busybox/util-linux/hwclock.c
Denys Vlasenko f560422fa0 Big cleanup in config help and description
Redundant help texts (one which only repeats the description)
are deleted.

Descriptions and help texts are trimmed.

Some config options are moved, even across menus.

No config option _names_ are changed.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-01-10 14:58:54 +01:00

367 lines
10 KiB
C

/* 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 source tree.
*/
//config:config HWCLOCK
//config: bool "hwclock"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: The hwclock utility is used to read and set the hardware clock
//config: on a system. This is primarily used to set the current time on
//config: shutdown in the hardware clock, so the hardware will keep the
//config: correct time when Linux is _not_ running.
//config:
//config:config FEATURE_HWCLOCK_LONG_OPTIONS
//config: bool "Support long options (--hctosys,...)"
//config: default y
//config: depends on HWCLOCK && LONG_OPTS
//config:
//config:config FEATURE_HWCLOCK_ADJTIME_FHS
//config: bool "Use FHS /var/lib/hwclock/adjtime"
//config: default n # util-linux-ng in Fedora 13 still uses /etc/adjtime
//config: depends on HWCLOCK
//config: help
//config: Starting with FHS 2.3, the adjtime state file is supposed to exist
//config: at /var/lib/hwclock/adjtime instead of /etc/adjtime. If you wish
//config: to use the FHS behavior, answer Y here, otherwise answer N for the
//config: classic /etc/adjtime path.
//config:
//config: pathname.com/fhs/pub/fhs-2.3.html#VARLIBHWCLOCKSTATEDIRECTORYFORHWCLO
//applet:IF_HWCLOCK(APPLET(hwclock, BB_DIR_SBIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_HWCLOCK) += hwclock.o
#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 != (int)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 = read_rtc(pp_rtcname, &sys_tv, utc);
#if ENABLE_LOCALE_SUPPORT
/* Standard hwclock uses locale-specific output format */
char cp[64];
struct tm *ptm = localtime(&t);
strftime(cp, sizeof(cp), "%c", ptm);
#else
char *cp = ctime(&t);
chomp(cp);
#endif
#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 we need diff++? */
/* 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;
/* ^^^ used to also subtract 60*daylight, but it's wrong:
* daylight!=0 means "this timezone has some DST
* during the year", not "DST is in effect now".
*/
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);
}
/*
* At system boot, kernel may set system time from RTC,
* but it knows nothing about timezones. If RTC is in local time,
* then system time is wrong - it is offset by timezone.
* This option corrects system time if RTC is in local time,
* and (always) sets in-kernel timezone.
*
* This is an alternate option to --hctosys that does not read the
* hardware clock.
*/
static void set_system_clock_timezone(int utc)
{
struct timeval tv;
struct tm *broken;
struct timezone tz;
gettimeofday(&tv, NULL);
broken = localtime(&tv.tv_sec);
tz.tz_minuteswest = timezone / 60;
if (broken->tm_isdst > 0)
tz.tz_minuteswest -= 60;
tz.tz_dsttime = 0;
gettimeofday(&tv, NULL);
if (!utc)
tv.tv_sec += tz.tz_minuteswest * 60;
if (settimeofday(&tv, &tz))
bb_perror_msg_and_die("settimeofday");
}
//usage:#define hwclock_trivial_usage
//usage: IF_FEATURE_HWCLOCK_LONG_OPTIONS(
//usage: "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
//usage: " [-l|--localtime] [-u|--utc]"
//usage: " [-f|--rtc FILE]"
//usage: )
//usage: IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
//usage: "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
//usage: )
//usage:#define hwclock_full_usage "\n\n"
//usage: "Query and set hardware clock (RTC)\n"
//usage: "\n -r Show hardware clock time"
//usage: "\n -s Set system time from hardware clock"
//usage: "\n -w Set hardware clock from system time"
//usage: "\n -t Set in-kernel timezone, correct system time"
//usage: "\n if hardware clock is in local time"
//usage: "\n -u Assume hardware clock is kept in UTC"
//usage: "\n -l Assume hardware clock is kept in local time"
//usage: "\n -f FILE Use specified device (e.g. /dev/rtc2)"
#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_SYSTZ 0x20
#define HWCLOCK_OPT_RTCFILE 0x40
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" /* short opt is non-standard */
"utc\0" No_argument "u"
"show\0" No_argument "r"
"hctosys\0" No_argument "s"
"systohc\0" No_argument "w"
"systz\0" No_argument "t" /* short opt is non-standard */
"rtc\0" Required_argument "f"
;
applet_long_options = hwclock_longopts;
#endif
/* Initialize "timezone" (libc global variable) */
tzset();
opt_complementary = "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
opt = getopt32(argv, "lurswtf:", &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 if (opt & HWCLOCK_OPT_SYSTZ)
set_system_clock_timezone(utc);
else
/* default HWCLOCK_OPT_SHOW */
show_clock(&rtcname, utc);
return 0;
}