%poky; ] > Many development models exist for which you can use the Yocto Project. This chapter overviews the following methods: System Development: System Development covers Board Support Package (BSP) development and kernel modification or configuration. If you want to examine specific examples of the system development models, see the "BSP Development Example" appendix and the "Kernel Modification Example" appendix. User Application Development: User Application Development covers development of applications that you intend to run on some target hardware. For information on how to set up your host development system for user-space application development, see the Yocto Project Application Developer's Guide. For a simple example of user-space application development using the Eclipse IDE, see the "Application Development Workflow" section. Temporary Source Code Modification: Direct modification of temporary source code is a convenient development model to quickly iterate and develop towards a solution. Once the solution has been implemented, you should of course take steps to get the changes upstream and applied in the affected recipes. Image Development using Hob: You can use the Hob to build custom operating system images within the build environment. Hob provides an efficient interface to the OpenEmbedded build system. Using a Development Shell: You can use a devshell to efficiently debug commands or simply edit packages. Working inside a development shell is a quick way to set up the OpenEmbedded build environment to work on parts of a project.

System development involves modification or creation of an image that you want to run on a specific hardware target. Usually, when you want to create an image that runs on embedded hardware, the image does not require the same number of features that a full-fledged Linux distribution provides. Thus, you can create a much smaller image that is designed to use only the features for your particular hardware. To help you understand how system development works in the Yocto Project, this section covers two types of image development: BSP creation and kernel modification or configuration.

A BSP is a package of recipes that, when applied during a build, results in an image that you can run on a particular board. Thus, the package when compiled into the new image, supports the operation of the board. For a brief list of terms used when describing the development process in the Yocto Project, see the "Yocto Project Terms" section. The remainder of this section presents the basic steps used to create a BSP based on an existing BSP that ships with the Yocto Project. You can reference the "BSP Development Example" appendix for a detailed example that uses the Crown Bay BSP as a base BSP from which to start. The following illustration and list summarize the BSP creation general workflow. Set up your host development system to support development using the Yocto Project: See the "The Linux Distributions" and the "The Packages" sections both in the Yocto Project Quick Start for requirements. Establish a local copy of the project files on your system: You need this Source Directory available on your host system. Having these files on your system gives you access to the build process and to the tools you need. For information on how to set up the Source Directory, see the "Getting Setup" section. Establish a local copy of the base BSP files: Having the BSP files on your system gives you access to the build process and to the tools you need for creating a BSP. For information on how to get these files, see the "Getting Setup" section. Choose a BSP that is supported by the Yocto Project as your base BSP: The Yocto Project ships with several BSPs that support various hardware. It is best to base your new BSP on an existing BSP rather than create all the recipes and configuration files from scratch. While it is possible to create everything from scratch, basing your new BSP on something that is close is much easier. Or, at a minimum, leveraging off an existing BSP gives you some structure with which to start. At this point you need to understand your target hardware well enough to determine which existing BSP it most closely matches. Things to consider are your hardware’s on-board features, such as CPU type and graphics support. You should look at the README files for supported BSPs to get an idea of which one you could use. A generic Intel Atom-based BSP to consider is the Crown Bay that does not support the Intel Embedded Media Graphics Driver (EMGD). The remainder of this example uses that base BSP. To see the supported BSPs, go to the Downloads page on the Yocto Project website and click on “BSP Downloads.” Create your own BSP layer: Layers are ideal for isolating and storing work for a given piece of hardware. A layer is really just a location or area in which you place the recipes for your BSP. In fact, a BSP is, in itself, a special type of layer. Another example that illustrates a layer is an application. Suppose you are creating an application that has library or other dependencies in order for it to compile and run. The layer, in this case, would be where all the recipes that define those dependencies are kept. The key point for a layer is that it is an isolated area that contains all the relevant information for the project that the OpenEmbedded build system knows about. For more information on layers, see the "Understanding and Creating Layers" section. For more information on BSP layers, see the "BSP Layers" section in the Yocto Project Board Support Package (BSP) Developer's Guide. Four BSPs exist that are part of the Yocto Project release: atom-pc, beagleboard, mpc8315e, and routerstationpro. The recipes and configurations for these four BSPs are located and dispersed within the Source Directory. On the other hand, BSP layers for Cedar Trail, Chief River, Crown Bay, Crystal Forest, Emenlow, Fish River, Fish River 2, Jasper Forest, N450, Romley, sys940x, Sugar Bay, and tlk exist in their own separate layers within the larger meta-intel layer. When you set up a layer for a new BSP, you should follow a standard layout. This layout is described in the section "Example Filesystem Layout" section of the Board Support Package (BSP) Development Guide. In the standard layout, you will notice a suggested structure for recipes and configuration information. You can see the standard layout for the Crown Bay BSP in this example by examining the directory structure of the meta-crownbay layer inside the Source Directory. Make configuration changes to your new BSP layer: The standard BSP layer structure organizes the files you need to edit in conf and several recipes-* directories within the BSP layer. Configuration changes identify where your new layer is on the local system and identify which kernel you are going to use. Make recipe changes to your new BSP layer: Recipe changes include altering recipes (.bb files), removing recipes you don't use, and adding new recipes that you need to support your hardware. Prepare for the build: Once you have made all the changes to your BSP layer, there remains a few things you need to do for the OpenEmbedded build system in order for it to create your image. You need to get the build environment ready by sourcing an environment setup script and you need to be sure two key configuration files are configured appropriately. The entire process for building an image is overviewed in the section "Building an Image" section of the Yocto Project Quick Start. You might want to reference this information. Build the image: The OpenEmbedded build system uses the BitBake tool to build images based on the type of image you want to create. You can find more information about BitBake in the user manual, which is found in the bitbake/doc/manual directory of the Source Directory. The build process supports several types of images to satisfy different needs. See the "Images" chapter in the Yocto Project Reference Manual for information on supported images. You can view a video presentation on "Building Custom Embedded Images with Yocto" at Free Electrons. You can also find supplemental information in The Board Support Package (BSP) Development Guide. Finally, there is wiki page write up of the example also located here that you might find helpful.

Kernel modification involves changing the Yocto Project kernel, which could involve changing configuration options as well as adding new kernel recipes. Configuration changes can be added in the form of configuration fragments, while recipe modification comes through the kernel's recipes-kernel area in a kernel layer you create. The remainder of this section presents a high-level overview of the Yocto Project kernel architecture and the steps to modify the kernel. For a complete discussion of the kernel, see the Yocto Project Kernel Architecture and Use Manual. You can reference the appendix "Kernel Modification Example" for a detailed example that changes the configuration of a kernel.

Traditionally, when one thinks of a patched kernel, they think of a base kernel source tree and a fixed structure that contains kernel patches. The Yocto Project, however, employs mechanisms, that in a sense, result in a kernel source generator. By the end of this section, this analogy will become clearer. You can find a web interface to the Yocto Project kernel source repositories at . If you look at the interface, you will see to the left a grouping of Git repositories titled "Yocto Linux Kernel." Within this group, you will find several kernels supported by the Yocto Project: linux-yocto-2.6.34 - The stable Yocto Project kernel that is based on the Linux 2.6.34 released kernel. linux-yocto-2.6.37 - The stable Yocto Project kernel that is based on the Linux 2.6.37 released kernel. linux-yocto-3.0 - The stable Yocto Project kernel that is based on the Linux 3.0 released kernel. linux-yocto-3.0-1.1.x - The stable Yocto Project kernel to use with the Yocto Project Release 1.1.x. This kernel is based on the Linux 3.0 released kernel. linux-yocto-3.2 - The stable Yocto Project kernel to use with the Yocto Project Release 1.2. This kernel is based on the Linux 3.2 released kernel. linux-yocto-3.4 - The stable Yocto Project kernel to use with the Yocto Project Release 1.3. This kernel is based on the Linux 3.4 released kernel. linux-yocto-dev - A development kernel based on the latest upstream release candidate available. The kernels are maintained using the Git revision control system that structures them using the familiar "tree", "branch", and "leaf" scheme. Branches represent diversions from general code to more specific code, while leaves represent the end-points for a complete and unique kernel whose source files when gathered from the root of the tree to the leaf accumulate to create the files necessary for a specific piece of hardware and its features. The following figure displays this concept: Within the figure, the "Kernel.org Branch Point" represents the point in the tree where a supported base kernel is modified from the Linux kernel. For example, this could be the branch point for the linux-yocto-3.0 kernel. Thus, everything further to the right in the structure is based on the linux-yocto-3.0 kernel. Branch points to right in the figure represent where the linux-yocto-3.0 kernel is modified for specific hardware or types of kernels, such as real-time kernels. Each leaf thus represents the end-point for a kernel designed to run on a specific targeted device. The overall result is a Git-maintained repository from which all the supported kernel types can be derived for all the supported devices. A big advantage to this scheme is the sharing of common features by keeping them in "larger" branches within the tree. This practice eliminates redundant storage of similar features shared among kernels. Keep in mind the figure does not take into account all the supported Yocto Project kernel types, but rather shows a single generic kernel just for conceptual purposes. Also keep in mind that this structure represents the Yocto Project source repositories that are either pulled from during the build or established on the host development system prior to the build by either cloning a particular kernel's Git repository or by downloading and unpacking a tarball. Storage of all the available kernel source code is one thing, while representing the code on your host development system is another. Conceptually, you can think of the kernel source repositories as all the source files necessary for all the supported kernels. As a developer, you are just interested in the source files for the kernel on on which you are working. And, furthermore, you need them available on your host system. You make kernel source code available on your host development system by using Git to create a bare clone of the Yocto Project kernel Git repository in which you are interested. Then, you use Git again to clone a copy of that bare clone. This copy represents the directory structure on your host system that is particular to the kernel you want. The files in the copy of the bare clone are the files you actually modify to change the kernel. See the Yocto Project Kernel item earlier in this manual for an example of how to set up the kernel source directory structure on your host system. This next figure illustrates how the kernel source files might be arranged on your host system. In the previous figure, the file structure on the left represents the bare clone set up to track the Yocto Project kernel Git repository. The structure on the right represents the copy of the bare clone. When you make modifcations to the kernel source code, this is the area in which you work. Once you make corrections, you must use Git to push the committed changes to the bare clone. The example in Modifying the Kernel Source Code provides a detailed example. What happens during the build? When you build the kernel on your development system, all files needed for the build are taken from the source repositories pointed to by the SRC_URI variable and gathered in a temporary work area where they are subsequently used to create the unique kernel. Thus, in a sense, the process constructs a local source tree specific to your kernel to generate the new kernel image - a source generator if you will. The following figure shows the temporary file structure created on your host system when the build occurs. This build directory contains all the source files used during the build. Again, for a complete discussion of the Yocto Project kernel's architecture and its branching strategy, see the Yocto Project Kernel Architecture and Use Manual. You can also reference the "Modifying the Kernel Source Code" section for a detailed example that modifies the kernel.

This illustration and the following list summarizes the kernel modification general workflow. Set up your host development system to support development using the Yocto Project: See "The Linux Distributions" and "The Packages" sections both in the Yocto Project Quick Start for requirements. Establish a local copy of project files on your system: Having the source directory on your system gives you access to the build process and tools you need. For information on how to get these files, see the bulleted item "Yocto Project Release" earlier in this manual. Set up a local copy of the poky-extras Git repository: This local repository is the area for your configuration fragments, new kernel recipes, and the kernel .bbappend file used during the build. It is good practice to set this repository up inside your local Source Directory. For information on how to get these files, see the bulleted item "The poky-extras Git Repository" earlier in this manual. While it is certainly possible to modify the kernel without involving a local Git repository, the suggested workflow for kernel modification using the Yocto Project does use a Git repository. Establish a local copy of the Yocto Project kernel files on your system: In order to make modifications to the kernel you need two things: a bare clone of the Yocto Project kernel you are modifying and a copy of that bare clone. The bare clone is required by the build process and is the area to which you push your kernel source changes (pulling does not work with bare clones). The copy of the bare clone is a local Git repository that contains all the kernel's source files. You make your changes to the files in this copy of the bare clone. For information on how to set these two items up, see the bulleted item "Yocto Project Kernel" earlier in this manual. Make changes to the kernel source code if applicable: Modifying the kernel does not always mean directly changing source files. However, if you have to do this, you make the changes in the local Git repository you set up to hold the source files (i.e. the copy of the bare clone). Once the changes are made, you need to use Git commands to commit the changes and then push them to the bare clone. Make kernel configuration changes if applicable: If your situation calls for changing the kernel's configuration, you can use menuconfig to enable and disable kernel configurations. Using menuconfig allows you to interactively develop and test the configuration changes you are making to the kernel. When saved, changes using menuconfig update the kernel's .config. Try to resist the temptation of directly editing the .config file found in the build directory at tmp/sysroots/<machine-name>/kernel. Doing so, can produce unexpected results when the OpenEmbedded build system regenerates the configuration file. Once you are satisfied with the configuration changes made using menuconfig, you can directly examine the .config file against a saved original and gather those changes into a config fragment to be referenced from within the kernel's .bbappend file. Add or extend kernel recipes if applicable: The standard layer structure organizes recipe files inside the meta-kernel-dev layer that is within the local poky-extras Git repository. If you need to add new kernel recipes, you add them within this layer. Also within this area, you will find the .bbappend file that appends information to the kernel's recipe file used during the build. Prepare for the build: Once you have made all the changes to your kernel (configurations, source code changes, recipe additions, or recipe changes), there remains a few things you need to do in order for the build system to create your image. If you have not done so, you need to get the build environment ready by sourcing the environment setup script described earlier. You also need to be sure two key configuration files (local.conf and bblayers.conf) are configured appropriately. The entire process for building an image is overviewed in the "Building an Image" section of the Yocto Project Quick Start. You might want to reference this information. Also, you should look at the detailed examples found in the appendices at at the end of this manual. Build the image: The OpenEmbedded build system uses the BitBake tool to build images based on the type of image you want to create. You can find more information on BitBake in the user manual, which is found in the bitbake/doc/manual directory of the Source Directory. The build process supports several types of images to satisfy different needs. See the "Images" chapter in the Yocto Project Reference Manual for information on supported images. Make your configuration changes available in the kernel layer: Up to this point, all the configuration changes to the kernel have been done and tested iteratively. Once they are tested and ready to go, you can move them into the kernel layer, which allows you to distribute the layer. If applicable, share your in-tree changes: If the changes you made are suited for all Yocto Project kernel users, you might want to send them on for inclusion into the upstream kernel's Git repository. If the changes are accepted, the Yocto Project Maintainer pulls them into the master branch of the kernel tree. Doing so makes them available to everyone using the kernel. For information on how to submit a change to the Yocto Project, see the "How to Submit a Change" section earlier in this manual.

Application development involves creating an application that you want to run on your target hardware, which is running a kernel image created using the OpenEmbedded build system. The Yocto Project provides an Application Development Toolkit (ADT) and stand-alone cross-development toolchains that facilitate quick development and integration of your application into its run-time environment. Using the ADT and toolchains, you can compile and link your application. You can then deploy your application to the actual hardware or to the QEMU emulator for testing. If you are familiar with the popular Eclipse IDE, you can use an Eclipse Yocto Plug-in to allow you to develop, deploy, and test your application all from within Eclipse. While we strongly suggest using the ADT to develop your application, this option might not be best for you. If this is the case, you can still use pieces of the Yocto Project for your development process. However, because the process can vary greatly, this manual does not provide detail on the process.

To help you understand how application development works using the ADT, this section provides an overview of the general development process and a detailed example of the process as it is used from within the Eclipse IDE. The following illustration and list summarize the application development general workflow. Prepare the Host System for the Yocto Project: See "The Linux Distributions" and "The Packages" sections both in the Yocto Project Quick Start for requirements. Secure the Yocto Project Kernel Target Image: You must have a target kernel image that has been built using the OpenEmbeded build system. Depending on whether the Yocto Project has a pre-built image that matches your target architecture and where you are going to run the image while you develop your application (QEMU or real hardware), the area from which you get the image differs. Download the image from machines if your target architecture is supported and you are going to develop and test your application on actual hardware. Download the image from the machines/qemu if your target architecture is supported and you are going to develop and test your application using the QEMU emulator. Build your image if you cannot find a pre-built image that matches your target architecture. If your target architecture is similar to a supported architecture, you can modify the kernel image before you build it. See the "Kernel Modification Example" appendix later in this manual for an example. For information on pre-built kernel image naming schemes for images that can run on the QEMU emulator, see the "Downloading the Pre-Built Linux Kernel" section in the Yocto Project Quick Start. Install the ADT: The ADT provides a target-specific cross-development toolchain, the root filesystem, the QEMU emulator, and other tools that can help you develop your application. While it is possible to get these pieces separately, the ADT Installer provides an easy method. You can get these pieces by running an ADT installer script, which is configurable. For information on how to install the ADT, see the "Using the ADT Installer" section in the Yocto Project Application Developer's Guide. If Applicable, Secure the Target Root Filesystem and the Cross-development Toolchain: If you choose not to install the ADT using the ADT Installer, you need to find and download the appropriate root filesystem and the cross-development toolchain. You can find the tarballs for the root filesystem in the same area used for the kernel image. Depending on the type of image you are running, the root filesystem you need differs. For example, if you are developing an application that runs on an image that supports Sato, you need to get root filesystem that supports Sato. You can find the cross-development toolchains at toolchains. Be sure to get the correct toolchain for your development host and your target architecture. See the "Using a Cross-Toolchain Tarball" section in the Yocto Project Application Developer's Guide for information and the "Installing the Toolchain" in the Yocto Project Quick Start for information on finding and installing the correct toolchain based on your host development system and your target architecture. Create and Build your Application: At this point, you need to have source files for your application. Once you have the files, you can use the Eclipse IDE to import them and build the project. If you are not using Eclipse, you need to use the cross-development tools you have installed to create the image. Deploy the Image with the Application: If you are using the Eclipse IDE, you can deploy your image to the hardware or to QEMU through the project's preferences. If you are not using the Eclipse IDE, then you need to deploy the application to the hardware using other methods. Or, if you are using QEMU, you need to use that tool and load your image in for testing. Test and Debug the Application: Once your application is deployed, you need to test it. Within the Eclipse IDE, you can use the debubbing environment along with the set of user-space tools installed along with the ADT to debug your application. Of course, the same user-space tools are available separately if you choose not to use the Eclipse IDE.

The Eclipse IDE is a popular development environment and it fully supports development using the Yocto Project. This release of the Yocto Project supports both the Juno and Indigo versions of the Eclipse IDE. Thus, the following information provides setup information for both versions. When you install and configure the Eclipse Yocto Project Plug-in into the Eclipse IDE, you maximize your Yocto Project experience. Installing and configuring the Plug-in results in an environment that has extensions specifically designed to let you more easily develop software. These extensions allow for cross-compilation, deployment, and execution of your output into a QEMU emulation session. You can also perform cross-debugging and profiling. The environment also supports a suite of tools that allows you to perform remote profiling, tracing, collection of power data, collection of latency data, and collection of performance data. This section describes how to install and configure the Eclipse IDE Yocto Plug-in and how to use it to develop your application.

To develop within the Eclipse IDE, you need to do the following: Install the optimal version of the Eclipse IDE. Configure the Eclipse IDE. Install the Eclipse Yocto Plug-in. Configure the Eclipse Yocto Plug-in. Do not install Eclipse from your distribution's package repository. Be sure to install Eclipse from the official Eclipse download site as directed in the next section.

It is recommended that you have the Juno 4.2 version of the Eclipse IDE installed on your development system. However, if you currently have the Indigo 3.7.2 version installed and you do not want to upgrade the IDE, you can configure Indigo to work with the Yocto Project. See the "Configuring the Eclipse IDE (Indigo)" section. If you don’t have the Juno 4.2 Eclipse IDE installed, you can find the tarball at . From that site, choose the Eclipse Classic version particular to your development host. This version contains the Eclipse Platform, the Java Development Tools (JDT), and the Plug-in Development Environment. Once you have downloaded the tarball, extract it into a clean directory. For example, the following commands unpack and install the downloaded Eclipse IDE tarball into a clean directory using the default name eclipse: $ cd ~ $ tar -xzvf ~/Downloads/eclipse-SDK-4.2-linux-gtk-x86_64.tar.gz If you have the Indigo 3.7.2 Eclipse IDE already installed and you want to use that version, one issue exists that you need to be aware of regarding the Java Virtual machine’s garbage collection (GC) process. The GC process does not clean up the permanent generation space (PermGen). This space stores metadata descriptions of classes. The default value is set too small and it could trigger an out-of-memory error such as the following: Java.lang.OutOfMemoryError: PermGen space This error causes the application to hang. To fix this issue, you can use the --vmargs option when you start the Indigo 3.7.2 Eclipse IDE to increase the size of the permanent generation space: eclipse --vmargs --XX:PermSize=256M

This section presents the steps needed to configure the Juno 4.2 Eclipse IDE. If you are using Indigo 3.7.2, see the "Configuring the Eclipse IDE (Indigo)". Before installing and configuring the Eclipse Yocto Plug-in, you need to configure the Juno 4.2 Eclipse IDE. Follow these general steps: Start the Eclipse IDE. Make sure you are in your Workbench and select "Install New Software" from the "Help" pull-down menu. Select Juno - &ECLIPSE_JUNO_URL; from the "Work with:" pull-down menu. Expand the box next to "Linux Tools" and select the "LTTng - Linux Tracing Toolkit" boxes. Expand the box next to "Mobile and Device Development" and select the following boxes: C/C++ Remote Launch Remote System Explorer End-user Runtime Remote System Explorer User Actions Target Management Terminal TCF Remote System Explorer add-in TCF Target Explorer Expand the box next to Programming Languages and select the Autotools Support for CDT and C/C++ Development Tools boxes. Complete the installation and restart the Eclipse IDE.

This section presents the steps needed to configure the Indigo 3.7.2 Eclipse IDE. If you are using Juno 4.2, see the "Configuring the Eclipse IDE (Juno)". Before installing and configuring the Eclipse Yocto Plug-in, you need to configure the Indigo 3.7.2 Eclipse IDE. Follow these general steps: Start the Eclipse IDE. Make sure you are in your Workbench and select "Install New Software" from the "Help" pull-down menu. Select indigo - &ECLIPSE_INDIGO_URL; from the "Work with:" pull-down menu. Expand the box next to Programming Languages and select the Autotools Support for CDT (incubation) and C/C++ Development Tools boxes. Expand the box next to "Linux Tools" and select the "LTTng - Linux Tracing Toolkit(incubation)" boxes. Complete the installation and restart the Eclipse IDE. After the Eclipse IDE restarts and from the Workbench, select "Install New Software" from the "Help" pull-down menu. Click the "Available Software Sites" link. Check the box next to &ECLIPSE_UPDATES_URL; and click "OK". Select &ECLIPSE_UPDATES_URL; from the "Work with:" pull-down menu. Check the box next to TM and RSE Main Features. Expand the box next to TM and RSE Optional Add-ons and select every item except RSE Unit Tests and RSE WinCE Services (incubation). Complete the installation and restart the Eclipse IDE. If necessary, select "Install New Software" from the "Help" pull-down menu so you can click the "Available Software Sites" link again. After clicking "Available Software Sites", check the box next to http://download.eclipse.org/tools/cdt/releases/indigo and click "OK". Select &ECLIPSE_INDIGO_CDT_URL; from the "Work with:" pull-down menu. Check the box next to CDT Main Features. Expand the box next to CDT Optional Features and select C/C++ Remote Launch and Target Communication Framework (incubation). Complete the installation and restart the Eclipse IDE.

You can install the Eclipse Yocto Plug-in into the Eclipse IDE one of two ways: use the Yocto Project's Eclipse Update site to install the pre-built plug-in, or build and install the plug-in from the latest source code. If you don't want to permanently install the plug-in but just want to try it out within the Eclipse environment, you can import the plug-in project from the Yocto Project's Source Repositories.

To install the Eclipse Yocto Plug-in from the update site, follow these steps: Start up the Eclipse IDE. In Eclipse, select "Install New Software" from the "Help" menu. Click "Add..." in the "Work with:" area. Enter &ECLIPSE_DL_PLUGIN_URL; in the URL field and provide a meaningful name in the "Name" field. Click "OK" to have the entry added to the "Work with:" drop-down list. Select the entry for the plug-in from the "Work with:" drop-down list. Check the box next to Development tools and SDKs for Yocto Linux. Complete the remaining software installation steps and then restart the Eclipse IDE to finish the installation of the plug-in.

To install the Eclipse Yocto Plug-in from the latest source code, follow these steps: Open a shell and create a Git repository with: $ git clone git://git.yoctoproject.org/eclipse-poky yocto-eclipse For this example, the repository is named ~/yocto-eclipse. Be sure you are in the right branch for your Git repository. For this release set the branch to &DISTRO_NAME;: $ git checkout -b &DISTRO_NAME; origin/&DISTRO_NAME; Locate the build.sh script in the Git repository you created in the previous step. The script is located in the scripts. Be sure to set and export the ECLIPSE_HOME environment variable to the top-level directory in which you installed your version of Eclipse. For example, if your Eclipse directory is $HOME/eclipse, use the following: $ export ECLIPSE_HOME=$HOME/eclipse Be sure you have the right branch in the Poky Git repository checked out. For example, the following commands checkout the &DISTRO_NAME; branch in the local Poky Git repository: $ cd ~/poky $ git checkout -b &DISTRO_NAME; origin/&DISTRO_NAME; Move back to your Yocto Eclipse directory and run the build.sh script. Provide the name of the Git branch along with the Yocto Project release you are using. Here is an example that uses the &DISTRO_NAME; branches: $ scripts/build.sh &DISTRO_NAME; &DISTRO_NAME; After running the script, the file org.yocto.sdk-<release>-<date>-archive.zip is in the current directory. If necessary, start the Eclipse IDE and be sure you are in the Workbench. Select "Install New Software" from the "Help" pull-down menu. Click "Add". Provide anything you want in the "Name" field. Click "Archive" and browse to the ZIP file you built in step four. This ZIP file should not be "unzipped", and must be the *archive.zip file created by running the build.sh script. Click through the "Okay" buttons. Check the box next to the new entry in the installation window and complete the installation. Restart the Eclipse IDE if necessary. At this point you should be able to configure the Eclipse Yocto Plug-in as described in the "Configuring the Eclipse Yocto Plug-in" section.

Importing the Eclipse Yocto Plug-in project from the Yocto Project source repositories is useful when you want to try out the latest plug-in from the tip of plug-in's development tree. It is important to understand when you import the plug-in you are not installing it into the Eclipse application. Rather, you are importing the project and just using it. To import the plug-in project, follow these steps: Open a shell and create a Git repository with: $ git clone git://git.yoctoproject.org/eclipse-poky yocto-eclipse For this example, the repository is named ~/yocto-eclipse. In Eclipse, select "Import" from the "File" menu. Expand the "General" box and select "existing projects into workspace" and then click "Next". Select the root directory and browse to ~/yocto-eclipse/plugins. Three plug-ins exist: "org.yocto.bc.ui", "org.yocto.sdk.ide", and "org.yocto.sdk.remotetools". Select and import all of them. The left navigation pane in the Eclipse application shows the default projects. Right-click on one of these projects and run it as an Eclipse application. This brings up a second instance of Eclipse IDE that has the Yocto Plug-in.

Configuring the Eclipse Yocto Plug-in involves setting the Cross Compiler options and the Target options. The configurations you choose become the default settings for all projects. You do have opportunities to change them later when you configure the project (see the following section). To start, you need to do the following from within the Eclipse IDE: Choose Windows -> Preferences to display the Preferences Dialog Click Yocto Project ADT

To configure the Cross Compiler Options, you must select the type of toolchain, point to the toolchain, specify the sysroot location, and select the target architecture. Selecting the Toolchain Type: Choose between Standalone pre-built toolchain and Build system derived toolchain for Cross Compiler Options. Standalone Pre-built Toolchain: Select this mode when you are using a stand-alone cross-toolchain. For example, suppose you are an application developer and do not need to build a target image. Instead, you just want to use an architecture-specific toolchain on an existing kernel and target root filesystem. Build System Derived Toolchain: Select this mode if the cross-toolchain has been installed and built as part of the build directory. When you select Build system derived toolchain, you are using the toolchain bundled inside the build directory. Point to the Toolchain: If you are using a stand-alone pre-built toolchain, you should be pointing to the &YOCTO_ADTPATH_DIR; directory. This is the location for toolchains installed by the ADT Installer or by hand. Sections "Configuring and Running the ADT Installer Script" and "Using a Cross-Toolchain Tarball" in the Yocto Project Application Developer's Guide describe two ways to install a stand-alone cross-toolchain in the /opt/poky directory. It is possible to install a stand-alone cross-toolchain in a directory other than /opt/poky. However, doing so is discouraged. If you are using a system-derived toolchain, the path you provide for the Toolchain Root Location field is the build directory. See the "Using BitBake and the build directory" section in the Yocto Project Application Developer's Guide for information on how to install the toolchain into the build directory. Specify the Sysroot Location: This location is where the root filesystem for the target hardware resides. If you used the ADT Installer, then the location is /opt/poky/<release>. Additionally, when you use the ADT Installer, the same location is used for the QEMU user-space tools and the NFS boot process. If you used either of the other two methods to install the toolchain, then the location of the sysroot filesystem depends on where you separately extracted and intalled the filesystem. For information on how to install the toolchain and on how to extract and install the sysroot filesystem, see the "Installing the ADT and Toolchains" section. Select the Target Architecture: The target architecture is the type of hardware you are going to use or emulate. Use the pull-down Target Architecture menu to make your selection. The pull-down menu should have the supported architectures. If the architecture you need is not listed in the menu, you will need to build the image. See the "Building an Image" section of the Yocto Project Quick Start for more information.

You can choose to emulate hardware using the QEMU emulator, or you can choose to run your image on actual hardware. QEMU: Select this option if you will be using the QEMU emulator. If you are using the emulator, you also need to locate the kernel and specify any custom options. If you selected Build system derived toolchain, the target kernel you built will be located in the build directory in tmp/deploy/images directory. If you selected Standalone pre-built toolchain, the pre-built image you downloaded is located in the directory you specified when you downloaded the image. Most custom options are for advanced QEMU users to further customize their QEMU instance. These options are specified between paired angled brackets. Some options must be specified outside the brackets. In particular, the options serial, nographic, and kvm must all be outside the brackets. Use the man qemu command to get help on all the options and their use. The following is an example: serial ‘<-m 256 -full-screen>’ Regardless of the mode, Sysroot is already defined as part of the Cross Compiler Options configuration in the Sysroot Location: field. External HW: Select this option if you will be using actual hardware. Click the OK button to save your plug-in configurations.

You can create two types of projects: Autotools-based, or Makefile-based. This section describes how to create Autotools-based projects from within the Eclipse IDE. For information on creating Makefile-based projects in a terminal window, see the section "Using the Command Line" in the Yocto Project Application Developer's Guide. To create a project based on a Yocto template and then display the source code, follow these steps: Select File -> New -> Project. Double click CC++. Double click C Project to create the project. Expand Yocto Project ADT Project. Select Hello World ANSI C Autotools Project. This is an Autotools-based project based on a Yocto template. Put a name in the Project name: field. Do not use hyphens as part of the name. Click Next. Add information in the Author and Copyright notice fields. Be sure the License field is correct. Click Finish. If the "open perspective" prompt appears, click "Yes" so that you in the C/C++ perspective. The left-hand navigation pane shows your project. You can display your source by double clicking the project's source file.

The earlier section, "Configuring the Eclipse Yocto Plug-in", sets up the default project configurations. You can override these settings for a given project by following these steps: Select Project -> Change Yocto Project Settings: This selection brings up the Yocot Project Settings Dialog and allows you to make changes specific to an individual project. By default, the Cross Compiler Options and Target Options for a project are inherited from settings you provide using the Preferences Dialog as described earlier in the "Configuring the Eclipse Yocto Plug-in" section. The Yocto Project Settings Dialog allows you to override those default settings for a given project. Make your configurations for the project and click "OK". If you are running the Juno version of Eclipse, you can skip down to the next section where you build the project. If you are not working with Juno, you need to reconfigure the project as described in the next step. Select Project -> Reconfigure Project: This selection reconfigures the project by running autogen.sh in the workspace for your project. The script also runs libtoolize, aclocal, autoconf, autoheader, automake --a, and ./configure. Click on the Console tab beneath your source code to see the results of reconfiguring your project.

To build the project in Juno, right click on the project in the navigator pane and select Build Project. If you are not running Juno, select Project -> Build Project. The console should update and you can note the cross-compiler you are using.

To start the QEMU emulator from within Eclipse, follow these steps: Expose the Run -> External Tools menu. Your image should appear as a selectable menu item. Select your image from the menu to launch the emulator in a new window. If needed, enter your host root password in the shell window at the prompt. This sets up a Tap 0 connection needed for running in user-space NFS mode. Wait for QEMU to launch. Once QEMU launches, you can begin operating within that environment. For example, you could determine the IP Address for the user-space NFS by using the ifconfig command.

Once the QEMU emulator is running the image, using the Eclipse IDE you can deploy your application and use the emulator to perform debugging. Follow these steps to deploy the application. Select Run -> Debug Configurations... In the left area, expand C/C++Remote Application. Locate your project and select it to bring up a new tabbed view in the Debug Configurations Dialog. Enter the absolute path into which you want to deploy the application. Use the Remote Absolute File Path for C/C++Application: field. For example, enter /usr/bin/<programname>. Click on the Debugger tab to see the cross-tool debugger you are using. Click on the Main tab. Create a new connection to the QEMU instance by clicking on new. Select TCF, which means Target Communication Framework. Click Next. Clear out the host name field and enter the IP Address determined earlier. Click Finish to close the New Connections Dialog. Use the drop-down menu now in the Connection field and pick the IP Address you entered. Click Run to bring up a login screen and login. Accept the debug perspective.

As mentioned earlier in the manual, several tools exist that enhance your development experience. These tools are aids in developing and debugging applications and images. You can run these user-space tools from within the Eclipse IDE through the YoctoTools menu. Once you pick a tool, you need to configure it for the remote target. Every tool needs to have the connection configured. You must select an existing TCF-based RSE connection to the remote target. If one does not exist, click New to create one. Here are some specifics about the remote tools: OProfile: Selecting this tool causes the oprofile-server on the remote target to launch on the local host machine. The oprofile-viewer must be installed on the local host machine and the oprofile-server must be installed on the remote target, respectively, in order to use. You must compile and install the oprofile-viewer from the source code on your local host machine. Furthermore, in order to convert the target's sample format data into a form that the host can use, you must have oprofile version 0.9.4 or greater installed on the host. You can locate both the viewer and server from . The oprofile-server is installed by default on the core-image-sato-sdk image. Lttng-ust: Selecting this tool runs usttrace on the remote target, transfers the output data back to the local host machine, and uses the lttng Eclipse plug-in to graphically display the output. For information on how to use lttng to trace an application, see . For Application, you must supply the absolute path name of the application to be traced by user mode lttng. For example, typing /path/to/foo triggers usttrace /path/to/foo on the remote target to trace the program /path/to/foo. Argument is passed to usttrace running on the remote target. Before you use the lttng-ust tool, you need to setup the lttng Eclipse plug-in and create a lttng project. Do the following: Follow the instructions from the Linux Tools Projec/LTTng2/User Guide to download and install the lttng parser library. Select Window -> Open Perspective -> Other and then select LTTng. Click OK to change the Eclipse perspective into the LTTng perspective. Create a new LTTng project by selecting File -> New -> Project. Choose LTTng -> LTTng Project. Click YoctoTools -> lttng-ust to start user mode lttng on the remote target. After the output data has been transferred from the remote target back to the local host machine, new traces will be imported into the selected LTTng project. Then you can go to the LTTng project, right click the imported trace, and set the trace type as the LTTng kernel trace. Finally, right click the imported trace and select Open to display the data graphically. PowerTOP: Selecting this tool runs powertop on the remote target machine and displays the results in a new view called powertop. Time to gather data(sec): is the time passed in seconds before data is gathered from the remote target for analysis. show pids in wakeups list: corresponds to the -p argument passed to powertop. LatencyTOP and Perf: latencytop identifies system latency, while perf monitors the system's performance counter registers. Selecting either of these tools causes an RSE terminal view to appear from which you can run the tools. Both tools refresh the entire screen to display results while they run.

Within Eclipse, you can create a Yocto BitBake Commander project, edit the metadata, and then use the Hob to build a customized image all within one IDE.

To create a Yocto BitBake Commander project, follow these steps: Select Window -> Open Perspective -> Other and then choose Bitbake Commander. Click OK to change the Eclipse perspective into the Bitbake Commander perspective. Select File -> New -> Project to create a new Yocto Bitbake Commander project. Choose Yocto Project Bitbake Commander -> New Yocto Project and click Next. Enter the Project Name and choose the Project Location. The Yocto project's metadata files will be put under the directory <project_location>/<project_name>. If that directory does not exist, you need to check the "Clone from Yocto Git Repository" box, which would execute a git clone command to get the project's metadata files. Select Finish to create the project.

After you create the Yocto Bitbake Commander project, you can modify the metadata files by opening them in the project. When editing recipe files (.bb files), you can view BitBake variable values and information by hovering the mouse pointer over the variable name and waiting a few seconds. To edit the metadata, follow these steps: Select your Yocto Bitbake Commander project. Select File -> New -> Yocto BitBake Commander -> BitBake Recipe to open a new recipe wizard. Point to your source by filling in the "SRC_URL" field. For example, you can add a recipe to your Source Directory by defining "SRC_URL" as follows: ftp://ftp.gnu.org/gnu/m4/m4-1.4.9.tar.gz Click "Populate" to calculate the archive md5, sha256, license checksum values and to auto-generate the recipe filename. Fill in the "Description" field. Be sure values for all required fields exist. Click Finish.

To build and customize the image in Eclipse, follow these steps: Select your Yocto Bitbake Commander project. Select Project -> Launch HOB. Enter the build directory where you want to put your final images. Click OK to launch Hob. Use Hob to customize and build your own images. For information on Hob, see the Hob Project Page on the Yocto Project website.

If you want to develop an application without prior installation of the ADT, you still can employ the cross-development toolchain, the QEMU emulator, and a number of supported target image files. You just need to follow these general steps: Install the cross-development toolchain for your target hardware: For information on how to install the toolchain, see the "Using a Cross-Toolchain Tarball" section in the Yocto Project Application Developer's Guide. Download the Target Image: The Yocto Project supports several target architectures and has many pre-built kernel images and root filesystem images. If you are going to develop your application on hardware, go to the machines download area and choose a target machine area from which to download the kernel image and root filesystem. This download area could have several files in it that support development using actual hardware. For example, the area might contain .hddimg files that combine the kernel image with the filesystem, boot loaders, etc. Be sure to get the files you need for your particular development process. If you are going to develop your application and then run and test it using the QEMU emulator, go to the machines/qemu download area. From this area, go down into the directory for your target architecture (e.g. qemux86_64 for an Intel-based 64-bit architecture). Download kernel, root filesystem, and any other files you need for your process. In order to use the root filesystem in QEMU, you need to extract it. See the "Extracting the Root Filesystem" section for information on how to extract the root filesystem. Develop and Test your Application: At this point, you have the tools to develop your application. If you need to separately install and use the QEMU emulator, you can go to QEMU Home Page to download and learn about the emulator.

You might find it helpful during development to modify the temporary source code used by recipes to build packages. For example, suppose you are developing a patch and you need to experiment a bit to figure out your solution. After you have initially built the package, you can iteratively tweak the source code, which is located in the build directory, and then you can force a re-compile and quickly test your altered code. Once you settle on a solution, you can then preserve your changes in the form of patches. You can accomplish these steps all within either a Quilt or Git workflow.

During a build, the unpacked temporary source code used by recipes to build packages is available in the build directory as defined by the S variable. Below is the default value for the S variable as defined in the meta/conf/bitbake.conf configuration file in the Source Directory: S = ${WORKDIR}/${BP} You should be aware that many recipes override the S variable. For example, recipes that fetch their source from Git usually set S to ${WORKDIR}/git. BP represents the "Base Package", which is the base package name and the package version: BP = ${BPN}-${PV} The path to the work directory for the recipe (WORKDIR) depends on the package name and the architecture of the target device. For example, here is the work directory for packages whose targets are not device-dependent: ${TMPDIR}/work/${PACKAGE_ARCH}-poky-${TARGET_OS}/${PN}-${PV}-${PR} Let's look at an example without variables. Assuming a top-level Source Directory named poky and a default build directory of poky/build, the following is the work directory for the acl package: ~/poky/build/tmp/work/i586-poky-linux/acl-2.2.51-r3 If your package is dependent on the target device, the work directory varies slightly: ${TMPDIR}/work/${MACHINE}-poky-${TARGET_OS}/${PN}-${PV}-${PR} Again, assuming top-level Source Directory named poky and a default build directory of poky/build, the following is the work directory for the acl package that is being built for a MIPS-based device: ~/poky/build/tmp/work/mips-poky-linux/acl-2.2.51-r2 To better understand how the OpenEmbedded build system resolves directories during the build process, see the glossary entries for the WORKDIR, TMPDIR, TOPDIR, PACKAGE_ARCH, TARGET_OS, PN, PV, and PR variables in the Yocto Project Reference Manual. Now that you know where to locate the directory that has the temporary source code, you can use a Quilt or Git workflow to make your edits, test the changes, and preserve the changes in the form of patches.

Quilt is a powerful tool that allows you to capture source code changes without having a clean source tree. This section outlines the typical workflow you can use to modify temporary source code, test changes, and then preserve the changes in the form of a patch all using Quilt. Follow these general steps: Find the Source Code: The temporary source code used by the OpenEmbedded build system is kept in the build directory. See the "Finding the Temporary Source Code" section to learn how to locate the directory that has the temporary source code for a particular package. Change Your Working Directory: You need to be in the directory that has the temporary source code. That directory is defined by the S variable. Create a New Patch: Before modifying source code, you need to create a new patch. To create a new patch file, use quilt new as below: $ quilt new my_changes.patch Notify Quilt and Add Files: After creating the patch, you need to notify Quilt about the files you will be changing. Add the files you will be modifying into the patch you just created: $ quilt add file1.c file2.c file3.c Edit the Files: Make the changes to the temporary source code. Test Your Changes: Once you have modified the source code, the easiest way to test your changes is by calling the compile task as shown in the following example: $ bitbake -c compile -f <name_of_package> The -f or --force option forces re-execution of the specified task. If you find problems with your code, you can just keep editing and re-testing iteratively until things work as expected. All the modifications you make to the temporary source code disappear once you -c clean or -c cleanall with BitBake for the package. Modifications will also disappear if you use the rm_work feature as described in the "Building an Image" section of the Yocto Project Quick Start. Generate the Patch: Once your changes work as expected, you need to use Quilt to generate the final patch that contains all your modifications. $ quilt refresh At this point the my_changes.patch file has all your edits made to the file1.c, file2.c, and file3.c files. You can find the resulting patch file in the patches/ subdirectory of the source (S) directory. Copy the Patch File: For simplicity, copy the patch file into a directory named files, which you can create in the same directory as the recipe. Placing the patch here guarantees that the OpenEmbedded build system will find the patch. Next, add the patch into the SRC_URI of the recipe. Here is an example: SRC_URI += "file://my_changes.patch" Increment the Package Revision Number: Finally, don't forget to 'bump' the PR value in the same recipe since the resulting packages have changed.

Git is an even more powerful tool that allows you to capture source code changes without having a clean source tree. This section outlines the typical workflow you can use to modify temporary source code, test changes, and then preserve the changes in the form of a patch all using Git. For general information on Git as it is used in the Yocto Project, see the "Git" section. This workflow uses Git only for its ability to manage local changes to the source code and produce patches independent of any version control system used with the Yocto Project. Follow these general steps: Find the Source Code: The temporary source code used by the OpenEmbedded build system is kept in the build directory. See the "Finding the Temporary Source Code" section to learn how to locate the directory that has the temporary source code for a particular package. Change Your Working Directory: You need to be in the directory that has the temporary source code. That directory is defined by the S variable. Initialize a Git Repository: Use the git init command to initialize a new local repository that is based on the work directory: $ git init Stage all the files: Use the git add * command to stage all the files in the source code directory so that they can be committed: $ git add * Commit the Source Files: Use the git commit command to initially commit all the files in the work directory: $ git commit At this point, your Git repository is aware of all the source code files. Any edits you now make to files will be tracked by Git. Edit the Files: Make the changes to the temporary source code. Test Your Changes: Once you have modified the source code, the easiest way to test your changes is by calling the compile task as shown in the following example: $ bitbake -c compile -f <name_of_package> The -f or --force option forces re-execution of the specified task. If you find problems with your code, you can just keep editing and re-testing iteratively until things work as expected. All the modifications you make to the temporary source code disappear once you -c clean or -c cleanall with BitBake for the package. Modifications will also disappear if you use the rm_work feature as described in the "Building an Image" section of the Yocto Project Quick Start. See the List of Files You Changed: Use the git status command to see what files you have actually edited. The ability to have Git track the files you have changed is an advantage that this workflow has over the Quilt workflow. Here is the Git command to list your changed files: $ git status Stage the Modified Files: Use the git add command to stage the changed files so they can be committed as follows: $ git add file1.c file2.c file3.c Commit the Staged Files and View Your Changes: Use the git commit command to commit the changes to the local repository. Once you have committed the files, you can use the git log command to see your changes: $ git commit $ git log Generate the Patch: Once the changes are committed, use the git format-patch command to generate a patch file: $ git format-patch HEAD~1 The HEAD~1 part of the command causes Git to generate the patch file for the most recent commit. At this point, the patch file has all your edits made to the file1.c, file2.c, and file3.c files. You can find the resulting patch file in the current directory. The patch file ends with .patch. Copy the Patch File: For simplicity, copy the patch file into a directory named files, which you can create in the same directory as the recipe. Placing the patch here guarantees that the OpenEmbedded build system will find the patch. Next, add the patch into the SRC_URI of the recipe. Here is an example: SRC_URI += "file://my_changes.patch" Increment the Package Revision Number: Finally, don't forget to 'bump' the PR value in the same recipe since the resulting packages have changed.

The Hob is a graphical user interface for the OpenEmbedded build system, which is based on BitBake. You can use the Hob to build custom operating system images within the Yocto Project build environment. Hob simply provides a friendly interface over the build system used during system development. In other words, building images with the Hob lets you take care of common build tasks more easily. For a better understanding of Hob, see the project page at on the Yocto Project website. The page has a short introductory training video on Hob. The following lists some features of Hob: You can setup and run Hob using these commands: $ source oe-init-build-env $ hob You can set the MACHINE for which you are building the image. You can modify various policy settings such as the package format used to build with, the parrallelism BitBake uses, whether or not to build an external toolchain, and which host to build against. You can manage layers. You can select a base image and then add extra packages for your custom build. You can launch and monitor the build from within Hob.

When debugging certain commands or even when just editing packages, devshell can be a useful tool. When you invoke devshell, source files are extracted into your working directory and patches are applied. Then, a new terminal is opened and you are placed in the working directory. In the new terminal, all the OpenEmbedded build-related environment variables are still defined so you can use commands such as configure and make. The commands execute just as if the OpenEmbedded build system were executing them. Consequently, working this way can be helpful when debugging a build or preparing software to be used with the OpenEmbedded build system. Following is an example that uses devshell on a target named matchbox-desktop: $ bitbake matchbox-desktop -c devshell This command opens a terminal with a shell prompt within the OpenEmbedded build environment. The default shell is xterm. The following occurs: The PATH variable includes the cross-toolchain. The pkgconfig variables find the correct .pc files. The configure command finds the Yocto Project site files as well as any other necessary files. Within this environment, you can run configure or compile commands as if they were being run by the OpenEmbedded build system itself. As noted earlier, the working directory also automatically changes to the Source Directory (S). When you are finished, you just exit the shell or close the terminal window. Because an external shell is launched rather than opening directly into the original terminal window, it allows easier interaction with BitBake's multiple threads as well as accomodates a future client/server split. It is worth remembering that when using devshell you need to use the full compiler name such as arm-poky-linux-gnueabi-gcc instead of just using gcc. The same applies to other applications such as binutils, libtool and so forth. BitBake sets up environment variables such as CC to assist applications, such as make to find the correct tools. It is also worth noting that devshell still works over X11 forwarding and similar situations