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Diffstat (limited to 'lib/libc/sys/ntp_adjtime.2')
| -rw-r--r-- | lib/libc/sys/ntp_adjtime.2 | 315 |
1 files changed, 315 insertions, 0 deletions
diff --git a/lib/libc/sys/ntp_adjtime.2 b/lib/libc/sys/ntp_adjtime.2 new file mode 100644 index 0000000..8ce78e7 --- /dev/null +++ b/lib/libc/sys/ntp_adjtime.2 @@ -0,0 +1,315 @@ +.\" $NetBSD: ntp_adjtime.2,v 1.6 2003/04/16 13:34:55 wiz Exp $ +.\" +.\" Copyright (c) 2001 The NetBSD Foundation, Inc. +.\" All rights reserved. +.\" +.\" This code is derived from software contributed to The NetBSD Foundation +.\" by Thomas Klausner. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd July 13, 2005 +.Dt NTP_ADJTIME 2 +.Os +.Sh NAME +.Nm ntp_adjtime , +.Nm ntp_gettime +.Nd Network Time Protocol (NTP) daemon interface system calls +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/timex.h +.Ft int +.Fn ntp_adjtime "struct timex *" +.Ft int +.Fn ntp_gettime "struct ntptimeval *" +.Sh DESCRIPTION +The two system calls +.Fn ntp_adjtime +and +.Fn ntp_gettime +are the kernel interface to the Network Time Protocol (NTP) daemon +.Xr ntpd 8 . +.Pp +The +.Fn ntp_adjtime +function is used by the NTP daemon to adjust the system clock to an +externally derived time. +The time offset and related variables which are set by +.Fn ntp_adjtime +are used by +.Fn hardclock +to adjust the phase and frequency of the phase- or frequency-lock loop +(PLL resp. FLL) which controls the system clock. +.Pp +The +.Fn ntp_gettime +function provides the time, maximum error (sync distance) and +estimated error (dispersion) to client user application programs. +.Pp +In the following, all variables that refer PPS are only relevant if +the +.Em PPS_SYNC +option is enabled in the kernel. +.Pp +.Fn ntp_adjtime +has as argument a +.Va struct timex * +of the following form: +.Bd -literal +struct timex { + unsigned int modes; /* clock mode bits (wo) */ + long offset; /* time offset (us) (rw) */ + long freq; /* frequency offset (scaled ppm) (rw) */ + long maxerror; /* maximum error (us) (rw) */ + long esterror; /* estimated error (us) (rw) */ + int status; /* clock status bits (rw) */ + long constant; /* pll time constant (rw) */ + long precision; /* clock precision (us) (ro) */ + long tolerance; /* clock frequency tolerance (scaled + * ppm) (ro) */ + /* + * The following read-only structure members are implemented + * only if the PPS signal discipline is configured in the + * kernel. + */ + long ppsfreq; /* pps frequency (scaled ppm) (ro) */ + long jitter; /* pps jitter (us) (ro) */ + int shift; /* interval duration (s) (shift) (ro) */ + long stabil; /* pps stability (scaled ppm) (ro) */ + long jitcnt; /* jitter limit exceeded (ro) */ + long calcnt; /* calibration intervals (ro) */ + long errcnt; /* calibration errors (ro) */ + long stbcnt; /* stability limit exceeded (ro) */ +}; +.Ed +.Pp +The members of this struct have the following meanings when used as +argument for +.Fn ntp_adjtime : +.Bl -tag -width tolerance -compact +.It Fa modes +Defines what settings should be changed with the current +.Fn ntp_adjtime +call (write-only). +Bitwise OR of the following: +.Bl -tag -width MOD_TIMECONST -compact -offset indent +.It MOD_OFFSET +set time offset +.It MOD_FREQUENCY +set frequency offset +.It MOD_MAXERROR +set maximum time error +.It MOD_ESTERROR +set estimated time error +.It MOD_STATUS +set clock status bits +.It MOD_TIMECONST +set PLL time constant +.It MOD_CLKA +set clock A +.It MOD_CLKB +set clock B +.El +.It Fa offset +Time offset (in microseconds), used by the PLL/FLL to adjust the +system time in small increments (read-write). +.It Fa freq +Frequency offset (scaled ppm) (read-write). +.It Fa maxerror +Maximum error (in microseconds). +Initialized by an +.Fn ntp_adjtime +call, and increased by the kernel once each second to reflect the maximum +error bound growth (read-write). +.It Fa esterror +Estimated error (in microseconds). +Set and read by +.Fn ntp_adjtime , +but unused by the kernel (read-write). +.It Fa status +System clock status bits (read-write). +Bitwise OR of the following: +.Bl -tag -width STA_PPSJITTER -compact -offset indent +.It STA_PLL +Enable PLL updates (read-write). +.It STA_PPSFREQ +Enable PPS freq discipline (read-write). +.It STA_PPSTIME +Enable PPS time discipline (read-write). +.It STA_FLL +Select frequency-lock mode (read-write). +.It STA_INS +Insert leap (read-write). +.It STA_DEL +Delete leap (read-write). +.It STA_UNSYNC +Clock unsynchronized (read-write). +.It STA_FREQHOLD +Hold frequency (read-write). +.It STA_PPSSIGNAL +PPS signal present (read-only). +.It STA_PPSJITTER +PPS signal jitter exceeded (read-only). +.It STA_PPSWANDER +PPS signal wander exceeded (read-only). +.It STA_PPSERROR +PPS signal calibration error (read-only). +.It STA_CLOCKERR +Clock hardware fault (read-only). +.El +.It Fa constant +PLL time constant, determines the bandwidth, or +.Dq stiffness , +of the PLL (read-write). +.It Fa precision +Clock precision (in microseconds). +In most cases the same as the kernel tick variable (see +.Xr hz 9 ) . +If a precision clock counter or external time-keeping signal is available, +it could be much lower (and depend on the state of the signal) +(read-only). +.It Fa tolerance +Maximum frequency error, or tolerance of the CPU clock oscillator (scaled +ppm). +Ordinarily a property of the architecture, but could change under +the influence of external time-keeping signals (read-only). +.It Fa ppsfreq +PPS frequency offset produced by the frequency median filter (scaled +ppm) (read-only). +.It Fa jitter +PPS jitter measured by the time median filter in microseconds +(read-only). +.It Fa shift +Logarithm to base 2 of the interval duration in seconds (PPS, +read-only). +.It Fa stabil +PPS stability (scaled ppm); dispersion (wander) measured by the +frequency median filter (read-only). +.It Fa jitcnt +Number of seconds that have been discarded because the jitter measured +by the time median filter exceeded the limit +.Em MAXTIME +(PPS, read-only). +.It Fa calcnt +Count of calibration intervals (PPS, read-only). +.It Fa errcnt +Number of calibration intervals that have been discarded because the +wander exceeded the limit +.Em MAXFREQ +or where the calibration interval jitter exceeded two ticks (PPS, +read-only). +.It Fa stbcnt +Number of calibration intervals that have been discarded because the +frequency wander exceeded the limit +.Em MAXFREQ Ns /4 +(PPS, read-only). +.El +After the +.Fn ntp_adjtime +call, the +.Va struct timex * +structure contains the current values of the corresponding variables. +.Pp +.Fn ntp_gettime +has as argument a +.Va struct ntptimeval * +with the following members: +.Bd -literal +struct ntptimeval { + struct timeval time; /* current time (ro) */ + long maxerror; /* maximum error (us) (ro) */ + long esterror; /* estimated error (us) (ro) */ +}; +.Ed +.Pp +These have the following meaning: +.Bl -tag -width tolerance -compact +.It Fa time +Current time (read-only). +.It Fa maxerror +Maximum error in microseconds (read-only). +.It Fa esterror +Estimated error in microseconds (read-only). +.El +.Sh RETURN VALUES +.Fn ntp_adjtime +and +.Fn ntp_gettime +return the current state of the clock on success, or any of the errors +of +.Xr copyin 9 +and +.Xr copyout 9 . +.Fn ntp_adjtime +may additionally return +.Er EPERM +if the user calling +.Fn ntp_adjtime +does not have sufficient permissions. +.Pp +Possible states of the clock are: +.Bl -tag -width TIME_ERROR -compact -offset indent +.It TIME_OK +Everything okay, no leap second warning. +.It TIME_INS +.Dq insert leap second +warning. +At the end of the day, a leap second will be inserted after 23:59:59. +.It TIME_DEL +.Dq delete leap second +warning. +At the end of the day, second 23:59:59 will be skipped. +.It TIME_OOP +Leap second in progress. +.It TIME_WAIT +Leap second has occurred within the last few seconds. +.It TIME_ERROR +Clock not synchronized. +.El +.Sh ERRORS +The +.Fn ntp_adjtime +system call may return +.Er EPERM +if the caller +does not have sufficient permissions. +.Sh SEE ALSO +.Xr options 4 , +.Xr ntpd 8 , +.Xr hardclock 9 , +.Xr hz 9 +.Bl -tag -width indent +.It Pa http://www.bipm.fr/enus/5_Scientific/c_time/time_1.html +.It Pa http://www.boulder.nist.gov/timefreq/general/faq.htm +.It Pa ftp://time.nist.gov/pub/leap-seconds.list +.El +.Sh BUGS +Take note that this +.Tn API +is extremely complex and stateful. +Users should not attempt modification without first +reviewing the +.Xr ntpd 8 +sources in depth. |
