[LinuxPPS] Patches for kernel 2.6.26-rc8

[Rodolfo Giometti]

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.

>    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.

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

>    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

-- 

GNU/Linux Solutions                  e-mail: giometti at enneenne.com
Linux Device Driver                          giometti at linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti