405 lines
19 KiB
XML
405 lines
19 KiB
XML
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='sdk-intro'>
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<title>Introduction</title>
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<section id='sdk-manual-intro'>
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<title>Introduction</title>
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<para>
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Welcome to the Yocto Project Application Development and the
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Extensible Software Development Kit (eSDK) manual.
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This manual provides information that explains how to use both the
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Yocto Project extensible and standard SDKs to develop
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applications and images.
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Additionally, the manual also provides information on how to use
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the popular <trademark class='trade'>Eclipse</trademark> IDE as part
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of your application development workflow within the SDK environment.
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<note>
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Prior to the 2.0 Release of the Yocto Project, application
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development was primarily accomplished through the use of the
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Application Development Toolkit (ADT) and the availability
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of stand-alone cross-development toolchains and other tools.
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With the 2.1 Release of the Yocto Project, application development
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has transitioned to within a tool-rich extensible SDK and the more
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traditional standard SDK.
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</note>
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</para>
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<para>
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All SDKs consist of the following:
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<itemizedlist>
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<listitem><para><emphasis>Cross-Development Toolchain</emphasis>:
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This toolchain contains a compiler, debugger, and various
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miscellaneous tools.
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</para></listitem>
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<listitem><para><emphasis>Libraries, Headers, and Symbols</emphasis>:
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The libraries, headers, and symbols are specific to the image
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(i.e. they match the image).
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</para></listitem>
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<listitem><para><emphasis>Environment Setup Script</emphasis>:
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This <filename>*.sh</filename> file, once run, sets up the
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cross-development environment by defining variables and
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preparing for SDK use.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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Additionally an extensible SDK has tools that allow you to easily add
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new applications and libraries to an image, modify the source of an
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existing component, test changes on the target hardware, and easily
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integrate an application into the
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<ulink url='&YOCTO_DOCS_REF_URL;#build-system-term'>OpenEmbedded build system</ulink>.
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</para>
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<para>
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You can use an SDK to independently develop and test code
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that is destined to run on some target machine.
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SDKs are completely self-contained.
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The binaries are linked against their own copy of
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<filename>libc</filename>, which results in no dependencies
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on the target system.
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To achieve this, the pointer to the dynamic loader is
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configured at install time since that path cannot be dynamically
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altered.
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This is the reason for a wrapper around the
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<filename>populate_sdk</filename> and
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<filename>populate_sdk_ext</filename> archives.
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</para>
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<para>
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Another feature for the SDKs is that only one set of cross-compiler
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toolchain binaries are produced for any given architecture.
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This feature takes advantage of the fact that the target hardware can
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be passed to <filename>gcc</filename> as a set of compiler options.
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Those options are set up by the environment script and contained in
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variables such as
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<ulink url='&YOCTO_DOCS_REF_URL;#var-CC'><filename>CC</filename></ulink>
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and
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<ulink url='&YOCTO_DOCS_REF_URL;#var-LD'><filename>LD</filename></ulink>.
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This reduces the space needed for the tools.
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Understand, however, that a sysroot is still needed for every target
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since those binaries are target-specific.
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</para>
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<para>
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The SDK development environment consists of the following:
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<itemizedlist>
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<listitem><para>The self-contained SDK, which is an
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architecture-specific cross-toolchain and
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matching sysroots (target and native) all built by the
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OpenEmbedded build system (e.g. the SDK).
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The toolchain and sysroots are based on a
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<ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>
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configuration and extensions,
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which allows you to cross-develop on the host machine for the
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target hardware.
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Additionally, the extensible SDK contains the
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<filename>devtool</filename> functionality.
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</para></listitem>
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<listitem><para>The Quick EMUlator (QEMU), which lets you simulate
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target hardware.
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QEMU is not literally part of the SDK.
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You must build and include this emulator separately.
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However, QEMU plays an important role in the development
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process that revolves around use of the SDK.
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</para></listitem>
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<listitem><para>The Eclipse IDE Yocto Plug-in.
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This plug-in is available for you if you are an Eclipse
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user.
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In the same manner as QEMU, the plug-in is not literally part
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of the SDK but is rather available for use as part of the
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development process.
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</para></listitem>
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<listitem><para>Various performance-related
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<ulink url='http://www.eclipse.org/linuxtools/index.php'>tools</ulink>
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that can enhance your development experience.
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These tools are also separate from the actual SDK but can be
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independently obtained and used in the development process.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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In summary, the extensible and standard SDK share many features.
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However, the extensible SDK has powerful development tools to help you
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more quickly develop applications.
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Following is a table that summarizes the primary differences between
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the standard and extensible SDK types when considering which to
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build:
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<informaltable frame='none'>
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<tgroup cols='3' align='left' colsep='1' rowsep='1'>
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<colspec colname='c1' colwidth='1*'/>
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<colspec colname='c2' colwidth='1*'/>
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<colspec colname='c3' colwidth='1*'/>
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<thead>
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<row>
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<entry align="left"><emphasis>Feature</emphasis></entry>
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<entry align="left"><emphasis>Standard SDK</emphasis></entry>
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<entry align="left"><emphasis>Extensible SDK</emphasis></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry align="left">Toolchain</entry>
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<entry align="left">Yes</entry>
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<entry align="left">Yes*</entry>
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</row>
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<row>
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<entry align="left">Debugger</entry>
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<entry align="left">Yes</entry>
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<entry align="left">Yes*</entry>
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</row>
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<row>
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<entry align="left">Size</entry>
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<entry align="left">100+ MBytes</entry>
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<entry align="left">1+ GBytes (or 300+ MBytes for minimal w/toolchain)</entry>
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</row>
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<row>
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<entry align="left"><filename>devtool</filename></entry>
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<entry align="left">No</entry>
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<entry align="left">Yes</entry>
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</row>
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<row>
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<entry align="left">Build Images</entry>
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<entry align="left">No</entry>
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<entry align="left">Yes</entry>
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</row>
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<row>
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<entry align="left">Updateable</entry>
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<entry align="left">No</entry>
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<entry align="left">Yes</entry>
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</row>
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<row>
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<entry align="left">Managed Sysroot**</entry>
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<entry align="left">No</entry>
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<entry align="left">Yes</entry>
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</row>
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<row>
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<entry align="left">Installed Packages</entry>
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<entry align="left">No***</entry>
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<entry align="left">Yes****</entry>
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</row>
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<row>
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<entry align="left">Construction</entry>
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<entry align="left">Packages</entry>
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<entry align="left">Shared State</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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<literallayout class='monospaced'>
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* Extensible SDK will contain the toolchain and debugger if <ulink url='&YOCTO_DOCS_REF_URL;#var-SDK_EXT_TYPE'><filename>SDK_EXT_TYPE</filename></ulink> is "full" or <ulink url='&YOCTO_DOCS_REF_URL;#var-SDK_INCLUDE_TOOLCHAIN'><filename>SDK_INCLUDE_TOOLCHAIN</filename></ulink> is "1", which is the default.
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** Sysroot is managed through use of <filename>devtool</filename>. Thus, it is less likely that you will corrupt your SDK sysroot when you try to add additional libraries.
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*** Runtime package management can be added to the standard SDK but it is not supported by default.
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**** You must build and make the shared state available to extensible SDK users for "packages" you want to enable users to install.
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</literallayout>
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</para>
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<section id='the-cross-development-toolchain'>
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<title>The Cross-Development Toolchain</title>
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<para>
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The
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<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain'>Cross-Development Toolchain</ulink>
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consists of a cross-compiler, cross-linker, and cross-debugger
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that are used to develop user-space applications for targeted
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hardware.
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Additionally, for an extensible SDK, the toolchain also has
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built-in <filename>devtool</filename> functionality.
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This toolchain is created by running a SDK installer script
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or through a
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<ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>
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that is based on your Metadata configuration or extension for
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your targeted device.
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The cross-toolchain works with a matching target sysroot.
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</para>
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</section>
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<section id='sysroot'>
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<title>Sysroots</title>
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<para>
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The native and target sysroots contain needed headers and libraries
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for generating binaries that run on the target architecture.
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The target sysroot is based on the target root filesystem image
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that is built by the OpenEmbedded build system and uses the same
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Metadata configuration used to build the cross-toolchain.
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</para>
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</section>
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<section id='the-qemu-emulator'>
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<title>The QEMU Emulator</title>
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<para>
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The QEMU emulator allows you to simulate your hardware while
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running your application or image.
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QEMU is not part of the SDK but is made available a number of ways:
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<itemizedlist>
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<listitem><para>
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If you have cloned the <filename>poky</filename> Git
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repository to create a
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<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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and you have sourced the environment setup script, QEMU is
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installed and automatically available.
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</para></listitem>
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<listitem><para>
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If you have downloaded a Yocto Project release and unpacked
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it to create a Source Directory and you have sourced the
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environment setup script, QEMU is installed and
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automatically available.
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</para></listitem>
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<listitem><para>
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If you have installed the cross-toolchain tarball and you
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have sourced the toolchain's setup environment script, QEMU
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is also installed and automatically available.
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='eclipse-overview'>
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<title>Eclipse Yocto Plug-in</title>
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<para>
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The Eclipse IDE is a popular development environment and it fully
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supports development using the Yocto Project.
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When you install and configure the Eclipse Yocto Project Plug-in
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into the Eclipse IDE, you maximize your Yocto Project experience.
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Installing and configuring the Plug-in results in an environment
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that has extensions specifically designed to let you more easily
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develop software.
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These extensions allow for cross-compilation, deployment, and
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execution of your output into a QEMU emulation session.
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You can also perform cross-debugging and profiling.
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The environment also supports many performance-related
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<ulink url='http://www.eclipse.org/linuxtools/index.php'>tools</ulink>
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that enhance your development experience.
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<note>
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Previous releases of the Eclipse Yocto Plug-in supported
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"user-space tools" (i.e. LatencyTOP, PowerTOP, Perf, SystemTap,
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and Lttng-ust) that also added to the development experience.
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These tools have been deprecated beginning with this release
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of the plug-in.
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</note>
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</para>
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<para>
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For information about the application development workflow that
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uses the Eclipse IDE and for a detailed example of how to install
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and configure the Eclipse Yocto Project Plug-in, see the
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"<link linkend='sdk-eclipse-project'>Developing Applications Using <trademark class='trade'>Eclipse</trademark></link>"
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Chapter.
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</para>
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</section>
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<section id='performance-enhancing-tools'>
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<title>Performance Enhancing Tools</title>
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<para>
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Supported performance enhancing tools are available that let you
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profile, debug, and perform tracing on your projects developed
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using Eclipse.
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For information on these tools see
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<ulink url='http://www.eclipse.org/linuxtools/'>http://www.eclipse.org/linuxtools/</ulink>.
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</para>
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</section>
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</section>
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<section id='sdk-development-model'>
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<title>SDK Development Model</title>
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<para>
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Fundamentally, the SDK fits into the development process as follows:
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<imagedata fileref="figures/sdk-environment.png" align="center" width="6in" depth="5in" scalefit="100" />
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The SDK is installed on any machine and can be used to develop
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applications, images, and kernels.
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An SDK can even be used by a QA Engineer or Release Engineer.
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The fundamental concept is that the machine that has the SDK installed
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does not have to be associated with the machine that has the
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Yocto Project installed.
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A developer can independently compile and test an object on their
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machine and then, when the object is ready for integration into an
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image, they can simply make it available to the machine that has the
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Yocto Project.
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Once the object is available, the image can be rebuilt using the
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Yocto Project to produce the modified image.
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</para>
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<para>
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You just need to follow these general steps:
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<orderedlist>
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<listitem><para><emphasis>Install the SDK for your target hardware:</emphasis>
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For information on how to install the SDK, see the
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"<link linkend='sdk-installing-the-sdk'>Installing the SDK</link>"
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section.</para></listitem>
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<listitem><para><emphasis>Download or Build the Target Image:</emphasis>
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The Yocto Project supports several target architectures
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and has many pre-built kernel images and root filesystem
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images.</para>
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<para>If you are going to develop your application on
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hardware, go to the
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<ulink url='&YOCTO_MACHINES_DL_URL;'><filename>machines</filename></ulink>
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||
|
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download area and choose a target machine area
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|
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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>
|
||
|
|
To use the root filesystem in QEMU, you
|
||
|
|
need to extract it.
|
||
|
|
See the
|
||
|
|
"<link linkend='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.
|
||
|
|
See the
|
||
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#dev-manual-qemu'>Using the Quick EMUlator (QEMU)</ulink>"
|
||
|
|
chapter in the Yocto Project Development Tasks 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
|
||
|
|
-->
|