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Raspberry Pi – Setting up driver/module development environment

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Abstract: This post gives the steps required to set up a cross-compiling development environment for Raspberry Pi.
The base platform is a Linux computer (examples are given for a SuSE 12.2 installation running as a virtual computer on SuSE 12.2 using KVM as the hypervisor).
  1. Installing some prerequisites:
    1. git (use to access the source code repositories)
      On SuSE, use YaST to install if it’s not already there
      On Debian, use apt-get git to install
    2. Create your base directory: we will use ~/Projects
  2. Installing a cross-compiler:
    1. Download and compile the latest crosstool-ng from crosstool-ng.org (you will need to be root for the final make install)
      wget crosstool-ng.org/download/crosstool-ng/crosstool-ng-1.17.0.tar.bz2
      tar -xvz crosstool-ng-1.17.0.tar.bz2
      cd crosstool-ng-1.17.0
      ./configure
      make
      make install
    2. Configure a cross compiler
      mkdir ~/Projects/souce/ccc;cd ~/Projects/souce/ccc
      ct-ng menuconfig
      The cross compiler configuration requires the following settings:

      Section Setting
      Paths and misc [x] Try features marked as EXPERIMENTAL)
      (/tools/x-tools/${CT_TARGET}) Prefix directory
      Target options Target Architecture (arm)
      Endianness: (Little endian)
      Bitness: (32-bit)
      Operating System Target OS (linux)
      Linux kernel version (3.?.?) – use the correct value!
      Binary utilities binutils version: choose the latest not marked EXPERIMENTAL
      C Compiler [x] Show Linaro vesions (EXPERIMENTAL)
      gcc version – choose one of the Lenaro versions: 4.6-2-12.04 does work
      Exit from ct-ng menu configuration.
    3. Build a cross-compiler.
      As root (or with sudo prefix):
      ct-ng buid
      Note: if build fails with a message about Static linking impossible, edit the .config file and change CT_WANTS_STATIC_LINKING=n and try again.
      The compiler will be in /tools/x-tools/arm-unknown-linux-gnueabi
      The build takes quite a while… (42 minutes on a single core of i5-2500 at 3.3GHz)
  3. Installing the Linux Kernel Sources (which are required for compiling modules and drivers):
    1. Create a source directory ~/Projects/source an running the following commands from that directory:
    2. git clone git://github.com/raspberrypi/linux.git
    3. git clone git://github.com/raspberrypi/firmware.git
    4. git clone git://github.com/raspberrypi/tools.git
    You will now have three directories under ~/Projects/source: linux, firmware and tools.
  4. Set the right version of the Linux Kernel – which needs to be the same version you are using on the RaspberryPi.
    You can find the version RaspberryPi is running using the command:

    raspberrypi:~> uname -sr
Linux 3.2.27+
    You can see the available versions of the Linux kernel by:
    rpidev:~> cd ~/Projects/source/linux
rpidev:linux> git branch -r
  origin/HEAD -> origin/rpi-3.6.y
  origin/master
  origin/rpi-3.2.27
  origin/rpi-3.6.y
  origin/rpi-patches
    You can set the version to rpi-3.2.27 using:
    git checkout rpi-3.2.27
    • ARM System Type=Broadcom BCM2708 family
      • When changing the kernel version, you need to initialize it. This process will remove the .config file, so it’s a good idea to keep a copy in (eg) ../linux.config
      make mrproper
      To set the configuration, use one or more of the following
      • Copy from your backup: cp ../linux.config .config
      • Get it from the Raspberry Pi ssh root@rpi zcat /proc/config > .config
      • Check the configuration: make ARCH=arm CROSS_COMPILE=/tools/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- oldconfig
        This will prompt you to confirm any new options – use the default except for:
    • Edit the configuration: make ARCH=arm CROSS_COMPILE=/tools/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- menuconfig
      Some areas you might want to configure (especially if you’re planning to use this kernel on the device):

      • Floating Point emulation: you need one emulation set
      • Networking support (enable for more, disable for smaller)
      • Device drivers (enable for more, disable for smaller)
      • You can check the version your source code tree is at using:
      make kernelversion
    • Build the kernel using: (-j2 means use 2 core in parallel)
      make ARCH=arm CROSS_COMPILE=/tools/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- -j2
    • To compile my_module, use the following makefile:
      obj-m:=mymodule.o
      And compile with:
      make ARCH=arm CROSS_COMPILE=/tools/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi- -C ~/Projects/source/linux SUBDIRS=`pwd` modules

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