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