Building a Linux kernel module

Two solutions exist for compiling a kernel module:

• The first solution is when code is outside of the kernel source tree, which is also known as out-of-tree building. The module source code is in a different directory. Building a module this way does not allow integration into the kernel configuration/compilation process, and the module needs to be built separately. It must be noted that with this solution, the module cannot be statically linked in the final kernel image – that is, it cannot be built in. Out-of-tree compilation only allows loadable kernel modules to be produced.
• The second solution is inside the kernel tree, which allows you to upstream your code, since it is well integrated into the kernel configuration/compilation process. This solution allows you to produce either a statically linked module (also known as built-in) or a loadable kernel module.

Now that we have enumerated and given the characteristics of the...