[oe] linux-libc-headers version (reloaded)

[Steffen Sledz]

While doing some maintenance for our hipox machine i hit a problem which was discussed controversially a few months before on this ML[1] but was not solved completely in my opinion.

The basic question was if it is valid to use PREFERRED_VERSION_linux-libc-headers higher than the kernel version (like e.g angstrom-2008.1 does).

After some research on that topic i really believe this is not allowed. My strongest argument is the kernel docu itself:

"Kernel headers are backwards compatible, but not forwards compatible.  This
means that a program built against a C library using older kernel headers
should run on a newer kernel (although it may not have access to new
features), but a program built against newer kernel headers may not work on an
older kernel."[2]

Also i did not found a linux distribution providing kernel headers newer than the kernel (whilst there are some with kernel headers older than the used kernel, e.g. openSUSE 11.3 with latest updates).

So i think the way the Ångström distribution handles this is wrong. If PREFERRED_VERSION_linux-libc-headers is set to 2.6.31 no kernel older than 2.6.31 should be allowed to guarantee the full functionality of all programs!

[1] <http://thread.gmane.org/gmane.comp.handhelds.openembedded/32375>
[2] Documentation/make/headers_install.txt

Steffen

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