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81 lines
2.3 KiB
81 lines
2.3 KiB
10 years ago
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/* gpsdate - small utility to set system RTC based on gpsd time
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* (C) 2013 by sysmocom - s.f.m.c. GmbH, Author: Harald Welte
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* All Rights Reserved
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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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/* The idea of this program is that you run it once at system boot time,
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* to set the local RTC to the time received by GPS. Further synchronization
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* during system runtime is then handled by ntpd, interfacing with gpsd using
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* the ntp shared memory protocol.
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*
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* However, ntpd is unable to accept a GPS time that's off by more than four
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* hours from the system RTC, so initial synchronization has to be done
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* externally. 'ntpdate' is the usual option, but doesn't work if you're
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* offline. Thus, this gpsdate utilith was created to fill the gap.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <sys/time.h>
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#include <gps.h>
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static struct gps_data_t gpsdata;
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static void callback(struct gps_data_t *gpsdata)
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{
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struct timeval tv;
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int rc;
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if (!(gpsdata->set & TIME_SET))
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return;
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tv.tv_sec = gpsdata->fix.time;
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/* FIXME: use the fractional part for microseconds */
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tv.tv_usec = 0;
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rc = settimeofday(&tv, NULL);
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gps_close(gpsdata);
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if (rc == 0)
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exit(EXIT_SUCCESS);
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else
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exit(EXIT_FAILURE);
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}
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int main(int argc, char **argv)
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{
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char *host = "localhost";
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if (argc > 1)
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host = argv[1];
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if (gps_open(host, DEFAULT_GPSD_PORT, &gpsdata)) {
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fprintf(stderr, "no gpsd running or network error: %d, %s\n",
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errno, gps_errstr(errno));
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exit(EXIT_FAILURE);
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}
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gps_stream(&gpsdata, WATCH_ENABLE|WATCH_JSON, NULL);
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gps_mainloop(&gpsdata, 5000000, callback);
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gps_close(&gpsdata);
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exit(EXIT_SUCCESS);
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}
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