projects/linux·blob v2.6.21 · refs

201 lines · 4.5 KiB

1/*
2 * rtc and date/time utility functions
3 *
4 * Copyright (C) 2005-06 Tower Technologies
5 * Author: Alessandro Zummo <[email protected]>
6 *
7 * based on arch/arm/common/rtctime.c and other bits
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12*/
13
14#include <linux/module.h>
15#include <linux/rtc.h>
16
17static const unsigned char rtc_days_in_month[] = {
18 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
19};
20
21static const unsigned short rtc_ydays[2][13] = {
22 /* Normal years */
23 { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
24 /* Leap years */
25 { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
26};
27
28#define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)
29#define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))
30
31/*
32 * The number of days in the month.
33 */
34int rtc_month_days(unsigned int month, unsigned int year)
35{
36 return rtc_days_in_month[month] + (LEAP_YEAR(year) && month == 1);
37}
38EXPORT_SYMBOL(rtc_month_days);
39
40/*
41 * The number of days since January 1. (0 to 365)
42 */
43int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
44{
45 return rtc_ydays[LEAP_YEAR(year)][month] + day-1;
46}
47EXPORT_SYMBOL(rtc_year_days);
48
49/*
50 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
51 */
52void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
53{
54 register int days, month, year;
55
56 days = time / 86400;
57 time -= days * 86400;
58
59 /* day of the week, 1970-01-01 was a Thursday */
60 tm->tm_wday = (days + 4) % 7;
61
62 year = 1970 + days / 365;
63 days -= (year - 1970) * 365
64 + LEAPS_THRU_END_OF(year - 1)
65 - LEAPS_THRU_END_OF(1970 - 1);
66 if (days < 0) {
67 year -= 1;
68 days += 365 + LEAP_YEAR(year);
69 }
70 tm->tm_year = year - 1900;
71 tm->tm_yday = days + 1;
72
73 for (month = 0; month < 11; month++) {
74 int newdays;
75
76 newdays = days - rtc_month_days(month, year);
77 if (newdays < 0)
78 break;
79 days = newdays;
80 }
81 tm->tm_mon = month;
82 tm->tm_mday = days + 1;
83
84 tm->tm_hour = time / 3600;
85 time -= tm->tm_hour * 3600;
86 tm->tm_min = time / 60;
87 tm->tm_sec = time - tm->tm_min * 60;
88}
89EXPORT_SYMBOL(rtc_time_to_tm);
90
91/*
92 * Does the rtc_time represent a valid date/time?
93 */
94int rtc_valid_tm(struct rtc_time *tm)
95{
96 if (tm->tm_year < 70
97 || ((unsigned)tm->tm_mon) >= 12
98 || tm->tm_mday < 1
99 || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
100 || ((unsigned)tm->tm_hour) >= 24
101 || ((unsigned)tm->tm_min) >= 60
102 || ((unsigned)tm->tm_sec) >= 60)
103 return -EINVAL;
104
105 return 0;
106}
107EXPORT_SYMBOL(rtc_valid_tm);
108
109/*
110 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
111 */
112int rtc_tm_to_time(struct rtc_time *tm, unsigned long *time)
113{
114 *time = mktime(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
115 tm->tm_hour, tm->tm_min, tm->tm_sec);
116 return 0;
117}
118EXPORT_SYMBOL(rtc_tm_to_time);
119
120
121/* Merge the valid (i.e. non-negative) fields of alarm into the current
122 * time. If the valid alarm fields are earlier than the equivalent
123 * fields in the time, carry one into the least significant invalid
124 * field, so that the alarm expiry is in the future. It assumes that the
125 * least significant invalid field is more significant than the most
126 * significant valid field, and that the seconds field is valid.
127 *
128 * This is used by alarms that take relative (rather than absolute)
129 * times, and/or have a simple binary second counter instead of
130 * day/hour/minute/sec registers.
131 */
132void rtc_merge_alarm(struct rtc_time *now, struct rtc_time *alarm)
133{
134 int *alarmp = &alarm->tm_sec;
135 int *timep = &now->tm_sec;
136 int carry_into, i;
137
138 /* Ignore everything past the 6th element (tm_year). */
139 for (i = 5; i > 0; i--) {
140 if (alarmp[i] < 0)
141 alarmp[i] = timep[i];
142 else
143 break;
144 }
145
146 /* No carry needed if all fields are valid. */
147 if (i == 5)
148 return;
149
150 for (carry_into = i + 1; i >= 0; i--) {
151 if (alarmp[i] < timep[i])
152 break;
153
154 if (alarmp[i] > timep[i])
155 return;
156 }
157
158 switch (carry_into) {
159 case 1:
160 alarm->tm_min++;
161
162 if (alarm->tm_min < 60)
163 return;
164
165 alarm->tm_min = 0;
166 /* fall-through */
167
168 case 2:
169 alarm->tm_hour++;
170
171 if (alarm->tm_hour < 60)
172 return;
173
174 alarm->tm_hour = 0;
175 /* fall-through */
176
177 case 3:
178 alarm->tm_mday++;
179
180 if (alarm->tm_mday <= rtc_days_in_month[alarm->tm_mon])
181 return;
182
183 alarm->tm_mday = 1;
184 /* fall-through */
185
186 case 4:
187 alarm->tm_mon++;
188
189 if (alarm->tm_mon <= 12)
190 return;
191
192 alarm->tm_mon = 1;
193 /* fall-through */
194
195 case 5:
196 alarm->tm_year++;
197 }
198}
199EXPORT_SYMBOL(rtc_merge_alarm);
200
201MODULE_LICENSE("GPL");