From b3967067c273359c7462f4be9a887c3d1a515f49 Mon Sep 17 00:00:00 2001 From: Joshua Clayton Date: Fri, 5 Feb 2016 12:41:11 -0800 Subject: rtc: Add functions to set and read rtc offset A number of rtc devices, such as the NXP pcf2123 include a facility to adjust the clock in order to compensate for temperature or a crystal, capacitor, etc, that results in the rtc clock not running at exactly 32.768 kHz. Data sheets I have seen refer to this as a clock offset, and measure it in parts per million, however they often reference ppm to 2 digits of precision, which makes integer ppm less than ideal. We use parts per billion, which more than covers the precision needed and works nicely within 32 bits Signed-off-by: Joshua Clayton Signed-off-by: Alexandre Belloni --- include/linux/rtc.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/rtc.h') diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 3359f0422c6b..b693adac853b 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -89,6 +89,8 @@ struct rtc_class_ops { int (*set_mmss)(struct device *, unsigned long secs); int (*read_callback)(struct device *, int data); int (*alarm_irq_enable)(struct device *, unsigned int enabled); + int (*read_offset)(struct device *, long *offset); + int (*set_offset)(struct device *, long offset); }; #define RTC_DEVICE_NAME_SIZE 20 @@ -208,6 +210,8 @@ void rtc_timer_init(struct rtc_timer *timer, void (*f)(void *p), void *data); int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer *timer, ktime_t expires, ktime_t period); void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer); +int rtc_read_offset(struct rtc_device *rtc, long *offset); +int rtc_set_offset(struct rtc_device *rtc, long offset); void rtc_timer_do_work(struct work_struct *work); static inline bool is_leap_year(unsigned int year) -- cgit v1.2.3