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Diffstat (limited to 'drivers/rtc/lib.c')
| -rw-r--r-- | drivers/rtc/lib.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/drivers/rtc/lib.c b/drivers/rtc/lib.c new file mode 100644 index 000000000..fe3616527 --- /dev/null +++ b/drivers/rtc/lib.c @@ -0,0 +1,199 @@ +// 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. + * (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); |