util-linux/hwclock.c - codeaurora/busybox - Gitiles

 /* vi: set sw=4 ts=4: */
 /*
  * Mini hwclock implementation for busybox
  *
  * Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
  *
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

 #include "libbb.h"
 /* After libbb.h, since it needs sys/types.h on some systems */
 #include <sys/utsname.h>
 #include "rtc_.h"

 /* diff code is disabled: it's not sys/hw clock diff, it's some useless
  * "time between hwclock was started and we saw CMOS tick" quantity.
  * It's useless since hwclock is started at a random moment,
  * thus the quantity is also random, useless. Showing 0.000000 does not
  * deprive us from any useful info.
  *
  * SHOW_HWCLOCK_DIFF code in this file shows the difference between system
  * and hw clock. It is useful, but not compatible with standard hwclock.
  * Thus disabled.
  */
 #define SHOW_HWCLOCK_DIFF 0


 #if !SHOW_HWCLOCK_DIFF
 # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
 #endif
 static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
 {
 	struct tm tm_time;
 	int fd;

 	fd = rtc_xopen(pp_rtcname, O_RDONLY);

 	rtc_read_tm(&tm_time, fd);

 #if SHOW_HWCLOCK_DIFF
 	{
 		int before = tm_time.tm_sec;
 		while (1) {
 			rtc_read_tm(&tm_time, fd);
 			gettimeofday(sys_tv, NULL);
 			if (before != tm_time.tm_sec)
 				break;
 		}
 	}
 #endif

 	if (ENABLE_FEATURE_CLEAN_UP)
 		close(fd);

 	return rtc_tm2time(&tm_time, utc);
 }

 static void show_clock(const char **pp_rtcname, int utc)
 {
 #if SHOW_HWCLOCK_DIFF
 	struct timeval sys_tv;
 #endif
 	time_t t;
 	char *cp;

 	t = read_rtc(pp_rtcname, &sys_tv, utc);
 	cp = ctime(&t);
 	strchrnul(cp, '\n')[0] = '\0';
 #if !SHOW_HWCLOCK_DIFF
 	printf("%s  0.000000 seconds\n", cp);
 #else
 	{
 		long diff = sys_tv.tv_sec - t;
 		if (diff < 0 /*&& tv.tv_usec != 0*/) {
 			/* Why? */
 			/* diff >= 0 is ok:   diff < 0, can't just use tv.tv_usec: */
 			/*   45.520820          43.520820 */
 			/* - 44.000000        - 45.000000 */
 			/* =  1.520820        = -1.479180, not -2.520820! */
 			diff++;
 			/* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
 			sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
 		}
 		printf("%s  %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
 	}
 #endif
 }

 static void to_sys_clock(const char **pp_rtcname, int utc)
 {
 	struct timeval tv;
 	struct timezone tz;

 	tz.tz_minuteswest = timezone/60 - 60*daylight;
 	tz.tz_dsttime = 0;

 	tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
 	tv.tv_usec = 0;
 	if (settimeofday(&tv, &tz))
 		bb_perror_msg_and_die("settimeofday");
 }

 static void from_sys_clock(const char **pp_rtcname, int utc)
 {
 #if 1
 	struct timeval tv;
 	struct tm tm_time;
 	int rtc;

 	rtc = rtc_xopen(pp_rtcname, O_WRONLY);
 	gettimeofday(&tv, NULL);
 	/* Prepare tm_time */
 	if (sizeof(time_t) == sizeof(tv.tv_sec)) {
 		if (utc)
 			gmtime_r((time_t*)&tv.tv_sec, &tm_time);
 		else
 			localtime_r((time_t*)&tv.tv_sec, &tm_time);
 	} else {
 		time_t t = tv.tv_sec;
 		if (utc)
 			gmtime_r(&t, &tm_time);
 		else
 			localtime_r(&t, &tm_time);
 	}
 #else
 /* Bloated code which tries to set hw clock with better precision.
  * On x86, even though code does set hw clock within <1ms of exact
  * whole seconds, apparently hw clock (at least on some machines)
  * doesn't reset internal fractional seconds to 0,
  * making all this a pointless excercise.
  */
 	/* If we see that we are N usec away from whole second,
 	 * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
 	 * that CPU is not infinitely fast.
 	 * On infinitely fast CPU, next wakeup would be
 	 * on (exactly_next_whole_second - ADJ). On real CPUs,
 	 * this difference between current time and whole second
 	 * is less than ADJ (assuming system isn't heavily loaded).
 	 */
 	/* Small value of 256us gives very precise sync for 2+ GHz CPUs.
 	 * Slower CPUs will fail to sync and will go to bigger
 	 * ADJ values. qemu-emulated armv4tl with ~100 MHz
 	 * performance ends up using ADJ ~= 4*1024 and it takes
 	 * 2+ secs (2 tries with successively larger ADJ)
 	 * to sync. Even straced one on the same qemu (very slow)
 	 * takes only 4 tries.
 	 */
 #define TWEAK_USEC 256
 	unsigned adj = TWEAK_USEC;
 	struct tm tm_time;
 	struct timeval tv;
 	int rtc = rtc_xopen(pp_rtcname, O_WRONLY);

 	/* Try to catch the moment when whole second is close */
 	while (1) {
 		unsigned rem_usec;
 		time_t t;

 		gettimeofday(&tv, NULL);

 		t = tv.tv_sec;
 		rem_usec = 1000000 - tv.tv_usec;
 		if (rem_usec < adj) {
 			/* Close enough */
  small_rem:
 			t++;
 		}

 		/* Prepare tm_time from t */
 		if (utc)
 			gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
 		else
 			localtime_r(&t, &tm_time); /* same */

 		if (adj >= 32*1024) {
 			break; /* 32 ms diff and still no luck?? give up trying to sync */
 		}

 		/* gmtime/localtime took some time, re-get cur time */
 		gettimeofday(&tv, NULL);

 		if (tv.tv_sec < t /* we are still in old second */
 		 || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
 		) {
 			break; /* good, we are in sync! */
 		}

 		rem_usec = 1000000 - tv.tv_usec;
 		if (rem_usec < adj) {
 			t = tv.tv_sec;
 			goto small_rem; /* already close to next sec, don't sleep */
 		}

 		/* Try to sync up by sleeping */
 		usleep(rem_usec - adj);

 		/* Jump to 1ms diff, then increase fast (x2): EVERY loop
 		 * takes ~1 sec, people won't like slowly converging code here!
 		 */
 	//bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
 		if (adj < 512)
 			adj = 512;
 		/* ... and if last "overshoot" does not look insanely big,
 		 * just use it as adj increment. This makes convergence faster.
 		 */
 		if (tv.tv_usec < adj * 8) {
 			adj += tv.tv_usec;
 			continue;
 		}
 		adj *= 2;
 	}
 	/* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
 	 * Look for a value which makes tv_usec close to 999999 or 0.
 	 * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
 	 */
 	//bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
 #endif

 	tm_time.tm_isdst = 0;
 	xioctl(rtc, RTC_SET_TIME, &tm_time);

 	if (ENABLE_FEATURE_CLEAN_UP)
 		close(rtc);
 }

 #define HWCLOCK_OPT_LOCALTIME   0x01
 #define HWCLOCK_OPT_UTC         0x02
 #define HWCLOCK_OPT_SHOW        0x04
 #define HWCLOCK_OPT_HCTOSYS     0x08
 #define HWCLOCK_OPT_SYSTOHC     0x10
 #define HWCLOCK_OPT_RTCFILE     0x20

 int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int hwclock_main(int argc UNUSED_PARAM, char **argv)
 {
 	const char *rtcname = NULL;
 	unsigned opt;
 	int utc;

 #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
 	static const char hwclock_longopts[] ALIGN1 =
 		"localtime\0" No_argument "l"
 		"utc\0"       No_argument "u"
 		"show\0"      No_argument "r"
 		"hctosys\0"   No_argument "s"
 		"systohc\0"   No_argument "w"
 		"file\0"      Required_argument "f"
 		;
 	applet_long_options = hwclock_longopts;
 #endif
 	opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l";
 	opt = getopt32(argv, "lurswf:", &rtcname);

 	/* If -u or -l wasn't given check if we are using utc */
 	if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
 		utc = (opt & HWCLOCK_OPT_UTC);
 	else
 		utc = rtc_adjtime_is_utc();

 	if (opt & HWCLOCK_OPT_HCTOSYS)
 		to_sys_clock(&rtcname, utc);
 	else if (opt & HWCLOCK_OPT_SYSTOHC)
 		from_sys_clock(&rtcname, utc);
 	else
 		/* default HWCLOCK_OPT_SHOW */
 		show_clock(&rtcname, utc);

 	return 0;
 }
	/* vi: set sw=4 ts=4: */
	/*
	* Mini hwclock implementation for busybox
	*
	* Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
	*
	* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
	*/

	#include "libbb.h"
	/* After libbb.h, since it needs sys/types.h on some systems */
	#include <sys/utsname.h>
	#include "rtc_.h"

	/* diff code is disabled: it's not sys/hw clock diff, it's some useless
	* "time between hwclock was started and we saw CMOS tick" quantity.
	* It's useless since hwclock is started at a random moment,
	* thus the quantity is also random, useless. Showing 0.000000 does not
	* deprive us from any useful info.
	*
	* SHOW_HWCLOCK_DIFF code in this file shows the difference between system
	* and hw clock. It is useful, but not compatible with standard hwclock.
	* Thus disabled.
	*/
	#define SHOW_HWCLOCK_DIFF 0


	#if !SHOW_HWCLOCK_DIFF
	# define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
	#endif
	static time_t read_rtc(const char *pp_rtcname, struct timeval sys_tv, int utc)
	{
	struct tm tm_time;
	int fd;

	fd = rtc_xopen(pp_rtcname, O_RDONLY);

	rtc_read_tm(&tm_time, fd);

	#if SHOW_HWCLOCK_DIFF
	{
	int before = tm_time.tm_sec;
	while (1) {
	rtc_read_tm(&tm_time, fd);
	gettimeofday(sys_tv, NULL);
	if (before != tm_time.tm_sec)
	break;
	}
	}
	#endif

	if (ENABLE_FEATURE_CLEAN_UP)
	close(fd);

	return rtc_tm2time(&tm_time, utc);
	}

	static void show_clock(const char **pp_rtcname, int utc)
	{
	#if SHOW_HWCLOCK_DIFF
	struct timeval sys_tv;
	#endif
	time_t t;
	char *cp;

	t = read_rtc(pp_rtcname, &sys_tv, utc);
	cp = ctime(&t);
	strchrnul(cp, '\n')[0] = '\0';
	#if !SHOW_HWCLOCK_DIFF
	printf("%s 0.000000 seconds\n", cp);
	#else
	{
	long diff = sys_tv.tv_sec - t;
	if (diff < 0 /&& tv.tv_usec != 0/) {
	/* Why? */
	/* diff >= 0 is ok: diff < 0, can't just use tv.tv_usec: */
	/* 45.520820 43.520820 */
	/* - 44.000000 - 45.000000 */
	/* = 1.520820 = -1.479180, not -2.520820! */
	diff++;
	/* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
	sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
	}
	printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
	}
	#endif
	}

	static void to_sys_clock(const char **pp_rtcname, int utc)
	{
	struct timeval tv;
	struct timezone tz;

	tz.tz_minuteswest = timezone/60 - 60*daylight;
	tz.tz_dsttime = 0;

	tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
	tv.tv_usec = 0;
	if (settimeofday(&tv, &tz))
	bb_perror_msg_and_die("settimeofday");
	}

	static void from_sys_clock(const char **pp_rtcname, int utc)
	{
	#if 1
	struct timeval tv;
	struct tm tm_time;
	int rtc;

	rtc = rtc_xopen(pp_rtcname, O_WRONLY);
	gettimeofday(&tv, NULL);
	/* Prepare tm_time */
	if (sizeof(time_t) == sizeof(tv.tv_sec)) {
	if (utc)
	gmtime_r((time_t*)&tv.tv_sec, &tm_time);
	else
	localtime_r((time_t*)&tv.tv_sec, &tm_time);
	} else {
	time_t t = tv.tv_sec;
	if (utc)
	gmtime_r(&t, &tm_time);
	else
	localtime_r(&t, &tm_time);
	}
	#else
	/* Bloated code which tries to set hw clock with better precision.
	* On x86, even though code does set hw clock within <1ms of exact
	* whole seconds, apparently hw clock (at least on some machines)
	* doesn't reset internal fractional seconds to 0,
	* making all this a pointless excercise.
	*/
	/* If we see that we are N usec away from whole second,
	* we'll sleep for N-ADJ usecs. ADJ corrects for the fact
	* that CPU is not infinitely fast.
	* On infinitely fast CPU, next wakeup would be
	* on (exactly_next_whole_second - ADJ). On real CPUs,
	* this difference between current time and whole second
	* is less than ADJ (assuming system isn't heavily loaded).
	*/
	/* Small value of 256us gives very precise sync for 2+ GHz CPUs.
	* Slower CPUs will fail to sync and will go to bigger
	* ADJ values. qemu-emulated armv4tl with ~100 MHz
	* performance ends up using ADJ ~= 4*1024 and it takes
	* 2+ secs (2 tries with successively larger ADJ)
	* to sync. Even straced one on the same qemu (very slow)
	* takes only 4 tries.
	*/
	#define TWEAK_USEC 256
	unsigned adj = TWEAK_USEC;
	struct tm tm_time;
	struct timeval tv;
	int rtc = rtc_xopen(pp_rtcname, O_WRONLY);

	/* Try to catch the moment when whole second is close */
	while (1) {
	unsigned rem_usec;
	time_t t;

	gettimeofday(&tv, NULL);

	t = tv.tv_sec;
	rem_usec = 1000000 - tv.tv_usec;
	if (rem_usec < adj) {
	/* Close enough */
	small_rem:
	t++;
	}

	/* Prepare tm_time from t */
	if (utc)
	gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
	else
	localtime_r(&t, &tm_time); /* same */

	if (adj >= 32*1024) {
	break; /* 32 ms diff and still no luck?? give up trying to sync */
	}

	/* gmtime/localtime took some time, re-get cur time */
	gettimeofday(&tv, NULL);

	if (tv.tv_sec < t /* we are still in old second */
	\|\| (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
	) {
	break; /* good, we are in sync! */
	}

	rem_usec = 1000000 - tv.tv_usec;
	if (rem_usec < adj) {
	t = tv.tv_sec;
	goto small_rem; /* already close to next sec, don't sleep */
	}

	/* Try to sync up by sleeping */
	usleep(rem_usec - adj);

	/* Jump to 1ms diff, then increase fast (x2): EVERY loop
	* takes ~1 sec, people won't like slowly converging code here!
	*/
	//bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
	if (adj < 512)
	adj = 512;
	/* ... and if last "overshoot" does not look insanely big,
	* just use it as adj increment. This makes convergence faster.
	*/
	if (tv.tv_usec < adj * 8) {
	adj += tv.tv_usec;
	continue;
	}
	adj *= 2;
	}
	/* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
	* Look for a value which makes tv_usec close to 999999 or 0.
	* For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
	*/
	//bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
	#endif

	tm_time.tm_isdst = 0;
	xioctl(rtc, RTC_SET_TIME, &tm_time);

	if (ENABLE_FEATURE_CLEAN_UP)
	close(rtc);
	}

	#define HWCLOCK_OPT_LOCALTIME 0x01
	#define HWCLOCK_OPT_UTC 0x02
	#define HWCLOCK_OPT_SHOW 0x04
	#define HWCLOCK_OPT_HCTOSYS 0x08
	#define HWCLOCK_OPT_SYSTOHC 0x10
	#define HWCLOCK_OPT_RTCFILE 0x20

	int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
	int hwclock_main(int argc UNUSED_PARAM, char **argv)
	{
	const char *rtcname = NULL;
	unsigned opt;
	int utc;

	#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
	static const char hwclock_longopts[] ALIGN1 =
	"localtime\0" No_argument "l"
	"utc\0" No_argument "u"
	"show\0" No_argument "r"
	"hctosys\0" No_argument "s"
	"systohc\0" No_argument "w"
	"file\0" Required_argument "f"
	;
	applet_long_options = hwclock_longopts;
	#endif
	opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l";
	opt = getopt32(argv, "lurswf:", &rtcname);

	/* If -u or -l wasn't given check if we are using utc */
	if (opt & (HWCLOCK_OPT_UTC \| HWCLOCK_OPT_LOCALTIME))
	utc = (opt & HWCLOCK_OPT_UTC);
	else
	utc = rtc_adjtime_is_utc();

	if (opt & HWCLOCK_OPT_HCTOSYS)
	to_sys_clock(&rtcname, utc);
	else if (opt & HWCLOCK_OPT_SYSTOHC)
	from_sys_clock(&rtcname, utc);
	else
	/* default HWCLOCK_OPT_SHOW */
	show_clock(&rtcname, utc);

	return 0;
	}