linux/drivers/rtc/lib.c
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   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
  14static const unsigned char rtc_days_in_month[] = {
  15        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  16};
  17
  18static 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 */
  30int rtc_month_days(unsigned int month, unsigned int year)
  31{
  32        return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
  33}
  34EXPORT_SYMBOL(rtc_month_days);
  35
  36/*
  37 * The number of days since January 1. (0 to 365)
  38 */
  39int 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}
  43EXPORT_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 */
  49void 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}
  89EXPORT_SYMBOL(rtc_time64_to_tm);
  90
  91/*
  92 * Does the rtc_time represent a valid date/time?
  93 */
  94int 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}
 109EXPORT_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 */
 115time64_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}
 120EXPORT_SYMBOL(rtc_tm_to_time64);
 121
 122/*
 123 * Convert rtc_time to ktime
 124 */
 125ktime_t rtc_tm_to_ktime(struct rtc_time tm)
 126{
 127        return ktime_set(rtc_tm_to_time64(&tm), 0);
 128}
 129EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
 130
 131/*
 132 * Convert ktime to rtc_time
 133 */
 134struct 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}
 146EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);
 147