rtc-lib.c

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/*
 * rtc and date/time utility functions
 *
 * Copyright (C) 2005-06 Tower Technologies
 * Author: Alessandro Zummo <[email protected]>
 *
 * 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)

/*
 * 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);

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

    days = time / 86400;
    time -= (unsigned int) 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 + 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 = time / 3600;
    time -= tm->tm_hour * 3600;
    tm->tm_min = time / 60;
    tm->tm_sec = time - tm->tm_min * 60;

    tm->tm_isdst = 0;
}
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);

/*
 * Convert rtc_time to ktime
 */
ktime_t rtc_tm_to_ktime(struct rtc_time tm)
{
    time_t time;
    rtc_tm_to_time(&tm, &time);
    return ktime_set(time, 0);
}
EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);

/*
 * Convert ktime to rtc_time
 */
struct rtc_time rtc_ktime_to_tm(ktime_t kt)
{
    struct timespec ts;
    struct rtc_time ret;

    ts = ktime_to_timespec(kt);
    /* Round up any ns */
    if (ts.tv_nsec)
        ts.tv_sec++;
    rtc_time_to_tm(ts.tv_sec, &ret);
    return ret;
}
EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);

MODULE_LICENSE("GPL");