Re: build -->/usr/src/linux

[Jamie Lokier <lk@tantalophile.demon.co.uk>]

richard offer wrote:
> What if your application contains some user code and a kernel module ?
> Want an obvious example ? X.

VMware is another.  In such cases, they have to do the same as any other
system-specific packages: guess, or ask the user.  Autoconf apps prefer
guessing; X uses Imake and would probably have the kernel source path
hard-coded in an Imake template :-)

The discussions here have suggested ways for a third-party module
package to guess how to install themselves, so that they will just work
on most systems.  /lib/modules/`uname -r`/build is the best anyone's
come up with so far, and it does just work on "plain old" 2.4 systems.
/usr/src/linux-`uname -r` is the next best.

This fails in certain cases such as cross-compiling, when the kernel
isn't living in /usr/src or its not configured, and when it's not the
running kernel.

But then, this is true of userspace too.  Build an app on a Red Hat
system, don't be surprised to find it fails to run on a Debian.

When cross-compiling a userspace app, you have to explicitly tell the
package how to build, libraries to use etc. whether by command line
flags or editing the source.  That's the joy of
cross-compiling.  /usr/lib doesn't contain the right libraries, but it's
ok for apps to look there _unless_ you say otherwise.

Same goes for kernel modules.  /lib/modules/`uname -r`/build doesn't
contain the right files when cross-compiling, but it's ok for module
packages to look there _unless_ you say otherwise.

-- Jamie