OpenWrt Kernel Module Creation Howto

OpenWrt Kernel Module Creation Howto

About OpenWrt Kernel Module Compilation

You are planning to compile a kernel module? This howto will explain what you have to do, to have your kernel module installable as an ipkg.

Enable the kernel options

Enable the kernel options you want by modifying build_mipsel/linux/.config. We are assuming, that you already had your kernel compiled once here. You can do the modification by hand or by 

$ cd build_mipsel/linux
$ make menuconfig

And copy it, so your changes are not getting lost, when doing a 'make dirclean'. Here we assume that you are compiling for Broadcom chipset based devices:

 $ cp .config ../../../target/linux/linux-2.4/config/brcm 

Create a buildroot option

Create a buildroot option by modifying/inserting into target/linux/Config.in, e.g.

config BR2_PACKAGE_KMOD_USB_KEYBOARD
        tristate "Support for USB keyboards"
        default m
        depends BR2_PACKAGE_KMOD_USB_CONTROLLER

Define the binary files for the kernel module

Define the binary files for the kernel module by modifying/inserting into target/linux/linux-2.4/Makefile, e.g.

$(eval $(call KMOD_template,USB_KEYBOARD,usb-kbd,
	$(MODULES_DIR)/kernel/drivers/input/input.o 
	$(MODULES_DIR)/kernel/drivers/input/keybdev.o 
	$(MODULES_DIR)/kernel/drivers/usb/usbkbd.o 
,CONFIG_USB_KEYB,kmod-usb-core,60,input keybdev usbkbd))

Where CONFIG_USB_KEYB is the kernel option, USB_KEYBOARD is the last part of BR2_PACKAGE_KMOD_USB_KEYBOARD and usb-kbd is part of the filename of the created ipkg.

Specify the ipkg control file

Create e.g. target/linux/control/kmod-usb-kbd.control with content similar to this:

Package: kmod-usb-kbd
Priority: optional
Section: sys
Maintainer: Markus Becker <mab@comnets.uni-bremen.de>
Source: buildroot internal
Description: Kernel Support for USB Keyboards

Compile the kernel module

Enable the kernel module with

$ make menuconfig

in TOPDIR and selecting it. Compile with

$ make dirclean && make