarmtime() to return the requested alarm timeout bound by
the maxmum alarm timeout that is supported by a given RTC.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230915152238.1144706-2-linux@roeck-us.net

---
 include/linux/rtc.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 4c0bcbe..5f8e438 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -225,6 +225,23 @@ static inline bool is_leap_year(unsigned int year)
 	return (!(year % 4) && (year % 100)) || !(year % 400);
 }
 
+/**
+ * rtc_bound_alarmtime() - Return alarm time bound by rtc limit
+ * @rtc: Pointer to rtc device structure
+ * @requested: Requested alarm timeout
+ *
+ * Return: Alarm timeout bound by maximum alarm time supported by rtc.
+ */
+static inline ktime_t rtc_bound_alarmtime(struct rtc_device *rtc,
+					  ktime_t requested)
+{
+	if (rtc->alarm_offset_max &&
+	    rtc->alarm_offset_max * MSEC_PER_SEC < ktime_to_ms(requested))
+		return ms_to_ktime(rtc->alarm_offset_max * MSEC_PER_SEC);
+
+	return requested;
+}
+
 #define devm_rtc_register_device(device) \
 	__devm_rtc_register_device(THIS_MODULE, device)