[LinuxPPS] refclock_nmea patch

[Rodolfo Giometti]

On Mon, Oct 22, 2007 at 08:20:04PM +0200, Udo van den Heuvel wrote:
> Rodolfo Giometti wrote:
> >> Note the %d in the message string and that the first gps0 device is not
> >> used. %d was fixed with your suggestion.
> > 
> > Good.
> 
> /dev/gps0 is not used!...

Is /dev/gps0 the GPS data device or not? It points to /dev/ttyS0,
isn't it?

> >> /dev/gps0 points to /dev/ttyS0. Is the fd still open when it reaches the
> >> LinuxPPS part that we change? Maybe reopen the fd?
> > 
> > No, the fd is opened since it is passed to the first
> > pps_time_create().
> 
> So why is the alternate devise used?

Because your main device may not be a PPS data source. In LinuxPPS
it's _always_ true.

> >> [root at epia ntpd]# setserial /dev/ttyS0
> >> /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4, Flags: hardpps low_latency
> >> [root at epia ntpd]# setserial /dev/gps0
> >> /dev/gps0, UART: 16550A, Port: 0x03f8, IRQ: 4, Flags: hardpps low_latency
> > 
> > Are yo uusing patched setserial? If so I don't see the hardpps
> > flag. 
> 
> See the output...

Glom! O_o Sorry, you are rigth again! Time to stop working today! ;)

> >> [root at epia ntpd]# setserial /dev/pps0
> > 
> > Why do you use setserial on /dev/pps0?
> 
> Just to see what it is.
> Apparently it is created by the LinuxPPS patch.
> But why only for pps0 and not for gps0?

gps0 is the GPS data source, not the PPS data one.

> > 
> >> [root at epia ntpd]# ls -l /dev/?ps0
> >> lrwxrwxrwx 1 root root     10 2007-10-22 19:17 /dev/gps0 -> /dev/ttyS0
> >> crw------- 1 root root 254, 0 2007-10-22 19:17 /dev/pps0
> >> [root at epia ntpd]# ls -l /dev/ttyS0
> >> crw-rw---- 1 root uucp 4, 64 2007-10-22 19:36 /dev/ttyS0
> >>
> >> Any ideas!?
> > 
> > About what?
> 
> Why only for pps0 and not for gps0?
> /dev/gps0 is not used at all!

gps0 should be use by NTPD in order to get GPS data.

> > Great job! Just fix these few errors and you may submit your patch to
> > the NTPD mail list for inclusion! :)
> 
> First I want to understand why /dev/gps0 is not used.
> Then I can send it out I think.

After running ntpd get its PID and then look into /proc/<pid>/fd/
which files has been opened.

Ciao,

Rodolfo

-- 

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