drivers/rtc/rtc-lib.c

   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");