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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-extensible'>
<title>Using the Extensible SDK</title>
<para>
This chapter describes the extensible SDK and how to install it.
Information covers the pieces of the SDK, how to install it, and
presents a look at using the <filename>devtool</filename>
functionality.
The extensible SDK makes it easy to add new applications and libraries
to an image, modify the source for an existing component, test
changes on the target hardware, and ease integration into the rest of
the
<ulink url='&YOCTO_DOCS_REF_URL;#build-system-term'>OpenEmbedded build system</ulink>.
<note>
For a side-by-side comparison of main features supported for an
extensible SDK as compared to a standard SDK, see the
"<link linkend='sdk-manual-intro'>Introduction</link>"
section.
</note>
</para>
<para>
In addition to the functionality available through
<filename>devtool</filename>, you can alternatively make use of the
toolchain directly, for example from Makefile, Autotools, and
Eclipse-based projects.
See the
"<link linkend='sdk-working-projects'>Using the SDK Toolchain Directly</link>"
chapter for more information.
</para>
<section id='sdk-extensible-sdk-intro'>
<title>Why use the Extensible SDK and What is in It?</title>
<para>
The extensible SDK provides a cross-development toolchain and
libraries tailored to the contents of a specific image.
You would use the Extensible SDK if you want a toolchain experience
supplemented with the powerful set of <filename>devtool</filename>
commands tailored for the Yocto Project environment.
</para>
<para>
The installed extensible SDK consists of several files and
directories.
Basically, it contains an SDK environment setup script, some
configuration files, an internal build system, and the
<filename>devtool</filename> functionality.
</para>
</section>
<section id='sdk-setting-up-to-use-the-extensible-sdk'>
<title>Setting Up to Use the Extensible SDK</title>
<para>
The first thing you need to do is install the SDK on your host
development machine by running the <filename>*.sh</filename>
installation script.
</para>
<para>
You can download a tarball installer, which includes the
pre-built toolchain, the <filename>runqemu</filename>
script, the internal build system, <filename>devtool</filename>,
and support files from the appropriate directory under
<ulink url='&YOCTO_TOOLCHAIN_DL_URL;'></ulink>.
Toolchains are available for 32-bit and 64-bit x86 development
systems from the <filename>i686</filename> and
<filename>x86_64</filename> directories, respectively.
The toolchains the Yocto Project provides are based off the
<filename>core-image-sato</filename> image and contain
libraries appropriate for developing against that image.
Each type of development system supports five or more target
architectures.
</para>
<para>
The names of the tarball installer scripts are such that a
string representing the host system appears first in the
filename and then is immediately followed by a string
representing the target architecture.
An extensible SDK has the string "-ext" as part of the name.
<literallayout class='monospaced'>
poky-glibc-<replaceable>host_system</replaceable>-<replaceable>image_type</replaceable>-<replaceable>arch</replaceable>-toolchain-ext-<replaceable>release_version</replaceable>.sh
Where:
<replaceable>host_system</replaceable> is a string representing your development system:
i686 or x86_64.
<replaceable>image_type</replaceable> is the image for which the SDK was built.
<replaceable>arch</replaceable> is a string representing the tuned target architecture:
i586, x86_64, powerpc, mips, armv7a or armv5te
<replaceable>release_version</replaceable> is a string representing the release number of the
Yocto Project:
&DISTRO;, &DISTRO;+snapshot
</literallayout>
For example, the following SDK installer is for a 64-bit
development host system and a i586-tuned target architecture
based off the SDK for <filename>core-image-sato</filename> and
using the current &DISTRO; snapshot:
<literallayout class='monospaced'>
poky-glibc-x86_64-core-image-sato-i586-toolchain-ext-&DISTRO;.sh
</literallayout>
<note>
As an alternative to downloading an SDK, you can build the
SDK installer.
For information on building the installer, see the
"<link linkend='sdk-building-an-sdk-installer'>Building an SDK Installer</link>"
section.
Another helpful resource for building an installer is the
<ulink url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/RunningEclipseAgainstBuiltImage'>Cookbook guide to Making an Eclipse Debug Capable Image</ulink>
wiki page.
This wiki page focuses on development when using the Eclipse
IDE.
</note>
</para>
<para>
The SDK and toolchains are self-contained and by default are
installed into the <filename>poky_sdk</filename> folder in your
home directory.
You can choose to install the extensible SDK in any location when
you run the installer.
However, the location you choose needs to be writable for whichever
users need to use the SDK, since files will need to be written
under that directory during the normal course of operation.
</para>
<para>
The following command shows how to run the installer given a
toolchain tarball for a 64-bit x86 development host system and
a 64-bit x86 target architecture.
The example assumes the SDK installer is located in
<filename>~/Downloads/</filename>.
<note>
If you do not have write permissions for the directory
into which you are installing the SDK, the installer
notifies you and exits.
Be sure you have write permissions in the directory and
run the installer again.
</note>
<literallayout class='monospaced'>
$ ./poky-glibc-x86_64-core-image-minimal-core2-64-toolchain-ext-&DISTRO;.sh
Poky (Yocto Project Reference Distro) Extensible SDK installer version &DISTRO;
===================================================================================
Enter target directory for SDK (default: ~/poky_sdk):
You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed[Y/n]? Y
Extracting SDK......................................................................done
Setting it up...
Extracting buildtools...
Preparing build system...
done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
$ . /home/scottrif/poky_sdk/environment-setup-core2-64-poky-linux
</literallayout>
</para>
</section>
<section id='sdk-running-the-extensible-sdk-environment-setup-script'>
<title>Running the Extensible SDK Environment Setup Script</title>
<para>
Once you have the SDK installed, you must run the SDK environment
setup script before you can actually use it.
This setup script resides in the directory you chose when you
installed the SDK, which is either the default
<filename>poky_sdk</filename> directory or the directory you
chose during installation.
</para>
<para>
Before running the script, be sure it is the one that matches the
architecture for which you are developing.
Environment setup scripts begin with the string
"<filename>environment-setup</filename>" and include as part of
their name the tuned target architecture.
As an example, the following commands set the working directory
to where the SDK was installed and then source the environment
setup script.
In this example, the setup script is for an IA-based
target machine using i586 tuning:
<literallayout class='monospaced'>
$ cd /home/scottrif/poky_sdk
$ source environment-setup-core2-64-poky-linux
SDK environment now set up; additionally you may now run devtool to perform development tasks.
Run devtool --help for further details.
</literallayout>
When you run the setup script, many environment variables are
defined:
<literallayout class='monospaced'>
<ulink url='&YOCTO_DOCS_REF_URL;#var-SDKTARGETSYSROOT'><filename>SDKTARGETSYSROOT</filename></ulink> - The path to the sysroot used for cross-compilation
<ulink url='&YOCTO_DOCS_REF_URL;#var-PKG_CONFIG_PATH'><filename>PKG_CONFIG_PATH</filename></ulink> - The path to the target pkg-config files
<ulink url='&YOCTO_DOCS_REF_URL;#var-CONFIG_SITE'><filename>CONFIG_SITE</filename></ulink> - A GNU autoconf site file preconfigured for the target
<ulink url='&YOCTO_DOCS_REF_URL;#var-CC'><filename>CC</filename></ulink> - The minimal command and arguments to run the C compiler
<ulink url='&YOCTO_DOCS_REF_URL;#var-CXX'><filename>CXX</filename></ulink> - The minimal command and arguments to run the C++ compiler
<ulink url='&YOCTO_DOCS_REF_URL;#var-CPP'><filename>CPP</filename></ulink> - The minimal command and arguments to run the C preprocessor
<ulink url='&YOCTO_DOCS_REF_URL;#var-AS'><filename>AS</filename></ulink> - The minimal command and arguments to run the assembler
<ulink url='&YOCTO_DOCS_REF_URL;#var-LD'><filename>LD</filename></ulink> - The minimal command and arguments to run the linker
<ulink url='&YOCTO_DOCS_REF_URL;#var-GDB'><filename>GDB</filename></ulink> - The minimal command and arguments to run the GNU Debugger
<ulink url='&YOCTO_DOCS_REF_URL;#var-STRIP'><filename>STRIP</filename></ulink> - The minimal command and arguments to run 'strip', which strips symbols
<ulink url='&YOCTO_DOCS_REF_URL;#var-RANLIB'><filename>RANLIB</filename></ulink> - The minimal command and arguments to run 'ranlib'
<ulink url='&YOCTO_DOCS_REF_URL;#var-OBJCOPY'><filename>OBJCOPY</filename></ulink> - The minimal command and arguments to run 'objcopy'
<ulink url='&YOCTO_DOCS_REF_URL;#var-OBJDUMP'><filename>OBJDUMP</filename></ulink> - The minimal command and arguments to run 'objdump'
<ulink url='&YOCTO_DOCS_REF_URL;#var-AR'><filename>AR</filename></ulink> - The minimal command and arguments to run 'ar'
<ulink url='&YOCTO_DOCS_REF_URL;#var-NM'><filename>NM</filename></ulink> - The minimal command and arguments to run 'nm'
<ulink url='&YOCTO_DOCS_REF_URL;#var-TARGET_PREFIX'><filename>TARGET_PREFIX</filename></ulink> - The toolchain binary prefix for the target tools
<ulink url='&YOCTO_DOCS_REF_URL;#var-CROSS_COMPILE'><filename>CROSS_COMPILE</filename></ulink> - The toolchain binary prefix for the target tools
<ulink url='&YOCTO_DOCS_REF_URL;#var-CONFIGURE_FLAGS'><filename>CONFIGURE_FLAGS</filename></ulink> - The minimal arguments for GNU configure
<ulink url='&YOCTO_DOCS_REF_URL;#var-CFLAGS'><filename>CFLAGS</filename></ulink> - Suggested C flags
<ulink url='&YOCTO_DOCS_REF_URL;#var-CXXFLAGS'><filename>CXXFLAGS</filename></ulink> - Suggested C++ flags
<ulink url='&YOCTO_DOCS_REF_URL;#var-LDFLAGS'><filename>LDFLAGS</filename></ulink> - Suggested linker flags when you use CC to link
<ulink url='&YOCTO_DOCS_REF_URL;#var-CPPFLAGS'><filename>CPPFLAGS</filename></ulink> - Suggested preprocessor flags
</literallayout>
</para>
</section>
<section id='using-devtool-in-your-sdk-workflow'>
<title>Using <filename>devtool</filename> in Your SDK Workflow</title>
<para>
The cornerstone of the extensible SDK is a command-line tool
called <filename>devtool</filename>.
This tool provides a number of features that help
you build, test and package software within the extensible SDK, and
optionally integrate it into an image built by the OpenEmbedded
build system.
<note><title>Tip</title>
The use of <filename>devtool</filename> is not limited to
the extensible SDK.
You can use <filename>devtool</filename> to help you easily
develop any project whose build output must be part of an
image built using the OpenEmbedded build system.
</note>
</para>
<para>
The <filename>devtool</filename> command line is organized
similarly to
<ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink> in that it has a
number of sub-commands for each function.
You can run <filename>devtool --help</filename> to see all the
commands.
<note>
See the
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-devtool-reference'><filename>devtool</filename>&nbsp;Quick Reference</ulink>"
in the Yocto Project Reference Manual for a
<filename>devtool</filename> quick reference.
</note>
</para>
<para>
Three <filename>devtool</filename> subcommands that provide
entry-points into development are:
<itemizedlist>
<listitem><para>
<emphasis><filename>devtool add</filename></emphasis>:
Assists in adding new software to be built.
</para></listitem>
<listitem><para>
<emphasis><filename>devtool modify</filename></emphasis>:
Sets up an environment to enable you to modify the source of
an existing component.
</para></listitem>
<listitem><para>
<emphasis><filename>devtool upgrade</filename></emphasis>:
Updates an existing recipe so that you can build it for
an updated set of source files.
</para></listitem>
</itemizedlist>
As with the OpenEmbedded build system, "recipes" represent software
packages within <filename>devtool</filename>.
When you use <filename>devtool add</filename>, a recipe is
automatically created.
When you use <filename>devtool modify</filename>, the specified
existing recipe is used in order to determine where to get the source
code and how to patch it.
In both cases, an environment is set up so that when you build the
recipe a source tree that is under your control is used in order to
allow you to make changes to the source as desired.
By default, both new recipes and the source go into a "workspace"
directory under the SDK.
</para>
<para>
The remainder of this section presents the
<filename>devtool add</filename>,
<filename>devtool modify</filename>, and
<filename>devtool upgrade</filename> workflows.
</para>
<section id='sdk-use-devtool-to-add-an-application'>
<title>Use <filename>devtool add</filename> to Add an Application</title>
<para>
The <filename>devtool add</filename> command generates
a new recipe based on existing source code.
This command takes advantage of the
<ulink url='&YOCTO_DOCS_REF_URL;#devtool-the-workspace-layer-structure'>workspace</ulink>
layer that many <filename>devtool</filename> commands
use.
The command is flexible enough to allow you to extract source
code into both the workspace or a separate local Git repository
and to use existing code that does not need to be extracted.
</para>
<para>
Depending on your particular scenario, the arguments and options
you use with <filename>devtool add</filename> form different
combinations.
The following diagram shows common development flows
you would use with the <filename>devtool add</filename>
command:
</para>
<para>
<imagedata fileref="figures/sdk-devtool-add-flow.png" align="center" />
</para>
<para>
<orderedlist>
<listitem><para><emphasis>Generating the New Recipe</emphasis>:
The top part of the flow shows three scenarios by which
you could use <filename>devtool add</filename> to
generate a recipe based on existing source code.</para>
<para>In a shared development environment, it is
typical where other developers are responsible for
various areas of source code.
As a developer, you are probably interested in using
that source code as part of your development using
the Yocto Project.
All you need is access to the code, a recipe, and a
controlled area in which to do your work.</para>
<para>Within the diagram, three possible scenarios
feed into the <filename>devtool add</filename> workflow:
<itemizedlist>
<listitem><para><emphasis>Left</emphasis>:
The left scenario represents a common situation
where the source code does not exist locally
and needs to be extracted.
In this situation, you just let it get
extracted to the default workspace - you do not
want it in some specific location outside of the
workspace.
Thus, everything you need will be located in the
workspace:
<literallayout class='monospaced'>
$ devtool add <replaceable>recipe fetchuri</replaceable>
</literallayout>
With this command, <filename>devtool</filename>
creates a recipe and an append file in the
workspace as well as extracts the upstream
source files into a local Git repository also
within the <filename>sources</filename> folder.
</para></listitem>
<listitem><para><emphasis>Middle</emphasis>:
The middle scenario also represents a situation where
the source code does not exist locally.
In this case, the code is again upstream
and needs to be extracted to some
local area - this time outside of the default
workspace.
If required, <filename>devtool</filename>
always creates
a Git repository locally during the extraction.
Furthermore, the first positional argument
<replaceable>srctree</replaceable> in this case
identifies where the
<filename>devtool add</filename> command
will locate the extracted code outside of the
workspace:
<literallayout class='monospaced'>
$ devtool add <replaceable>recipe srctree fetchuri</replaceable>
</literallayout>
In summary, the source code is pulled from
<replaceable>fetchuri</replaceable> and extracted
into the location defined by
<replaceable>srctree</replaceable> as a local
Git repository.</para>
<para>Within workspace, <filename>devtool</filename>
creates both the recipe and an append file
for the recipe.
</para></listitem>
<listitem><para><emphasis>Right</emphasis>:
The right scenario represents a situation
where the source tree (srctree) has been
previously prepared outside of the
<filename>devtool</filename> workspace.
</para>
<para>The following command names the recipe
and identifies where the existing source tree
is located:
<literallayout class='monospaced'>
$ devtool add <replaceable>recipe srctree</replaceable>
</literallayout>
The command examines the source code and creates
a recipe for it placing the recipe into the
workspace.</para>
<para>Because the extracted source code already exists,
<filename>devtool</filename> does not try to
relocate it into the workspace - just the new
the recipe is placed in the workspace.</para>
<para>Aside from a recipe folder, the command
also creates an append folder and places an initial
<filename>*.bbappend</filename> within.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para><emphasis>Edit the Recipe</emphasis>:
At this point, you can use <filename>devtool edit-recipe</filename>
to open up the editor as defined by the
<filename>$EDITOR</filename> environment variable
and modify the file:
<literallayout class='monospaced'>
$ devtool edit-recipe <replaceable>recipe</replaceable>
</literallayout>
From within the editor, you can make modifications to the
recipe that take affect when you build it later.
</para></listitem>
<listitem><para><emphasis>Build the Recipe or Rebuild the Image</emphasis>:
At this point in the flow, the next step you
take depends on what you are going to do with
the new code.</para>
<para>If you need to take the build output and eventually
move it to the target hardware, you would use
<filename>devtool build</filename>:
<literallayout class='monospaced'>
$ devtool build <replaceable>recipe</replaceable>
</literallayout></para>
<para>On the other hand, if you want an image to
contain the recipe's packages for immediate deployment
onto a device (e.g. for testing purposes), you can use
the <filename>devtool build-image</filename> command:
<literallayout class='monospaced'>
$ devtool build-image <replaceable>image</replaceable>
</literallayout>
</para></listitem>
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
When you use the <filename>devtool build</filename>
command to build out your recipe, you probably want to
see if the resulting build output works as expected on target
hardware.
<note>
This step assumes you have a previously built
image that is already either running in QEMU or
running on actual hardware.
Also, it is assumed that for deployment of the image
to the target, SSH is installed in the image and if
the image is running on real hardware that you have
network access to and from your development machine.
</note>
You can deploy your build output to that target hardware by
using the <filename>devtool deploy-target</filename> command:
<literallayout class='monospaced'>
$ devtool deploy-target <replaceable>recipe target</replaceable>
</literallayout>
The <replaceable>target</replaceable> is a live target machine
running as an SSH server.</para>
<para>You can, of course, also deploy the image you build
using the <filename>devtool build-image</filename> command
to actual hardware.
However, <filename>devtool</filename> does not provide a
specific command that allows you to do this.
</para></listitem>
<listitem><para>
<emphasis>Finish Your Work With the Recipe</emphasis>:
The <filename>devtool finish</filename> command creates
any patches corresponding to commits in the local
Git repository, moves the new recipe to a more permanent
layer, and then resets the recipe so that the recipe is
built normally rather than from the workspace.
<literallayout class='monospaced'>
$ devtool finish <replaceable>recipe layer</replaceable>
</literallayout>
<note>
Any changes you want to turn into patches must be
committed to the Git repository in the source tree.
</note></para>
<para>As mentioned, the <filename>devtool finish</filename>
command moves the final recipe to its permanent layer.
</para>
<para>As a final process of the
<filename>devtool finish</filename> command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
<note>
You can use the <filename>devtool reset</filename>
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
</note>
</para></listitem>
</orderedlist>
</para>
</section>
<section id='sdk-devtool-use-devtool-modify-to-modify-the-source-of-an-existing-component'>
<title>Use <filename>devtool modify</filename> to Modify the Source of an Existing Component</title>
<para>
The <filename>devtool modify</filename> command prepares the
way to work on existing code that already has a recipe in
place.
The command is flexible enough to allow you to extract code,
specify the existing recipe, and keep track of and gather any
patch files from other developers that are
associated with the code.
</para>
<para>
Depending on your particular scenario, the arguments and options
you use with <filename>devtool modify</filename> form different
combinations.
The following diagram shows common development flows
you would use with the <filename>devtool modify</filename>
command:
</para>
<para>
<imagedata fileref="figures/sdk-devtool-modify-flow.png" align="center" />
</para>
<para>
<orderedlist>
<listitem><para><emphasis>Preparing to Modify the Code</emphasis>:
The top part of the flow shows three scenarios by which
you could use <filename>devtool modify</filename> to
prepare to work on source files.
Each scenario assumes the following:
<itemizedlist>
<listitem><para>The recipe exists in some layer external
to the <filename>devtool</filename> workspace.
</para></listitem>
<listitem><para>The source files exist upstream in an
un-extracted state or locally in a previously
extracted state.
</para></listitem>
</itemizedlist>
The typical situation is where another developer has
created some layer for use with the Yocto Project and
their recipe already resides in that layer.
Furthermore, their source code is readily available
either upstream or locally.
<itemizedlist>
<listitem><para><emphasis>Left</emphasis>:
The left scenario represents a common situation
where the source code does not exist locally
and needs to be extracted.
In this situation, the source is extracted
into the default workspace location.
The recipe, in this scenario, is in its own
layer outside the workspace
(i.e.
<filename>meta-</filename><replaceable>layername</replaceable>).
</para>
<para>The following command identifies the recipe
and by default extracts the source files:
<literallayout class='monospaced'>
$ devtool modify <replaceable>recipe</replaceable>
</literallayout>
Once <filename>devtool</filename>locates the recipe,
it uses the
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
variable to locate the source code and
any local patch files from other developers are
located.
<note>
You cannot provide an URL for
<replaceable>srctree</replaceable> when using the
<filename>devtool modify</filename> command.
</note>
With this scenario, however, since no
<replaceable>srctree</replaceable> argument exists, the
<filename>devtool modify</filename> command by default
extracts the source files to a Git structure.
Furthermore, the location for the extracted source is the
default area within the workspace.
The result is that the command sets up both the source
code and an append file within the workspace with the
recipe remaining in its original location.
</para></listitem>
<listitem><para><emphasis>Middle</emphasis>:
The middle scenario represents a situation where
the source code also does not exist locally.
In this case, the code is again upstream
and needs to be extracted to some
local area as a Git repository.
The recipe, in this scenario, is again in its own
layer outside the workspace.</para>
<para>The following command tells
<filename>devtool</filename> what recipe with
which to work and, in this case, identifies a local
area for the extracted source files that is outside
of the default workspace:
<literallayout class='monospaced'>
$ devtool modify <replaceable>recipe srctree</replaceable>
</literallayout>
As with all extractions, the command uses
the recipe's <filename>SRC_URI</filename> to locate the
source files.
Once the files are located, the command by default
extracts them.
Providing the <replaceable>srctree</replaceable>
argument instructs <filename>devtool</filename> where
to place the extracted source.</para>
<para>Within workspace, <filename>devtool</filename>
creates an append file for the recipe.
The recipe remains in its original location but
the source files are extracted to the location you
provided with <replaceable>srctree</replaceable>.
</para></listitem>
<listitem><para><emphasis>Right</emphasis>:
The right scenario represents a situation
where the source tree
(<replaceable>srctree</replaceable>) exists as a
previously extracted Git structure outside of
the <filename>devtool</filename> workspace.
In this example, the recipe also exists
elsewhere in its own layer.
</para>
<para>The following command tells
<filename>devtool</filename> the recipe
with which to work, uses the "-n" option to indicate
source does not need to be extracted, and uses
<replaceable>srctree</replaceable> to point to the
previously extracted source files:
<literallayout class='monospaced'>
$ devtool modify -n <replaceable>recipe srctree</replaceable>
</literallayout>
</para>
<para>Once the command finishes, it creates only
an append file for the recipe in the workspace.
The recipe and the source code remain in their
original locations.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para><emphasis>Edit the Source</emphasis>:
Once you have used the <filename>devtool modify</filename>
command, you are free to make changes to the source
files.
You can use any editor you like to make and save
your source code modifications.
</para></listitem>
<listitem><para><emphasis>Build the Recipe</emphasis>:
Once you have updated the source files, you can build
the recipe.
</para></listitem>
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
When you use the <filename>devtool build</filename>
command to build out your recipe, you probably want to see
if the resulting build output works as expected on target
hardware.
<note>
This step assumes you have a previously built
image that is already either running in QEMU or
running on actual hardware.
Also, it is assumed that for deployment of the image
to the target, SSH is installed in the image and if
the image is running on real hardware that you have
network access to and from your development machine.
</note>
You can deploy your build output to that target hardware by
using the <filename>devtool deploy-target</filename> command:
<literallayout class='monospaced'>
$ devtool deploy-target <replaceable>recipe target</replaceable>
</literallayout>
The <replaceable>target</replaceable> is a live target machine
running as an SSH server.</para>
<para>You can, of course, also deploy the image you build
using the <filename>devtool build-image</filename> command
to actual hardware.
However, <filename>devtool</filename> does not provide a
specific command that allows you to do this.
</para></listitem>
<listitem><para>
<emphasis>Finish Your Work With the Recipe</emphasis>:
The <filename>devtool finish</filename> command creates
any patches corresponding to commits in the local
Git repository, updates the recipe to point to them
(or creates a <filename>.bbappend</filename> file to do
so, depending on the specified destination layer), and
then resets the recipe so that the recipe is built normally
rather than from the workspace.
<literallayout class='monospaced'>
$ devtool finish <replaceable>recipe layer</replaceable>
</literallayout>
<note>
Any changes you want to turn into patches must be
committed to the Git repository in the source tree.
</note></para>
<para>Because there is no need to move the recipe,
<filename>devtool finish</filename> either updates the
original recipe in the original layer or the command
creates a <filename>.bbappend</filename> in a different
layer as provided by <replaceable>layer</replaceable>.
</para>
<para>As a final process of the
<filename>devtool finish</filename> command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
<note>
You can use the <filename>devtool reset</filename>
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
</note>
</para></listitem>
</orderedlist>
</para>
</section>
<section id='sdk-devtool-use-devtool-upgrade-to-create-a-version-of-the-recipe-that-supports-a-newer-version-of-the-software'>
<title>Use <filename>devtool upgrade</filename> to Create a Version of the Recipe that Supports a Newer Version of the Software</title>
<para>
The <filename>devtool upgrade</filename> command updates
an existing recipe so that you can build it for an updated
set of source files.
The command is flexible enough to allow you to specify
source code revision and versioning schemes, extract code into
or out of the <filename>devtool</filename> workspace, and
work with any source file forms that the fetchers support.
</para>
<para>
Depending on your particular scenario, the arguments and options
you use with <filename>devtool upgrade</filename> form different
combinations.
The following diagram shows a common development flow
you would use with the <filename>devtool modify</filename>
command:
</para>
<para>
<imagedata fileref="figures/sdk-devtool-upgrade-flow.png" align="center" />
</para>
<para>
<orderedlist>
<listitem><para><emphasis>Initiate the Upgrade</emphasis>:
The top part of the flow shows a typical scenario by which
you could use <filename>devtool upgrade</filename>.
The following conditions exist:
<itemizedlist>
<listitem><para>The recipe exists in some layer external
to the <filename>devtool</filename> workspace.
</para></listitem>
<listitem><para>The source files for the new release
exist adjacent to the same location pointed to by
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
in the recipe (e.g. a tarball with the new version
number in the name, or as a different revision in
the upstream Git repository).
</para></listitem>
</itemizedlist>
A common situation is where third-party software has
undergone a revision so that it has been upgraded.
The recipe you have access to is likely in your own layer.
Thus, you need to upgrade the recipe to use the
newer version of the software:
<literallayout class='monospaced'>
$ devtool upgrade -V <replaceable>version recipe</replaceable>
</literallayout>
By default, the <filename>devtool upgrade</filename> command
extracts source code into the <filename>sources</filename>
directory in the workspace.
If you want the code extracted to any other location, you
need to provide the <replaceable>srctree</replaceable>
positional argument with the command as follows:
<literallayout class='monospaced'>
$ devtool upgrade -V <replaceable>version recipe srctree</replaceable>
</literallayout>
Also, in this example, the "-V" option is used to specify
the new version.
If the source files pointed to by the
<filename>SRC_URI</filename> statement in the recipe are
in a Git repository, you must provide the "-S" option and
specify a revision for the software.</para>
<para>Once <filename>devtool</filename> locates the recipe,
it uses the <filename>SRC_URI</filename> variable to locate
the source code and any local patch files from other
developers are located.
The result is that the command sets up the source
code, the new version of the recipe, and an append file
all within the workspace.
</para></listitem>
<listitem><para><emphasis>Resolve any Conflicts created by the Upgrade</emphasis>:
At this point, there could be some conflicts due to the
software being upgraded to a new version.
This would occur if your recipe specifies some patch files in
<filename>SRC_URI</filename> that conflict with changes
made in the new version of the software.
If this is the case, you need to resolve the conflicts
by editing the source and following the normal
<filename>git rebase</filename> conflict resolution
process.</para>
<para>Before moving onto the next step, be sure to resolve any
such conflicts created through use of a newer or different
version of the software.
</para></listitem>
<listitem><para><emphasis>Build the Recipe</emphasis>:
Once you have your recipe in order, you can build it.
You can either use <filename>devtool build</filename> or
<filename>bitbake</filename>.
Either method produces build output that is stored
in
<ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>.
</para></listitem>
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
When you use the <filename>devtool build</filename>
command or <filename>bitbake</filename> to build out your
recipe, you probably want to see if the resulting build
output works as expected on target hardware.
<note>
This step assumes you have a previously built
image that is already either running in QEMU or
running on actual hardware.
Also, it is assumed that for deployment of the image
to the target, SSH is installed in the image and if
the image is running on real hardware that you have
network access to and from your development machine.
</note>
You can deploy your build output to that target hardware by
using the <filename>devtool deploy-target</filename> command:
<literallayout class='monospaced'>
$ devtool deploy-target <replaceable>recipe target</replaceable>
</literallayout>
The <replaceable>target</replaceable> is a live target machine
running as an SSH server.</para>
<para>You can, of course, also deploy the image you build
using the <filename>devtool build-image</filename> command
to actual hardware.
However, <filename>devtool</filename> does not provide a
specific command that allows you to do this.
</para></listitem>
<listitem><para>
<emphasis>Finish Your Work With the Recipe</emphasis>:
The <filename>devtool finish</filename> command creates
any patches corresponding to commits in the local
Git repository, moves the new recipe to a more permanent
layer, and then resets the recipe so that the recipe is
built normally rather than from the workspace.
If you specify a destination layer that is the same as
the original source, then the old version of the
recipe and associated files will be removed prior to
adding the new version.
<literallayout class='monospaced'>
$ devtool finish <replaceable>recipe layer</replaceable>
</literallayout>
<note>
Any changes you want to turn into patches must be
committed to the Git repository in the source tree.
</note></para>
<para>As a final process of the
<filename>devtool finish</filename> command, the state
of the standard layers and the upstream source is
restored so that you can build the recipe from those
areas rather than the workspace.
<note>
You can use the <filename>devtool reset</filename>
command to put things back should you decide you
do not want to proceed with your work.
If you do use this command, realize that the source
tree is preserved.
</note>
</para></listitem>
</orderedlist>
</para>
</section>
</section>
<section id='sdk-a-closer-look-at-devtool-add'>
<title>A Closer Look at <filename>devtool add</filename></title>
<para>
The <filename>devtool add</filename> command automatically creates a
recipe based on the source tree with which you provide it.
Currently, the command has support for the following:
<itemizedlist>
<listitem><para>
Autotools (<filename>autoconf</filename> and
<filename>automake</filename>)
</para></listitem>
<listitem><para>
CMake
</para></listitem>
<listitem><para>
Scons
</para></listitem>
<listitem><para>
<filename>qmake</filename>
</para></listitem>
<listitem><para>
Plain <filename>Makefile</filename>
</para></listitem>
<listitem><para>
Out-of-tree kernel module
</para></listitem>
<listitem><para>
Binary package (i.e. "-b" option)
</para></listitem>
<listitem><para>
Node.js module
</para></listitem>
<listitem><para>
Python modules that use <filename>setuptools</filename>
or <filename>distutils</filename>
</para></listitem>
</itemizedlist>
</para>
<para>
Apart from binary packages, the determination of how a source tree
should be treated is automatic based on the files present within
that source tree.
For example, if a <filename>CMakeLists.txt</filename> file is found,
then the source tree is assumed to be using
CMake and is treated accordingly.
<note>
In most cases, you need to edit the automatically generated
recipe in order to make it build properly.
Typically, you would go through several edit and build cycles
until you can build the recipe.
Once the recipe can be built, you could use possible further
iterations to test the recipe on the target device.
</note>
</para>
<para>
The remainder of this section covers specifics regarding how parts
of the recipe are generated.
</para>
<section id='sdk-name-and-version'>
<title>Name and Version</title>
<para>
If you do not specify a name and version on the command
line, <filename>devtool add</filename> attempts to determine
the name and version of the software being built from
various metadata within the source tree.
Furthermore, the command sets the name of the created recipe
file accordingly.
If the name or version cannot be determined, the
<filename>devtool add</filename> command prints an error and
you must re-run the command with both the name and version
or just the name or version specified.
</para>
<para>
Sometimes the name or version determined from the source tree
might be incorrect.
For such a case, you must reset the recipe:
<literallayout class='monospaced'>
$ devtool reset -n <replaceable>recipename</replaceable>
</literallayout>
After running the <filename>devtool reset</filename> command,
you need to run <filename>devtool add</filename> again and
provide the name or the version.
</para>
</section>
<section id='sdk-dependency-detection-and-mapping'>
<title>Dependency Detection and Mapping</title>
<para>
The <filename>devtool add</filename> command attempts to
detect build-time dependencies and map them to other recipes
in the system.
During this mapping, the command fills in the names of those
recipes in the
<ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink>
value within the recipe.
If a dependency cannot be mapped, then a comment is placed in
the recipe indicating such.
The inability to map a dependency might be caused because the
naming is not recognized or because the dependency simply is
not available.
For cases where the dependency is not available, you must use
the <filename>devtool add</filename> command to add an
additional recipe to satisfy the dependency and then come
back to the first recipe and add its name to
<filename>DEPENDS</filename>.
</para>
<para>
If you need to add runtime dependencies, you can do so by
adding the following to your recipe:
<literallayout class='monospaced'>
RDEPENDS_${PN} += "dependency1 dependency2 ..."
</literallayout>
<note>
The <filename>devtool add</filename> command often cannot
distinguish between mandatory and optional dependencies.
Consequently, some of the detected dependencies might
in fact be optional.
When in doubt, consult the documentation or the configure
script for the software the recipe is building for further
details.
In some cases, you might find you can substitute the
dependency for an option to disable the associated
functionality passed to the configure script.
</note>
</para>
</section>
<section id='sdk-license-detection'>
<title>License Detection</title>
<para>
The <filename>devtool add</filename> command attempts to
determine if the software you are adding is able to be
distributed under a common open-source license and sets the
<ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE</filename></ulink>
value accordingly.
You should double-check this value against the documentation
or source files for the software you are building and update
that <filename>LICENSE</filename> value if necessary.
</para>
<para>
The <filename>devtool add</filename> command also sets the
<ulink url='&YOCTO_DOCS_REF_URL;#var-LIC_FILES_CHKSUM'><filename>LIC_FILES_CHKSUM</filename></ulink>
value to point to all files that appear to be license-related.
However, license statements often appear in comments at the top
of source files or within documentation.
Consequently, you might need to amend the
<filename>LIC_FILES_CHKSUM</filename> variable to point to one
or more of those comments if present.
Setting <filename>LIC_FILES_CHKSUM</filename> is particularly
important for third-party software.
The mechanism attempts to ensure correct licensing should you
upgrade the recipe to a newer upstream version in future.
Any change in licensing is detected and you receive an error
prompting you to check the license text again.
</para>
<para>
If the <filename>devtool add</filename> command cannot
determine licensing information, the
<filename>LICENSE</filename> value is set to "CLOSED" and the
<filename>LIC_FILES_CHKSUM</filename> value remains unset.
This behavior allows you to continue with development but is
unlikely to be correct in all cases.
Consequently, you should check the documentation or source
files for the software you are building to determine the actual
license.
</para>
</section>
<section id='sdk-adding-makefile-only-software'>
<title>Adding Makefile-Only Software</title>
<para>
The use of <filename>make</filename> by itself is very common
in both proprietary and open source software.
Unfortunately, Makefiles are often not written with
cross-compilation in mind.
Thus, <filename>devtool add</filename> often cannot do very
much to ensure that these Makefiles build correctly.
It is very common, for example, to explicitly call
<filename>gcc</filename> instead of using the
<ulink url='&YOCTO_DOCS_REF_URL;#var-CC'><filename>CC</filename></ulink>
variable.
Usually, in a cross-compilation environment,
<filename>gcc</filename> is the compiler for the build host
and the cross-compiler is named something similar to
<filename>arm-poky-linux-gnueabi-gcc</filename> and might
require some arguments (e.g. to point to the associated sysroot
for the target machine).
</para>
<para>
When writing a recipe for Makefile-only software, keep the
following in mind:
<itemizedlist>
<listitem><para>
You probably need to patch the Makefile to use
variables instead of hardcoding tools within the
toolchain such as <filename>gcc</filename> and
<filename>g++</filename>.
</para></listitem>
<listitem><para>
The environment in which <filename>make</filename> runs
is set up with various standard variables for
compilation (e.g. <filename>CC</filename>,
<filename>CXX</filename>, and so forth) in a similar
manner to the environment set up by the SDK's
environment setup script.
One easy way to see these variables is to run the
<filename>devtool build</filename> command on the
recipe and then look in
<filename>oe-logs/run.do_compile</filename>.
Towards the top of this file you will see a list of
environment variables that are being set.
You can take advantage of these variables within the
Makefile.
</para></listitem>
<listitem><para>
If the Makefile sets a default for a variable using "=",
that default overrides the value set in the environment,
which is usually not desirable.
In this situation, you can either patch the Makefile
so it sets the default using the "?=" operator, or
you can alternatively force the value on the
<filename>make</filename> command line.
To force the value on the command line, add the
variable setting to
<ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OEMAKE'><filename>EXTRA_OEMAKE</filename></ulink>
or
<ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGECONFIG_CONFARGS'><filename>PACKAGECONFIG_CONFARGS</filename></ulink>
within the recipe.
Here is an example using <filename>EXTRA_OEMAKE</filename>:
<literallayout class='monospaced'>
EXTRA_OEMAKE += "'CC=${CC}' 'CXX=${CXX}'"
</literallayout>
In the above example, single quotes are used around the
variable settings as the values are likely to contain
spaces because required default options are passed to
the compiler.
</para></listitem>
<listitem><para>
Hardcoding paths inside Makefiles is often problematic
in a cross-compilation environment.
This is particularly true because those hardcoded paths
often point to locations on the build host and thus
will either be read-only or will introduce
contamination into the cross-compilation by virtue of
being specific to the build host rather than the target.
Patching the Makefile to use prefix variables or other
path variables is usually the way to handle this.
</para></listitem>
<listitem><para>
Sometimes a Makefile runs target-specific commands such
as <filename>ldconfig</filename>.
For such cases, you might be able to simply apply
patches that remove these commands from the Makefile.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='sdk-adding-native-tools'>
<title>Adding Native Tools</title>
<para>
Often, you need to build additional tools that run on the
build host system as opposed to the target.
You should indicate this using one of the following methods
when you run <filename>devtool add</filename>:
<itemizedlist>
<listitem><para>
Specify the name of the recipe such that it ends
with "-native".
Specifying the name like this produces a recipe that
only builds for the build host.
</para></listitem>
<listitem><para>
Specify the "&dash;&dash;also-native" option with the
<filename>devtool add</filename> command.
Specifying this option creates a recipe file that still
builds for the target but also creates a variant with
a "-native" suffix that builds for the build host.
</para></listitem>
</itemizedlist>
<note>
If you need to add a tool that is shipped as part of a
source tree that builds code for the target, you can
typically accomplish this by building the native and target
parts separately rather than within the same compilation
process.
Realize though that with the "&dash;&dash;also-native" option, you
can add the tool using just one recipe file.
</note>
</para>
</section>
<section id='sdk-adding-node-js-modules'>
<title>Adding Node.js Modules</title>
<para>
You can use the <filename>devtool add</filename> command two
different ways to add Node.js modules: 1) Through
<filename>npm</filename> and, 2) from a repository or local
source.
</para>
<para>
Use the following form to add Node.js modules through
<filename>npm</filename>:
<literallayout class='monospaced'>
$ devtool add "npm://registry.npmjs.org;name=forever;version=0.15.1"
</literallayout>
The name and version parameters are mandatory.
Lockdown and shrinkwrap files are generated and pointed to by
the recipe in order to freeze the version that is fetched for
the dependencies according to the first time.
This also saves checksums that are verified on future fetches.
Together, these behaviors ensure the reproducibility and
integrity of the build.
<note><title>Notes</title>
<itemizedlist>
<listitem><para>
You must use quotes around the URL.
The <filename>devtool add</filename> does not require
the quotes, but the shell considers ";" as a splitter
between multiple commands.
Thus, without the quotes,
<filename>devtool add</filename> does not receive the
other parts, which results in several "command not
found" errors.
</para></listitem>
<listitem><para>
In order to support adding
Node.js modules, a
<filename>nodejs</filename> recipe must be part of your
SDK in order to provide Node.js
itself.
</para></listitem>
</itemizedlist>
</note>
</para>
<para>
As mentioned earlier, you can also add Node.js modules
directly from a repository or local source tree.
To add modules this way, use <filename>devtool add</filename> in
the following form:
<literallayout class='monospaced'>
$ devtool add https://github.com/diversario/node-ssdp
</literallayout>
In this example, <filename>devtool</filename> fetches the specified
Git repository, detects that the code is Node.js code, fetches
dependencies using <filename>npm</filename>, and sets
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
accordingly.
</para>
</section>
</section>
<section id='sdk-working-with-recipes'>
<title>Working With Recipes</title>
<para>
When building a recipe with <filename>devtool build</filename>, the
typical build progression is as follows:
<orderedlist>
<listitem><para>
Fetch the source
</para></listitem>
<listitem><para>
Unpack the source
</para></listitem>
<listitem><para>
Configure the source
</para></listitem>
<listitem><para>
Compiling the source
</para></listitem>
<listitem><para>
Install the build output
</para></listitem>
<listitem><para>
Package the installed output
</para></listitem>
</orderedlist>
For recipes in the workspace, fetching and unpacking is disabled
as the source tree has already been prepared and is persistent.
Each of these build steps is defined as a function, usually with a
"do_" prefix.
These functions are typically shell scripts but can instead be written
in Python.
</para>
<para>
If you look at the contents of a recipe, you will see that the
recipe does not include complete instructions for building the
software.
Instead, common functionality is encapsulated in classes inherited
with the <filename>inherit</filename> directive, leaving the recipe
to describe just the things that are specific to the software to be
built.
A <ulink url='&YOCTO_DOCS_REF_URL;#ref-classes-base'><filename>base</filename></ulink>
class exists that is implicitly inherited by all recipes and provides
the functionality that most typical recipes need.
</para>
<para>
The remainder of this section presents information useful when
working with recipes.
</para>
<section id='sdk-finding-logs-and-work-files'>
<title>Finding Logs and Work Files</title>
<para>
When you are debugging a recipe that you previously created using
<filename>devtool add</filename> or whose source you are modifying
by using the <filename>devtool modify</filename> command, after
the first run of <filename>devtool build</filename>, you will
find some symbolic links created within the source tree:
<filename>oe-logs</filename>, which points to the directory in
which log files and run scripts for each build step are created
and <filename>oe-workdir</filename>, which points to the temporary
work area for the recipe.
You can use these links to get more information on what is
happening at each build step.
</para>
<para>
These locations under <filename>oe-workdir</filename> are
particularly useful:
<itemizedlist>
<listitem><para><filename>image/</filename>:
Contains all of the files installed at the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink>
stage.
Within a recipe, this directory is referred to by the
expression
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-D'><filename>D</filename></ulink><filename>}</filename>.
</para></listitem>
<listitem><para><filename>sysroot-destdir/</filename>:
Contains a subset of files installed within
<filename>do_install</filename> that have been put into the
shared sysroot.
For more information, see the
"<link linkend='sdk-sharing-files-between-recipes'>Sharing Files Between Recipes</link>"
section.
</para></listitem>
<listitem><para><filename>packages-split/</filename>:
Contains subdirectories for each package produced by the
recipe.
For more information, see the
"<link linkend='sdk-packaging'>Packaging</link>" section.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='sdk-setting-configure-arguments'>
<title>Setting Configure Arguments</title>
<para>
If the software your recipe is building uses GNU autoconf,
then a fixed set of arguments is passed to it to enable
cross-compilation plus any extras specified by
<ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OECONF'><filename>EXTRA_OECONF</filename></ulink>
or
<ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGECONFIG_CONFARGS'><filename>PACKAGECONFIG_CONFARGS</filename></ulink>
set within the recipe.
If you wish to pass additional options, add them to
<filename>EXTRA_OECONF</filename> or
<filename>PACKAGECONFIG_CONFARGS</filename>.
Other supported build tools have similar variables
(e.g.
<ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OECMAKE'><filename>EXTRA_OECMAKE</filename></ulink>
for CMake,
<ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OESCONS'><filename>EXTRA_OESCONS</filename></ulink>
for Scons, and so forth).
If you need to pass anything on the <filename>make</filename>
command line, you can use <filename>EXTRA_OEMAKE</filename> or the
<ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGECONFIG_CONFARGS'><filename>PACKAGECONFIG_CONFARGS</filename></ulink>
variables to do so.
</para>
<para>
You can use the <filename>devtool configure-help</filename> command
to help you set the arguments listed in the previous paragraph.
The command determines the exact options being passed, and shows
them to you along with any custom arguments specified through
<filename>EXTRA_OECONF</filename> or
<filename>PACKAGECONFIG_CONFARGS</filename>.
If applicable, the command also shows you the output of the
configure script's "&dash;&dash;help" option as a reference.
</para>
</section>
<section id='sdk-sharing-files-between-recipes'>
<title>Sharing Files Between Recipes</title>
<para>
Recipes often need to use files provided by other recipes on
the build host.
For example, an application linking to a common library needs
access to the library itself and its associated headers.
The way this access is accomplished within the extensible SDK is
through the sysroot.
One sysroot exists per "machine" for which the SDK is being built.
In practical terms, this means a sysroot exists for the target
machine, and a sysroot exists for the build host.
</para>
<para>
Recipes should never write files directly into the sysroot.
Instead, files should be installed into standard locations
during the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink>
task within the
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-D'><filename>D</filename></ulink><filename>}</filename>
directory.
A subset of these files automatically go into the sysroot.
The reason for this limitation is that almost all files that go
into the sysroot are cataloged in manifests in order to ensure
they can be removed later when a recipe is modified or removed.
Thus, the sysroot is able to remain free from stale files.
</para>
</section>
<section id='sdk-packaging'>
<title>Packaging</title>
<para>
Packaging is not always particularly relevant within the
extensible SDK.
However, if you examine how build output gets into the final image
on the target device, it is important to understand packaging
because the contents of the image are expressed in terms of
packages and not recipes.
</para>
<para>
During the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-package'><filename>do_package</filename></ulink>
task, files installed during the
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink>
task are split into one main package, which is almost always named
the same as the recipe, and several other packages.
This separation is done because not all of those installed files
are always useful in every image.
For example, you probably do not need any of the documentation
installed in a production image.
Consequently, for each recipe the documentation files are separated
into a <filename>-doc</filename> package.
Recipes that package software that has optional modules or
plugins might do additional package splitting as well.
</para>
<para>
After building a recipe you can see where files have gone by
looking in the <filename>oe-workdir/packages-split</filename>
directory, which contains a subdirectory for each package.
Apart from some advanced cases, the
<ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGES'><filename>PACKAGES</filename></ulink>
and
<ulink url='&YOCTO_DOCS_REF_URL;#var-FILES'><filename>FILES</filename></ulink>
variables controls splitting.
The <filename>PACKAGES</filename> variable lists all of the
packages to be produced, while the <filename>FILES</filename>
variable specifies which files to include in each package,
using an override to specify the package.
For example, <filename>FILES_${PN}</filename> specifies the files
to go into the main package (i.e. the main package is named the
same as the recipe and
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename>
evaluates to the recipe name).
The order of the <filename>PACKAGES</filename> value is significant.
For each installed file, the first package whose
<filename>FILES</filename> value matches the file is the package
into which the file goes.
Defaults exist for both the <filename>PACKAGES</filename> and
<filename>FILES</filename> variables.
Consequently, you might find you do not even need to set these
variables in your recipe unless the software the recipe is
building installs files into non-standard locations.
</para>
</section>
</section>
<section id='sdk-restoring-the-target-device-to-its-original-state'>
<title>Restoring the Target Device to its Original State</title>
<para>
If you use the <filename>devtool deploy-target</filename>
command to write a recipe's build output to the target, and
you are working on an existing component of the system, then you
might find yourself in a situation where you need to restore the
original files that existed prior to running the
<filename>devtool deploy-target</filename> command.
Because the <filename>devtool deploy-target</filename> command
backs up any files it overwrites, you can use the
<filename>devtool undeploy-target</filename> to restore those files
and remove any other files the recipe deployed.
Consider the following example:
<literallayout class='monospaced'>
$ devtool undeploy-target lighttpd root@192.168.7.2
</literallayout>
If you have deployed multiple applications, you can remove them
all at once thus restoring the target device back to its
original state:
<literallayout class='monospaced'>
$ devtool undeploy-target -a root@192.168.7.2
</literallayout>
Information about files deployed to the target as well as any
backed up files are stored on the target itself.
This storage of course requires some additional space
on the target machine.
<note>
The <filename>devtool deploy-target</filename> and
<filename>devtool undeploy-target</filename> command do not
currently interact with any package management system on the
target device (e.g. RPM or OPKG).
Consequently, you should not intermingle operations
<filename>devtool deploy-target</filename> and the package
manager operations on the target device.
Doing so could result in a conflicting set of files.
</note>
</para>
</section>
<section id='sdk-installing-additional-items-into-the-extensible-sdk'>
<title>Installing Additional Items Into the Extensible SDK</title>
<para>
The extensible SDK typically only comes with a small number of tools
and libraries out of the box.
If you have a minimal SDK, then it starts mostly empty and is
populated on-demand.
However, sometimes you will need to explicitly install extra items
into the SDK.
If you need these extra items, you can first search for the items
using the <filename>devtool search</filename> command.
For example, suppose you need to link to libGL but you are not sure
which recipe provides it.
You can use the following command to find out:
<literallayout class='monospaced'>
$ devtool search libGL
mesa A free implementation of the OpenGL API
</literallayout>
Once you know the recipe (i.e. <filename>mesa</filename> in this
example), you can install it:
<literallayout class='monospaced'>
$ devtool sdk-install mesa
</literallayout>
By default, the <filename>devtool sdk-install</filename> assumes the
item is available in pre-built form from your SDK provider.
If the item is not available and it is acceptable to build the item
from source, you can add the "-s" option as follows:
<literallayout class='monospaced'>
$ devtool sdk-install -s mesa
</literallayout>
It is important to remember that building the item from source takes
significantly longer than installing the pre-built artifact.
Also, if no recipe exists for the item you want to add to the SDK, you
must instead add it using the <filename>devtool add</filename> command.
</para>
</section>
<section id='sdk-updating-the-extensible-sdk'>
<title>Updating the Extensible SDK</title>
<para>
If you are working with an extensible SDK that gets occasionally
updated (e.g. typically when that SDK has been provided to you by
another party), then you will need to manually pull down those
updates to your installed SDK.
</para>
<para>
To update your installed SDK, run the following:
<literallayout class='monospaced'>
$ devtool sdk-update
</literallayout>
The previous command assumes your SDK provider has set the default
update URL for you.
If that URL has not been set, you need to specify it yourself as
follows:
<literallayout class='monospaced'>
$ devtool sdk-update <replaceable>path_to_update_directory</replaceable>
</literallayout>
<note>
The URL needs to point specifically to a published SDK and not an
SDK installer that you would download and install.
</note>
</para>
</section>
<section id='sdk-creating-a-derivative-sdk-with-additional-components'>
<title>Creating a Derivative SDK With Additional Components</title>
<para>
You might need to produce an SDK that contains your own custom
libraries for sending to a third party (e.g., if you are a vendor with
customers needing to build their own software for the target platform).
If that is the case, then you can produce a derivative SDK based on
the currently installed SDK fairly easily.
Use these steps:
<orderedlist>
<listitem><para>If necessary, install an extensible SDK that
you want to use as a base for your derivative SDK.
</para></listitem>
<listitem><para>Source the environment script for the SDK.
</para></listitem>
<listitem><para>Add the extra libraries or other components
you want by using the <filename>devtool add</filename>
command.
</para></listitem>
<listitem><para>Run the <filename>devtool build-sdk</filename>
command.
</para></listitem>
</orderedlist>
The above procedure takes the recipes added to the workspace and
constructs a new SDK installer containing those recipes and the
resulting binary artifacts.
The recipes go into their own separate layer in the constructed
derivative SDK, leaving the workspace clean and ready for users
to add their own recipes.
</para>
</section>
</chapter>
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