[yocto] Shouldn't linux/version.h appear in the SDK's host sysroot?

[Patrick Turley]

I'm using a Yocto-based SDK, produced by:

    bitbake meta-toolchain-sdk

This creates the file 

    poky-eglibc-x86_64-arm-toolchain-gmae-1.3.sh

in the directory

    build/tmp/deploy/sdk

I ran the installation script to install the SDK on my build system. Within the SDK installation directory, under "sysroots", I have the following two directories:

    armv7a-vfp-neon-poky-linux-gnueabi
    x86_64-pokysdk-linux

Unless I'm mistaken, the first one reflects the target environment, and the second one contains what I need to do cross-compilation. Thus, the latter contains the cross-compilation tools, and that's the sysroot to which all my builds are directed.

I'm compiling the lm_sensors package for my target. As part of its work, it tries to discover the version of the target linux kernel. To do this, it compiles a very small file (etc/config.c) that includes the header file <linux/kernel.h>.

As it happens, <linux/kernel.h> does *not* appear in the cross-compilation sysroot, so this simple task fails. That header file *does* appear in the target sysroot, but that's of no use to me in the cross-compilation process.

I believe one of the following is true:

1) The lm_sensors package is doing something entirely legitimate, and the file <linux/kernel.h> *should* appear in the cross-compilation sysroot to support this. The Yocto SDK build target needs a small fix so that <linux/kernel.h> is properly added to the cross-compilation sys root. In the meantime, I can work around this oversight by creating a symbolic link.

2) I've made a mistake in setting up my build environment because I don't understand how cross-compilation *should* be done. If done properly, the cross-compilation process will have access to *both* sysroots and get what it needs from each. If this is the case, please tell me what I appear to have done wrong.

3) Something else.