How to compile a single module in Ubuntu linux

Occasionally you may experience problems in a specific kernel module that requires a patch.  Once patched, you can follow these directions to compile only the module affected, saving a bunch of time.

Assume the following, for this example:

• You are building a module for Ubuntu 3.2.0-21-generic kernel.
• Your source tree with the patched module is located in /usr/src/linux-source-3.2.0
• Your linux header source is located in /usr/src/linux-headers-3.2.0-21-generic
• Your working folder ( where you are building the new module )   is /usr/src/mytree

In this case, your EXTRAVERSION is -21-generic ( this is the specific flavor of the 3.2.0 kernel we are building ) this is important to note, and will be used later in this example.

Now to create your working folder and change into it:

mkdir /usr/src/mytree
cd /usr/src/mytree

Now that you are in your working folder, you need to copy over your kernel configuration file and Module.symvers file.

cp /boot/config-`uname -r`  .config
cp /usr/src/linux-headers-3.2.0-21-generic/Module.symvers .

Now with those files in place, you need to change to your source folder and prep your work area by running a few make commands.  These commands make use of the EXTRAVERSION we noted above:

cd /usr/src/linux-source-3.2.0
make EXTRAVERSION=-21-generic O=/usr/src/mytree oldconfig
make EXTRAVERSION=-21-generic O=/usr/src/mytree prepare
make EXTRAVERSION=-21-generic O=/usr/src/mytree outputmakefile
make EXTRAVERSION=-21-generic O=/usr/src/mytree archprepare
make EXTRAVERSION=-21-generic O=/usr/src/mytree modules SUBDIRS=scripts

At this point you are ready to compile the module you have patched.  Suppose it is the drivers/net/wireless/rt2x00 module:

make EXTRAVERSION=-21-generic O=/usr/src/mytree modules SUBDIRS=drivers/net/wireless/rt2x00

At this point you should have a drivers/net/wireless/rt2x00 folder in your working folder ( /usr/src/mytree ) which contains the .ko module files.

Simply backup the old modules in /lib/modules/3.2.0-21-generic/kernel/drivers/net/wireless/rt2x00 , and replace them with your new ones, then reload or reboot to test the new modules!

Good Luck!