[debian/all] wake when needed

[Timo Juhani Lindfors]

"Nikita V. Youshchenko" <yoush at debian.org> writes:
> Is there any working methond to make freerunner suspend sleep and later 
> wakeup not later than at a given moment?

Yes.

#include <stdio.h>
#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <time.h>

int main(int argc, char **argv) {
    int fd, ret;
    struct rtc_wkalrm wkalrm;

    assert(argc == 2);

    fd = open("/dev/rtc0", O_RDONLY);
    assert(fd);

    {
        struct tm *tm;
        time_t secs;

        secs = atol(argv[1]);
        assert(secs > 86400*365*(2000-1970));
        assert(secs < 86400*365*(2030-1970));
        tm = gmtime(&secs);
        assert(tm);

        wkalrm.time.tm_sec = tm->tm_sec;
        wkalrm.time.tm_min = tm->tm_min;
        wkalrm.time.tm_hour = tm->tm_hour;
        wkalrm.time.tm_mday = tm->tm_mday;
        wkalrm.time.tm_mon = tm->tm_mon;
        wkalrm.time.tm_year = tm->tm_year;
        wkalrm.time.tm_wday = tm->tm_wday;
        wkalrm.time.tm_yday = tm->tm_yday;
        wkalrm.time.tm_isdst = tm->tm_isdst;
    }

    wkalrm.enabled = 1;
    ret = ioctl(fd, RTC_WKALM_SET, &wkalrm);
    assert(ret != -1);

    return 0;
}

works for me with andy-tracking b8b36e5ec3d.