diff options
| -rw-r--r-- | TODO | 12 | ||||
| -rw-r--r-- | gpsd.xml | 39 | ||||
| -rw-r--r-- | libgpsd_core.c | 11 |
3 files changed, 55 insertions, 7 deletions
@@ -169,6 +169,18 @@ This is a good idea for supporting hands-free operation, e.g. while driving. It would be an easy first project for somebody who wants to get into the client code. +*** Enable gpsd to open chronyd socket as root in /var/run + +At the moment gpsd drops priviledges as soon as the command line +options are parsed. A way needs to be found to open the chronyd +sockets in /var/run before dropping root. + +*** Enhance libgps to decode SUBFRAME JSON + +gpsd now passes along GPS subframe date in JSON. The libgps needs to +be extended to decode this data. A sample program to dump the SUBFRAME +data would also be useful. + *** Set the system time zone from latitude/longitude If we're going to give gpsd the capability to set system time via @@ -2652,9 +2652,8 @@ century.</para> <para>gpsd can provide reference clock information to <application>ntpd</application>, to keep the system clock synchronized -to the time provided by the GPS receiver. This facility is -only available when the daemon is started from root. If you're going -to use <application>gpsd</application> you probably want to run it +to the time provided by the GPS receiver. If you're going to +use <application>gpsd</application> you probably want to run it <option>-n</option> mode so the clock will be updated even when no clients are active.</para> @@ -2667,7 +2666,9 @@ of every clock second on the carrier-detect lines of some serial GPSes; this pulse can be used to update NTP at much higher accuracy than message time provides. You can determine whether your GPS emits this pulse by running at -D 5 and watching for carrier-detect state -change messages in the logfile.</para> +change messages in the logfile. In addition, if your kernel provides +the RFC 2783 kernel PPS API then <application>gpsd</application> will +use that for extra accuracy.</para> <para>When <application>gpsd</application> receives a sentence with a timestamp, it packages the received timestamp with current local time @@ -2741,6 +2742,36 @@ type of receiver. Please send us the output of the "ntpq -p" command and the make and type of receiver.</para> </refsect1> +<refsect1 id='chrony'><title>USE WITH CHRONY</title> +<para>gpsd can provide reference clock information to +<application>chronyd</application> similar to the way it talks to +<application>ntpd</application>. The advantage to using chrony is +that the PPS time resolution is in nSec. This is 1,000 times more +precision than the time resolution provided to ntpd. +</para> +<para>gpsd talks to <application>chronyd</application> using a socket +named /tmp/chrony.ttyXX.sock (where ttyXX is replaced by the GPS +device name. This allows multiple GPS to feed one <application>chronyd +</application>. +</para> +<para>No gpsd configuration is required to talk to chronyd. To get +chronyd to connect to gpsd using the SHM method add this to your +/etc/chrony/chonry.conf file. +</para> +<screen> +# delay 0.0 is right, but use 0.2 to avoid NMEA +# time fighting with PPS time +refclock SHM 0 offset 0.0 delay 0.2 +refclock SHM 1 offset 0.0 delay 0.0 +</screen> +<para>To get chronyd to connect to gpsd using the more precise socket +method add this to your /etc/chrony/chrony.conf file (replacing ttyXX +with your device name): </para> +<screen> +#refclock PPS +/dev/pps0 refclock SOCK /var/run/chrony.ttyXX.sock +</screen> +</refsect1> <refsect1 id='dbus'><title>USE WITH D-BUS</title> <para>On operating systems that support D-BUS, diff --git a/libgpsd_core.c b/libgpsd_core.c index a561201d..5d383a51 100644 --- a/libgpsd_core.c +++ b/libgpsd_core.c @@ -394,19 +394,24 @@ static /*@null@*/ void *gpsd_ppsmonitor(void *arg) char *chrony_path = NULL; gpsd_report(LOG_PROG, "PPS Create Thread gpsd_ppsmonitor\n"); +#ifdef __UNUSED__ + /* sadly root was dropped very early, until a way if found to run this + * before dropping root it will not work. */ if( 0 == getuid() ) { /* only root can use /var/run */ chrony_path = "/var/run/chrony"; - } else { + } else +#endif + { chrony_path = "/tmp/chrony"; } s.sun_family = AF_UNIX; (void)snprintf(s.sun_path, sizeof (s.sun_path), "%s.%s.sock", chrony_path, basename(session->gpsdata.dev.path)); - /* the socket will be either, for root: + /* TODO the socket for root would be * /var/run/chrony.ttyXX.sock - * or for non-root: + * for now it is always * /tmp/chrony.ttyXX.sock */ |