Re: [gpsd-dev] RFC2783 vs TIOCMIWAIT, PPS on NetBSD

[Andy Walls]

On linux all the RFC2783 time_pps_*() functions funnel through here:

http://lxr.free-electrons.com/source/drivers/pps/pps.c#L67

To call time_pps_setparams() to set things up (like which edges you want to capture) requires root, or the POSIX capability CAP_SYS_TIME to be retained after you drop root.

To call time_pps_fetch(), the underlying PPS_FETCH ioctl() call does not seem to impose additional permission checks for admin privledges or capabilities.

I don't know how distributions normally set the permissions on /dev/pps? nodes though.

Regards,
Andy

"Eric S. Raymond" <address@hidden> wrote:

Greg Troxel <address@hidden>:
So my current belief is that RFC2783 should be entirely adeequate for
gpsd to read pps, and I don't understand why TIOCMIWAIT is really
needed.

This creates several TODO items:

add pps support to NetBSD ucom(4), so the GR601-W will work

enable gpsd to find sys/timepps.h on NetBSD (sys/types.h is needed
first, at least)

enable gpsd to do pps with RFC2783 and without TIOCMIWAIT

This seems like a good long-term direction.  My only concern is that
it sounds as though gpsd might have to keep root privileges through
its lifetime to use this API. That would be undesirable.

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