rtc_time64_to_tm()和rtc_tm_to_time64()主要用于RTC的驱动程序，在Linux外部RTC驱动中较常见。
打开"drivers/rtc/lib.c"
/*
* rtc_time64_to_tm - Converts time64_t to rtc_time.
* Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
*/
//将time转换为年月日时分秒和星期几
void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
{
unsigned int month, year, secs;
int days;
/* time must be positive */
days = div_s64_rem(time, 86400, &secs);/*计算总共有多少天*/
/* day of the week, 1970-01-01 was a Thursday */
tm->tm_wday = (days + 4) % 7;/*计算是星期几*/
year = 1970 + days / 365;/*计算公元年数值*/
days -= (year - 1970) * 365
- LEAPS_THRU_END_OF(year - 1)
- LEAPS_THRU_END_OF(1970 - 1);
while (days < 0) {
year -= 1;
days += 365 + is_leap_year(year);
}
tm->tm_year = year - 1900;/*计算年*/
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 = secs / 3600;/*计算小时*/
secs -= tm->tm_hour * 3600;
tm->tm_min = secs / 60;/*计算分钟*/
tm->tm_sec = secs - tm->tm_min * 60;/*计算秒*/
tm->tm_isdst = 0;
}
/*
* rtc_tm_to_time64 - Converts rtc_time to time64_t.
* Convert Gregorian date to seconds since 01-01-1970 00:00:00.
*/
//将年月日时分秒和星期几转换为64位的time
time64_t rtc_tm_to_time64(struct rtc_time *tm)
{
return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
}