summaryrefslogtreecommitdiff
path: root/drivers/rtc/lib.c
blob: 3d0dc70ff7d85dbb3e5c2f7066f5d7156c2a7442 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
// 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
 */

#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 }
};

#define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)

/*
 * 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.
 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
 */
void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
{
	unsigned int month, year, secs;
	int days;

	/* 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;

	year = 1970 + days / 365;
	days -= (year - 1970) * 365
		+ LEAPS_THRU_END_OF(year - 1)
		- LEAPS_THRU_END_OF(1970 - 1);
	while (days < 0) {
		year -= 1;
		days += 365 + is_leap_year(year);
	}
	tm->tm_year = year - 1900;
	tm->tm_yday = days + 1;

	for (month = 0; month < 11; month++) {
		int newdays;

		newdays = days - rtc_month_days(month, year);
		if (newdays < 0)
			break;
		days = newdays;
	}
	tm->tm_mon = month;
	tm->tm_mday = days + 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
		|| ((unsigned)tm->tm_mon) >= 12
		|| tm->tm_mday < 1
		|| tm->tm_mday > rtc_month_days(tm->tm_mon, ((unsigned)tm->tm_year + 1900))
		|| ((unsigned)tm->tm_hour) >= 24
		|| ((unsigned)tm->tm_min) >= 60
		|| ((unsigned)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)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);