open SHM data only after cgps start

[Hans Kurscheidt]

OK,

I am now more than ever convinced that there's an issue in gpsd!

1): fresh & clean boot; sudo lsof | grep /dev/ttyACM0 (my device (ublox 
6 via USB)) => nothing open.

2) starting my app; sudo lsof | grep /dev/ttyACM0 (my device (ublox 6)) 
=> nothing open

starting cgps in parallel; sudo lsof | grep /dev/ttyACM0
gpsd        700           nobody    9u      CHR      166,0 0t0      
14619 /dev/ttyACM0

my app starts to receive data as well, like cgps.

stop (^C) cgps

my app continues reading the buffer from /dev/ACM0; sudo lsof | grep 
/dev/ttyACM0
gpsd        700           nobody    9u      CHR      166,0 0t0      
14619 /dev/ttyACM0

means although cgps has been closed, the fd remains open, (because my 
app is still hanging on ??)

after a while, my app does not receive anymore data (most likely when 
buffer has become empty); sudo lsof | grep /dev/ttyACM0 (my device 
(ublox 6)) => nothing open.

To avoid any ambiguity coming from my app running the gps_get function 
as a thread, I changed my SW and gps_get runs now as a plain vanilla 
function under main.

RGDS

hk