Revert "poky: subtree update:b23aa6b753..ad30a6d470"
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This commit introduced openbmc/openbmc#3720 and no solution has been
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Change-Id: I2fb0d81eb26cf3dadb2f2abdd1a1bb7a95eaf03c
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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; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
+
+<chapter id='sdk-intro'>
+<title>Introduction</title>
+
+<section id='sdk-manual-intro'>
+ <title>Introduction</title>
+
+ <para>
+ Welcome to the Yocto Project Application Development and the
+ Extensible Software Development Kit (eSDK) manual.
+ This manual provides information that explains how to use both the
+ Yocto Project extensible and standard SDKs to develop
+ applications and images.
+ <note>
+ 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 tool-rich extensible SDK and the more
+ traditional standard SDK.
+ </note>
+ </para>
+
+ <para>
+ All SDKs consist of the following:
+ <itemizedlist>
+ <listitem><para>
+ <emphasis>Cross-Development Toolchain</emphasis>:
+ This toolchain contains a compiler, debugger, and various
+ miscellaneous tools.
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Libraries, Headers, and Symbols</emphasis>:
+ The libraries, headers, and symbols are specific to the image
+ (i.e. they match the image).
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Environment Setup Script</emphasis>:
+ This <filename>*.sh</filename> file, once run, sets up the
+ cross-development environment by defining variables and
+ preparing for SDK use.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ Additionally, an extensible SDK has 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_REF_URL;#build-system-term'>OpenEmbedded build system</ulink>.
+ </para>
+
+ <para>
+ You can use an SDK to independently develop and test code
+ that is destined to run on some target machine.
+ 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-compiler
+ toolchain binaries are produced for any given 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 every target still needs a sysroot because
+ those binaries are target-specific.
+ </para>
+
+ <para>
+ The SDK development environment consists of the following:
+ <itemizedlist>
+ <listitem><para>
+ The self-contained SDK, which is an
+ architecture-specific cross-toolchain and
+ matching sysroots (target and native) all built by the
+ OpenEmbedded build system (e.g. the SDK).
+ The toolchain and sysroots are based on a
+ <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>
+ configuration and extensions,
+ which allows you to cross-develop on the host machine for the
+ target hardware.
+ Additionally, the extensible SDK contains the
+ <filename>devtool</filename> functionality.
+ </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 the SDK.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ In summary, the extensible and standard SDK share many features.
+ However, the extensible SDK has powerful development tools to help you
+ more quickly develop applications.
+ Following is a table that summarizes the primary differences between
+ the standard and extensible SDK types when considering which to
+ build:
+ <informaltable frame='none'>
+ <tgroup cols='3' align='left' colsep='1' rowsep='1'>
+ <colspec colname='c1' colwidth='1*'/>
+ <colspec colname='c2' colwidth='1*'/>
+ <colspec colname='c3' colwidth='1*'/>
+ <thead>
+ <row>
+ <entry align="left"><emphasis>Feature</emphasis></entry>
+ <entry align="left"><emphasis>Standard SDK</emphasis></entry>
+ <entry align="left"><emphasis>Extensible SDK</emphasis></entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry align="left">Toolchain</entry>
+ <entry align="left">Yes</entry>
+ <entry align="left">Yes*</entry>
+ </row>
+ <row>
+ <entry align="left">Debugger</entry>
+ <entry align="left">Yes</entry>
+ <entry align="left">Yes*</entry>
+ </row>
+ <row>
+ <entry align="left">Size</entry>
+ <entry align="left">100+ MBytes</entry>
+ <entry align="left">1+ GBytes (or 300+ MBytes for minimal w/toolchain)</entry>
+ </row>
+ <row>
+ <entry align="left"><filename>devtool</filename></entry>
+ <entry align="left">No</entry>
+ <entry align="left">Yes</entry>
+ </row>
+ <row>
+ <entry align="left">Build Images</entry>
+ <entry align="left">No</entry>
+ <entry align="left">Yes</entry>
+ </row>
+ <row>
+ <entry align="left">Updateable</entry>
+ <entry align="left">No</entry>
+ <entry align="left">Yes</entry>
+ </row>
+ <row>
+ <entry align="left">Managed Sysroot**</entry>
+ <entry align="left">No</entry>
+ <entry align="left">Yes</entry>
+ </row>
+ <row>
+ <entry align="left">Installed Packages</entry>
+ <entry align="left">No***</entry>
+ <entry align="left">Yes****</entry>
+ </row>
+ <row>
+ <entry align="left">Construction</entry>
+ <entry align="left">Packages</entry>
+ <entry align="left">Shared State</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ <literallayout class='monospaced'>
+ * Extensible SDK contains 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.
+
+ ** Sysroot is managed through the use of <filename>devtool</filename>. Thus, it is less likely that you will corrupt your SDK sysroot when you try to add additional libraries.
+
+ *** You can add runtime package management to the standard SDK but it is not supported by default.
+
+ **** You must build and make the shared state available to extensible SDK users for "packages" you want to enable users to install.
+ </literallayout>
+ </para>
+
+ <section id='the-cross-development-toolchain'>
+ <title>The Cross-Development Toolchain</title>
+
+ <para>
+ The
+ <ulink url='&YOCTO_DOCS_REF_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.
+ Additionally, for an extensible SDK, the toolchain also has
+ built-in <filename>devtool</filename> functionality.
+ This toolchain is created by running a SDK installer script
+ or through a
+ <ulink url='&YOCTO_DOCS_REF_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
+ different ways:
+ <itemizedlist>
+ <listitem><para>
+ If you have cloned the <filename>poky</filename> Git
+ repository to create a
+ <ulink url='&YOCTO_DOCS_REF_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 Source Directory 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>
+
+<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
+ 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 linkend='sdk-installing-the-sdk'>Installing the SDK</link>"
+ section.
+ </para></listitem>
+ <listitem><para>
+ <emphasis>Download or Build 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 the 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 the extensible
+ and standard SDKs.
+ 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
+-->