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