[LinuxPPS] HOWTO (was - Kernel Include files needed in Userland.)

[Rodolfo Giometti]

On Tue, Aug 26, 2008 at 04:47:20PM -0700, Hal V. Engel wrote:

>    Remco has a cookbook recipe here
> 
>    http://rembl.org/index.php/2008/04/19/motorola-oncore-ut-and-linuxpps/
> 
>    that covers some of this stuff as it relates to getting NTP working with

I saw it and I already asked to turn it into a more general HOWTO.

>    an OnCore. The recipe is also not generalized in that it is distro
>    specific (I had to change some things to get this to work with my distro)
>    and it only covers one refclock type. There are other sources of
>    information available such as items on this list that can be used to
>    generalize this.
> 
>    Reg suggested that there might be a small list of header files that need
>    to be copied to /usr/include/linux. Rodolfo replied "This info is
>    temporary ... Also this info is reported into the wiki." I agree that hand
>    copying or creating links is a temporary situation but the wiki uses brute
>    force to deal with this:
> 
>    /usr/include# ln -s /lib/modules/$(uname -r)/build/include/linux
> 
>    /usr/include# ln -s /lib/modules/$(uname -r)/build/include/asm
> 
>    /usr/include# ln -s /lib/modules/$(uname -r)/build/include/asm-generic
> 
>    I think that what Reg was trying to get at is that the specific list of
>    LinuxPPS header files that need to be made available for user land tool
>    builds is a small list and that perhaps there is a better way to handle
>    this than to use brute force like is currently used in the wiki. If in
>    fact there are only 2 or 3 files that need to be copied from the kernel
>    tree to /usr/include... then perhaps it would be better to change from
>    using brute force links to just copying those missing files to were they
>    are needed or by using links only to those files like the Wiki does for
>    timepps.h. Initially this would be done by hand but when LinuxPPS becomes

This is true __iif__ your distro has the same linux version of the one
you compiled LinuxPPS to. Otherwise you __must__ do the above links!

>    part of the kernel then the normal kernel installation will make the
>    problem go away for the /usr/include/linux/* files. On my system it
>    appears that the only kernel header file that would be needed is pps.h.
> 
>    I just did a test and to get NTP and the linuxpps user land tools to build
>    all I needed was:
> 
>    /usr/include/linux # ln -s /lib/modules/$(uname
>    -r)/build/include/linux/pps.h
> 
>    /usr/include # ln -s /lib/modules/$(uname
>    -r)/build/Documentation/pps/timepps.h
> 
>    Which makes things much simpler (and less dangerous) since it is very
>    specific and only involves two files.

Maybe less for userland but not for kernel land.

>    In addition to the two sym links I also needed to patch
>    /usr/include/sys/timex.h to get NTP to build with nano support. So this is
>    not handled correctly yet by my distro even though I have the distro
>    package for the 2.6.26 linux headers installed. In fact this package over
>    wrote the changes I had made to /usr/include/sys/timex.h to get nano
>    working when I installed the 2.6.26 linux headers. I suspect that most
>    distros will have similar issues with these newer kernels.

In this situation the-right-think(TM) is to do the links and __then__
patch the timex.h file.

>    With regard to timepps.h, longer term there needs to be a simple way to
>    install this header file otherwise it will be an ongoing issue. It clearly
>    is not correct to include it in the NTP tree since it is OS specific. In
>    addition, it is needed by ppstest.c. The root issue here is that the user
>    land tools are sitting in a directory in the kernel tree (which is where
>    this header is also located) but this code is not really a part of the
>    kernel. These should be pulled out into a seperate package - prehaps
>    called ppstools or ppsusertools - and this package should include
>    timepps.h and handle installing the header file along with ppsldisc and
>    ppstest. This would make ntp dependant on this new package if the user
>    wanted to build it with PPS refclock support since it needs both the
>    header file to build and the user land tools to function. It would also
>    make the process of installing userland tools much simpler and cleaner.
>    This will have to happen at some point so why not now? The biggest issue
>    is that the build needs to be generalized and also needs an install
>    target. Moving this into it's own package would also simplify maintaince
>    since it would no longer be tightly coupled to the kernel code.

After kernel inclusion files pps.h and timex.h should be installed by
the kernel package; regarding timepps.h distro's maintainers should
provide a specific package (libpps, pps-dev, etc.) to install into the
system the header timepps.g and other pps related programs/docs.

>    Getting back to a HOWTO for LinuxPPS. I would be willing to help and in
>    fact I would be willing to write a draft version which would consist
>    mostly of reorganized materials pulled together from existing sources. But
>    I suspect I will also need a lot of feed back from others here on the
>    list. Give me a few days to see what I can pull together. Perhaps someone
>    else can pull the LinuxPPS user land tools into a seperate package and
>    generalize it's build?

Great! :)

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti at enneenne.com
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