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