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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212// 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 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;
/* * The time represented by `time` is given in seconds since 1970-01-01 * (UTC). As the division done below might misbehave for negative * values, we convert it to seconds since 0000-03-01 and then assume it * will be non-negative. * Below we do 4 * udays + 3 which should fit into a 32 bit unsigned * variable. So the latest date this algorithm works for is 1073741823 * days after 0000-03-01 which is in the year 2939805. */ time += (u64)719468 * 86400;
udays = div_s64_rem(time, 86400, &secs);
/* * day of the week, 0000-03-01 was a Wednesday (in the proleptic * Gregorian calendar) */ tm->tm_wday = (udays + 3) % 7;
/* * The following algorithm is, basically, Figure 12 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] Neri C, Schneider L. Euclidean affine functions and their * application to calendar algorithms. Softw Pract Exper. * 2023;53(4):937-970. doi: 10.1002/spe.3172 * https://doi.org/10.1002/spe.3172 * * (*) The numbering of months follows rtc_time more closely and * thus, is slightly different from [1]. */
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);