util-linux/rtcwake.c

/*
 * rtcwake -- enter a system sleep state until specified wakeup time.
 *
 * This version was taken from util-linux and scrubbed down for busybox.
 *
 * This uses cross-platform Linux interfaces to enter a system sleep state,
 * and leave it no later than a specified time.  It uses any RTC framework
 * driver that supports standard driver model wakeup flags.
 *
 * This is normally used like the old "apmsleep" utility, to wake from a
 * suspend state like ACPI S1 (standby) or S3 (suspend-to-RAM).  Most
 * platforms can implement those without analogues of BIOS, APM, or ACPI.
 *
 * On some systems, this can also be used like "nvram-wakeup", waking
 * from states like ACPI S4 (suspend to disk).  Not all systems have
 * persistent media that are appropriate for such suspend modes.
 *
 * The best way to set the system's RTC is so that it holds the current
 * time in UTC.  Use the "-l" flag to tell this program that the system
 * RTC uses a local timezone instead (maybe you dual-boot MS-Windows).
 * That flag should not be needed on systems with adjtime support.
 */

#include "libbb.h"
#include "rtc_.h"

#define SYS_RTC_PATH   "/sys/class/rtc/%s/device/power/wakeup"
#define SYS_POWER_PATH "/sys/power/state"
#define DEFAULT_MODE   "standby"

static time_t rtc_time;

static bool may_wakeup(const char *rtcname)
{
	ssize_t ret;
	char buf[128];

	/* strip the '/dev/' from the rtcname here */
	if (!strncmp(rtcname, "/dev/", 5))
		rtcname += 5;

	snprintf(buf, sizeof(buf), SYS_RTC_PATH, rtcname);
	ret = open_read_close(buf, buf, sizeof(buf));
	if (ret < 0)
		return false;

	/* wakeup events could be disabled or not supported */
	return strncmp(buf, "enabled\n", 8) == 0;
}

static void setup_alarm(int fd, time_t *wakeup)
{
	struct tm *tm;
	struct linux_rtc_wkalrm	wake;

	/* The wakeup time is in POSIX time (more or less UTC).
	 * Ideally RTCs use that same time; but PCs can't do that
	 * if they need to boot MS-Windows.  Messy...
	 *
	 * When running in utc mode this process's timezone is UTC,
	 * so we'll pass a UTC date to the RTC.
	 *
	 * Else mode is local so the time given to the RTC
	 * will instead use the local time zone.
	 */
	tm = localtime(wakeup);

	wake.time.tm_sec = tm->tm_sec;
	wake.time.tm_min = tm->tm_min;
	wake.time.tm_hour = tm->tm_hour;
	wake.time.tm_mday = tm->tm_mday;
	wake.time.tm_mon = tm->tm_mon;
	wake.time.tm_year = tm->tm_year;
	/* wday, yday, and isdst fields are unused by Linux */
	wake.time.tm_wday = -1;
	wake.time.tm_yday = -1;
	wake.time.tm_isdst = -1;

	/* many rtc alarms only support up to 24 hours from 'now',
	 * so use the "more than 24 hours" request only if we must
	 */
	if ((rtc_time + (24 * 60 * 60)) > *wakeup) {
		xioctl(fd, RTC_ALM_SET, &wake.time);
		xioctl(fd, RTC_AIE_ON, 0);
	} else {
		/* avoid an extra AIE_ON call */
		wake.enabled = 1;
		xioctl(fd, RTC_WKALM_SET, &wake);
	}
}

#define RTCWAKE_OPT_AUTO         0x01
#define RTCWAKE_OPT_LOCAL        0x02
#define RTCWAKE_OPT_UTC          0x04
#define RTCWAKE_OPT_DEVICE       0x08
#define RTCWAKE_OPT_SUSPEND_MODE 0x10
#define RTCWAKE_OPT_SECONDS      0x20
#define RTCWAKE_OPT_TIME         0x40

int rtcwake_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int rtcwake_main(int argc UNUSED_PARAM, char **argv)
{
	unsigned opt;
	const char *rtcname = NULL;
	const char *suspend;
	const char *opt_seconds;
	const char *opt_time;

	time_t sys_time;
	time_t alarm_time = 0;
	unsigned seconds = 0;
	int utc = -1;
	int fd;

#if ENABLE_GETOPT_LONG
	static const char rtcwake_longopts[] ALIGN1 =
		"auto\0"    No_argument "a"
		"local\0"   No_argument "l"
		"utc\0"     No_argument "u"
		"device\0"  Required_argument "d"
		"mode\0"    Required_argument "m"
		"seconds\0" Required_argument "s"
		"time\0"    Required_argument "t"
		;
	applet_long_options = rtcwake_longopts;
#endif
	opt = getopt32(argv, "alud:m:s:t:", &rtcname, &suspend, &opt_seconds, &opt_time);

	/* this is the default
	if (opt & RTCWAKE_OPT_AUTO)
		utc = -1;
	*/
	if (opt & (RTCWAKE_OPT_UTC | RTCWAKE_OPT_LOCAL))
		utc = opt & RTCWAKE_OPT_UTC;
	if (!(opt & RTCWAKE_OPT_SUSPEND_MODE))
		suspend = DEFAULT_MODE;
	if (opt & RTCWAKE_OPT_SECONDS)
		/* alarm time, seconds-to-sleep (relative) */
		seconds = xatoi(opt_seconds);
	if (opt & RTCWAKE_OPT_TIME)
		/* alarm time, time_t (absolute, seconds since 1/1 1970 UTC) */
		alarm_time = xatoi(opt_time);

	if (!alarm_time && !seconds)
		bb_error_msg_and_die("must provide wake time");

	if (utc == -1)
		utc = rtc_adjtime_is_utc();

	/* the rtcname is relative to /dev */
	xchdir("/dev");

	/* this RTC must exist and (if we'll sleep) be wakeup-enabled */
	fd = rtc_xopen(&rtcname, O_RDONLY);

	if (strcmp(suspend, "on") && !may_wakeup(rtcname))
		bb_error_msg_and_die("%s not enabled for wakeup events", rtcname);

	/* relative or absolute alarm time, normalized to time_t */
	sys_time = time(0);
	if (sys_time == (time_t)-1)
		bb_perror_msg_and_die("read system time");
	rtc_time = rtc_read_time(fd, utc);

	if (alarm_time) {
		if (alarm_time < sys_time)
			bb_error_msg_and_die("time doesn't go backward to %s", ctime(&alarm_time));
		alarm_time += sys_time - rtc_time;
	} else
		alarm_time = rtc_time + seconds + 1;
	setup_alarm(fd, &alarm_time);

	sync();
	printf("wakeup from \"%s\" at %s", suspend, ctime(&alarm_time));
	fflush(stdout);
	usleep(10 * 1000);

	if (strcmp(suspend, "on"))
		xopen_xwrite_close(SYS_POWER_PATH, suspend);
	else {
		/* "fake" suspend ... we'll do the delay ourselves */
		unsigned long data;

		do {
			ssize_t ret = safe_read(fd, &data, sizeof(data));
			if (ret < 0) {
				bb_perror_msg("rtc read");
				break;
			}
		} while (!(data & RTC_AF));
	}

	xioctl(fd, RTC_AIE_OFF, 0);

	if (ENABLE_FEATURE_CLEAN_UP)
		close(fd);

	return EXIT_SUCCESS;
}