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- // SPDX-License-Identifier: GPL-2.0
- /*
- * rtc and date/time utility functions
- *
- * Copyright (C) 2005-06 Tower Technologies
- * Author: Alessandro Zummo <[email protected]>
- *
- * based on arch/arm/common/rtctime.c and other bits
- *
- * Author: Cassio Neri <[email protected]> (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.
- * (Must be positive.)
- * @tm: Pointer to the struct rtc_time.
- */
- void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
- {
- unsigned int secs;
- int days;
- 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;
- /* time must be positive */
- days = div_s64_rem(time, 86400, &secs);
- /* day of the week, 1970-01-01 was a Thursday */
- tm->tm_wday = (days + 4) % 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 = ((u32) 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);
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