On 03/16/2015 06:33 PM, Eric S. Raymond wrote: > Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>: >> Can I ask why you're using TIOCMIWAIT rather than the Linux PPS api? >> Perhaps the kernel api needs extended to support other requirements? > > Short answer: the question about TIOCMIWAIT support is really about > whether hardware like the Oxford Expresso can pass through > handshake-line transitions in a form Linux can see. I deduced that earlier, before I pointed you at your own page :) http://www.catb.org/gpsd/gpsd-time-service-howto.html > If that isn't true, > the PPS API won't work either. My research suggests this is an issue > with some popular multiport cards like the Comtrol Rocketport that > soft-emulate multiple UARTs in firmware. > > The longer answer is...it's complicated. > > GPSD actually supports both methods. We haven't switched over to > the PPS API fully because RFC2783 is a touch underspecified and doesn't > say how to do association from the tty to the associated PPS device > portably, and we're not only concerned with Linux. The maintainer for > our PPS code, Gary Miller, is working the problem. > > The test lab I'm designing is intended for the reference NTP > implementation as well as (or more than) GPSD. NTP (and GPSD) > need to retain the option to *explicitly* wait on DCD for > operating systems like old legacy Unixes or VxWorks or QNX that > don't include RFC2783 but might turn out to have a functional > equivalent of TIOCMIWAIT to wait on handshake lines when we dig > enough. While these are only of minor importance for GPSD, NTP > has a lot of legacy customers. > > One of the things I did last week was factor the TIOCMIWAIT/RFC2738 > handling in GPSD into a detachable little library that can be plugged > into other programs, with NTP first on the list. I'm pretty sure Gary's > pulse-discrimination code is the best there is, and this is a problem > that should only be solved once. Thanks for the overview; I (wrongly) assumed GPSD was already doing this. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
