Compile Linux Kernel

Install the required packages

Some packages are needed to compile the Linux Kernel for UDOO boards. E.g. in Ubuntu 14.04 it is necessary to install the following packages:

sudo apt-get update
sudo apt-get install gawk wget git diffstat unzip texinfo gcc-multilib \
     build-essential chrpath socat libsdl1.2-dev xterm picocom ncurses-dev lzop \
     gcc-arm-linux-gnueabihf

Get the kernel sources from GitHub

Create a develop folder

mkdir udoo-dev
cd udoo-dev

then download the sources:

git clone https://github.com/UDOOboard/linux_kernel
cd linux_kernel

The default branch 3.14-1.0.x-udoo is the one where we are working on for the UDOO QUAD/DUAL. It is based on 3.14.56 Freescale community kernel.

Load the default kernel configuration

UDOO Neo has a dedicated default kernel configuration that you can import with:

ARCH=arm make udoo_neo_defconfig

(optional) Personalize the kernel configuration

Add or remove kernel modules to fit your project:

ARCH=arm make menuconfig

Compile sources

To build the kernel image, type:

ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make zImage -j5

You can safely tweak the -jX parameter. For instance, on quad core CPUs with two threads per core, you can use -j8.

The build can take several minutes, approximately from 2 to 15, depending on your PC host or VM configuration.

[...]
  Kernel: arch/arm/boot/Image is ready
  LZO     arch/arm/boot/compressed/piggy.lzo
  CC      arch/arm/boot/compressed/decompress.o
  CC      arch/arm/boot/compressed/string.o
  SHIPPED arch/arm/boot/compressed/hyp-stub.S
  SHIPPED arch/arm/boot/compressed/lib1funcs.S
  SHIPPED arch/arm/boot/compressed/ashldi3.S
  SHIPPED arch/arm/boot/compressed/bswapsdi2.S
  AS      arch/arm/boot/compressed/hyp-stub.o
  AS      arch/arm/boot/compressed/lib1funcs.o
  AS      arch/arm/boot/compressed/ashldi3.o
  AS      arch/arm/boot/compressed/bswapsdi2.o
  AS      arch/arm/boot/compressed/piggy.lzo.o
  LD      arch/arm/boot/compressed/vmlinux
  OBJCOPY arch/arm/boot/zImage
  Kernel: arch/arm/boot/zImage is ready

Compile Device Trees

ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make dtbs -j5

Compile the modules

ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make modules -j5

Copy the kernel to the SD card

You can overwrite the kernel on a UDOObuntu SD card with the following commands:

BOOT_PARTITION=/path/to/boot-partition
ROOT_PARTITION=/path/to/root-partition

cp arch/arm/boot/zImage $BOOT_PARTITION
cp arch/arm/boot/dts/*.dtb $BOOT_PARTITION/dts
ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make firmware_install modules_install INSTALL_MOD_PATH=$ROOT_PARTITION

Heads up! Be aware that if you have used the DTEditor previously, u-boot will load DTBs from /boot/dts-overlay. Disable this via /boot/uEnv.txt or copy your modified DTBs to that directory.