summaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-lib.c
blob: 7bbc26a34bd25d7007abaaea57d017343f24ce59 (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
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
/*
 * 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
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
*/

#include <linux/module.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)
#define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))

/*
 * The number of days in the month.
 */
int rtc_month_days(unsigned int month, unsigned int year)
{
	return rtc_days_in_month[month] + (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[LEAP_YEAR(year)][month] + day-1;
}
EXPORT_SYMBOL(rtc_year_days);

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

	days = time / 86400;
	time -= days * 86400;

	/* 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);
	if (days < 0) {
		year -= 1;
		days += 365 + 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 = time / 3600;
	time -= tm->tm_hour * 3600;
	tm->tm_min = time / 60;
	tm->tm_sec = time - tm->tm_min * 60;
}
EXPORT_SYMBOL(rtc_time_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, 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);

/*
 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
 */
int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
{
	*time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
			tm->tm_hour, tm->tm_min, tm->tm_sec);
	return 0;
}
EXPORT_SYMBOL(rtc_tm_to_time);


/* Merge the valid (i.e. non-negative) fields of alarm into the current
 * time.  If the valid alarm fields are earlier than the equivalent
 * fields in the time, carry one into the least significant invalid
 * field, so that the alarm expiry is in the future.  It assumes that the
 * least significant invalid field is more significant than the most
 * significant valid field, and that the seconds field is valid.
 *
 * This is used by alarms that take relative (rather than absolute)
 * times, and/or have a simple binary second counter instead of
 * day/hour/minute/sec registers.
 */
void rtc_merge_alarm(struct rtc_time *now, struct rtc_time *alarm)
{
	int *alarmp = &alarm->tm_sec;
	int *timep = &now->tm_sec;
	int carry_into, i;

	/* Ignore everything past the 6th element (tm_year). */
	for (i = 5; i > 0; i--) {
		if (alarmp[i] < 0)
			alarmp[i] = timep[i];
		else
			break;
	}

	/* No carry needed if all fields are valid. */
	if (i == 5)
		return;

	for (carry_into = i + 1; i >= 0; i--) {
		if (alarmp[i] < timep[i])
			break;

		if (alarmp[i] > timep[i])
			return;
	}

	switch (carry_into) {
		case 1:
			alarm->tm_min++;

			if (alarm->tm_min < 60)
				return;

			alarm->tm_min = 0;
			/* fall-through */

		case 2:
			alarm->tm_hour++;

			if (alarm->tm_hour < 60)
				return;

			alarm->tm_hour = 0;
			/* fall-through */

		case 3:
			alarm->tm_mday++;

			if (alarm->tm_mday <= rtc_days_in_month[alarm->tm_mon])
				return;

			alarm->tm_mday = 1;
			/* fall-through */

		case 4:
			alarm->tm_mon++;

			if (alarm->tm_mon <= 12)
				return;

			alarm->tm_mon = 1;
			/* fall-through */

		case 5:
			alarm->tm_year++;
	}
}
EXPORT_SYMBOL(rtc_merge_alarm);

MODULE_LICENSE("GPL");
OpenPOWER on IntegriCloud