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(dividend: time, divisor: 86400, remainder: &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(year: ((unsigned int)tm->tm_year + 1900), mon: tm->tm_mon + 1, |
171 | day: tm->tm_mday, hour: tm->tm_hour, min: tm->tm_min, sec: 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(secs: rtc_tm_to_time64(&tm), nsecs: 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 | |