Re: [gpsd-users] More than two GPS device

[Miroslav Lichvar]

On Fri, Sep 26, 2014 at 03:53:59PM +0000, Sandor R. Repas wrote:
> I have just found the solution.
> The gpsd handles the PPS as a different device. Actually, my 3 gps devices 
> were 6 devices in GPSD.
> I have modified the #define NTPSHMSEGS line in the gpsd.h file, and it works 
> now.
> It could be a build option, but I was not able to find it.

Please note that the 3rd and later SHM segments are created with world
access, meaning any user on the system can write there and disrupt the
timekeeping if there are no other sources that would outvote the SHM
source.

For ntpd, there is a request to make this configurable with the flag2
option
https://bugs.ntp.org/show_bug.cgi?id=2627

For gpsd I'm not sure how this could be configurable, maybe it'd be
better to always use owner-only access.

-- 
Miroslav Lichvar