[PATCH] RTC Subsystem: library functions

RTC and date/time related functions.

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
new file mode 100644
index 000000000000..cfedc1d28ee1
--- /dev/null
+++ b/drivers/rtc/rtc-lib.c
@@ -0,0 +1,101 @@
+/*
+ * 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
+};
+
+#define LEAPS_THRU_END_OF(y) ((y)/4 - (y)/100 + (y)/400)
+#define LEAP_YEAR(year) ((!(year % 4) && (year % 100)) || !(year % 400))
+
+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);
+
+/*
+ * 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
+                || tm->tm_mon >= 12
+                || tm->tm_mday < 1
+                || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
+                || tm->tm_hour >= 24
+                || tm->tm_min >= 60
+                || 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);
+
+MODULE_LICENSE("GPL");