Re: open SHM data only after cgps start

[Hans Kurscheidt]

Hi Frank

BINGO, you got it!

unfortunately just your mail ended up in SPAM, don't know why, all the 
others don't!

1. Dirty system with multiple installations of various versions of GPSd
YES, I cleaned this up.

all your messages are coming individually - not recognized as part of a 
discussion/thread.

Sorry, I'm new here, don't know any better; there's no "answer" button except 
for unwanted replies to individuals.

The solution is to add -n into the systemd UNIT file as a GPSD_OPTION

cat /etc/default/gpsd
# Start the gpsd daemon automatically at boot time
START_DAEMON="true"

# Use USB hotplugging to add new USB devices automatically to the daemon
USBAUTO="true"

# Devices gpsd should collect to at boot time.
# They need to be read/writeable, either by user gpsd or the group dialout.
# DEVICES="/dev/ttyUSB0"
DEVICES="/dev/ttyACM0"

# Other options you want to pass to gpsd
GPSD_OPTIONS="-n"


I did not expect/understand this! I was assuming, if the service is started at 
boot time, it would also start the GPS com. I have still questions: Why is my 
app not recognized as client, when opening
if ((gps_open(GPSD_SHARED_MEMORY, NULL, &gps_data)) == -1)
OK, it works,
thanks a lot, from good old Europe
Best Regards
hk

Am 05.02.2021 um 16:40 schrieb Frank Nicholas:
> I think you have two issues:
> 1. Dirty system with multiple installations of various versions of GPSd
> 2. You are using SystemD, which with the most common service file, only 
> launched GPSd when an app/client attempts to attach.  As long as GPSd is 
> launched, and there is an attached client/consumer, it will continue to run, 
> until there is nothing else using it and the last client closes the connection.
>
> Gary Miller suggested adding the switch to make GPSd run as a daemon all the 
> time (doesn’t exit when there are no clients attached).  This would also 
> require something to change with the SystemD config file - you want SystemD to 
> start GPSd at boot, not wait until there’s a client attempting to access it.  I 
> think Gary even provided a one line command line that could be put in a startup 
> script, anywhere you wanted, depending on the flavor of Linux you are using 
> (this would not use SystemD).
>
> For some reason all your messages are coming individually - not recognized as 
> part of a discussion/thread.  Not sure if you can do something about that, but 
> it makes it difficult to follow - that’s why I couldn’t easily find Gary’s 
> suggestions.
>
> Thanks,
> Frank
>
> > On Feb 5, 2021, at 8:59 AM, Hans Kurscheidt <lve0200@gmail.com> wrote:
> >
> > Sorry, if I keep talking to myself here, but I'm crawling forward.
> >
> > After I got gpsd running as service, I cleaned out all old references to libgps 
> > and libgps-dev and cleaned Visual Studio's cache.
> >
> > Should be OK now.
> >
> > There's no dpkg -l libgps* output anymore
> >
> > VisualStudio finds the richgt gps.h under ../gpsd-master/..; there is no other 
> > gps.h somewhere.
> >
> > and the linker points to so.28
> >
> > ldconfig -p | grep gps
> >          libgpsdpacket.so.28 (libc6,hard-float) => 
> > /usr/local/lib/libgpsdpacket.so.28
> >          libgpsdpacket.so (libc6,hard-float) => /usr/local/lib/libgpsdpacket.so
> >          libgps.so.28 (libc6,hard-float) => /usr/local/lib/libgps.so.28
> >          libgps.so (libc6,hard-float) => /usr/local/lib/libgps.so
> >          libQgpsmm.so.28 (libc6,hard-float) => /usr/local/lib/libQgpsmm.so.28
> >          libQgpsmm.so (libc6,hard-float) => /usr/local/lib/libQgpsmm.so
> >
> > The compilation/linking is OK w/out errors or warnings and the executable is 
> > runable
> >
> > BUT, I still have the old problem. (assume gpsd service running and fix 
> > available)
> >
> > If I run my app after boot, No gps data is available and just once I got an 
> > error message, which I cannot reproduce, saying something like:
> >
> > shared library error cannot ... data: No such file or directory
> >
> > After running cgps once, data is available and remains 2b supplied to my app, 
> > even if I close cgps. This is reproduceable.
> >
> > RGDS
> >
> > hk