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+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
+[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+
+<chapter id='sdk-intro'>
+<title>Introduction</title>
+
+<section id='sdk-manual-intro'>
+ <title>Introduction</title>
+
+ <para>
+ Welcome to the Yocto Project Software Development Kit (SDK)
+ Developer's Guide.
+ This manual provides information that lets you use both the standard
+ Yocto Project SDK and an extensible SDK to develop applications and
+ images using the Yocto Project.
+ Additionally, the manual also provides information on how to use
+ the popular <trademark class='trade'>Eclipse</trademark> IDE as part
+ of your application development workflow.
+ </para>
+
+ <para>
+ Prior to the 2.0 Release of the Yocto Project, application
+ development was primarily accomplished through the use of the
+ Application Development Toolkit (ADT) and the availability
+ of stand-alone cross-development toolchains and other tools.
+ With the 2.1 Release of the Yocto Project, application development
+ has transitioned to within a more traditional SDK and extensible
+ SDK.
+ </para>
+
+ <para>
+ A standard SDK consists of a cross-development toolchain that contains
+ a compiler, debugger, and various miscellaneous tools; libraries,
+ headers, and symbols to match an image; and environment setup script.
+ You can use this SDK to independently develop and test code that is
+ destined to run on some target machine.
+ </para>
+
+ <para>
+ An extensible SDK consists of everything that the standard SDK has plus
+ tools that allow you to easily add new applications and libraries to
+ an image, modify the source of an existing component, test changes on
+ the target hardware, and easily integrate an application into the
+ <ulink url='&YOCTO_DOCS_DEV_URL;#build-system-term'>OpenEmbedded build system</ulink>.
+ </para>
+
+ <para>
+ SDKs are completely self-contained.
+ The binaries are linked against their own copy of
+ <filename>libc</filename>, which results in no dependencies
+ on the target system.
+ To achieve this, the pointer to the dynamic loader is
+ configured at install time since that path cannot be dynamically
+ altered.
+ This is the reason for a wrapper around the
+ <filename>populate_sdk</filename> and
+ <filename>populate_sdk_ext</filename> archives.
+ </para>
+
+ <para>
+ Another feature for the SDKs is that only one set of cross-canadian
+ toolchain binaries are produced per architecture.
+ This feature takes advantage of the fact that the target hardware can
+ be passed to <filename>gcc</filename> as a set of compiler options.
+ Those options are set up by the environment script and contained in
+ variables such as
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-CC'><filename>CC</filename></ulink>
+ and
+ <ulink url='&YOCTO_DOCS_REF_URL;#var-LD'><filename>LD</filename></ulink>.
+ This reduces the space needed for the tools.
+ Understand, however, that a sysroot is still needed for every target
+ since those binaries are target-specific.
+ </para>
+
+ <para>
+ Going beyond the actual SDK, the SDK development environment consists
+ of the following:
+ <itemizedlist>
+ <listitem><para>An architecture-specific cross-toolchain and
+ matching sysroots (target and native) all built by the
+ OpenEmbedded build system.
+ The toolchain and sysroots are based on a
+ <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>
+ configuration and extensions,
+ which allows you to cross-develop on the host machine for the
+ target hardware.
+ </para></listitem>
+ <listitem><para>The Quick EMUlator (QEMU), which lets you simulate
+ target hardware.
+ QEMU is not literally part of the SDK.
+ You must build and include this emulator separately.
+ However, QEMU plays an important role in the development
+ process that revolves around use of and SDK.
+ </para></listitem>
+ <listitem><para>The Eclipse IDE Yocto Plug-in.
+ This plug-in is also available for you if you are an Eclipse
+ user.
+ In the same manner as QEMU, the plug-in is not literally part
+ of the SDK but is rather available for use as part of the
+ development process.
+ </para></listitem>
+ <listitem><para>Various user-space tools that greatly enhance
+ your application development experience.
+ These tools are also separate from the actual SDK but can be
+ independently obtained and used in the development process.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <section id='the-cross-development-toolchain'>
+ <title>The Cross-Development Toolchain</title>
+
+ <para>
+ The
+ <ulink url='&YOCTO_DOCS_DEV_URL;#cross-development-toolchain'>Cross-Development Toolchain</ulink>
+ consists of a cross-compiler, cross-linker, and cross-debugger
+ that are used to develop user-space applications for targeted
+ hardware.
+ This toolchain is created by running a toolchain installer script
+ or through a
+ <ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>
+ that is based on your Metadata configuration or extension for
+ your targeted device.
+ The cross-toolchain works with a matching target sysroot.
+ </para>
+ </section>
+
+ <section id='sysroot'>
+ <title>Sysroots</title>
+
+ <para>
+ The native and target sysroots contain needed headers and libraries
+ for generating binaries that run on the target architecture.
+ The target sysroot is based on the target root filesystem image
+ that is built by the OpenEmbedded build system and uses the same
+ Metadata configuration used to build the cross-toolchain.
+ </para>
+ </section>
+
+ <section id='the-qemu-emulator'>
+ <title>The QEMU Emulator</title>
+
+ <para>
+ The QEMU emulator allows you to simulate your hardware while
+ running your application or image.
+ QEMU is not part of the SDK but is made available a number of ways:
+ <itemizedlist>
+ <listitem><para>
+ If you have cloned the <filename>poky</filename> Git
+ repository to create a
+ <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
+ and you have sourced the environment setup script, QEMU is
+ installed and automatically available.
+ </para></listitem>
+ <listitem><para>
+ If you have downloaded a Yocto Project release and unpacked
+ it to create a
+ <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
+ and you have sourced the environment setup script, QEMU is
+ installed and automatically available.
+ </para></listitem>
+ <listitem><para>
+ If you have installed the cross-toolchain tarball and you
+ have sourced the toolchain's setup environment script, QEMU
+ is also installed and automatically available.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+
+ <section id='eclipse-overview'>
+ <title>Eclipse Yocto Plug-in</title>
+
+ <para>
+ The Eclipse IDE is a popular development environment and it fully
+ supports development using the Yocto Project.
+ When you install and configure the Eclipse Yocto Project Plug-in
+ into the Eclipse IDE, you maximize your Yocto Project experience.
+ Installing and configuring the Plug-in results in an environment
+ that has extensions specifically designed to let you more easily
+ develop software.
+ These extensions allow for cross-compilation, deployment, and
+ execution of your output into a QEMU emulation session.
+ You can also perform cross-debugging and profiling.
+ The environment also supports a suite of tools that allows you to
+ perform remote profiling, tracing, collection of power data,
+ collection of latency data, and collection of performance data.
+ </para>
+
+ <para>
+ For information about the application development workflow that
+ uses the Eclipse IDE and for a detailed example of how to install
+ and configure the Eclipse Yocto Project Plug-in, see the
+ "<link link='sdk-developing-applications-using-eclipse'>Developing Applications Using <trademark class='trade'>Eclipse</trademark></link>"
+ section.
+ </para>
+ </section>
+
+ <section id='user-space-tools'>
+ <title>User-Space Tools</title>
+
+ <para>
+ User-space tools are available as part of the SDK development
+ process and can be helpful.
+ The tools include LatencyTOP, PowerTOP, Perf, SystemTap,
+ and Lttng-ust.
+ These tools are common development tools for the Linux platform.
+ <itemizedlist>
+ <listitem><para><emphasis>LatencyTOP:</emphasis> LatencyTOP
+ focuses on latency that causes skips in audio, stutters in
+ your desktop experience, or situations that overload your
+ server even when you have plenty of CPU power left.
+ </para></listitem>
+ <listitem><para><emphasis>PowerTOP:</emphasis> Helps you
+ determine what software is using the most power.
+ You can find out more about PowerTOP at
+ <ulink url='https://01.org/powertop/'></ulink>.</para></listitem>
+ <listitem><para><emphasis>Perf:</emphasis> Performance counters
+ for Linux used to keep track of certain types of hardware
+ and software events.
+ For more information on these types of counters see
+ <ulink url='https://perf.wiki.kernel.org/'></ulink>.
+ For examples on how to setup and use this tool, see the
+ "<ulink url='&YOCTO_DOCS_PROF_URL;#profile-manual-perf'>perf</ulink>"
+ section in the Yocto Project Profiling and Tracing Manual.
+ </para></listitem>
+ <listitem><para><emphasis>SystemTap:</emphasis> A free software
+ infrastructure that simplifies information gathering about
+ a running Linux system.
+ This information helps you diagnose performance or
+ functional problems.
+ SystemTap is not available as a user-space tool through
+ the Eclipse IDE Yocto Plug-in.
+ See <ulink url='http://sourceware.org/systemtap'></ulink>
+ for more information on SystemTap.
+ For examples on how to setup and use this tool, see the
+ "<ulink url='&YOCTO_DOCS_PROF_URL;#profile-manual-systemtap'>SystemTap</ulink>"
+ section in the Yocto Project Profiling and Tracing Manual.
+ </para></listitem>
+ <listitem><para><emphasis>Lttng-ust:</emphasis> A User-space
+ Tracer designed to provide detailed information on
+ user-space activity.
+ See <ulink url='http://lttng.org/ust'></ulink> for more
+ information on Lttng-ust.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+</section>
+
+<section id='sdk-development-model'>
+ <title>SDK Development Model</title>
+
+ <para>
+ Fundamentally, the SDK fits into the development process as follows:
+ <imagedata fileref="figures/sdk-environment.png" align="center" width="6in" depth="5in" scalefit="100" />
+ The SDK is installed on any machine and can be used to develop
+ applications, images, and kernels.
+ An SDK can even be used by a QA Engineer or Release Engineer.
+ The fundamental concept is that the machine that has the SDK installed
+ does not have to be associated with the machine that has the
+ Yocto Project installed.
+ A developer can independently compile and test an object on their
+ machine and then, when the object is ready for integration into an
+ image, they can simply make it available to the machine that has the
+ the Yocto Project.
+ Once the object is available, the image can be rebuilt using the
+ Yocto Project to produce the modified image.
+ </para>
+
+ <para>
+ You just need to follow these general steps:
+ <orderedlist>
+ <listitem><para><emphasis>Install the SDK for your target hardware:</emphasis>
+ For information on how to install the SDK, see the
+ "<link url='sdk-installing-the-sdk'>Installing the SDK</link>"
+ section.</para></listitem>
+ <listitem><para><emphasis>Download the Target Image:</emphasis>
+ The Yocto Project supports several target architectures
+ and has many pre-built kernel images and root filesystem
+ images.</para>
+ <para>If you are going to develop your application on
+ hardware, go to the
+ <ulink url='&YOCTO_MACHINES_DL_URL;'><filename>machines</filename></ulink>
+ download area and choose a target machine area
+ from which to download the kernel image and root filesystem.
+ This download area could have several files in it that
+ support development using actual hardware.
+ For example, the area might contain
+ <filename>.hddimg</filename> files that combine the
+ kernel image with the filesystem, boot loaders, and
+ so forth.
+ Be sure to get the files you need for your particular
+ development process.</para>
+ <para>If you are going to develop your application and
+ then run and test it using the QEMU emulator, go to the
+ <ulink url='&YOCTO_QEMU_DL_URL;'><filename>machines/qemu</filename></ulink>
+ download area.
+ From this area, go down into the directory for your
+ target architecture (e.g. <filename>qemux86_64</filename>
+ for an <trademark class='registered'>Intel</trademark>-based
+ 64-bit architecture).
+ Download kernel, root filesystem, and any other files you
+ need for your process.
+ <note>In order to use the root filesystem in QEMU, you
+ need to extract it.
+ See the
+ "<link url='sdk-extracting-the-root-filesystem'>Extracting the Root Filesystem</link>"
+ section for information on how to extract the root
+ filesystem.</note></para></listitem>
+ <listitem><para><emphasis>Develop and Test your
+ Application:</emphasis> At this point, you have the tools
+ to develop your application.
+ If you need to separately install and use the QEMU
+ emulator, you can go to
+ <ulink url='http://wiki.qemu.org/Main_Page'>QEMU Home Page</ulink>
+ to download and learn about the emulator.
+ You can see the
+ "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-manual-qemu'>Using the Quick EMUlator (QEMU)</ulink>"
+ chapter in the Yocto Project Development Manual
+ for information on using QEMU within the Yocto
+ Project.</para></listitem>
+ </orderedlist>
+ </para>
+
+ <para>
+ The remainder of this manual describes how to use both the standard
+ SDK and the extensible SDK.
+ Information also exists in appendix form that describes how you can
+ build, install, and modify an SDK.
+ </para>
+</section>
+
+</chapter>
+<!--
+vim: expandtab tw=80 ts=4
+-->
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