1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * rtc and date/time utility functions 4 * 5 * Copyright (C) 2005-06 Tower Technologies 6 * Author: Alessandro Zummo <a.zummo@towertech.it> 7 * 8 * based on arch/arm/common/rtctime.c and other bits 9 * 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 16 static const unsigned char rtc_days_in_month[] = { 17 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 18 }; 19 20 static 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 */ 30 int rtc_month_days(unsigned int month, unsigned int year) 31 { 32 return rtc_days_in_month[month] + (is_leap_year(year) && month == 1); 33 } 34 EXPORT_SYMBOL(rtc_month_days); 35 36 /* 37 * The number of days since January 1. (0 to 365) 38 */ 39 int 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 } 43 EXPORT_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 */ 52 void 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 Neri 70 * and Schneider [1]. In a few words: it works on the computational 71 * (fictitious) calendar where the year starts in March, month = 2 72 * (*), and finishes in February, month = 13. This calendar is 73 * mathematically convenient because the day of the year does not 74 * 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 calendar 86 * (using just arithmetics) it's easy to convert it to the 87 * corresponding date in the Gregorian calendar. 88 * 89 * [1] "Euclidean Affine Functions and Applications to Calendar 90 * Algorithms". https://arxiv.org/abs/2102.06959 91 * 92 * (*) The numbering of months follows rtc_time more closely and 93 * 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 the 117 * 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 } 142 EXPORT_SYMBOL(rtc_time64_to_tm); 143 144 /* 145 * Does the rtc_time represent a valid date/time? 146 */ 147 int 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 } 162 EXPORT_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 */ 168 time64_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 } 173 EXPORT_SYMBOL(rtc_tm_to_time64); 174 175 /* 176 * Convert rtc_time to ktime 177 */ 178 ktime_t rtc_tm_to_ktime(struct rtc_time tm) 179 { 180 return ktime_set(rtc_tm_to_time64(&tm), 0); 181 } 182 EXPORT_SYMBOL_GPL(rtc_tm_to_ktime); 183 184 /* 185 * Convert ktime to rtc_time 186 */ 187 struct 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 } 199 EXPORT_SYMBOL_GPL(rtc_ktime_to_tm); 200