1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * rtc and date/time utility functions
  4 *
  5 * Copyright (C) 2005-06 Tower Technologies
  6 * Author: Alessandro Zummo <a.zummo@towertech.it>
  7 *
  8 * based on arch/arm/common/rtctime.c and other bits
  9 */
 10
 11#include <linux/export.h>
 12#include <linux/rtc.h>
 13
 14static const unsigned char rtc_days_in_month[] = {
 15	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 16};
 17
 18static const unsigned short rtc_ydays[2][13] = {
 19	/* Normal years */
 20	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
 21	/* Leap years */
 22	{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
 23};
 24
 25#define LEAPS_THRU_END_OF(y) ((y) / 4 - (y) / 100 + (y) / 400)
 26
 27/*
 28 * The number of days in the month.
 29 */
 30int rtc_month_days(unsigned int month, unsigned int year)
 31{
 32	return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
 33}
 34EXPORT_SYMBOL(rtc_month_days);
 35
 36/*
 37 * The number of days since January 1. (0 to 365)
 38 */
 39int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
 40{
 41	return rtc_ydays[is_leap_year(year)][month] + day - 1;
 42}
 43EXPORT_SYMBOL(rtc_year_days);
 44
 45/*
 46 * rtc_time64_to_tm - Converts time64_t to rtc_time.
 47 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
 48 */
 49void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
 50{
 51	unsigned int month, year, secs;
 52	int days;
 53
 54	/* time must be positive */
 55	days = div_s64_rem(time, 86400, &secs);
 56
 57	/* day of the week, 1970-01-01 was a Thursday */
 58	tm->tm_wday = (days + 4) % 7;
 59
 60	year = 1970 + days / 365;
 61	days -= (year - 1970) * 365
 62		+ LEAPS_THRU_END_OF(year - 1)
 63		- LEAPS_THRU_END_OF(1970 - 1);
 64	while (days < 0) {
 65		year -= 1;
 66		days += 365 + is_leap_year(year);
 67	}
 68	tm->tm_year = year - 1900;
 69	tm->tm_yday = days + 1;
 70
 71	for (month = 0; month < 11; month++) {
 72		int newdays;
 73
 74		newdays = days - rtc_month_days(month, year);
 75		if (newdays < 0)
 76			break;
 77		days = newdays;
 78	}
 79	tm->tm_mon = month;
 80	tm->tm_mday = days + 1;
 81
 82	tm->tm_hour = secs / 3600;
 83	secs -= tm->tm_hour * 3600;
 84	tm->tm_min = secs / 60;
 85	tm->tm_sec = secs - tm->tm_min * 60;
 86
 87	tm->tm_isdst = 0;
 88}
 89EXPORT_SYMBOL(rtc_time64_to_tm);
 90
 91/*
 92 * Does the rtc_time represent a valid date/time?
 93 */
 94int rtc_valid_tm(struct rtc_time *tm)
 95{
 96	if (tm->tm_year < 70 ||
 97	    tm->tm_year > (INT_MAX - 1900) ||
 98	    ((unsigned int)tm->tm_mon) >= 12 ||
 99	    tm->tm_mday < 1 ||
100	    tm->tm_mday > rtc_month_days(tm->tm_mon,
101					 ((unsigned int)tm->tm_year + 1900)) ||
102	    ((unsigned int)tm->tm_hour) >= 24 ||
103	    ((unsigned int)tm->tm_min) >= 60 ||
104	    ((unsigned int)tm->tm_sec) >= 60)
105		return -EINVAL;
106
107	return 0;
108}
109EXPORT_SYMBOL(rtc_valid_tm);
110
111/*
112 * rtc_tm_to_time64 - Converts rtc_time to time64_t.
113 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
114 */
115time64_t rtc_tm_to_time64(struct rtc_time *tm)
116{
117	return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
118			tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
119}
120EXPORT_SYMBOL(rtc_tm_to_time64);
121
122/*
123 * Convert rtc_time to ktime
124 */
125ktime_t rtc_tm_to_ktime(struct rtc_time tm)
126{
127	return ktime_set(rtc_tm_to_time64(&tm), 0);
128}
129EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
130
131/*
132 * Convert ktime to rtc_time
133 */
134struct rtc_time rtc_ktime_to_tm(ktime_t kt)
135{
136	struct timespec64 ts;
137	struct rtc_time ret;
138
139	ts = ktime_to_timespec64(kt);
140	/* Round up any ns */
141	if (ts.tv_nsec)
142		ts.tv_sec++;
143	rtc_time64_to_tm(ts.tv_sec, &ret);
144	return ret;
145}
146EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);