linux/drivers/rtc/rtc-lib.c
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   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
  30/*
  31 * The number of days in the month.
  32 */
  33int rtc_month_days(unsigned int month, unsigned int year)
  34{
  35        return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
  36}
  37EXPORT_SYMBOL(rtc_month_days);
  38
  39/*
  40 * The number of days since January 1. (0 to 365)
  41 */
  42int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
  43{
  44        return rtc_ydays[is_leap_year(year)][month] + day-1;
  45}
  46EXPORT_SYMBOL(rtc_year_days);
  47
  48/*
  49 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
  50 */
  51void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
  52{
  53        unsigned int month, year;
  54        int days;
  55
  56        days = time / 86400;
  57        time -= (unsigned int) 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 + is_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        tm->tm_isdst = 0;
  90}
  91EXPORT_SYMBOL(rtc_time_to_tm);
  92
  93/*
  94 * Does the rtc_time represent a valid date/time?
  95 */
  96int rtc_valid_tm(struct rtc_time *tm)
  97{
  98        if (tm->tm_year < 70
  99                || ((unsigned)tm->tm_mon) >= 12
 100                || tm->tm_mday < 1
 101                || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
 102                || ((unsigned)tm->tm_hour) >= 24
 103                || ((unsigned)tm->tm_min) >= 60
 104                || ((unsigned)tm->tm_sec) >= 60)
 105                return -EINVAL;
 106
 107        return 0;
 108}
 109EXPORT_SYMBOL(rtc_valid_tm);
 110
 111/*
 112 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
 113 */
 114int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
 115{
 116        *time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
 117                        tm->tm_hour, tm->tm_min, tm->tm_sec);
 118        return 0;
 119}
 120EXPORT_SYMBOL(rtc_tm_to_time);
 121
 122/*
 123 * Convert rtc_time to ktime
 124 */
 125ktime_t rtc_tm_to_ktime(struct rtc_time tm)
 126{
 127        time_t time;
 128        rtc_tm_to_time(&tm, &time);
 129        return ktime_set(time, 0);
 130}
 131EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
 132
 133/*
 134 * Convert ktime to rtc_time
 135 */
 136struct rtc_time rtc_ktime_to_tm(ktime_t kt)
 137{
 138        struct timespec ts;
 139        struct rtc_time ret;
 140
 141        ts = ktime_to_timespec(kt);
 142        /* Round up any ns */
 143        if (ts.tv_nsec)
 144                ts.tv_sec++;
 145        rtc_time_to_tm(ts.tv_sec, &ret);
 146        return ret;
 147}
 148EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);
 149
 150MODULE_LICENSE("GPL");
 151
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