[LinuxPPS] Patches for kernel 2.6.26-rc8

[Hal V. Engel]

On Friday 04 July 2008 05:34:10 am Rodolfo Giometti wrote:
> On Thu, Jul 03, 2008 at 05:34:41PM -0700, Hal V. Engel wrote:
> >    OK I got it working. But I am not real happy with what has to be done
> > to get everything started. Since there are some things going on that
> > don't seem to be correct based on what little documentation is available
> > and some of what I have done is an ugly hack.
>
> Sorry for poor documentation but currently I have *no* time to update
> it. I suppose this list is currently the best LinuxPPS documentation
> available. :)
>
> I need help on this topic.


The issue for me and I suspect most on the list is that in order to help with 
documentation first we need to understand what is going on.  Right now this is 
changing so fast that I am having trouble understanding the current state of 
things.  Mind you I am a developer with a degree in computer science and 
several decades of IT experience and have my own widely distributed open 
source project that I maintain (unrelated to ntp or time stuff).  So I am 
probably better able to follow this than the non-developers on this list and I 
am still confused.


>
> >    One change that I didn't expect that was causing me problems initially
> > is that pps_core can not be built into the kernel anymore and is now a
> > module only. For prior versions this could be built into the kernel.
> > Perhaps this can be fixed?
>
> That's strange... if you take a look at drivers/pps/Kconfig you can
> see that "config PPS" is defined as tristate.


Yes I can see that.   So I don't know why xconfig will not let me set this to 
be built into the kernel.


>
> >    Even after setting up my boot process so that it now loads pps_core I
> >    found getting ppsldisc to actually work is problematic. I found that
> >    running setserial ... before ppsldisc worked? I stumbled onto this by
> >    accident. So I am not sure that I understand the current
> > implementation. But at this point I have not found any other combination
> > of commands that works. Wasn't ppsldisc supposed to get rid of setserial
> > and friends or is there something else going on here that I missed?
>
> With full ldisc support the setserial command is going to be no more
> needed. Please, take a look at these posts:
>
>    http://ml.enneenne.com/pipermail/linuxpps/2008-June/002020.html


I applied this patch and I am using these tools (ppsldisc) but this does not 
work with out running setserial.


>    http://ml.enneenne.com/pipermail/linuxpps/2008-June/002021.html


OK I missed this one.  Does this need to be applied on top of ntp-pps-2.6.26-
rc8.diff?  Will this make setserial obsolete?


Since it was not clear what sequence of patches where needed I think this is 
why I was confused.  So the correct sequence is to apply patches in this order 
(assumes kernel 2.6.26-rc8 as a base):


ntp-pps-2.6.26-rc8.diff
set-ldisc.patch
ppsldisc.patch


Is that correct?  If so I will apply set-ldisc.patch and retest things.


>
> >    I also tried using ttyctrl before ppsldisc and that did not work. To
> > try to get things working without having to run stuff by hand I found
> > that the following udev rules resulted in there being a working pps
> > signal at startup:
> >
> >    KERNEL=="ttyS1", RUN+="/bin/setserial -v /dev/%k low_latency hardpps",
> >    SYMLINK+="oncore.serial.0"
> >    KERNEL=="ttyS1", RUN+="/bin/ppsldisc /dev/%k"
> >
> >    KERNEL=="pps0", OWNER="root", GROUP="uucp", MODE="0660",
> >    SYMLINK+="oncore.pps.0", OPTIONS+="last_rule"
> >
> >    Since the above rules resulted in running ppstest having the expected
> >    output. But it also resulted in ntpd not seeing the GPS:
> >
> >    54650 85410.279 127.127.30.0 ONCORE DRIVER -- CONFIGURING
> >    54650 85410.279 127.127.30.0 state = ONCORE_NO_IDEA
> >    54650 85410.279 127.127.30.0 Input mode = 1
> >    54650 85410.279 127.127.30.0 Initializing timeing to Assert..
> >    54650 85410.279 127.127.30.0 SHMEM (size = 3584) is CONFIGURED and
> >    available as /var/log/ntp/oncore.0
> >    54650 85410.279 127.127.30.0 state = ONCORE_CHECK_ID
> >    54650 85411.272 127.127.30.0 Oncore: Resend @@Cj
> >    54650 85426.272 127.127.30.0 Oncore: Resend @@Cj
> >    54650 85442.272 127.127.30.0 Oncore: Resend @@Cj
> >    54650 85460.272 127.127.30.0 Oncore: No response from @@Cj, shutting
> > down driver
> >
> >    So this looks like this somehow makes the serial interface not work
> > but I can run WinOncore and it sees the GPS so that does not make sense.
> > Based on this it appears that for this to work the following had to
> > happen.
> >
> >    1. setserial with hardpps either by hand or in a udev rule
> >    2. run ppsldisc
> >    3. while #2 is still running start ntpd.
> >
> >    So I ended up removing the ppsldisc line from the udev rule and
> > modifying /etc/init.d/ntpd so that the line that starts the ntp deamon
> > looks like this:
> >
> >    /bin/ppsldisc /dev/ttyS1 & start-stop-daemon --start --exec
> > /usr/sbin/ntpd \
> >
> >    and this works and will start up everything at boot time. Of course
> > this is hard coded for my hardware and my distro will want to clobber
> > this if I happen to reinstall ntp. So at best this is an ugly hack.
> >
> >    I used kernel 2.6.26-rc8 and the 2.6.26-rc8 patch set and the ppsldisc
> >    patch to build my kernel and the new user land tools. But I happen to
> > have a patched setserial on my machine because I am using it with my
> > older kernel built with older linuxpps patch sets.
> >
> >    OK perhaps that gives someone some clues about what is going on and
> >    possibily how it can be fixed.
>
> Ok, the right-thing(TM) is exactly what you did. Even bluetooth
> subsystem has something similar (see hciattach command). :)
>
> Ciao,
>
> Rodolfo

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