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 #define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)
  22 #define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))
  23
  24 int rtc_month_days(unsigned int month, unsigned int year)
  25 {
  26         return rtc_days_in_month[month] + (LEAP_YEAR(year) && month == 1);
  27 }
  28 EXPORT_SYMBOL(rtc_month_days);
  29
  30 /*
  31  * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
  32  */
  33 void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
  34 {
  35         register int days, month, year;
  36
  37         days = time / 86400;
  38         time -= days * 86400;
  39
  40         /* day of the week, 1970-01-01 was a Thursday */
  41         tm->tm_wday = (days + 4) % 7;
  42
  43         year = 1970 + days / 365;
  44         days -= (year - 1970) * 365
  45                 + LEAPS_THRU_END_OF(year - 1)
  46                 - LEAPS_THRU_END_OF(1970 - 1);
  47         if (days < 0) {
  48                 year -= 1;
  49                 days += 365 + LEAP_YEAR(year);
  50         }
  51         tm->tm_year = year - 1900;
  52         tm->tm_yday = days + 1;
  53
  54         for (month = 0; month < 11; month++) {
  55                 int newdays;
  56
  57                 newdays = days - rtc_month_days(month, year);
  58                 if (newdays < 0)
  59                         break;
  60                 days = newdays;
  61         }
  62         tm->tm_mon = month;
  63         tm->tm_mday = days + 1;
  64
  65         tm->tm_hour = time / 3600;
  66         time -= tm->tm_hour * 3600;
  67         tm->tm_min = time / 60;
  68         tm->tm_sec = time - tm->tm_min * 60;
  69 }
  70 EXPORT_SYMBOL(rtc_time_to_tm);
  71
  72 /*
  73  * Does the rtc_time represent a valid date/time?
  74  */
  75 int rtc_valid_tm(struct rtc_time *tm)
  76 {
  77         if (tm->tm_year < 70
  78                 || tm->tm_mon >= 12
  79                 || tm->tm_mday < 1
  80                 || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
  81                 || tm->tm_hour >= 24
  82                 || tm->tm_min >= 60
  83                 || tm->tm_sec >= 60)
  84                 return -EINVAL;
  85
  86         return 0;
  87 }
  88 EXPORT_SYMBOL(rtc_valid_tm);
  89
  90 /*
  91  * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
  92  */
  93 int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
  94 {
  95         *time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
  96                         tm->tm_hour, tm->tm_min, tm->tm_sec);
  97         return 0;
  98 }
  99 EXPORT_SYMBOL(rtc_tm_to_time);
 100
 101 MODULE_LICENSE("GPL");