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/module.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#define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))
30
31/*
32 * The number of days in the month.
33 */
34int rtc_month_days(unsigned int month, unsigned int year)
35{
36	return rtc_days_in_month[month] + (LEAP_YEAR(year) && month == 1);
37}
38EXPORT_SYMBOL(rtc_month_days);
39
40/*
41 * The number of days since January 1. (0 to 365)
42 */
43int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
44{
45	return rtc_ydays[LEAP_YEAR(year)][month] + day-1;
46}
47EXPORT_SYMBOL(rtc_year_days);
48
49/*
50 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
51 */
52void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
53{
54	register int days, month, year;
55
56	days = time / 86400;
57	time -= days * 86400;
58
59	/* day of the week, 1970-01-01 was a Thursday */
60	tm->tm_wday = (days + 4) % 7;
61
62	year = 1970 + days / 365;
63	days -= (year - 1970) * 365
64		+ LEAPS_THRU_END_OF(year - 1)
65		- LEAPS_THRU_END_OF(1970 - 1);
66	if (days < 0) {
67		year -= 1;
68		days += 365 + LEAP_YEAR(year);
69	}
70	tm->tm_year = year - 1900;
71	tm->tm_yday = days + 1;
72
73	for (month = 0; month < 11; month++) {
74		int newdays;
75
76		newdays = days - rtc_month_days(month, year);
77		if (newdays < 0)
78			break;
79		days = newdays;
80	}
81	tm->tm_mon = month;
82	tm->tm_mday = days + 1;
83
84	tm->tm_hour = time / 3600;
85	time -= tm->tm_hour * 3600;
86	tm->tm_min = time / 60;
87	tm->tm_sec = time - tm->tm_min * 60;
88}
89EXPORT_SYMBOL(rtc_time_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		|| ((unsigned)tm->tm_mon) >= 12
98		|| tm->tm_mday < 1
99		|| tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
100		|| ((unsigned)tm->tm_hour) >= 24
101		|| ((unsigned)tm->tm_min) >= 60
102		|| ((unsigned)tm->tm_sec) >= 60)
103		return -EINVAL;
104
105	return 0;
106}
107EXPORT_SYMBOL(rtc_valid_tm);
108
109/*
110 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
111 */
112int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
113{
114	*time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
115			tm->tm_hour, tm->tm_min, tm->tm_sec);
116	return 0;
117}
118EXPORT_SYMBOL(rtc_tm_to_time);
119
120MODULE_LICENSE("GPL");
121