drivers/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/export.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
  30 /*
  31  * The number of days in the month.
  32  */
  33 int rtc_month_days(unsigned int month, unsigned int year)
  34 {
  35         return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
  36 }
  37 EXPORT_SYMBOL(rtc_month_days);
  38
  39 /*
  40  * The number of days since January 1. (0 to 365)
  41  */
  42 int 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 }
  46 EXPORT_SYMBOL(rtc_year_days);
  47
  48
  49 /*
  50  * rtc_time64_to_tm - Converts time64_t to rtc_time.
  51  * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
  52  */
  53 void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
  54 {
  55         unsigned int month, year, secs;
  56         int days;
  57
  58         /* time must be positive */
  59         days = div_s64_rem(time, 86400, &secs);
  60
  61         /* day of the week, 1970-01-01 was a Thursday */
  62         tm->tm_wday = (days + 4) % 7;
  63
  64         year = 1970 + days / 365;
  65         days -= (year - 1970) * 365
  66                 + LEAPS_THRU_END_OF(year - 1)
  67                 - LEAPS_THRU_END_OF(1970 - 1);
  68         while (days < 0) {
  69                 year -= 1;
  70                 days += 365 + is_leap_year(year);
  71         }
  72         tm->tm_year = year - 1900;
  73         tm->tm_yday = days + 1;
  74
  75         for (month = 0; month < 11; month++) {
  76                 int newdays;
  77
  78                 newdays = days - rtc_month_days(month, year);
  79                 if (newdays < 0)
  80                         break;
  81                 days = newdays;
  82         }
  83         tm->tm_mon = month;
  84         tm->tm_mday = days + 1;
  85
  86         tm->tm_hour = secs / 3600;
  87         secs -= tm->tm_hour * 3600;
  88         tm->tm_min = secs / 60;
  89         tm->tm_sec = secs - tm->tm_min * 60;
  90
  91         tm->tm_isdst = 0;
  92 }
  93 EXPORT_SYMBOL(rtc_time64_to_tm);
  94
  95 /*
  96  * Does the rtc_time represent a valid date/time?
  97  */
  98 int rtc_valid_tm(struct rtc_time *tm)
  99 {
 100         if (tm->tm_year < 70
 101                 || ((unsigned)tm->tm_mon) >= 12
 102                 || tm->tm_mday < 1
 103                 || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
 104                 || ((unsigned)tm->tm_hour) >= 24
 105                 || ((unsigned)tm->tm_min) >= 60
 106                 || ((unsigned)tm->tm_sec) >= 60)
 107                 return -EINVAL;
 108
 109         return 0;
 110 }
 111 EXPORT_SYMBOL(rtc_valid_tm);
 112
 113 /*
 114  * rtc_tm_to_time64 - Converts rtc_time to time64_t.
 115  * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
 116  */
 117 time64_t rtc_tm_to_time64(struct rtc_time *tm)
 118 {
 119         return mktime64(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
 120                         tm->tm_hour, tm->tm_min, tm->tm_sec);
 121 }
 122 EXPORT_SYMBOL(rtc_tm_to_time64);
 123
 124 /*
 125  * Convert rtc_time to ktime
 126  */
 127 ktime_t rtc_tm_to_ktime(struct rtc_time tm)
 128 {
 129         return ktime_set(rtc_tm_to_time64(&tm), 0);
 130 }
 131 EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
 132
 133 /*
 134  * Convert ktime to rtc_time
 135  */
 136 struct rtc_time rtc_ktime_to_tm(ktime_t kt)
 137 {
 138         struct timespec64 ts;
 139         struct rtc_time ret;
 140
 141         ts = ktime_to_timespec64(kt);
 142         /* Round up any ns */
 143         if (ts.tv_nsec)
 144                 ts.tv_sec++;
 145         rtc_time64_to_tm(ts.tv_sec, &ret);
 146         return ret;
 147 }
 148 EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);