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88840341 | 1 | /* |
6672f045 | 2 | $Header: /cvs/src/chrony/local.c,v 1.21 2003/09/22 21:22:30 richard Exp $ |
88840341 RC |
3 | |
4 | ======================================================================= | |
5 | ||
6 | chronyd/chronyc - Programs for keeping computer clocks accurate. | |
7 | ||
8 | ********************************************************************** | |
6672f045 | 9 | * Copyright (C) Richard P. Curnow 1997-2003 |
88840341 RC |
10 | * |
11 | * This program is free software; you can redistribute it and/or modify | |
12 | * it under the terms of version 2 of the GNU General Public License as | |
13 | * published by the Free Software Foundation. | |
14 | * | |
15 | * This program is distributed in the hope that it will be useful, but | |
16 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | * General Public License for more details. | |
19 | * | |
20 | * You should have received a copy of the GNU General Public License along | |
21 | * with this program; if not, write to the Free Software Foundation, Inc., | |
8e23110a | 22 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
88840341 RC |
23 | * |
24 | ********************************************************************** | |
25 | ||
26 | ======================================================================= | |
27 | ||
28 | The routines in this file present a common local (system) clock | |
29 | interface to the rest of the software. | |
30 | ||
31 | They interface with the system specific driver files in sys_*.c | |
32 | */ | |
33 | ||
34 | #include <assert.h> | |
35 | #include <stddef.h> | |
36 | ||
37 | #include "local.h" | |
38 | #include "localp.h" | |
39 | #include "memory.h" | |
40 | #include "util.h" | |
41 | #include "logging.h" | |
42 | ||
43 | /* ================================================== */ | |
44 | ||
45 | /* Variable to store the current frequency, in ppm */ | |
46 | static double current_freq_ppm; | |
47 | ||
c386d117 ML |
48 | /* Temperature compensation, in ppm */ |
49 | static double temp_comp_ppm; | |
50 | ||
88840341 RC |
51 | /* ================================================== */ |
52 | /* Store the system dependent drivers */ | |
53 | ||
54 | static lcl_ReadFrequencyDriver drv_read_freq; | |
55 | static lcl_SetFrequencyDriver drv_set_freq; | |
56 | static lcl_AccrueOffsetDriver drv_accrue_offset; | |
57 | static lcl_ApplyStepOffsetDriver drv_apply_step_offset; | |
58 | static lcl_OffsetCorrectionDriver drv_offset_convert; | |
8f9c2370 | 59 | static lcl_SetLeapDriver drv_set_leap; |
88840341 RC |
60 | |
61 | /* ================================================== */ | |
62 | ||
63 | /* Types and variables associated with handling the parameter change | |
64 | list */ | |
65 | ||
66 | typedef struct _ChangeListEntry { | |
67 | struct _ChangeListEntry *next; | |
68 | struct _ChangeListEntry *prev; | |
69 | LCL_ParameterChangeHandler handler; | |
70 | void *anything; | |
71 | } ChangeListEntry; | |
72 | ||
73 | static ChangeListEntry change_list; | |
74 | ||
75 | /* ================================================== */ | |
76 | ||
77 | /* Types and variables associated with handling the parameter change | |
78 | list */ | |
79 | ||
80 | typedef struct _DispersionNotifyListEntry { | |
81 | struct _DispersionNotifyListEntry *next; | |
82 | struct _DispersionNotifyListEntry *prev; | |
83 | LCL_DispersionNotifyHandler handler; | |
84 | void *anything; | |
85 | } DispersionNotifyListEntry; | |
86 | ||
87 | static DispersionNotifyListEntry dispersion_notify_list; | |
88 | ||
89 | /* ================================================== */ | |
90 | ||
91 | static int precision_log; | |
92 | static double precision_quantum; | |
93 | ||
94 | /* ================================================== */ | |
95 | ||
96 | /* Define the number of increments of the system clock that we want | |
97 | to see to be fairly sure that we've got something approaching | |
98 | the minimum increment. Even on a crummy implementation that can't | |
99 | interpolate between 10ms ticks, we should get this done in | |
100 | under 1s of busy waiting. */ | |
101 | #define NITERS 100 | |
102 | ||
103 | static void | |
104 | calculate_sys_precision(void) | |
105 | { | |
106 | struct timeval tv, old_tv, first_tv; | |
88840341 RC |
107 | int dusec, best_dusec; |
108 | int iters; | |
109 | ||
2f2e524b | 110 | gettimeofday(&old_tv, NULL); |
88840341 RC |
111 | first_tv = old_tv; |
112 | best_dusec = 1000000; /* Assume we must be better than a second */ | |
113 | iters = 0; | |
114 | do { | |
2f2e524b | 115 | gettimeofday(&tv, NULL); |
88840341 RC |
116 | dusec = 1000000*(tv.tv_sec - old_tv.tv_sec) + (tv.tv_usec - old_tv.tv_usec); |
117 | old_tv = tv; | |
118 | if (dusec > 0) { | |
119 | if (dusec < best_dusec) { | |
120 | best_dusec = dusec; | |
121 | } | |
122 | iters++; | |
123 | } | |
124 | } while (iters < NITERS); | |
6b0198c2 ML |
125 | |
126 | assert(best_dusec > 0); | |
127 | ||
10c9a7d4 | 128 | precision_quantum = best_dusec * 1.0e-6; |
88840341 RC |
129 | precision_log = 0; |
130 | while (best_dusec < 500000) { | |
131 | precision_log--; | |
132 | best_dusec *= 2; | |
133 | } | |
134 | ||
88840341 RC |
135 | return; |
136 | } | |
137 | ||
138 | /* ================================================== */ | |
139 | ||
140 | void | |
141 | LCL_Initialise(void) | |
142 | { | |
143 | change_list.next = change_list.prev = &change_list; | |
144 | ||
145 | dispersion_notify_list.next = dispersion_notify_list.prev = &dispersion_notify_list; | |
146 | ||
147 | /* Null out the system drivers, so that we die | |
148 | if they never get defined before use */ | |
149 | ||
150 | drv_read_freq = NULL; | |
151 | drv_set_freq = NULL; | |
152 | drv_accrue_offset = NULL; | |
153 | drv_offset_convert = NULL; | |
154 | ||
155 | /* This ought to be set from the system driver layer */ | |
156 | current_freq_ppm = 0.0; | |
c386d117 | 157 | temp_comp_ppm = 0.0; |
88840341 RC |
158 | |
159 | calculate_sys_precision(); | |
160 | } | |
161 | ||
162 | /* ================================================== */ | |
163 | ||
164 | void | |
165 | LCL_Finalise(void) | |
166 | { | |
167 | return; | |
168 | } | |
169 | ||
170 | /* ================================================== */ | |
171 | ||
172 | /* Routine to read the system precision as a log to base 2 value. */ | |
173 | int | |
174 | LCL_GetSysPrecisionAsLog(void) | |
175 | { | |
176 | return precision_log; | |
177 | } | |
178 | ||
179 | /* ================================================== */ | |
180 | /* Routine to read the system precision in terms of the actual time step */ | |
181 | ||
182 | double | |
183 | LCL_GetSysPrecisionAsQuantum(void) | |
184 | { | |
185 | return precision_quantum; | |
186 | } | |
187 | ||
188 | /* ================================================== */ | |
189 | ||
190 | void | |
191 | LCL_AddParameterChangeHandler(LCL_ParameterChangeHandler handler, void *anything) | |
192 | { | |
193 | ChangeListEntry *ptr, *new_entry; | |
194 | ||
195 | /* Check that the handler is not already registered */ | |
196 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
197 | if (!(ptr->handler != handler || ptr->anything != anything)) { | |
6b0198c2 | 198 | assert(0); |
88840341 RC |
199 | } |
200 | } | |
201 | ||
202 | new_entry = MallocNew(ChangeListEntry); | |
203 | ||
204 | new_entry->handler = handler; | |
205 | new_entry->anything = anything; | |
206 | ||
207 | /* Chain it into the list */ | |
208 | new_entry->next = &change_list; | |
209 | new_entry->prev = change_list.prev; | |
210 | change_list.prev->next = new_entry; | |
211 | change_list.prev = new_entry; | |
212 | ||
213 | return; | |
214 | } | |
215 | ||
216 | /* ================================================== */ | |
217 | ||
218 | /* Remove a handler */ | |
219 | extern | |
220 | void LCL_RemoveParameterChangeHandler(LCL_ParameterChangeHandler handler, void *anything) | |
221 | { | |
222 | ||
223 | ChangeListEntry *ptr; | |
224 | int ok; | |
225 | ||
226 | ptr = NULL; | |
227 | ok = 0; | |
228 | ||
229 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
230 | if (ptr->handler == handler && ptr->anything == anything) { | |
231 | ok = 1; | |
232 | break; | |
233 | } | |
234 | } | |
235 | ||
6b0198c2 | 236 | assert(ok); |
88840341 RC |
237 | |
238 | /* Unlink entry from the list */ | |
239 | ptr->next->prev = ptr->prev; | |
240 | ptr->prev->next = ptr->next; | |
241 | ||
242 | free(ptr); | |
243 | ||
244 | return; | |
245 | } | |
246 | ||
247 | /* ================================================== */ | |
248 | ||
249 | void | |
250 | LCL_AddDispersionNotifyHandler(LCL_DispersionNotifyHandler handler, void *anything) | |
251 | { | |
252 | DispersionNotifyListEntry *ptr, *new_entry; | |
253 | ||
254 | /* Check that the handler is not already registered */ | |
255 | for (ptr = dispersion_notify_list.next; ptr != &dispersion_notify_list; ptr = ptr->next) { | |
256 | if (!(ptr->handler != handler || ptr->anything != anything)) { | |
6b0198c2 | 257 | assert(0); |
88840341 RC |
258 | } |
259 | } | |
260 | ||
261 | new_entry = MallocNew(DispersionNotifyListEntry); | |
262 | ||
263 | new_entry->handler = handler; | |
264 | new_entry->anything = anything; | |
265 | ||
266 | /* Chain it into the list */ | |
267 | new_entry->next = &dispersion_notify_list; | |
268 | new_entry->prev = dispersion_notify_list.prev; | |
269 | dispersion_notify_list.prev->next = new_entry; | |
270 | dispersion_notify_list.prev = new_entry; | |
271 | ||
272 | return; | |
273 | } | |
274 | ||
275 | /* ================================================== */ | |
276 | ||
277 | /* Remove a handler */ | |
278 | extern | |
279 | void LCL_RemoveDispersionNotifyHandler(LCL_DispersionNotifyHandler handler, void *anything) | |
280 | { | |
281 | ||
282 | DispersionNotifyListEntry *ptr; | |
283 | int ok; | |
284 | ||
285 | ptr = NULL; | |
286 | ok = 0; | |
287 | ||
288 | for (ptr = dispersion_notify_list.next; ptr != &dispersion_notify_list; ptr = ptr->next) { | |
289 | if (ptr->handler == handler && ptr->anything == anything) { | |
290 | ok = 1; | |
291 | break; | |
292 | } | |
293 | } | |
294 | ||
6b0198c2 | 295 | assert(ok); |
88840341 RC |
296 | |
297 | /* Unlink entry from the list */ | |
298 | ptr->next->prev = ptr->prev; | |
299 | ptr->prev->next = ptr->next; | |
300 | ||
301 | free(ptr); | |
302 | ||
303 | return; | |
304 | } | |
305 | ||
306 | /* ================================================== */ | |
307 | /* At the moment, this is just gettimeofday(), because | |
308 | I can't think of a Unix system where it would not be */ | |
309 | ||
310 | void | |
311 | LCL_ReadRawTime(struct timeval *result) | |
312 | { | |
2f2e524b | 313 | if (gettimeofday(result, NULL) < 0) { |
6b0198c2 | 314 | LOG_FATAL(LOGF_Local, "gettimeofday() failed"); |
88840341 | 315 | } |
88840341 RC |
316 | } |
317 | ||
318 | /* ================================================== */ | |
319 | ||
320 | void | |
321 | LCL_ReadCookedTime(struct timeval *result, double *err) | |
322 | { | |
323 | struct timeval raw; | |
88840341 RC |
324 | |
325 | LCL_ReadRawTime(&raw); | |
20d898d1 ML |
326 | LCL_CookTime(&raw, result, err); |
327 | } | |
88840341 | 328 | |
20d898d1 | 329 | /* ================================================== */ |
88840341 | 330 | |
20d898d1 ML |
331 | void |
332 | LCL_CookTime(struct timeval *raw, struct timeval *cooked, double *err) | |
333 | { | |
334 | double correction; | |
88840341 | 335 | |
20d898d1 ML |
336 | LCL_GetOffsetCorrection(raw, &correction, err); |
337 | UTI_AddDoubleToTimeval(raw, correction, cooked); | |
88840341 RC |
338 | } |
339 | ||
340 | /* ================================================== */ | |
341 | ||
20d898d1 ML |
342 | void |
343 | LCL_GetOffsetCorrection(struct timeval *raw, double *correction, double *err) | |
88840341 | 344 | { |
20d898d1 | 345 | /* Call system specific driver to get correction */ |
1faeb450 | 346 | (*drv_offset_convert)(raw, correction, err); |
88840341 RC |
347 | } |
348 | ||
349 | /* ================================================== */ | |
350 | /* This is just a simple passthrough of the system specific routine */ | |
351 | ||
352 | double | |
353 | LCL_ReadAbsoluteFrequency(void) | |
354 | { | |
c386d117 ML |
355 | double freq; |
356 | ||
357 | freq = (*drv_read_freq)(); | |
358 | ||
359 | /* Undo temperature compensation */ | |
360 | if (temp_comp_ppm != 0.0) { | |
361 | freq = (freq + temp_comp_ppm) / (1.0 - 1.0e-6 * temp_comp_ppm); | |
362 | } | |
363 | ||
364 | return freq; | |
88840341 RC |
365 | } |
366 | ||
367 | /* ================================================== */ | |
368 | /* This involves both setting the absolute frequency with the | |
369 | system-specific driver, as well as calling all notify handlers */ | |
370 | ||
371 | void | |
372 | LCL_SetAbsoluteFrequency(double afreq_ppm) | |
373 | { | |
374 | ChangeListEntry *ptr; | |
375 | struct timeval raw, cooked; | |
88840341 RC |
376 | double dfreq; |
377 | ||
c386d117 ML |
378 | /* Apply temperature compensation */ |
379 | if (temp_comp_ppm != 0.0) { | |
380 | afreq_ppm = afreq_ppm * (1.0 - 1.0e-6 * temp_comp_ppm) - temp_comp_ppm; | |
381 | } | |
382 | ||
88840341 RC |
383 | /* Call the system-specific driver for setting the frequency */ |
384 | ||
1a7415a6 | 385 | afreq_ppm = (*drv_set_freq)(afreq_ppm); |
88840341 | 386 | |
99d18abf | 387 | dfreq = (afreq_ppm - current_freq_ppm) / (1.0e6 + current_freq_ppm); |
88840341 RC |
388 | |
389 | LCL_ReadRawTime(&raw); | |
20d898d1 | 390 | LCL_CookTime(&raw, &cooked, NULL); |
88840341 RC |
391 | |
392 | /* Dispatch to all handlers */ | |
393 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
14d25769 | 394 | (ptr->handler)(&raw, &cooked, dfreq, 0.0, 0, ptr->anything); |
88840341 RC |
395 | } |
396 | ||
397 | current_freq_ppm = afreq_ppm; | |
398 | ||
399 | } | |
400 | ||
401 | /* ================================================== */ | |
402 | ||
403 | void | |
404 | LCL_AccumulateDeltaFrequency(double dfreq) | |
405 | { | |
406 | ChangeListEntry *ptr; | |
407 | struct timeval raw, cooked; | |
1a7415a6 ML |
408 | double old_freq_ppm; |
409 | ||
410 | old_freq_ppm = current_freq_ppm; | |
88840341 RC |
411 | |
412 | /* Work out new absolute frequency. Note that absolute frequencies | |
413 | are handled in units of ppm, whereas the 'dfreq' argument is in | |
414 | terms of the gradient of the (offset) v (local time) function. */ | |
415 | ||
99d18abf | 416 | current_freq_ppm = (1.0 + dfreq) * current_freq_ppm + 1.0e6 * dfreq; |
88840341 RC |
417 | |
418 | /* Call the system-specific driver for setting the frequency */ | |
1a7415a6 ML |
419 | current_freq_ppm = (*drv_set_freq)(current_freq_ppm); |
420 | dfreq = (current_freq_ppm - old_freq_ppm) / (1.0e6 + old_freq_ppm); | |
88840341 RC |
421 | |
422 | LCL_ReadRawTime(&raw); | |
20d898d1 | 423 | LCL_CookTime(&raw, &cooked, NULL); |
88840341 RC |
424 | |
425 | /* Dispatch to all handlers */ | |
426 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
14d25769 | 427 | (ptr->handler)(&raw, &cooked, dfreq, 0.0, 0, ptr->anything); |
88840341 RC |
428 | } |
429 | ||
430 | } | |
431 | ||
432 | /* ================================================== */ | |
433 | ||
434 | void | |
435 | LCL_AccumulateOffset(double offset) | |
436 | { | |
437 | ChangeListEntry *ptr; | |
438 | struct timeval raw, cooked; | |
88840341 RC |
439 | |
440 | /* In this case, the cooked time to be passed to the notify clients | |
441 | has to be the cooked time BEFORE the change was made */ | |
442 | ||
443 | LCL_ReadRawTime(&raw); | |
20d898d1 | 444 | LCL_CookTime(&raw, &cooked, NULL); |
88840341 RC |
445 | |
446 | (*drv_accrue_offset)(offset); | |
447 | ||
448 | /* Dispatch to all handlers */ | |
449 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
14d25769 | 450 | (ptr->handler)(&raw, &cooked, 0.0, offset, 0, ptr->anything); |
88840341 RC |
451 | } |
452 | ||
453 | } | |
454 | ||
455 | /* ================================================== */ | |
456 | ||
457 | void | |
458 | LCL_ApplyStepOffset(double offset) | |
459 | { | |
460 | ChangeListEntry *ptr; | |
461 | struct timeval raw, cooked; | |
88840341 RC |
462 | |
463 | /* In this case, the cooked time to be passed to the notify clients | |
464 | has to be the cooked time BEFORE the change was made */ | |
465 | ||
466 | LCL_ReadRawTime(&raw); | |
20d898d1 | 467 | LCL_CookTime(&raw, &cooked, NULL); |
88840341 RC |
468 | |
469 | (*drv_apply_step_offset)(offset); | |
470 | ||
471 | /* Dispatch to all handlers */ | |
472 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
14d25769 | 473 | (ptr->handler)(&raw, &cooked, 0.0, offset, 1, ptr->anything); |
88840341 RC |
474 | } |
475 | ||
476 | } | |
477 | ||
478 | /* ================================================== */ | |
479 | ||
480 | void | |
481 | LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset) | |
482 | { | |
483 | ChangeListEntry *ptr; | |
484 | struct timeval raw, cooked; | |
88840341 RC |
485 | double old_freq_ppm; |
486 | ||
487 | LCL_ReadRawTime(&raw); | |
88840341 RC |
488 | /* Due to modifying the offset, this has to be the cooked time prior |
489 | to the change we are about to make */ | |
20d898d1 | 490 | LCL_CookTime(&raw, &cooked, NULL); |
88840341 RC |
491 | |
492 | old_freq_ppm = current_freq_ppm; | |
493 | ||
494 | /* Work out new absolute frequency. Note that absolute frequencies | |
495 | are handled in units of ppm, whereas the 'dfreq' argument is in | |
496 | terms of the gradient of the (offset) v (local time) function. */ | |
99d18abf | 497 | current_freq_ppm = (1.0 + dfreq) * old_freq_ppm + 1.0e6 * dfreq; |
88840341 RC |
498 | |
499 | #ifdef TRACEON | |
500 | LOG(LOGS_INFO, LOGF_Local, "old_freq=%.3fppm new_freq=%.3fppm offset=%.6fsec", | |
501 | old_freq_ppm, current_freq_ppm, doffset); | |
502 | #endif | |
503 | ||
504 | /* Call the system-specific driver for setting the frequency */ | |
1a7415a6 ML |
505 | current_freq_ppm = (*drv_set_freq)(current_freq_ppm); |
506 | dfreq = (current_freq_ppm - old_freq_ppm) / (1.0e6 + old_freq_ppm); | |
507 | ||
88840341 RC |
508 | (*drv_accrue_offset)(doffset); |
509 | ||
510 | /* Dispatch to all handlers */ | |
511 | for (ptr = change_list.next; ptr != &change_list; ptr = ptr->next) { | |
14d25769 | 512 | (ptr->handler)(&raw, &cooked, dfreq, doffset, 0, ptr->anything); |
88840341 RC |
513 | } |
514 | ||
515 | ||
516 | } | |
517 | ||
518 | /* ================================================== */ | |
519 | ||
520 | void | |
521 | lcl_InvokeDispersionNotifyHandlers(double dispersion) | |
522 | { | |
523 | DispersionNotifyListEntry *ptr; | |
524 | ||
525 | for (ptr = dispersion_notify_list.next; ptr != &dispersion_notify_list; ptr = ptr->next) { | |
526 | (ptr->handler)(dispersion, ptr->anything); | |
527 | } | |
528 | ||
529 | } | |
530 | ||
531 | /* ================================================== */ | |
532 | ||
533 | void | |
534 | lcl_RegisterSystemDrivers(lcl_ReadFrequencyDriver read_freq, | |
535 | lcl_SetFrequencyDriver set_freq, | |
536 | lcl_AccrueOffsetDriver accrue_offset, | |
537 | lcl_ApplyStepOffsetDriver apply_step_offset, | |
538 | lcl_OffsetCorrectionDriver offset_convert, | |
8f9c2370 | 539 | lcl_SetLeapDriver set_leap) |
88840341 RC |
540 | { |
541 | drv_read_freq = read_freq; | |
542 | drv_set_freq = set_freq; | |
543 | drv_accrue_offset = accrue_offset; | |
544 | drv_apply_step_offset = apply_step_offset; | |
545 | drv_offset_convert = offset_convert; | |
8f9c2370 | 546 | drv_set_leap = set_leap; |
88840341 RC |
547 | |
548 | current_freq_ppm = (*drv_read_freq)(); | |
549 | ||
550 | #ifdef TRACEON | |
551 | LOG(LOGS_INFO, LOGF_Local, "Local freq=%.3fppm", current_freq_ppm); | |
552 | #endif | |
553 | ||
554 | return; | |
555 | } | |
556 | ||
557 | /* ================================================== */ | |
558 | /* Look at the current difference between the system time and the NTP | |
8a00758c | 559 | time, and make a step to cancel it if it's larger than the threshold. */ |
88840341 RC |
560 | |
561 | int | |
8a00758c | 562 | LCL_MakeStep(double threshold) |
88840341 | 563 | { |
15e154c0 ML |
564 | struct timeval raw; |
565 | double correction; | |
566 | ||
567 | LCL_ReadRawTime(&raw); | |
20d898d1 | 568 | LCL_GetOffsetCorrection(&raw, &correction, NULL); |
15e154c0 | 569 | |
8a00758c ML |
570 | if (fabs(correction) <= threshold) |
571 | return 0; | |
572 | ||
15e154c0 ML |
573 | /* Cancel remaining slew and make the step */ |
574 | LCL_AccumulateOffset(correction); | |
575 | LCL_ApplyStepOffset(-correction); | |
576 | ||
577 | LOG(LOGS_WARN, LOGF_Local, "System clock was stepped by %.3f seconds", correction); | |
88840341 | 578 | |
15e154c0 | 579 | return 1; |
88840341 RC |
580 | } |
581 | ||
582 | /* ================================================== */ | |
8f9c2370 ML |
583 | |
584 | void | |
585 | LCL_SetLeap(int leap) | |
586 | { | |
587 | if (drv_set_leap) { | |
588 | (drv_set_leap)(leap); | |
589 | } | |
590 | ||
591 | return; | |
592 | } | |
593 | ||
594 | /* ================================================== */ | |
c386d117 | 595 | |
1a7415a6 | 596 | double |
c386d117 ML |
597 | LCL_SetTempComp(double comp) |
598 | { | |
1a7415a6 ML |
599 | double uncomp_freq_ppm; |
600 | ||
c386d117 | 601 | if (temp_comp_ppm == comp) |
1a7415a6 | 602 | return comp; |
c386d117 ML |
603 | |
604 | /* Undo previous compensation */ | |
605 | current_freq_ppm = (current_freq_ppm + temp_comp_ppm) / | |
606 | (1.0 - 1.0e-6 * temp_comp_ppm); | |
607 | ||
1a7415a6 ML |
608 | uncomp_freq_ppm = current_freq_ppm; |
609 | ||
c386d117 ML |
610 | /* Apply new compensation */ |
611 | current_freq_ppm = current_freq_ppm * (1.0 - 1.0e-6 * comp) - comp; | |
612 | ||
c386d117 | 613 | /* Call the system-specific driver for setting the frequency */ |
1a7415a6 | 614 | current_freq_ppm = (*drv_set_freq)(current_freq_ppm); |
c386d117 | 615 | |
1a7415a6 ML |
616 | temp_comp_ppm = (uncomp_freq_ppm - current_freq_ppm) / |
617 | (1.0e-6 * uncomp_freq_ppm + 1.0); | |
618 | ||
619 | return temp_comp_ppm; | |
c386d117 ML |
620 | } |
621 | ||
622 | /* ================================================== */ |