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
11 #include <linux/export.h>
12 #include <linux/rtc.h>
13
14 static const unsigned char rtc_days_in_month[] = {
15 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
16 };
17
18 static const unsigned short rtc_ydays[2][13] = {
19 /* Normal years */
20 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
21 /* Leap years */
22 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
23 };
24
25 #define LEAPS_THRU_END_OF(y) ((y) / 4 - (y) / 100 + (y) / 400)
26
27 /*
28 * The number of days in the month.
29 */
rtc_month_days(unsigned int month,unsigned int year)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 */
rtc_year_days(unsigned int day,unsigned int month,unsigned int year)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 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
48 */
rtc_time64_to_tm(time64_t time,struct rtc_time * tm)49 void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
50 {
51 unsigned int month, year, secs;
52 int days;
53
54 /* time must be positive */
55 days = div_s64_rem(time, 86400, &secs);
56
57 /* day of the week, 1970-01-01 was a Thursday */
58 tm->tm_wday = (days + 4) % 7;
59
60 year = 1970 + days / 365;
61 days -= (year - 1970) * 365
62 + LEAPS_THRU_END_OF(year - 1)
63 - LEAPS_THRU_END_OF(1970 - 1);
64 while (days < 0) {
65 year -= 1;
66 days += 365 + is_leap_year(year);
67 }
68 tm->tm_year = year - 1900;
69 tm->tm_yday = days + 1;
70
71 for (month = 0; month < 11; month++) {
72 int newdays;
73
74 newdays = days - rtc_month_days(month, year);
75 if (newdays < 0)
76 break;
77 days = newdays;
78 }
79 tm->tm_mon = month;
80 tm->tm_mday = days + 1;
81
82 tm->tm_hour = secs / 3600;
83 secs -= tm->tm_hour * 3600;
84 tm->tm_min = secs / 60;
85 tm->tm_sec = secs - tm->tm_min * 60;
86
87 tm->tm_isdst = 0;
88 }
89 EXPORT_SYMBOL(rtc_time64_to_tm);
90
91 /*
92 * Does the rtc_time represent a valid date/time?
93 */
rtc_valid_tm(struct rtc_time * tm)94 int rtc_valid_tm(struct rtc_time *tm)
95 {
96 if (tm->tm_year < 70 ||
97 tm->tm_year > (INT_MAX - 1900) ||
98 ((unsigned int)tm->tm_mon) >= 12 ||
99 tm->tm_mday < 1 ||
100 tm->tm_mday > rtc_month_days(tm->tm_mon,
101 ((unsigned int)tm->tm_year + 1900)) ||
102 ((unsigned int)tm->tm_hour) >= 24 ||
103 ((unsigned int)tm->tm_min) >= 60 ||
104 ((unsigned int)tm->tm_sec) >= 60)
105 return -EINVAL;
106
107 return 0;
108 }
109 EXPORT_SYMBOL(rtc_valid_tm);
110
111 /*
112 * rtc_tm_to_time64 - Converts rtc_time to time64_t.
113 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
114 */
rtc_tm_to_time64(struct rtc_time * tm)115 time64_t rtc_tm_to_time64(struct rtc_time *tm)
116 {
117 return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
118 tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
119 }
120 EXPORT_SYMBOL(rtc_tm_to_time64);
121
122 /*
123 * Convert rtc_time to ktime
124 */
rtc_tm_to_ktime(struct rtc_time tm)125 ktime_t rtc_tm_to_ktime(struct rtc_time tm)
126 {
127 return ktime_set(rtc_tm_to_time64(&tm), 0);
128 }
129 EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
130
131 /*
132 * Convert ktime to rtc_time
133 */
rtc_ktime_to_tm(ktime_t kt)134 struct rtc_time rtc_ktime_to_tm(ktime_t kt)
135 {
136 struct timespec64 ts;
137 struct rtc_time ret;
138
139 ts = ktime_to_timespec64(kt);
140 /* Round up any ns */
141 if (ts.tv_nsec)
142 ts.tv_sec++;
143 rtc_time64_to_tm(ts.tv_sec, &ret);
144 return ret;
145 }
146 EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);
147
