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
update_offset(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
read_frequency(void)69 read_frequency(void)
70 {
71 return freq;
72 }
73
74 /* ================================================== */
75
76 static double
set_frequency(double freq_ppm)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
accrue_offset(double offset,double corr_rate)88 accrue_offset(double offset, double corr_rate)
89 {
90 offset_register += offset;
91 }
92
93 /* ================================================== */
94
95 static int
apply_step_offset(double offset)96 apply_step_offset(double offset)
97 {
98 return 0;
99 }
100
101 /* ================================================== */
102
103 static void
offset_convert(struct timespec * raw,double * corr,double * err)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
SYS_Null_Initialise(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
SYS_Null_Finalise(void)138 SYS_Null_Finalise(void)
139 {
140 }
141