FreeBSD/Linux Kernel Cross Reference
sys/sys/timex.h

     /******************************************************************************
      *                                                                            *
      * Copyright (c) David L. Mills 1993, 1994                                    *
      *                                                                            *
      * Permission to use, copy, modify, and distribute this software and its      *
      * documentation for any purpose and without fee is hereby granted, provided  *
      * that the above copyright notice appears in all copies and that both the    *
      * copyright notice and this permission notice appear in supporting           *
      * documentation, and that the name University of Delaware not be used in     *
     * advertising or publicity pertaining to distribution of the software        *
     * without specific, written prior permission.  The University of Delaware    *
     * makes no representations about the suitability this software for any       *
     * purpose.  It is provided "as is" without express or implied warranty.      *
     *                                                                            *
     ******************************************************************************/
    
    /*
     * Modification history timex.h
     *
     * 26 Sep 94    David L. Mills
     *      Added defines for hybrid phase/frequency-lock loop.
     *
     * 19 Mar 94    David L. Mills
     *      Moved defines from kernel routines to header file and added new
     *      defines for PPS phase-lock loop.
     *
     * 20 Feb 94    David L. Mills
     *      Revised status codes and structures for external clock and PPS
     *      signal discipline.
     *
     * 28 Nov 93    David L. Mills
     *      Adjusted parameters to improve stability and increase poll
     *      interval.
     *
     * 17 Sep 93    David L. Mills
     *      Created file
     */
    /*
     * This header file defines the Network Time Protocol (NTP) interfaces
     * for user and daemon application programs. These are implemented using
     * private syscalls and data structures and require specific kernel
     * support.
     *
     * NAME
     *      ntp_gettime - NTP user application interface
     *
     * SYNOPSIS
     *      #include <sys/timex.h>
     *
     *      int syscall(SYS_ntp_gettime, tptr)
     *
     *      int SYS_ntp_gettime             defined in syscall.h header file
     *      struct ntptimeval *tptr         pointer to ntptimeval structure
     *
     * NAME
     *      ntp_adjtime - NTP daemon application interface
     *
     * SYNOPSIS
     *      #include <sys/timex.h>
     *
     *      int syscall(SYS_ntp_adjtime, mode, tptr)
     *
     *      int SYS_ntp_adjtime             defined in syscall.h header file
     *      struct timex *tptr              pointer to timex structure
     *
     */
    #ifndef _SYS_TIMEX_H_
    #define _SYS_TIMEX_H_ 1
    
    #ifndef MSDOS                   /* Microsoft specific */
    #include <sys/syscall.h>
    #endif /* MSDOS */
    
    /*
     * The following defines establish the engineering parameters of the
     * phase-lock loop (PLL) model used in the kernel implementation. These
     * parameters have been carefully chosen by analysis for good stability
     * and wide dynamic range.
     *
     * The hz variable is defined in the kernel build environment. It
     * establishes the timer interrupt frequency, 100 Hz for the SunOS
     * kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the OSF/1
     * kernel. SHIFT_HZ expresses the same value as the nearest power of two
     * in order to avoid hardware multiply operations.
     *
     * SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
     * for a slightly underdamped convergence characteristic. SHIFT_KH
     * establishes the damping of the FLL and is chosen by wisdom and black
     * art.
     *
     * MAXTC establishes the maximum time constant of the PLL. With the
     * SHIFT_KG and SHIFT_KF values given and a time constant range from
     * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
     * respectively.
     */
    #define SHIFT_HZ 7              /* log2(hz) */
    #define SHIFT_KG 6              /* phase factor (shift) */
    #define SHIFT_KF 16             /* PLL frequency factor (shift) */
    #define SHIFT_KH 2              /* FLL frequency factor (shift) */
   #define MAXTC 6                 /* maximum time constant (shift) */
   
   /*
    * The following defines establish the scaling of the various variables
    * used by the PLL. They are chosen to allow the greatest precision
    * possible without overflow of a 32-bit word.
    *
    * SHIFT_SCALE defines the scaling (shift) of the time_phase variable,
    * which serves as a an extension to the low-order bits of the system
    * clock variable time.tv_usec.
    *
    * SHIFT_UPDATE defines the scaling (shift) of the time_offset variable,
    * which represents the current time offset with respect to standard
    * time.
    *
    * SHIFT_USEC defines the scaling (shift) of the time_freq and
    * time_tolerance variables, which represent the current frequency
    * offset and maximum frequency tolerance.
    *
    * FINEUSEC is 1 us in SHIFT_UPDATE units of the time_phase variable.
    */
   #define SHIFT_SCALE 22          /* phase scale (shift) */
   #define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */
   #define SHIFT_USEC 16           /* frequency offset scale (shift) */
   #define FINEUSEC (1L << SHIFT_SCALE) /* 1 us in phase units */
   
   /*
    * The following defines establish the performance envelope of the PLL.
    * They insure it operates within predefined limits, in order to satisfy
    * correctness assertions. An excursion which exceeds these bounds is
    * clamped to the bound and operation proceeds accordingly. In practice,
    * this can occur only if something has failed or is operating out of
    * tolerance, but otherwise the PLL continues to operate in a stable
    * mode.
    *
    * MAXPHASE must be set greater than or equal to CLOCK.MAX (128 ms), as
    * defined in the NTP specification. CLOCK.MAX establishes the maximum
    * time offset allowed before the system time is reset, rather than
    * incrementally adjusted. Here, the maximum offset is clamped to
    * MAXPHASE only in order to prevent overflow errors due to defective
    * protocol implementations.
    *
    * MAXFREQ is the maximum frequency tolerance of the CPU clock
    * oscillator plus the maximum slew rate allowed by the protocol. It
    * should be set to at least the frequency tolerance of the oscillator
    * plus 100 ppm for vernier frequency adjustments. If the kernel
    * PPS discipline code is configured (PPS_SYNC), the oscillator time and
    * frequency are disciplined to an external source, presumably with
    * negligible time and frequency error relative to UTC, and MAXFREQ can
    * be reduced.
    *
    * MAXTIME is the maximum jitter tolerance of the PPS signal if the
    * kernel PPS discipline code is configured (PPS_SYNC).
    *
    * MINSEC and MAXSEC define the lower and upper bounds on the interval
    * between protocol updates.
    */
   #define MAXPHASE 512000L        /* max phase error (us) */
   #ifdef PPS_SYNC
   #define MAXFREQ (512L << SHIFT_USEC) /* max freq error (100 ppm) */
   #define MAXTIME (200L << PPS_AVG) /* max PPS error (jitter) (200 us) */
   #else
   #define MAXFREQ (512L << SHIFT_USEC) /* max freq error (200 ppm) */
   #endif /* PPS_SYNC */
   #define MINSEC 16L              /* min interval between updates (s) */
   #define MAXSEC 1200L            /* max interval between updates (s) */
   
   #ifdef PPS_SYNC
   /*
    * The following defines are used only if a pulse-per-second (PPS)
    * signal is available and connected via a modem control lead, such as
    * produced by the optional ppsclock feature incorporated in the Sun
    * asynch driver. They establish the design parameters of the frequency-
    * lock loop used to discipline the CPU clock oscillator to the PPS
    * signal.
    *
    * PPS_AVG is the averaging factor for the frequency loop, as well as
    * the time and frequency dispersion.
    *
    * PPS_SHIFT and PPS_SHIFTMAX specify the minimum and maximum
    * calibration intervals, respectively, in seconds as a power of two.
    *
    * PPS_VALID is the maximum interval before the PPS signal is considered
    * invalid and protocol updates used directly instead.
    *
    * MAXGLITCH is the maximum interval before a time offset of more than
    * MAXTIME is believed.
    */
   #define PPS_AVG 2               /* pps averaging constant (shift) */
   #define PPS_SHIFT 2             /* min interval duration (s) (shift) */
   #define PPS_SHIFTMAX 8          /* max interval duration (s) (shift) */
   #define PPS_VALID 120           /* pps signal watchdog max (s) */
   #define MAXGLITCH 30            /* pps signal glitch max (s) */
   #endif /* PPS_SYNC */
   
   /*
    * The following defines and structures define the user interface for
    * the ntp_gettime() and ntp_adjtime() system calls.
    *
    * Control mode codes (timex.modes)
    */
   #define MOD_OFFSET      0x0001  /* set time offset */
   #define MOD_FREQUENCY   0x0002  /* set frequency offset */
   #define MOD_MAXERROR    0x0004  /* set maximum time error */
   #define MOD_ESTERROR    0x0008  /* set estimated time error */
   #define MOD_STATUS      0x0010  /* set clock status bits */
   #define MOD_TIMECONST   0x0020  /* set pll time constant */
   #define MOD_CLKB        0x4000  /* set clock B */
   #define MOD_CLKA        0x8000  /* set clock A */
   
   /*
    * Status codes (timex.status)
    */
   #define STA_PLL         0x0001  /* enable PLL updates (rw) */
   #define STA_PPSFREQ     0x0002  /* enable PPS freq discipline (rw) */
   #define STA_PPSTIME     0x0004  /* enable PPS time discipline (rw) */
   #define STA_FLL         0x0008  /* select frequency-lock mode (rw) */
   
   #define STA_INS         0x0010  /* insert leap (rw) */
   #define STA_DEL         0x0020  /* delete leap (rw) */
   #define STA_UNSYNC      0x0040  /* clock unsynchronized (rw) */
   #define STA_FREQHOLD    0x0080  /* hold frequency (rw) */
   
   #define STA_PPSSIGNAL   0x0100  /* PPS signal present (ro) */
   #define STA_PPSJITTER   0x0200  /* PPS signal jitter exceeded (ro) */
   #define STA_PPSWANDER   0x0400  /* PPS signal wander exceeded (ro) */
   #define STA_PPSERROR    0x0800  /* PPS signal calibration error (ro) */
   
   #define STA_CLOCKERR    0x1000  /* clock hardware fault (ro) */
   
   #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
       STA_PPSERROR | STA_CLOCKERR) /* read-only bits */
   
   /*
    * Clock states (time_state)
    */
   #define TIME_OK         0       /* no leap second warning */
   #define TIME_INS        1       /* insert leap second warning */
   #define TIME_DEL        2       /* delete leap second warning */
   #define TIME_OOP        3       /* leap second in progress */
   #define TIME_WAIT       4       /* leap second has occured */
   #define TIME_ERROR      5       /* clock not synchronized */
   
   /*
    * NTP user interface (ntp_gettime()) - used to read kernel clock values
    *
    * Note: maximum error = NTP synch distance = dispersion + delay / 2;
    * estimated error = NTP dispersion.
    */
   struct ntptimeval {
           struct timeval time;    /* current time (ro) */
           long maxerror;          /* maximum error (us) (ro) */
           long esterror;          /* estimated error (us) (ro) */
           int time_state;         /* what ntp_gettime returns */
   };
   
   /*
    * NTP daemon interface - (ntp_adjtime()) used to discipline CPU clock
    * oscillator
    */
   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) */
   
   };
   #ifdef __FreeBSD__
   
   /*
    * sysctl identifiers underneath kern.ntp_pll
    */
   #define NTP_PLL_GETTIME 1       /* used by ntp_gettime() */
   #define NTP_PLL_MAXID   2       /* number of valid ids */
   
   #define NTP_PLL_NAMES { \
                             { 0, 0 }, \
                             { "gettime", CTLTYPE_STRUCT }, \
                         }
   
   #ifndef KERNEL
   #include <sys/cdefs.h>
   
   __BEGIN_DECLS
   extern int ntp_gettime  __P((struct ntptimeval *));
   extern int ntp_adjtime  __P((struct timex *));
   __END_DECLS
   
   #endif /* not KERNEL */
   
   #endif /* __FreeBSD__ */
   #endif /* _SYS_TIMEX_H_ */

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