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
17 static const unsigned char rtc_days_in_month[] = {
18 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
19 };
20
21 static 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 */
34 int rtc_month_days(unsigned int month, unsigned int year)
35 {
36 return rtc_days_in_month[month] + (LEAP_YEAR(year) && month == 1);
37 }
38 EXPORT_SYMBOL(rtc_month_days);
39
40 /*
41 * The number of days since January 1. (0 to 365)
42 */
43 int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
44 {
45 return rtc_ydays[LEAP_YEAR(year)][month] + day-1;
46 }
47 EXPORT_SYMBOL(rtc_year_days);
48
49 /*
50 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
51 */
52 void 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 }
89 EXPORT_SYMBOL(rtc_time_to_tm);
90
91 /*
92 * Does the rtc_time represent a valid date/time?
93 */
94 int 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 }
107 EXPORT_SYMBOL(rtc_valid_tm);
108
109 /*
110 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
111 */
112 int 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 }
118 EXPORT_SYMBOL(rtc_tm_to_time);
119
120 MODULE_LICENSE("GPL");
121
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