Question

When building the Linux kernel from sources one could decide if a certain functionality is statically built into the kernel or packed into a module for dynamic insertion by .config.

If on the other hand I have sources for any 3rd party module, like for example a packaged device driver, is it possible to programmatically integrate this code into the kernel statically instead? And not load the kernel module from the root filesystem?

Answer 1

Sure, you just need to do a bit of hacking to move the external module into the kernel source tree, tweak the Makefiles/Kconfig a bit so that the code is built-in, and then build your kernel image. For example, let’s say you move the module source into drivers/blah. Then you should add a line to then end of drivers/Makefile like

obj-y += blah/

and you should make sure that drivers/blah/Makefile is set up to build your module in, with something like

obj-y += mymodule.o
mymodule-objs := src.o other.o

and so on, where your Makefile is set up however it needs to be to build the particular module you’re working on.
Note: You have to use the output file name for mymodule-objs and not the input filename!