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[<!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
<trademark class='trade'>Eclipse</trademark>-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-installing-the-extensible-sdk'>
<title>Installing the Extensible SDK</title>
<para>
The first thing you need to do is install the SDK on your
<ulink url='&YOCTO_DOCS_REF_URL;#hardware-build-system-term'>Build Host</ulink>
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
<ulink url='&YOCTO_TOOLCHAIN_DL_URL;'>toolchain</ulink>
directory within the Index of Releases.
Toolchains are available for several 32-bit and 64-bit
architectures with the <filename>x86_64</filename> directories,
respectively.
The toolchains the Yocto Project provides are based off the
<filename>core-image-sato</filename> and
<filename>core-image-minimal</filename> images and contain
libraries appropriate for developing against that image.
</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.
Following is the general form:
<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:
core-image-sato or core-image-minimal
<replaceable>arch</replaceable> is a string representing the tuned target architecture:
aarch64, armv5e, core2-64, i586, mips32r2, mips64, ppc7400, or cortexa8hf-neon
<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, because files need to be written under that directory
during the normal course of operation, the location you choose
for installation must be writable for whichever
users need to use the SDK.
</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> and has execution rights.
<note>
If you do not have write permissions for the directory
into which you are installing the SDK, the installer
notifies you and exits.
For that case, set up the proper permissions in the directory
and run the installer again.
</note>
<literallayout class='monospaced'>
$ ./Downloads/poky-glibc-x86_64-core-image-minimal-core2-64-toolchain-ext-2.5.sh
Poky (Yocto Project Reference Distro) Extensible SDK installer version 2.5
==========================================================================
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...
Parsing recipes: 100% |##################################################################| Time: 0:00:52
Initialising tasks: 100% |###############################################################| Time: 0:00:00
Checking sstate mirror object availability: 100% |#######################################| Time: 0:00:00
Loading cache: 100% |####################################################################| Time: 0:00:00
Initialising tasks: 100% |###############################################################| Time: 0:00:00
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 the SDK.
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>
Running the setup script defines many environment variables needed
in order to use the SDK (e.g. <filename>PATH</filename>,
<ulink url='&YOCTO_DOCS_REF_URL;#var-CC'><filename>CC</filename></ulink>,
<ulink url='&YOCTO_DOCS_REF_URL;#var-LD'><filename>LD</filename></ulink>,
and so forth).
If you want to see all the environment variables the script
exports, examine the installation file itself.
</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 build system.
</note>
</para>
<para>
The <filename>devtool</filename> command line is organized
similarly to
<ulink url='&YOCTO_DOCS_OM_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 exist that provide
entry-points into development:
<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 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, 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 for other developers to be responsible for
various areas of source code.
As a developer, you are probably interested in using
that source code as part of your development within
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 in the figure represents a
common situation where the source code does not
exist locally and needs to be extracted.
In this situation, the source code is extracted
to the default workspace - you do not
want the files 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>
extracts the upstream source files into a local
Git repository within the
<filename>sources</filename> folder.
The command then creates a recipe named
<replaceable>recipe</replaceable> and a
corresponding append file in the workspace.
If you do not provide
<replaceable>recipe</replaceable>, the command
makes an attempt to determine the recipe name.
</para></listitem>
<listitem><para>
<emphasis>Middle</emphasis>:
The middle scenario in the figure 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.
<note>
If required, <filename>devtool</filename>
always creates
a Git repository locally during the
extraction.
</note>
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.
You need to specify an empty directory:
<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 a
recipe named <replaceable>recipe</replaceable>
along with an associated append file.
</para></listitem>
<listitem><para>
<emphasis>Right</emphasis>:
The right scenario in the figure represents a
situation where the
<replaceable>srctree</replaceable> has been
previously prepared outside of the
<filename>devtool</filename> workspace.</para>
<para>The following command provides a new
recipe name and identifies the existing source
tree location:
<literallayout class='monospaced'>
$ devtool add <replaceable>recipe srctree</replaceable>
</literallayout>
The command examines the source code and
creates a recipe named
<replaceable>recipe</replaceable> for the code
and places the recipe into the workspace.
</para>
<para>Because the extracted source code already
exists, <filename>devtool</filename> does not
try to relocate the source code into the
workspace - only the new recipe is placed
in the workspace.</para>
<para>Aside from a recipe folder, the command
also creates an associated append folder and
places an initial
<filename>*.bbappend</filename> file within.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para>
<emphasis>Edit the Recipe</emphasis>:
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>:
The next step you take depends on what you are going
to do with the new code.</para>
<para>If you need to eventually move the build output
to the target hardware, use the following
<filename>devtool</filename> command:
<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 from the workspace
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 the target hardware.
<note>
This step assumes you have a previously built
image that is already either running in QEMU or
is 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,
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 to actual hardware by using the
<filename>devtool build-image</filename> command.
However, <filename>devtool</filename> does not provide
a specific command that allows you to deploy the
image to actual hardware.
</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 local recipe in
place that is used to build the software.
The command is flexible enough to allow you to extract code
from an upstream source, 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 for 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 locally in a layer external
to the <filename>devtool</filename> workspace.
</para></listitem>
<listitem><para>
The source files exist either 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 a 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 in the figure represents a
common situation where the source code does
not exist locally and it needs to be extracted
from an upstream source.
In this situation, the source is extracted
into the default <filename>devtool</filename>
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, <filename>devtool</filename> uses the
recipe's
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
statements to locate the source code and any
local patch files from other developers.</para>
<para>With this scenario, no
<replaceable>srctree</replaceable> argument
exists.
Consequently, the default behavior of the
<filename>devtool modify</filename> command is
to extract the source files pointed to by the
<filename>SRC_URI</filename> statements into a
local Git structure.
Furthermore, the location for the extracted
source is the default area within the
<filename>devtool</filename> workspace.
The result is that the command sets up both
the source code and an append file within the
workspace while the recipe remains in its
original location.
</para></listitem>
<listitem><para>
<emphasis>Middle</emphasis>:
The middle scenario in the figure 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 local
and 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
<filename>devtool</filename> workspace:
<literallayout class='monospaced'>
$ devtool modify <replaceable>recipe srctree</replaceable>
</literallayout>
<note>
You cannot provide a URL for
<replaceable>srctree</replaceable> using
the <filename>devtool</filename> command.
</note>
As with all extractions, the command uses
the recipe's <filename>SRC_URI</filename>
statements to locate the source files and any
associated patch files.
Once the files are located, the command by
default extracts them into
<replaceable>srctree</replaceable>.</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 provide with
<replaceable>srctree</replaceable>.
</para></listitem>
<listitem><para>
<emphasis>Right</emphasis>:
The right scenario in the figure represents a
situation where the source tree
(<replaceable>srctree</replaceable>) already
exists locally as a previously extracted Git
structure outside of the
<filename>devtool</filename> workspace.
In this example, the recipe also exists
elsewhere locally 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
<filename>devtool</filename> 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 or Rebuild the Image</emphasis>:
The next step you take depends on what you are going
to do with the new code.</para>
<para>If you need to eventually move the build output
to the target hardware, use the following
<filename>devtool</filename> command:
<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 from the workspace
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, use other methods to deploy
the image you built using the
<filename>devtool build-image</filename> command to
actual hardware.
<filename>devtool</filename> does not provide
a specific command to deploy the image to actual
hardware.
</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
staged and committed within the local Git
repository before you use the
<filename>devtool finish</filename> command.
</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> file 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 from 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 upgrades
an existing recipe to that of a more up-to-date version
found upstream.
Throughout the life of software, recipes continually undergo
version upgrades by their upstream publishers.
You can use the <filename>devtool upgrade</filename>
workflow to make sure your recipes you are using for builds
are up-to-date with their upstream counterparts.
<note>
Several methods exist by which you can upgrade recipes -
<filename>devtool upgrade</filename> happens to be one.
You can read about all the methods by which you can
upgrade recipes in the
"<ulink url='&YOCTO_DOCS_DEV_URL;#gs-upgrading-recipes'>Upgrading Recipes</ulink>"
section of the Yocto Project Development Tasks Manual.
</note>
</para>
<para>
The <filename>devtool upgrade</filename> 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>
<ulink url='&YOCTO_DOCS_REF_URL;#devtool-the-workspace-layer-structure'>workspace</ulink>,
and work with any source file forms that the fetchers support.
</para>
<para>
The following diagram shows the common development flow
used with the <filename>devtool upgrade</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 the typical scenario by
which you use the <filename>devtool upgrade</filename>
command.
The following conditions exist:
<itemizedlist>
<listitem><para>
The recipe exists in a local layer external
to the <filename>devtool</filename> workspace.
</para></listitem>
<listitem><para>
The source files for the new release
exist in 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
<ulink url='&YOCTO_DOCS_REF_URL;#devtool-the-workspace-layer-structure'>workspace</ulink>.
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>
<note>
In this example, the "-V" option specifies the new
version.
If you don't use "-V", the command upgrades the
recipe to the latest version.
</note>
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.
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>:
Conflicts could exist due to the software being
upgraded to a new version.
Conflicts 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.
For such cases, 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 or Rebuild the Image</emphasis>:
The next step you take depends on what you are going
to do with the new code.</para>
<para>If you need to eventually move the build output
to the target hardware, use the following
<filename>devtool</filename> command:
<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 from the workspace
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 or <filename>bitbake</filename> to build
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 you provide with the command.
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 the recipe successfully builds.
Once the recipe builds, 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> uses various metadata
within the source tree in an attempt to determine
the name and version of the software being built.
Based on what the tool determines, <filename>devtool</filename>
sets the name of the created recipe file accordingly.
</para>
<para>
If <filename>devtool</filename> cannot determine the name and
version, the command prints an error.
For such cases, you must re-run the command and provide
the name and version, just the name, or just the version as
part of the command line.
</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 as part of the
<ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink>
variable within the recipe.
If a dependency cannot be mapped, <filename>devtool</filename>
places a comment in the recipe indicating such.
The inability to map a dependency can result from naming not
being 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 that satisfies the dependency.
Once you add that recipe, you need to update the
<filename>DEPENDS</filename> variable in the original recipe
to include the new recipe.
</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} += "<replaceable>dependency1 dependency2 ...</replaceable>"
</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 with an option that disables 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.
If so, the command sets the
<ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE</filename></ulink>
value accordingly.
You should double-check the value added by the command against
the documentation or source files for the software you are
building and, if necessary, update that
<filename>LICENSE</filename> value.
</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.
Realize that license statements often appear in comments at
the top of source files or within the documentation.
In such cases, the command does not recognize those license
statements.
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, <filename>devtool</filename>
sets the <filename>LICENSE</filename> value to "CLOSED" and
leaves the <filename>LIC_FILES_CHKSUM</filename> value unset.
This behavior allows you to continue with development even
though the settings are unlikely to be correct in all cases.
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 Make 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 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 Make 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, a list of environment
variables exists 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.
For this case, 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 because they
are 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
situation.
</para></listitem>
<listitem><para>
Sometimes a Makefile runs target-specific commands such
as <filename>ldconfig</filename>.
For such cases, you might be able to 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
<ulink url='&YOCTO_DOCS_REF_URL;#hardware-build-system-term'>build host</ulink>
as opposed to the target.
You should indicate this requirement by 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.
</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 the code as 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 using the
<filename>devtool build</filename> command, the typical build
progresses 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>
Compile 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 (task), usually
with a "do_" prefix (e.g.
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink>,
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-unpack'><filename>do_unpack</filename></ulink>,
and so forth).
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.
This technique leaves the recipe to describe just the things that
are specific to the software being 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 recipes typically 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>
After the first run of the <filename>devtool build</filename>
command, recipes that were previously created using the
<filename>devtool add</filename> command or whose sources were
modified using the <filename>devtool modify</filename>
command contain symbolic links created within the source tree:
<itemizedlist>
<listitem><para>
<filename>oe-logs</filename>:
This link points to the directory in which log files
and run scripts for each build step are created.
</para></listitem>
<listitem><para>
<filename>oe-workdir</filename>:
This link points to the temporary work area for the
recipe.
The following locations under
<filename>oe-workdir</filename> are particularly
useful:
<itemizedlist>
<listitem><para>
<filename>image/</filename>:
Contains all of the files installed during
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></listitem>
</itemizedlist>
You can use these links to get more information on what is
happening at each build step.
</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
<ulink url='&YOCTO_DOCS_REF_URL;#hardware-build-system-term'>build host</ulink>.
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 goes 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 into several other packages.
This separation exists because not all of those installed files
are 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 containing optional modules or
plugins might undergo 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 by
using an override to specify the package.
For example, <filename>FILES_${PN}</filename> specifies the
files to go into the main package (i.e. the main package has
the same name as the recipe and
<filename>${</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> command 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 using the "-a" option thus restoring the target device 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> commands do not
currently interact with any package management system on the
target device (e.g. RPM or OPKG).
Consequently, you should not intermingle
<filename>devtool deploy-target</filename> and 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>
Out of the box the extensible SDK typically only comes with a small
number of tools and libraries.
A minimal SDK starts mostly empty and is populated on-demand.
Sometimes you must 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 libGL.
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> command
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 the item 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.
A good example would be if you were a vendor with customers that
use your SDK to build their own platform-specific software and
those customers need an SDK that has custom libraries.
In such a case, you can produce a derivative SDK based on the
currently installed SDK fairly easily by following 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 previous steps take the recipes added to the workspace and
construct a new SDK installer that contains those recipes and the
resulting binary artifacts.
The recipes go into their own separate layer in the constructed
derivative SDK, which leaves the workspace clean and ready for
users to add their own recipes.
</para>
</section>
</chapter>
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