drivers/rtc/lib.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * rtc and date/time utility functions
   4  *
   5  * Copyright (C) 2005-06 Tower Technologies
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  *
   8  * based on arch/arm/common/rtctime.c and other bits
   9  */
  10
  11 #include <linux/export.h>
  12 #include <linux/rtc.h>
  13
  14 static const unsigned char rtc_days_in_month[] = {
  15         31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  16 };
  17
  18 static const unsigned short rtc_ydays[2][13] = {
  19         /* Normal years */
  20         { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
  21         /* Leap years */
  22         { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
  23 };
  24
  25 #define LEAPS_THRU_END_OF(y) ((y) / 4 - (y) / 100 + (y) / 400)
  26
  27 /*
  28  * The number of days in the month.
  29  */
  30 int rtc_month_days(unsigned int month, unsigned int year)
  31 {
  32         return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
  33 }
  34 EXPORT_SYMBOL(rtc_month_days);
  35
  36 /*
  37  * The number of days since January 1. (0 to 365)
  38  */
  39 int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
  40 {
  41         return rtc_ydays[is_leap_year(year)][month] + day - 1;
  42 }
  43 EXPORT_SYMBOL(rtc_year_days);
  44
  45 /*
  46  * rtc_time64_to_tm - Converts time64_t to rtc_time.
  47  * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
  48  */
  49 void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
  50 {
  51         unsigned int month, year, secs;
  52         int days;
  53
  54         /* time must be positive */
  55         days = div_s64_rem(time, 86400, &secs);
  56
  57         /* day of the week, 1970-01-01 was a Thursday */
  58         tm->tm_wday = (days + 4) % 7;
  59
  60         year = 1970 + days / 365;
  61         days -= (year - 1970) * 365
  62                 + LEAPS_THRU_END_OF(year - 1)
  63                 - LEAPS_THRU_END_OF(1970 - 1);
  64         while (days < 0) {
  65                 year -= 1;
  66                 days += 365 + is_leap_year(year);
  67         }
  68         tm->tm_year = year - 1900;
  69         tm->tm_yday = days + 1;
  70
  71         for (month = 0; month < 11; month++) {
  72                 int newdays;
  73
  74                 newdays = days - rtc_month_days(month, year);
  75                 if (newdays < 0)
  76                         break;
  77                 days = newdays;
  78         }
  79         tm->tm_mon = month;
  80         tm->tm_mday = days + 1;
  81
  82         tm->tm_hour = secs / 3600;
  83         secs -= tm->tm_hour * 3600;
  84         tm->tm_min = secs / 60;
  85         tm->tm_sec = secs - tm->tm_min * 60;
  86
  87         tm->tm_isdst = 0;
  88 }
  89 EXPORT_SYMBOL(rtc_time64_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             tm->tm_year > (INT_MAX - 1900) ||
  98             ((unsigned int)tm->tm_mon) >= 12 ||
  99             tm->tm_mday < 1 ||
 100             tm->tm_mday > rtc_month_days(tm->tm_mon,
 101                                          ((unsigned int)tm->tm_year + 1900)) ||
 102             ((unsigned int)tm->tm_hour) >= 24 ||
 103             ((unsigned int)tm->tm_min) >= 60 ||
 104             ((unsigned int)tm->tm_sec) >= 60)
 105                 return -EINVAL;
 106
 107         return 0;
 108 }
 109 EXPORT_SYMBOL(rtc_valid_tm);
 110
 111 /*
 112  * rtc_tm_to_time64 - Converts rtc_time to time64_t.
 113  * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
 114  */
 115 time64_t rtc_tm_to_time64(struct rtc_time *tm)
 116 {
 117         return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
 118                         tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
 119 }
 120 EXPORT_SYMBOL(rtc_tm_to_time64);
 121
 122 /*
 123  * Convert rtc_time to ktime
 124  */
 125 ktime_t rtc_tm_to_ktime(struct rtc_time tm)
 126 {
 127         return ktime_set(rtc_tm_to_time64(&tm), 0);
 128 }
 129 EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
 130
 131 /*
 132  * Convert ktime to rtc_time
 133  */
 134 struct rtc_time rtc_ktime_to_tm(ktime_t kt)
 135 {
 136         struct timespec64 ts;
 137         struct rtc_time ret;
 138
 139         ts = ktime_to_timespec64(kt);
 140         /* Round up any ns */
 141         if (ts.tv_nsec)
 142                 ts.tv_sec++;
 143         rtc_time64_to_tm(ts.tv_sec, &ret);
 144         return ret;
 145 }
 146 EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);