42b305478d
If the delay is known, print it together with the offset and frequency. Remove the time stamp from the output to fit it into 80 chars. Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
/**
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* @file sysoff.c
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* @brief Implements the system offset estimation method.
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* @note Copyright (C) 2012 Richard Cochran <richardcochran@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdio.h>
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#include <sys/ioctl.h>
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#include <linux/ptp_clock.h>
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#include "sysoff.h"
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#define NS_PER_SEC 1000000000LL
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#ifdef PTP_SYS_OFFSET
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static int64_t pctns(struct ptp_clock_time *t)
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{
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return t->sec * NS_PER_SEC + t->nsec;
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}
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static struct {
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int64_t interval;
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int64_t offset;
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uint64_t timestamp;
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} samples[PTP_MAX_SAMPLES];
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static void insertion_sort(int length, int64_t interval, int64_t offset, uint64_t ts)
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{
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int i = length - 1;
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while (i >= 0) {
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if (samples[i].interval < interval)
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break;
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samples[i+1] = samples[i];
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i--;
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}
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samples[i+1].interval = interval;
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samples[i+1].offset = offset;
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samples[i+1].timestamp = ts;
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}
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static int64_t sysoff_estimate(struct ptp_clock_time *pct, int n_samples,
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uint64_t *ts, int64_t *delay)
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{
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int64_t t1, t2, tp;
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int64_t interval, offset;
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int i;
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for (i = 0; i < n_samples; i++) {
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t1 = pctns(&pct[2*i]);
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tp = pctns(&pct[2*i+1]);
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t2 = pctns(&pct[2*i+2]);
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interval = t2 - t1;
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offset = (t2 + t1) / 2 - tp;
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insertion_sort(i, interval, offset, (t2 + t1) / 2);
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}
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*ts = samples[0].timestamp;
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*delay = samples[0].interval;
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return samples[0].offset;
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}
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int sysoff_measure(int fd, int n_samples,
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int64_t *result, uint64_t *ts, int64_t *delay)
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{
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struct ptp_sys_offset pso;
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pso.n_samples = n_samples;
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if (ioctl(fd, PTP_SYS_OFFSET, &pso)) {
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perror("ioctl PTP_SYS_OFFSET");
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return SYSOFF_RUN_TIME_MISSING;
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}
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*result = sysoff_estimate(pso.ts, n_samples, ts, delay);
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return SYSOFF_SUPPORTED;
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}
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int sysoff_probe(int fd, int n_samples)
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{
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int64_t junk, delay;
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uint64_t ts;
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if (n_samples > PTP_MAX_SAMPLES) {
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fprintf(stderr, "warning: %d exceeds kernel max readings %d\n",
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n_samples, PTP_MAX_SAMPLES);
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fprintf(stderr, "falling back to clock_gettime method\n");
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return SYSOFF_RUN_TIME_MISSING;
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}
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return sysoff_measure(fd, n_samples, &junk, &ts, &delay);
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}
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#else /* !PTP_SYS_OFFSET */
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int sysoff_measure(int fd, int n_samples,
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int64_t *result, uint64_t *ts, int64_t *delay)
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{
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return SYSOFF_COMPILE_TIME_MISSING;
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}
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int sysoff_probe(int fd, int n_samples)
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{
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return SYSOFF_COMPILE_TIME_MISSING;
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}
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#endif /* PTP_SYS_OFFSET */
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