Using the linux-headers package

There are two separate cases which have to be handled in different ways. The first case is for building out-of-kernel-tree modules (not included in standard Diablo kernel source tree), and the second case is for building in-kernel-tree modules.

Out-of-tree modules

Create a separate directory for your driver (./my_driver/ in the example below).
Create a standard kernel Makefile for your driver (./my_driver/Makefile), something like this:
```
my_driver-objs := a.o b.o c.o
obj-m += my_driver.o
```

Run kernel build system like this (./Makefile):

include /usr/share/cdbs/1/rules/kernel-module-oot.mk

DRVDIR = $(shell pwd)/my_driver

all:
	make -C $(K_BUILD) M=$(DRVDIR)/ modules

clean:
	make -C $(K_BUILD) M=$(DRVDIR)/ clean

Now you can invoke "make" to build the driver and "make clean" will clean the build directory.

If you want to create a Debian package for your out-of-tree modules, you can look at one of the module packages from our SVN:

svn checkout https://garage.maemo.org/svn/kmod

and model yours using one of existing packages as a template.

In-tree modules

Building in-tree modules is, on one hand, simpler but on other hand more complex :-)

First of all, you must prepare a special file called config-modules, which will contain the kernel config for the drivers you selected to build. The easiest way to build a config-modules file is the following:

Unpack the kernel and configure it:
```
make nokia_2420_defconfig
```

Enable the modules you want to build:

make menuconfig HOST_LOADLIBES=-lncurses

Create the config-modules file by running the mk-config-modules script from the kernel directory:
```
cp mk-config-modules [kernel directory]
cd [kernel directory]
./mk-config-modules
```
After the script finishes, you will get a file called config-modules. Now you must copy it into the debian/ directory of your package, and create a very simple rules file like this.
```
#!/usr/bin/make -f

K_MODULES.<name> = drivers/somewhere/something.ko

include /usr/share/cdbs/1/rules/debhelper.mk
include /usr/share/cdbs/1/rules/kernel-module.mk
```
Now create an appropiate control file with a description for your <name> package (don't forget to make your package depend on module-init-tools-maemo), and a postinst file like this:
```
#! /bin/sh

case "$1" in
    configure)
        depmod -a
        ;;
esac

#DEBHELPER#
```
and a postrm file like this:
```
#! /bin/sh

case "$1" in
    remove)
        depmod -a
        ;;
esac

#DEBHELPER#
```
Finally, you have to create a changelog file by using the dch command. I would suggest to use the same version number as the kernel, and use a revision number to differentiate between different builds (e.g. something like 2.6.21-1).
Now you may run dpkg-buildpackage and see if it works.