path: root/docs/usermanual/chapters/common_use_cases.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter id="chapter_common_use_cases">
  <title>Common Use-cases/tasks</title>

  <section id="commonuse_new_distro">
    <title>Creating a new Distribution</title>

    <para>Creating a new distribution is not complicated, however we urge you
    to try existing distributions first, because it's also very easy to do
    wrong. The config needs to be created in $OEBASE/openembedded/conf/distro 
    directory. So what has to be inside? 
      <itemizedlist>
        <listitem>
          <para><command>DISTRO_VERSION</command> so users will know which
          version of the distribution they are using.</para>
        </listitem>

        <listitem>
          <para><command>DISTRO_TYPE</command> (release/debug) variable is
          used in some recipes to enable/disable some features - for example
          kernel output on screen for "debug" builds.</para>
        </listitem>

        <listitem>
          <para>Type of libc used: will it be glibc
          (<command>TARGET_OS</command> = "linux") or uclibc
          (<command>TARGET_OS</command> = "linux-uclibc")?</para>
        </listitem>

        <listitem>
          <para>Toolchain versions - for example gcc 3.4.4 based distro will
          have: <screen>
PREFERRED_PROVIDERS += " virtual/${TARGET_PREFIX}gcc-initial:gcc-cross-initial"
PREFERRED_PROVIDERS += " virtual/${TARGET_PREFIX}gcc:gcc-cross"
PREFERRED_PROVIDERS += " virtual/${TARGET_PREFIX}g++:gcc-cross"

PREFERRED_VERSION_binutils = "2.16"
PREFERRED_VERSION_binutils-cross = "2.16"

PREFERRED_VERSION_gcc = "3.4.4"
PREFERRED_VERSION_gcc-cross = "3.4.4"
PREFERRED_VERSION_gcc-initial-cross = "3.4.4"
            </screen></para>
        </listitem>

        <listitem>
          <para><command>DISTRO_FEATURES</command> which describe which
          features distro has. More about it in <link
          linkend="task-base">task-base</link> section.</para>
        </listitem>

        <listitem>
          <para>Versions of kernels used for supported devices: <screen>
PREFERRED_VERSION_linux-omap1_omap5912osk ?= "2.6.18+git"
PREFERRED_VERSION_linux-openzaurus ?= "2.6.17"
            </screen></para>
        </listitem>

        <listitem>
          <para>To get more stable build it is good to make use of
          sane-srcdates.inc file which contain working SRCDATE for many of
          floating recipes. <screen>
require conf/distro/include/sane-srcdates.inc
            </screen> It also should have global <command>SRCDATE</command>
          value set (format is ISO date: YYYYMMDD): <screen>
SRCDATE = "20061014"
            </screen></para>
        </listitem>
      </itemizedlist></para>
  </section>

  <section id="commonuse_new_machine">
    <title>Adding a new Machine</title>

    <para>To be able to build for a device OpenEmbedded has to know about it, 
    so a machine config file needs to be written. All of the machine 
    configs are stored in $OEBASE/openembedded/conf/machine/ directory.</para>

    <para>As usual some variables are required: <itemizedlist>
        <listitem>
          <para><command>TARGET_ARCH</command> describes which CPU
          architecture the machine uses.</para>
        </listitem>

        <listitem>
          <para><command>MACHINE_FEATURES</command> which describes which
          features the device has. More about it in <link
          linkend="task-base">task-base</link> section.</para>
        </listitem>

        <listitem>
          <para><command>PREFERRED_PROVIDER_virtual/kernel</command> has to
          point to the proper kernel recipe for this machine.</para>
        </listitem>
      </itemizedlist></para>

    <para>Next the kernel recipe needs to be added if it doesn't already exist.
    </para>
  </section>

  <section id="commonuse_new_package">
    <title>Adding a new Package</title>

    <para>This section is a stub, help us by expanding it.  Learn by example, go through the
    recipes that are already there and mimic them to do what you want.</para>

    <section>
        <title>building from unstable source code</title>
        <para>Building against the latest, bleeding-edge source has some intricacies of its own.
        For one, it is desirable to pin down a code revision that is known to build to
        prevent random breakage in OE at the most inopportune time for all OE users.  Here is
        how to do that properly.
          <itemizedlist>
            <listitem><para>for svn: add 'PV = "1.1+svnr${SRCREV}"' to your bb file.</para></listitem>
            <listitem><para>for cvs: add 'PV = "1.1+cvs${SRCREV}"' to your bb file.</para></listitem>
          </itemizedlist>
        Accompany either with an entry to conf/distro/include/sane-srcrevs.inc for a revision that you know
        builds successfully.  It is also common to define the stable SRCREV 
        for your package directly in the package recipe.
        </para>
        <para>
        If you really absolutely have to follow the latest commits, you can do that by adding
        'SRCREV_pn-linux-davinci ?= ${AUTOREV}' to your local.conf, for example.  In this case,
        you'd build against the most recent and unstable source for the pn-linux-davinci package.
        </para>
    </section>
  </section>

  <section id="commonuse_new_image">
    <title>Creating your own image</title>

    <para>Creating own image is easy - only few variables need to be set:
    <itemizedlist>
        <listitem>
          <para><command>IMAGE_BASENAME</command> to give a name for your own
          image</para>
        </listitem>

        <listitem>
          <para><command>PACKAGE_INSTALL</command> to give a list of packages
          to install into the image</para>
        </listitem>

        <listitem>
          <para><command>RDEPENDS</command> to give a list of recipes which
          are needed to be built to create this image</para>
        </listitem>

        <listitem>
          <para><command>IMAGE_LINGUAS</command> is an optional list of
          languages which has to be installed into the image</para>
        </listitem>
      </itemizedlist> Then add the <emphasis>image</emphasis> class using:
    <screen>
inherit image
</screen> And the image recipe is ready for usage.</para>
  </section>

  <section id="commonuse_prebuilt_toolchain">
    <title>Using a prebuilt toolchain to create your packages</title>

    <para>It might be necessary to integrate a prebuilt toolchain and other
    libraries but still be use OpenEmbedded to build packages. One of many
    approaches is shown and discussed here.</para>

    <section>
      <title>The toolchain</title>

      <para>We assume the toolchain provides a C and C++ compiler, an
      assembler and other tools to build packages. The list below shows a gcc
      3.4.4 toolchain for ARM architectures using glibc. We assume that the
      toolchain is in your <command>PATH</command>.</para>

      <screen>
$ <command>ls</command> pre-built/cross/bin

arm-linux-g++
arm-linux-ld
arm-linux-ranlib
arm-linux-ar
arm-linux-g77
arm-linux-readelf
arm-linux-as
arm-linux-gcc
arm-linux-gcc-3.4.4
arm-linux-c++
arm-linux-size
arm-linux-c++filt
arm-linux-nm
arm-linux-strings
arm-linux-cpp
arm-linux-objcopy
arm-linux-strip
arm-linux-objdump
</screen>
    </section>

    <section>
      <title>The prebuilt libraries</title>

      <para>We need the header files and the libraries itself. The following
      directory layout is assumed. <command>PRE_BUILT</command> has two
      subdirectories one is called <emphasis>include</emphasis> and holds the
      header files and the other directory is called <emphasis>lib</emphasis>
      and holds the shared and static libraries. Additionally a Qt2 directory
      is present having a <emphasis>include</emphasis> and
      <emphasis>lib</emphasis> sub-directory.</para>

      <screen>
$ <command>ls</command> $PRE_BUILT
include
lib
qt2
</screen>
    </section>

    <section>
      <title>Setting up OpenEmbedded</title>

      <para>OpenEmbedded will be setup here. We assume that your machine and
      distribution is not part of OpenEmbedded and they will be created ad-hoc
      in the <emphasis>local.conf</emphasis> file. You will need to have
      <application>BitBake</application> and a current OpenEmbedded version
      available.</para>

      <section>
        <title>Sourceable script</title>

        <para>To ease the usage of OpenEmbedded we start by creating a
        source-able script. This is actually a small variation from the
        already seen script. We will name it <emphasis>build_source</emphasis>
        and you will need to source it.</para>

        <screen>
BITBAKE_PATH=/where/is/bitbake/bin
TOOLCHAIN=/where/is/toolchain/bin
HOST_TOOLS=/where/is/hosttools/bin
export PRE_BUILT=/where/is/pre-built

export PATH=$BITBAKE_PATH:$TOOLCHAIN:$HOST_TOOLS:$PATH
export OEDIR=$PWD
export LOCALDIR=$PWD/secret-isv
                    </screen>

        <para>Use <command>source build_source</command> to source the script,
        use <command>env</command> to check that the variables were
        exported.</para>
      </section>

      <section>
        <title>Creating the local.conf</title>

        <para>We will configure OpenEmbedded now, it is very similar to what
        we have done above.</para>

        <screen>
DL_DIR = "${OEDIR}/sources"
BBFILES := "${OEDIR}/openembedded/recipes/*/*.bb ${LOCALDIR}/recipes/*/*.bb"
BBFILE_COLLECTIONS = "upstream local"
BBFILE_PATTERN_upstream = "^${OEDIR}/openembedded/recipes/"
BBFILE_PATTERN_local = "^${LOCALDIR}/recipes/"
BBFILE_PRIORITY_upstream = "5"
BBFILE_PRIORITY_local = "10"
BBMASK = ""
                    </screen>

        <para>${OEDIR}/openembedded will be a upstream release of
        OpenEmbedded. Above we have assumed it is in the current working
        directory. Additionally we have a ${LOCALDIR}, we combine these two
        directories as a special <link linkend="collections">BitBake
        Collection</link>.</para>

        <screen>
#
# machine stuff
#
MACHINE = "secret-killer"
PACKAGE_EXTRA_ARCHS = "armv4 armv4t armv5te iwmmxt xscale""
TARGET_CC_ARCH = "-mcpu=xscale -mtune=iwmmxt"
TARGET_ARCH = "arm"
PACKAGE_ARCH="xscale"
                </screen>

        <para>We tell OpenEmbedded that we build for the ARM platform and
        optimize for xscale and iwmmxt.</para>

        <screen>
INHERIT += " package_ipk debian"
TARGET_OS  = "linux"
TARGET_FPU = "soft"
DISTRO = "secret-disro"
DISTRO_NAME = "secret-distro"
DISTRO_VERSION = "x.y.z"
DISTRO_TYPE = "release"
                </screen>

        <para>Create a distribution ad-hoc as well. We tell OpenEmbedded that
        we build for linux and glibc using soft float as fpu. If your
        toolchain is a uclibc toolchain you will need to set
        <command>TARGET_OS</command> to linux-uclibc.</para>

        <screen>
export CC="${CCACHE}arm-linux-gcc-3.4.4 ${HOST_CC_ARCH}"
export CXX="${CCACHE}arm-linux-g++ ${HOST_CC_ARCH}"
export CPP="arm-linux-gcc-3.4.4 -E"
export LD="arm-linux-ld"
export AR="arm-linux-ar"
export AS="arm-linux-as"
export RANLIB="arm-linux-ranlib"
export STRIP="arm-linux-strip"
                </screen>

        <para>The above variables replace the ones from
        <emphasis>bitbake.conf</emphasis>. This will make OpenEmbedded use the
        prebuilt toolchain.</para>

        <screen>
#
# point OE to the lib and include directory
#
TARGET_CPPFLAGS_append = " -I${PRE_BUILT}/include "
TARGET_LDFLAGS_prepend = " -L${PRE_BUILT}/qt2/lib -L${PRE_BUILT}/lib \
-Wl,-rpath-link,${PRE_BUILT}/lib -Wl,-rpath-link,${PRE_BUILT}/qt2/lib "

# special to Qt/Qtopia
QTDIR  = "${PRE_BUILT}/qt2"
QPEDIR = "${PRE_BUILT}"
palmtopdir = "/opt/Qtopia"
palmqtdir  = "/opt/Qtopia"
                </screen>

        <para>We will add the <command>PRE_BUILT</command> libraries to the
        include and library paths. And the same is done for the special
        version of Qt we have in your <command>PRE_BUILT</command>
        directory.</para>

        <screen>
ASSUME_PROVIDED += " virtual/${TARGET_PREFIX}gcc "
ASSUME_PROVIDED += " virtual/libc "
ASSUME_PROVIDED += " virtual/qte "
ASSUME_PROVIDED += " virtual/libqpe "
ASSUME_PROVIDED += " libqpe-opie "
                </screen>

        <para>Now we have told <application>BitBake</application> that the C
        library, compiler and Qtopia is already provided. These lines will
        avoid building binutils, gcc initial, glibc, gcc.</para>

        <screen>
<command>source</command> build_source
<command>bitbake</command> your-killer-app
                </screen>

        <para>You should be able to create the packages you want to using the
        prebuilt toolchain now.</para>
      </section>
    </section>

    <section>
      <title>Useful hints</title>

      <para>If you have more prebuilt libraries you need to add additional
      <command>ASSUME_PROVIDED</command> lines to your
      <emphasis>local.conf</emphasis>. Using <command>bitbake -vvv
      PACKAGE</command> you can easily see the package names you could
      <command>ASSUME_PROVIDED</command> if you have some prebuilt.</para>
    </section>

    <section>
      <title>Issues with this approach</title>

      <screen>
NOTE: Couldn't find shared library provider for libqtopia.so.1
NOTE: Couldn't find shared library provider for libqtopia2.so.2
NOTE: Couldn't find shared library provider for libqpe.so.1
NOTE: Couldn't find shared library provider for libpthread.so.0
NOTE: Couldn't find shared library provider for libstdc++.so.6
NOTE: Couldn't find shared library provider for libqte.so.2
NOTE: Couldn't find shared library provider for libgcc_s.so.1
NOTE: Couldn't find shared library provider for libc.so.6
NOTE: Couldn't find shared library provider for libm.so.6
</screen>

      <para>OpenEmbedded tries to automatically add run-time dependencies
      (RDEPENDS) to generated packages. It is inspecting binaries and
      libraries and uses the <emphasis><link linkend="shlibs">shlibs</link>
      </emphasis> system to do add dependencies for the linked libraries,
      however in this case it was not able to find packages providing these
      libraries as they were prebuilt.
      </para>

      <para>One way to resolve this problem is to provide an explicit mapping
      using the ASSUME_SHLIBS variable in a config file <filename>local.conf</filename>.
      For example, for the libraries above (partial):
      <screen>
ASSUME_SHLIBS = "libqtopia2.so.2:qtopia2_2.4 libc.so.6:libc"
</screen>
      The format is shlib_file_name:package[_version]. If a version is specified it will be
      used as the minimal (>=) version for the dependency.</para>
    </section>
  </section>

  <section id="commonuse_new_package_format">
    <title>Using a new package format</title>

    <para>This section is a stub, help us by expanding it</para>
  </section>

  <section id="commonuse_qte_sdk">
    <title>Creating Software Development Kits (SDKs)</title>

    <section>
        <title>What is provided by a SDK</title>

        <para>The Software Development Kit (SDK) should be easy to install and
        enable your user-base to create binaries and libraries that work on the
        target hardware.
        </para>

        <para>To accomplish this goal OpenEmbedded SDKs contain tools for the
        host and tools for the target hardware. Among these tools is a cross
        compiler, libraries and header files for additional dependencies, pkg-config
        files to allow buildsystems to easily find the dependencies, a file with
        results for autoconf and a script that can be sourced to setup the
        environment.
        </para>
    </section>

    <section>
        <title>Creating a SDK with your libraries pre-installed</title>

        <section>
            <title>Preparing the host side</title>
            <para>Your SDK might need utilities that will run on the
            host. These could include scripts, buildsystem software like
            cmake, or an emulator like qemu. For these dependencies it is
            imported that they <emphasis>inherit sdk</emphasis> and by
            convention end with <emphasis>-sdk</emphasis> in the
            <command>PN</command>.
            </para>

            <para>A new task should be created that will assure that all
            host utilities will be installed. Place a file called
            <filename>task-YOUR-toolchain-host.bb</filename> in the
            <filename>recipes/tasks</filename> directory and place the
            following content in it:
<screen>
require task-sdk-host.bb
DESCRIPTION = "Host packages for YOUR SDK"
LICENSE = "MIT"
ALLOW_EMPTY = "1"
RDEPENDS_${PN} += "YOUR-DEPENDENCY-sdk"
</screen>
            </para>
        </section>

        <section>
            <title>Preparing the target side</title>
            <para>Your SDK should provide your user with header files and libraries
            he will need when doing application development. In OpenEmbedded the
            <command>${PN}-dev</command> is providing the header files, pkg-config
            files and symbolic links to libraries to allow using the library. The SDK
            should install these development packages to the SDK.
            </para>

            <para>To install the development packages you will need to create a
            new task. Create a new file <filename>task-YOUR-toolchain-target.bb</filename>
            in the <filename>recipes/tasks</filename> directory and place the
            following content in it:
<screen>
DESCRIPTION = "Target package for YOUR SDK"
LICENSE = "MIT"
ALLOW_EMPTY = "1"

PR = "r0"

RDEPENDS_${PN} += "\
        task-sdk-bare \
        your-lib-dev \
        your-data
        "
</screen>
            </para>
        </section>

        <section>
            <title>Putting it together</title>
            <para>In the previous two sections we have prepared the host and
            target side. One thing that is missing is combining the two newly
            created tasks and actually creating the SDK. This is what we are 
            going to do now.</para>

            <para>Create <filename>meta-toolchain-YOU.bb</filename> in the
            <filename>recipes/meta</filename> directory and place the following
            content in it:
<screen>
PR = "r0"
TOOLCHAIN_TARGET_TASK = "task-YOUR-toolchain-target"
TOOLCHAIN_HOST_TASK = "task-YOUR-toolchain-host"

require meta-toolchain.bb
SDK_SUFFIX = "toolchain-YOUR"
</screen>

            </para>

            <para>Using <command>bitbake meta-toolchain-YOU</command> the SDK
            creation should be started and you should find a <filename>sdk</filename>
            directory inside your deploy directory with a SDK waiting for you. With
            the above command you still need to have OE configured with your
            <filename>conf/local.conf</filename> to select the machine and
            distribution you are targeting.
            </para>

            <note><para>SDK creation currently does not work with the <emphasis>DISTRO</emphasis>
            set to <emphasis>micro</emphasis>.</para></note>

            <note><para>If the environment-setup script packaged in the SDK should
            require more environment look at the <filename>meta-toolchain-qte.bb</filename>
            to accomplish this.</para></note>
        </section>
    </section>
  </section>

  <section>
    <title>Creating and Using a Qt Embedded SDK</title>

        <section>
            <title>Creating the SDK</title>

            <para>The SDK should contain a build of Qt Embedded, but also
            optional dependencies like directFB, glib-2.0, gstreamer-0.10, tslib
            and more esoteric dependencies like mysql and postgres. This allows
            developers to simply start developing using Qt and enables system
            integrators to easily recompile Qt and base libraries without tracking
            down extra dependencies.
            </para>

            <para>OpenEmbedded provides an easy way to create a Qt Embedded
            SDK. In
            <filename>recipes/tasks/task-qte-toolchain-host.bb</filename> host
            tools like moc, uic, rcc, qmake will get installed and in <filename>
            recipes/tasks/task-qte-toolchain-target.bb</filename> the Qt4 header
            files and libraries will be installed.
            </para>

            <para>To build the SDK, setup OpenEmbedded in the usual way by picking
            a <emphasis>DISTRO</emphasis> and <emphasis>MACHINE</emphasis>. Issue
            the below command and after the operation finished you should find
            a SDK in the deployment directory.
<screen>
$ <command>bitbake</command> meta-toolchain-qte
</screen>
            </para>

            <note><para>The deployment directory depends on the distribution
            and used C library. In the case of Angstrom and glibc it is
            located in <filename>tmp/deploy/glibc/sdk</filename>.</para></note>

            <note><para>Change <filename>qt4-embedded.inc</filename> and
            <filename>qt4.inc</filename> for using different Qt configuration
            flags. This might include a custom qconfig.h to produce a reduced
            size build.</para></note>

            <note><para>When distributing the SDK make sure to include a written offer
            to provide the sourcecode of GPL licensed applications or provide
            parts of the <filename>sources</filename> folder. The <filename>
            sources</filename> folder is located right next to the <filename>sdk</filename>
            one.</para></note>
        </section>


        <section>
            <title>Using the Qt Embedded SDK</title>

            <para>In this example we are assuming that the target hardware
            is an armv5t system and the SDK targets the Angstrom Distribution. You
            should start by downloading the SDK and untar it to the root folder
            (<filename>/</filename>). Once this operation is finished you will
            find a new directory <filename>/usr/local/angstrom/arm/</filename> and
            it contains the <filename>environment-setup</filename> file to setup the
            <emphasis>QMAKESPEC</emphasis> and various other paths.
            </para>

<screen>
Untar the SDK once
$ <command>tar</command> -C / -xjf angstrom-armv5te-linux-gnueabi-toolchain-qte.tar.bz2

Before using it source the environment
$ <command>.</command> /usr/local/angstrom/arm/environment-setup

Use qmake2 to build software for the target
$ <command>qmake2</command>
</screen>

            <para>Creating and building a simple example. We will create a simple
            Qt Embedded application and use <command>qmake2</command> and
            <command>make</command> to cross compile.

<screen>
$ <command>.</command> /usr/local/angstrom/arm/environment-setup
$ <command>cd</command> $HOME
$ <command>mkdir</command> qte-example
$ <command>cd</command> qte-example

$ <command>echo</command> "TEMPLATE=app
SOURCES=main.cpp
" > qte-example.pro

$ <command>echo</command> '#include &lt;QApplication&gt;
#include &lt;QPushButton&gt;

int main(int argc, char** argv) {
    QApplication app(argc, argv);

    QPushButton btn("Hello World");
    btn.show();
    btn.showMaximized();

    return app.exec();
}
' > main.cpp

$ <command>qmake2</command>
$ <command>make</command>
</screen>
            </para>

        </section>
  </section>
</chapter>