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1// SPDX-License-Identifier: GPL-2.02/*3 * rtc and date/time utility functions4 *5 * Copyright (C) 2005-06 Tower Technologies6 * Author: Alessandro Zummo <a.zummo@towertech.it>7 *8 * based on arch/arm/common/rtctime.c and other bits9 *10 * Author: Cassio Neri <cassio.neri@gmail.com> (rtc_time64_to_tm)11 */12 13#include <linux/export.h>14#include <linux/rtc.h>15 16static const unsigned char rtc_days_in_month[] = {17 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 3118};19 20static const unsigned short rtc_ydays[2][13] = {21 /* Normal years */22 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },23 /* Leap years */24 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }25};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 *48 * @time: The number of seconds since 01-01-1970 00:00:00.49 * (Must be positive.)50 * @tm: Pointer to the struct rtc_time.51 */52void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)53{54 unsigned int secs;55 int days;56 57 u64 u64tmp;58 u32 u32tmp, udays, century, day_of_century, year_of_century, year,59 day_of_year, month, day;60 bool is_Jan_or_Feb, is_leap_year;61 62 /* time must be positive */63 days = div_s64_rem(time, 86400, &secs);64 65 /* day of the week, 1970-01-01 was a Thursday */66 tm->tm_wday = (days + 4) % 7;67 68 /*69 * The following algorithm is, basically, Proposition 6.3 of Neri70 * and Schneider [1]. In a few words: it works on the computational71 * (fictitious) calendar where the year starts in March, month = 272 * (*), and finishes in February, month = 13. This calendar is73 * mathematically convenient because the day of the year does not74 * depend on whether the year is leap or not. For instance:75 *76 * March 1st 0-th day of the year;77 * ...78 * April 1st 31-st day of the year;79 * ...80 * January 1st 306-th day of the year; (Important!)81 * ...82 * February 28th 364-th day of the year;83 * February 29th 365-th day of the year (if it exists).84 *85 * After having worked out the date in the computational calendar86 * (using just arithmetics) it's easy to convert it to the87 * corresponding date in the Gregorian calendar.88 *89 * [1] "Euclidean Affine Functions and Applications to Calendar90 * Algorithms". https://arxiv.org/abs/2102.0695991 *92 * (*) The numbering of months follows rtc_time more closely and93 * thus, is slightly different from [1].94 */95 96 udays = ((u32) days) + 719468;97 98 u32tmp = 4 * udays + 3;99 century = u32tmp / 146097;100 day_of_century = u32tmp % 146097 / 4;101 102 u32tmp = 4 * day_of_century + 3;103 u64tmp = 2939745ULL * u32tmp;104 year_of_century = upper_32_bits(u64tmp);105 day_of_year = lower_32_bits(u64tmp) / 2939745 / 4;106 107 year = 100 * century + year_of_century;108 is_leap_year = year_of_century != 0 ?109 year_of_century % 4 == 0 : century % 4 == 0;110 111 u32tmp = 2141 * day_of_year + 132377;112 month = u32tmp >> 16;113 day = ((u16) u32tmp) / 2141;114 115 /*116 * Recall that January 01 is the 306-th day of the year in the117 * computational (not Gregorian) calendar.118 */119 is_Jan_or_Feb = day_of_year >= 306;120 121 /* Converts to the Gregorian calendar. */122 year = year + is_Jan_or_Feb;123 month = is_Jan_or_Feb ? month - 12 : month;124 day = day + 1;125 126 day_of_year = is_Jan_or_Feb ?127 day_of_year - 306 : day_of_year + 31 + 28 + is_leap_year;128 129 /* Converts to rtc_time's format. */130 tm->tm_year = (int) (year - 1900);131 tm->tm_mon = (int) month;132 tm->tm_mday = (int) day;133 tm->tm_yday = (int) day_of_year + 1;134 135 tm->tm_hour = secs / 3600;136 secs -= tm->tm_hour * 3600;137 tm->tm_min = secs / 60;138 tm->tm_sec = secs - tm->tm_min * 60;139 140 tm->tm_isdst = 0;141}142EXPORT_SYMBOL(rtc_time64_to_tm);143 144/*145 * Does the rtc_time represent a valid date/time?146 */147int rtc_valid_tm(struct rtc_time *tm)148{149 if (tm->tm_year < 70 ||150 tm->tm_year > (INT_MAX - 1900) ||151 ((unsigned int)tm->tm_mon) >= 12 ||152 tm->tm_mday < 1 ||153 tm->tm_mday > rtc_month_days(tm->tm_mon,154 ((unsigned int)tm->tm_year + 1900)) ||155 ((unsigned int)tm->tm_hour) >= 24 ||156 ((unsigned int)tm->tm_min) >= 60 ||157 ((unsigned int)tm->tm_sec) >= 60)158 return -EINVAL;159 160 return 0;161}162EXPORT_SYMBOL(rtc_valid_tm);163 164/*165 * rtc_tm_to_time64 - Converts rtc_time to time64_t.166 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.167 */168time64_t rtc_tm_to_time64(struct rtc_time *tm)169{170 return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,171 tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);172}173EXPORT_SYMBOL(rtc_tm_to_time64);174 175/*176 * Convert rtc_time to ktime177 */178ktime_t rtc_tm_to_ktime(struct rtc_time tm)179{180 return ktime_set(rtc_tm_to_time64(&tm), 0);181}182EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);183 184/*185 * Convert ktime to rtc_time186 */187struct rtc_time rtc_ktime_to_tm(ktime_t kt)188{189 struct timespec64 ts;190 struct rtc_time ret;191 192 ts = ktime_to_timespec64(kt);193 /* Round up any ns */194 if (ts.tv_nsec)195 ts.tv_sec++;196 rtc_time64_to_tm(ts.tv_sec, &ret);197 return ret;198}199EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);200