/*
   * 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)
  
  /*
   * 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");