sys_null.c

   1 /*
   2   chronyd/chronyc - Programs for keeping computer clocks accurate.
   3
   4  **********************************************************************
   5  * Copyright (C) Miroslav Lichvar  2017
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of version 2 of the GNU General Public License as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  19  *
  20  **********************************************************************
  21
  22   =======================================================================
  23
  24   Null clock driver for operation with no clock control.
  25   */
  26
  27 #include "config.h"
  28
  29 #include "sysincl.h"
  30
  31 #include "sys_null.h"
  32
  33 #include "local.h"
  34 #include "localp.h"
  35 #include "logging.h"
  36 #include "util.h"
  37
  38 /* Current frequency offset of the system clock (in ppm) */
  39 static double freq;
  40
  41 /* Offset of the system clock at the last update */
  42 static double offset_register;
  43
  44 /* Time of the last update */
  45 static struct timespec last_update;
  46
  47 /* Minimum interval between updates when frequency is constant */
  48 #define MIN_UPDATE_INTERVAL 1000.0
  49
  50 /* ================================================== */
  51
  52 static void
  53 update_offset(void)
  54 {
  55   struct timespec now;
  56   double duration;
  57
  58   LCL_ReadRawTime(&now);
  59   duration = UTI_DiffTimespecsToDouble(&now, &last_update);
  60   offset_register += 1.0e-6 * freq * duration;
  61   last_update = now;
  62
  63   DEBUG_LOG("System clock offset=%e freq=%f", offset_register, freq);
  64 }
  65
  66 /* ================================================== */
  67
  68 static double
  69 read_frequency(void)
  70 {
  71   return freq;
  72 }
  73
  74 /* ================================================== */
  75
  76 static double
  77 set_frequency(double freq_ppm)
  78 {
  79   update_offset();
  80   freq = freq_ppm;
  81
  82   return freq;
  83 }
  84
  85 /* ================================================== */
  86
  87 static void
  88 accrue_offset(double offset, double corr_rate)
  89 {
  90   offset_register += offset;
  91 }
  92
  93 /* ================================================== */
  94
  95 static int
  96 apply_step_offset(double offset)
  97 {
  98   return 0;
  99 }
 100
 101 /* ================================================== */
 102
 103 static void
 104 offset_convert(struct timespec *raw, double *corr, double *err)
 105 {
 106   double duration;
 107
 108   duration = UTI_DiffTimespecsToDouble(raw, &last_update);
 109
 110   if (duration > MIN_UPDATE_INTERVAL) {
 111     update_offset();
 112     duration = 0.0;
 113   }
 114
 115   *corr = -1.0e-6 * freq * duration - offset_register;
 116
 117   if (err)
 118     *err = 0.0;
 119 }
 120
 121 /* ================================================== */
 122
 123 void
 124 SYS_Null_Initialise(void)
 125 {
 126   offset_register = 0.0;
 127   LCL_ReadRawTime(&last_update);
 128
 129   lcl_RegisterSystemDrivers(read_frequency, set_frequency, accrue_offset,
 130                             apply_step_offset, offset_convert, NULL, NULL);
 131
 132   LOG(LOGS_INFO, "Disabled control of system clock");
 133 }
 134
 135 /* ================================================== */
 136
 137 void
 138 SYS_Null_Finalise(void)
 139 {
 140 }