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Kernel Modules

reference:

Table of contents

  1. In-Tree and Out-of-Tree
  2. Building Modules

The object files are placed in /lib/modules/2.6.12/. In the same directory, there exists:

  • modules.pcimap, modules.submap: PCI and USB IDs of the devices supported by the kernel and a reference to the associated kernel module.
  • modules.dep: dependency graph
# list
lsmod
# try to load from /lib/modules/(kernel version)/kernel/drivers 
#  and the dependencies by calling `insmod` incursively
modprobe bluetooth
# remove
modprobe -r bluetooth

# edit /etc/modprobe.d/ to load and not to load on bootup

In-Tree and Out-of-Tree

From Stackoverflow:

“in-tree” and “out-of-tree” are actually generic software development terms. It refers to where the resulting build output/artifacts are placed during a compile, either “in-tree”, right next to the files they come from, or “out-of-tree”, in a separate root directory that separates the build output from the source files.

I have not come across “in-tree” and “out-of-tree” outside of the Linux kernel source development and then only for working with modules. All modules start out as “out-of-tree” developments, that can be compiled using the context of a source-tree. Once a module gets accepted to be included, it becomes an in-tree module.

Building Modules

# prepare a kernel source tree
# but a full kernel build needs to be executed to make module versioning work.
make modules_prepare 

make -C /lib/modules/`uname -r`/build M=$PWD modules
make -C /lib/modules/`uname -r`/build M=$PWD modules_install
make -C /lib/modules/`uname -r`/build M=$PWD clean
make -C /lib/modules/`uname -r`/build M=$PWD help