1/*
  2 * rtc and date/time utility functions
  3 *
  4 * Copyright (C) 2005-06 Tower Technologies
  5 * Author: Alessandro Zummo <a.zummo@towertech.it>
  6 *
  7 * based on arch/arm/common/rtctime.c and other bits
  8 *
  9 * This program is free software; you can redistribute it and/or modify
 10 * it under the terms of the GNU General Public License version 2 as
 11 * published by the Free Software Foundation.
 12*/
 13
 14#include <linux/export.h>
 15#include <linux/rtc.h>
 16
 17static const unsigned char rtc_days_in_month[] = {
 18	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 19};
 20
 21static const unsigned short rtc_ydays[2][13] = {
 22	/* Normal years */
 23	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
 24	/* Leap years */
 25	{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
 26};
 27
 28#define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)
 29
 30/*
 31 * The number of days in the month.
 32 */
 33int rtc_month_days(unsigned int month, unsigned int year)
 34{
 35	return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
 36}
 37EXPORT_SYMBOL(rtc_month_days);
 38
 39/*
 40 * The number of days since January 1. (0 to 365)
 41 */
 42int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
 43{
 44	return rtc_ydays[is_leap_year(year)][month] + day-1;
 45}
 46EXPORT_SYMBOL(rtc_year_days);
 47
 48
 49/*
 50 * rtc_time_to_tm64 - Converts time64_t to rtc_time.
 51 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
 52 */
 53void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
 54{
 55	unsigned int month, year;
 56	unsigned long secs;
 57	int days;
 58
 59	/* time must be positive */
 60	days = div_s64(time, 86400);
 61	secs = time - (unsigned int) days * 86400;
 62
 63	/* day of the week, 1970-01-01 was a Thursday */
 64	tm->tm_wday = (days + 4) % 7;
 65
 66	year = 1970 + days / 365;
 67	days -= (year - 1970) * 365
 68		+ LEAPS_THRU_END_OF(year - 1)
 69		- LEAPS_THRU_END_OF(1970 - 1);
 70	if (days < 0) {
 71		year -= 1;
 72		days += 365 + is_leap_year(year);
 73	}
 74	tm->tm_year = year - 1900;
 75	tm->tm_yday = days + 1;
 76
 77	for (month = 0; month < 11; month++) {
 78		int newdays;
 79
 80		newdays = days - rtc_month_days(month, year);
 81		if (newdays < 0)
 82			break;
 83		days = newdays;
 84	}
 85	tm->tm_mon = month;
 86	tm->tm_mday = days + 1;
 87
 88	tm->tm_hour = secs / 3600;
 89	secs -= tm->tm_hour * 3600;
 90	tm->tm_min = secs / 60;
 91	tm->tm_sec = secs - tm->tm_min * 60;
 92
 93	tm->tm_isdst = 0;
 94}
 95EXPORT_SYMBOL(rtc_time64_to_tm);
 96
 97/*
 98 * Does the rtc_time represent a valid date/time?
 99 */
100int rtc_valid_tm(struct rtc_time *tm)
101{
102	if (tm->tm_year < 70
103		|| ((unsigned)tm->tm_mon) >= 12
104		|| tm->tm_mday < 1
105		|| tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
106		|| ((unsigned)tm->tm_hour) >= 24
107		|| ((unsigned)tm->tm_min) >= 60
108		|| ((unsigned)tm->tm_sec) >= 60)
109		return -EINVAL;
110
111	return 0;
112}
113EXPORT_SYMBOL(rtc_valid_tm);
114
115/*
116 * rtc_tm_to_time64 - Converts rtc_time to time64_t.
117 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
118 */
119time64_t rtc_tm_to_time64(struct rtc_time *tm)
120{
121	return mktime64(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
122			tm->tm_hour, tm->tm_min, tm->tm_sec);
123}
124EXPORT_SYMBOL(rtc_tm_to_time64);
125
126/*
127 * Convert rtc_time to ktime
128 */
129ktime_t rtc_tm_to_ktime(struct rtc_time tm)
130{
131	return ktime_set(rtc_tm_to_time64(&tm), 0);
132}
133EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
134
135/*
136 * Convert ktime to rtc_time
137 */
138struct rtc_time rtc_ktime_to_tm(ktime_t kt)
139{
140	struct timespec64 ts;
141	struct rtc_time ret;
142
143	ts = ktime_to_timespec64(kt);
144	/* Round up any ns */
145	if (ts.tv_nsec)
146		ts.tv_sec++;
147	rtc_time64_to_tm(ts.tv_sec, &ret);
148	return ret;
149}
150EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);