200 lines
5.2 KiB
C
200 lines
5.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* rtc and date/time utility functions
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*
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* Copyright (C) 2005-06 Tower Technologies
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* Author: Alessandro Zummo <a.zummo@towertech.it>
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*
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* based on arch/arm/common/rtctime.c and other bits
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*
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* Author: Cassio Neri <cassio.neri@gmail.com> (rtc_time64_to_tm)
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*/
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#include <linux/export.h>
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#include <linux/rtc.h>
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static const unsigned char rtc_days_in_month[] = {
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31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
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};
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static const unsigned short rtc_ydays[2][13] = {
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/* Normal years */
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{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
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/* Leap years */
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{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
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};
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/*
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* The number of days in the month.
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*/
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int rtc_month_days(unsigned int month, unsigned int year)
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{
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return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
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}
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EXPORT_SYMBOL(rtc_month_days);
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/*
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* The number of days since January 1. (0 to 365)
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*/
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int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
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{
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return rtc_ydays[is_leap_year(year)][month] + day - 1;
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}
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EXPORT_SYMBOL(rtc_year_days);
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/**
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* rtc_time64_to_tm - converts time64_t to rtc_time.
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*
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* @time: The number of seconds since 01-01-1970 00:00:00.
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* (Must be positive.)
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* @tm: Pointer to the struct rtc_time.
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*/
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void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
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{
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unsigned int secs;
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int days;
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u64 u64tmp;
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u32 u32tmp, udays, century, day_of_century, year_of_century, year,
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day_of_year, month, day;
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bool is_Jan_or_Feb, is_leap_year;
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/* time must be positive */
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days = div_s64_rem(time, 86400, &secs);
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/* day of the week, 1970-01-01 was a Thursday */
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tm->tm_wday = (days + 4) % 7;
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/*
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* The following algorithm is, basically, Proposition 6.3 of Neri
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* and Schneider [1]. In a few words: it works on the computational
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* (fictitious) calendar where the year starts in March, month = 2
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* (*), and finishes in February, month = 13. This calendar is
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* mathematically convenient because the day of the year does not
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* depend on whether the year is leap or not. For instance:
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*
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* March 1st 0-th day of the year;
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* ...
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* April 1st 31-st day of the year;
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* ...
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* January 1st 306-th day of the year; (Important!)
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* ...
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* February 28th 364-th day of the year;
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* February 29th 365-th day of the year (if it exists).
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*
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* After having worked out the date in the computational calendar
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* (using just arithmetics) it's easy to convert it to the
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* corresponding date in the Gregorian calendar.
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*
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* [1] "Euclidean Affine Functions and Applications to Calendar
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* Algorithms". https://arxiv.org/abs/2102.06959
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*
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* (*) The numbering of months follows rtc_time more closely and
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* thus, is slightly different from [1].
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*/
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udays = ((u32) days) + 719468;
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u32tmp = 4 * udays + 3;
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century = u32tmp / 146097;
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day_of_century = u32tmp % 146097 / 4;
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u32tmp = 4 * day_of_century + 3;
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u64tmp = 2939745ULL * u32tmp;
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year_of_century = upper_32_bits(u64tmp);
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day_of_year = lower_32_bits(u64tmp) / 2939745 / 4;
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year = 100 * century + year_of_century;
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is_leap_year = year_of_century != 0 ?
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year_of_century % 4 == 0 : century % 4 == 0;
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u32tmp = 2141 * day_of_year + 132377;
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month = u32tmp >> 16;
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day = ((u16) u32tmp) / 2141;
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/*
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* Recall that January 01 is the 306-th day of the year in the
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* computational (not Gregorian) calendar.
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*/
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is_Jan_or_Feb = day_of_year >= 306;
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/* Converts to the Gregorian calendar. */
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year = year + is_Jan_or_Feb;
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month = is_Jan_or_Feb ? month - 12 : month;
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day = day + 1;
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day_of_year = is_Jan_or_Feb ?
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day_of_year - 306 : day_of_year + 31 + 28 + is_leap_year;
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/* Converts to rtc_time's format. */
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tm->tm_year = (int) (year - 1900);
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tm->tm_mon = (int) month;
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tm->tm_mday = (int) day;
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tm->tm_yday = (int) day_of_year + 1;
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tm->tm_hour = secs / 3600;
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secs -= tm->tm_hour * 3600;
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tm->tm_min = secs / 60;
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tm->tm_sec = secs - tm->tm_min * 60;
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tm->tm_isdst = 0;
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}
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EXPORT_SYMBOL(rtc_time64_to_tm);
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/*
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* Does the rtc_time represent a valid date/time?
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*/
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int rtc_valid_tm(struct rtc_time *tm)
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{
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if (tm->tm_year < 70 ||
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tm->tm_year > (INT_MAX - 1900) ||
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((unsigned int)tm->tm_mon) >= 12 ||
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tm->tm_mday < 1 ||
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tm->tm_mday > rtc_month_days(tm->tm_mon,
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((unsigned int)tm->tm_year + 1900)) ||
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((unsigned int)tm->tm_hour) >= 24 ||
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((unsigned int)tm->tm_min) >= 60 ||
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((unsigned int)tm->tm_sec) >= 60)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL(rtc_valid_tm);
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/*
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* rtc_tm_to_time64 - Converts rtc_time to time64_t.
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* Convert Gregorian date to seconds since 01-01-1970 00:00:00.
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*/
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time64_t rtc_tm_to_time64(struct rtc_time *tm)
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{
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return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
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tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
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}
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EXPORT_SYMBOL(rtc_tm_to_time64);
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/*
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* Convert rtc_time to ktime
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*/
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ktime_t rtc_tm_to_ktime(struct rtc_time tm)
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{
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return ktime_set(rtc_tm_to_time64(&tm), 0);
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}
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EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
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/*
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* Convert ktime to rtc_time
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*/
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struct rtc_time rtc_ktime_to_tm(ktime_t kt)
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{
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struct timespec64 ts;
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struct rtc_time ret;
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ts = ktime_to_timespec64(kt);
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/* Round up any ns */
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if (ts.tv_nsec)
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ts.tv_sec++;
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rtc_time64_to_tm(ts.tv_sec, &ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);
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