.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ************************ Using the Extensible SDK ************************ 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 ``devtool`` 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 :term:`OpenEmbedded Build System`. .. note:: For a side-by-side comparison of main features supported for an extensible SDK as compared to a standard SDK, see the :ref:`sdk-manual/intro:introduction` section. In addition to the functionality available through ``devtool``, you can alternatively make use of the toolchain directly, for example from Makefile and Autotools. See the ":ref:`sdk-manual/working-projects:using the sdk toolchain directly`" chapter for more information. Why use the Extensible SDK and What is in It? ============================================= 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 ``devtool`` commands tailored for the Yocto Project environment. 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 ``devtool`` functionality. Installing the Extensible SDK ============================= Two ways to install the Extensible SDK -------------------------------------- Extensible SDK can be installed in two different ways, and both have their own pros and cons: 1. *Setting up the Extensible SDK environment directly in a Yocto build*. This avoids having to produce, test, distribute and maintain separate SDK installer archives, which can get very large. There is only one environment for the regular Yocto build and the SDK and less code paths where things can go not according to plan. It's easier to update the SDK: it simply means updating the Yocto layers with git fetch or layer management tooling. The SDK extensibility is better than in the second option: just run ``bitbake`` again to add more things to the sysroot, or add layers if even more things are required. 2. *Setting up the Extensible SDK from a standalone installer*. This has the benefit of having a single, self-contained archive that includes all the needed binary artifacts. So nothing needs to be rebuilt, and there is no need to provide a well-functioning binary artefact cache over the network for developers with underpowered laptops. Setting up the Extensible SDK environment directly in a Yocto build ------------------------------------------------------------------- 1. Set up all the needed layers and a Yocto build directory, e.g. a regular Yocto build where ``bitbake`` can be executed. 2. Run: $ bitbake meta-ide-support $ bitbake -c populate_sysroot gtk+3 (or any other target or native item that the application developer would need) $ bitbake build-sysroots Setting up the Extensible SDK from a standalone installer --------------------------------------------------------- The first thing you need to do is install the SDK on your :term:`Build Host` by running the ``*.sh`` installation script. You can download a tarball installer, which includes the pre-built toolchain, the ``runqemu`` script, the internal build system, ``devtool``, and support files from the appropriate :yocto_dl:`toolchain ` directory within the Index of Releases. Toolchains are available for several 32-bit and 64-bit architectures with the ``x86_64`` directories, respectively. The toolchains the Yocto Project provides are based off the ``core-image-sato`` and ``core-image-minimal`` images and contain libraries appropriate for developing against that image. 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:: poky-glibc-host_system-image_type-arch-toolchain-ext-release_version.sh Where: host_system is a string representing your development system: i686 or x86_64. image_type is the image for which the SDK was built: core-image-sato or core-image-minimal arch is a string representing the tuned target architecture: aarch64, armv5e, core2-64, i586, mips32r2, mips64, ppc7400, or cortexa8hf-neon release_version is a string representing the release number of the Yocto Project: &DISTRO;, &DISTRO;+snapshot 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 ``core-image-sato`` and using the current &DISTRO; snapshot:: poky-glibc-x86_64-core-image-sato-i586-toolchain-ext-&DISTRO;.sh .. note:: As an alternative to downloading an SDK, you can build the SDK installer. For information on building the installer, see the :ref:`sdk-manual/appendix-obtain:building an sdk installer` section. The SDK and toolchains are self-contained and by default are installed into the ``poky_sdk`` 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. 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 ``~/Downloads/`` 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. :: $ ./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 Running the Extensible SDK Environment Setup Script =================================================== Once you have the SDK installed, you must run the SDK environment setup script before you can actually use the SDK. When using a SDK directly in a Yocto build, you will find the script in ``tmp/deploy/images/qemux86-64/`` in your build directory. When using a standalone SDK installer, this setup script resides in the directory you chose when you installed the SDK, which is either the default ``poky_sdk`` directory or the directory you chose during installation. 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 "``environment-setup``" 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:: $ 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. When using the environment script directly in a Yocto build, it can be run similarly: $ source tmp/deploy/images/qemux86-64/environment-setup-core2-64-poky-linux Running the setup script defines many environment variables needed in order to use the SDK (e.g. ``PATH``, :term:`CC`, :term:`LD`, and so forth). If you want to see all the environment variables the script exports, examine the installation file itself. Using ``devtool`` in Your SDK Workflow ====================================== The cornerstone of the extensible SDK is a command-line tool called ``devtool``. 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:: The use of devtool is not limited to the extensible SDK. You can use devtool to help you easily develop any project whose build output must be part of an image built using the build system. The ``devtool`` command line is organized similarly to :ref:`overview-manual/development-environment:git` in that it has a number of sub-commands for each function. You can run ``devtool --help`` to see all the commands. .. note:: See the " devtool  Quick Reference " in the Yocto Project Reference Manual for a devtool quick reference. Three ``devtool`` subcommands provide entry-points into development: - *devtool add*: Assists in adding new software to be built. - *devtool modify*: Sets up an environment to enable you to modify the source of an existing component. - *devtool upgrade*: Updates an existing recipe so that you can build it for an updated set of source files. As with the build system, "recipes" represent software packages within ``devtool``. When you use ``devtool add``, a recipe is automatically created. When you use ``devtool modify``, 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. The remainder of this section presents the ``devtool add``, ``devtool modify``, and ``devtool upgrade`` workflows. Use ``devtool add`` to Add an Application ----------------------------------------- The ``devtool add`` command generates a new recipe based on existing source code. This command takes advantage of the :ref:`devtool-the-workspace-layer-structure` layer that many ``devtool`` 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. Depending on your particular scenario, the arguments and options you use with ``devtool add`` form different combinations. The following diagram shows common development flows you would use with the ``devtool add`` command: .. image:: figures/sdk-devtool-add-flow.png :width: 100% 1. *Generating the New Recipe*: The top part of the flow shows three scenarios by which you could use ``devtool add`` to generate a recipe based on existing source code. 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. Within the diagram, three possible scenarios feed into the ``devtool add`` workflow: - *Left*: 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:: $ devtool add recipe fetchuri With this command, ``devtool`` extracts the upstream source files into a local Git repository within the ``sources`` folder. The command then creates a recipe named recipe and a corresponding append file in the workspace. If you do not provide recipe, the command makes an attempt to determine the recipe name. - *Middle*: 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, devtool always creates a Git repository locally during the extraction. Furthermore, the first positional argument ``srctree`` in this case identifies where the ``devtool add`` command will locate the extracted code outside of the workspace. You need to specify an empty directory:: $ devtool add recipe srctree fetchuri In summary, the source code is pulled from fetchuri and extracted into the location defined by ``srctree`` as a local Git repository. Within workspace, ``devtool`` creates a recipe named recipe along with an associated append file. - *Right*: The right scenario in the figure represents a situation where the ``srctree`` has been previously prepared outside of the ``devtool`` workspace. The following command provides a new recipe name and identifies the existing source tree location:: $ devtool add recipe srctree The command examines the source code and creates a recipe named recipe for the code and places the recipe into the workspace. Because the extracted source code already exists, ``devtool`` does not try to relocate the source code into the workspace --- only the new recipe is placed in the workspace. Aside from a recipe folder, the command also creates an associated append folder and places an initial ``*.bbappend`` file within. 2. *Edit the Recipe*: You can use ``devtool edit-recipe`` to open up the editor as defined by the ``$EDITOR`` environment variable and modify the file:: $ devtool edit-recipe recipe From within the editor, you can make modifications to the recipe that take effect when you build it later. 3. *Build the Recipe or Rebuild the Image*: The next step you take depends on what you are going to do with the new code. If you need to eventually move the build output to the target hardware, use the following ``devtool`` command: :; $ devtool build recipe 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 ``devtool build-image`` command:: $ devtool build-image image 4. *Deploy the Build Output*: When you use the ``devtool build`` 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. You can deploy your build output to that target hardware by using the ``devtool deploy-target`` command: $ devtool deploy-target recipe target The target is a live target machine running as an SSH server. You can, of course, also deploy the image you build to actual hardware by using the ``devtool build-image`` command. However, ``devtool`` does not provide a specific command that allows you to deploy the image to actual hardware. 5. *Finish Your Work With the Recipe*: The ``devtool finish`` 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. :: $ devtool finish recipe layer .. note:: Any changes you want to turn into patches must be committed to the Git repository in the source tree. As mentioned, the ``devtool finish`` command moves the final recipe to its permanent layer. As a final process of the ``devtool finish`` 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 devtool reset 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. Use ``devtool modify`` to Modify the Source of an Existing Component -------------------------------------------------------------------- The ``devtool modify`` 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. Depending on your particular scenario, the arguments and options you use with ``devtool modify`` form different combinations. The following diagram shows common development flows for the ``devtool modify`` command: .. image:: figures/sdk-devtool-modify-flow.png :width: 100% 1. *Preparing to Modify the Code*: The top part of the flow shows three scenarios by which you could use ``devtool modify`` to prepare to work on source files. Each scenario assumes the following: - The recipe exists locally in a layer external to the ``devtool`` workspace. - The source files exist either upstream in an un-extracted state or locally in a previously extracted state. 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. - *Left*: 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 ``devtool`` workspace location. The recipe, in this scenario, is in its own layer outside the workspace (i.e. ``meta-``\ layername). The following command identifies the recipe and, by default, extracts the source files:: $ devtool modify recipe Once ``devtool``\ locates the recipe, ``devtool`` uses the recipe's :term:`SRC_URI` statements to locate the source code and any local patch files from other developers. With this scenario, there is no ``srctree`` argument. Consequently, the default behavior of the ``devtool modify`` command is to extract the source files pointed to by the :term:`SRC_URI` statements into a local Git structure. Furthermore, the location for the extracted source is the default area within the ``devtool`` 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. Additionally, if you have any non-patch local files (i.e. files referred to with ``file://`` entries in :term:`SRC_URI` statement excluding ``*.patch/`` or ``*.diff``), these files are copied to an ``oe-local-files`` folder under the newly created source tree. Copying the files here gives you a convenient area from which you can modify the files. Any changes or additions you make to those files are incorporated into the build the next time you build the software just as are other changes you might have made to the source. - *Middle*: 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. The following command tells ``devtool`` the recipe with which to work and, in this case, identifies a local area for the extracted source files that exists outside of the default ``devtool`` workspace:: $ devtool modify recipe srctree .. note:: You cannot provide a URL for srctree using the devtool command. As with all extractions, the command uses the recipe's :term:`SRC_URI` statements to locate the source files and any associated patch files. Non-patch files are copied to an ``oe-local-files`` folder under the newly created source tree. Once the files are located, the command by default extracts them into ``srctree``. Within workspace, ``devtool`` 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 ``srctree``. - *Right*: The right scenario in the figure represents a situation where the source tree (``srctree``) already exists locally as a previously extracted Git structure outside of the ``devtool`` workspace. In this example, the recipe also exists elsewhere locally in its own layer. The following command tells ``devtool`` the recipe with which to work, uses the "-n" option to indicate source does not need to be extracted, and uses ``srctree`` to point to the previously extracted source files:: $ devtool modify -n recipe srctree If an ``oe-local-files`` subdirectory happens to exist and it contains non-patch files, the files are used. However, if the subdirectory does not exist and you run the ``devtool finish`` command, any non-patch files that might exist next to the recipe are removed because it appears to ``devtool`` that you have deleted those files. Once the ``devtool modify`` command finishes, it creates only an append file for the recipe in the ``devtool`` workspace. The recipe and the source code remain in their original locations. 2. *Edit the Source*: Once you have used the ``devtool modify`` 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. 3. *Build the Recipe or Rebuild the Image*: The next step you take depends on what you are going to do with the new code. If you need to eventually move the build output to the target hardware, use the following ``devtool`` command:: $ devtool build recipe 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 ``devtool build-image`` command: $ devtool build-image image 4. *Deploy the Build Output*: When you use the ``devtool build`` 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. You can deploy your build output to that target hardware by using the ``devtool deploy-target`` command:: $ devtool deploy-target recipe target The target is a live target machine running as an SSH server. You can, of course, use other methods to deploy the image you built using the ``devtool build-image`` command to actual hardware. ``devtool`` does not provide a specific command to deploy the image to actual hardware. 5. *Finish Your Work With the Recipe*: The ``devtool finish`` command creates any patches corresponding to commits in the local Git repository, updates the recipe to point to them (or creates a ``.bbappend`` 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. :: $ devtool finish recipe layer .. note:: Any changes you want to turn into patches must be staged and committed within the local Git repository before you use the devtool finish command. Because there is no need to move the recipe, ``devtool finish`` either updates the original recipe in the original layer or the command creates a ``.bbappend`` file in a different layer as provided by layer. Any work you did in the ``oe-local-files`` directory is preserved in the original files next to the recipe during the ``devtool finish`` command. As a final process of the ``devtool finish`` 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 devtool reset 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. Use ``devtool upgrade`` to Create a Version of the Recipe that Supports a Newer Version of the Software ------------------------------------------------------------------------------------------------------- The ``devtool upgrade`` 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 ``devtool upgrade`` 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 - ``devtool upgrade`` happens to be one. You can read about all the methods by which you can upgrade recipes in the :ref:`dev-manual/common-tasks:upgrading recipes` section of the Yocto Project Development Tasks Manual. The ``devtool upgrade`` command is flexible enough to allow you to specify source code revision and versioning schemes, extract code into or out of the ``devtool`` :ref:`devtool-the-workspace-layer-structure`, and work with any source file forms that the :ref:`bitbake:bitbake-user-manual/bitbake-user-manual-fetching:fetchers` support. The following diagram shows the common development flow used with the ``devtool upgrade`` command: .. image:: figures/sdk-devtool-upgrade-flow.png :width: 100% 1. *Initiate the Upgrade*: The top part of the flow shows the typical scenario by which you use the ``devtool upgrade`` command. The following conditions exist: - The recipe exists in a local layer external to the ``devtool`` workspace. - The source files for the new release exist in the same location pointed to by :term:`SRC_URI` 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). 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:: $ devtool upgrade -V version recipe By default, the ``devtool upgrade`` command extracts source code into the ``sources`` directory in the :ref:`devtool-the-workspace-layer-structure`. If you want the code extracted to any other location, you need to provide the ``srctree`` positional argument with the command as follows:: $ devtool upgrade -V version recipe srctree .. 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. If the source files pointed to by the :term:`SRC_URI` statement in the recipe are in a Git repository, you must provide the "-S" option and specify a revision for the software. Once ``devtool`` locates the recipe, it uses the :term:`SRC_URI` 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. Additionally, if you have any non-patch local files (i.e. files referred to with ``file://`` entries in :term:`SRC_URI` statement excluding ``*.patch/`` or ``*.diff``), these files are copied to an ``oe-local-files`` folder under the newly created source tree. Copying the files here gives you a convenient area from which you can modify the files. Any changes or additions you make to those files are incorporated into the build the next time you build the software just as are other changes you might have made to the source. 2. *Resolve any Conflicts created by the Upgrade*: Conflicts could happen after upgrading the software to a new version. Conflicts occur if your recipe specifies some patch files in :term:`SRC_URI` 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 ``git rebase`` conflict resolution process. 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. 3. *Build the Recipe or Rebuild the Image*: The next step you take depends on what you are going to do with the new code. If you need to eventually move the build output to the target hardware, use the following ``devtool`` command:: $ devtool build recipe 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 ``devtool build-image`` command:: $ devtool build-image image 4. *Deploy the Build Output*: When you use the ``devtool build`` command or ``bitbake`` 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. You can deploy your build output to that target hardware by using the ``devtool deploy-target`` command: $ devtool deploy-target recipe target The target is a live target machine running as an SSH server. You can, of course, also deploy the image you build using the ``devtool build-image`` command to actual hardware. However, ``devtool`` does not provide a specific command that allows you to do this. 5. *Finish Your Work With the Recipe*: The ``devtool finish`` 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. Any work you did in the ``oe-local-files`` directory is preserved in the original files next to the recipe during the ``devtool finish`` command. If you specify a destination layer that is the same as the original source, then the old version of the recipe and associated files are removed prior to adding the new version. :: $ devtool finish recipe layer .. note:: Any changes you want to turn into patches must be committed to the Git repository in the source tree. As a final process of the ``devtool finish`` 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 devtool reset 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. A Closer Look at ``devtool add`` ================================ The ``devtool add`` command automatically creates a recipe based on the source tree you provide with the command. Currently, the command has support for the following: - Autotools (``autoconf`` and ``automake``) - CMake - Scons - ``qmake`` - Plain ``Makefile`` - Out-of-tree kernel module - Binary package (i.e. "-b" option) - Node.js module - Python modules that use ``setuptools`` or ``distutils`` 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 ``CMakeLists.txt`` 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. The remainder of this section covers specifics regarding how parts of the recipe are generated. Name and Version ---------------- If you do not specify a name and version on the command line, ``devtool add`` 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, ``devtool`` sets the name of the created recipe file accordingly. If ``devtool`` 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. Sometimes the name or version determined from the source tree might be incorrect. For such a case, you must reset the recipe:: $ devtool reset -n recipename After running the ``devtool reset`` command, you need to run ``devtool add`` again and provide the name or the version. Dependency Detection and Mapping -------------------------------- The ``devtool add`` 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 :term:`DEPENDS` variable within the recipe. If a dependency cannot be mapped, ``devtool`` 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 ``devtool add`` command to add an additional recipe that satisfies the dependency. Once you add that recipe, you need to update the :term:`DEPENDS` variable in the original recipe to include the new recipe. If you need to add runtime dependencies, you can do so by adding the following to your recipe:: RDEPENDS:${PN} += "dependency1 dependency2 ..." .. note:: The devtool add 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. License Detection ----------------- The ``devtool add`` 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 :term:`LICENSE` 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 :term:`LICENSE` value. The ``devtool add`` command also sets the :term:`LIC_FILES_CHKSUM` 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 :term:`LIC_FILES_CHKSUM` variable to point to one or more of those comments if present. Setting :term:`LIC_FILES_CHKSUM` 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. If the ``devtool add`` command cannot determine licensing information, ``devtool`` sets the :term:`LICENSE` value to "CLOSED" and leaves the :term:`LIC_FILES_CHKSUM` 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. Adding Makefile-Only Software ----------------------------- 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, ``devtool add`` often cannot do very much to ensure that these Makefiles build correctly. It is very common, for example, to explicitly call ``gcc`` instead of using the :term:`CC` variable. Usually, in a cross-compilation environment, ``gcc`` is the compiler for the build host and the cross-compiler is named something similar to ``arm-poky-linux-gnueabi-gcc`` and might require arguments (e.g. to point to the associated sysroot for the target machine). When writing a recipe for Makefile-only software, keep the following in mind: - You probably need to patch the Makefile to use variables instead of hardcoding tools within the toolchain such as ``gcc`` and ``g++``. - The environment in which Make runs is set up with various standard variables for compilation (e.g. :term:`CC`, :term:`CXX`, 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 ``devtool build`` command on the recipe and then look in ``oe-logs/run.do_compile``. Towards the top of this file, there is a list of environment variables that are set. You can take advantage of these variables within the Makefile. - 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 ``make`` command line. To force the value on the command line, add the variable setting to :term:`EXTRA_OEMAKE` or :term:`PACKAGECONFIG_CONFARGS` within the recipe. Here is an example using :term:`EXTRA_OEMAKE`:: EXTRA_OEMAKE += "'CC=${CC}' 'CXX=${CXX}'" 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. - 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. - Sometimes a Makefile runs target-specific commands such as ``ldconfig``. For such cases, you might be able to apply patches that remove these commands from the Makefile. Adding Native Tools ------------------- Often, you need to build additional tools that run on the :term:`Build Host` as opposed to the target. You should indicate this requirement by using one of the following methods when you run ``devtool add``: - 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. - Specify the "--also-native" option with the ``devtool add`` 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. .. 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 "--also-native" option, you can add the tool using just one recipe file. Adding Node.js Modules ---------------------- You can use the ``devtool add`` command two different ways to add Node.js modules: 1) Through ``npm`` and, 2) from a repository or local source. Use the following form to add Node.js modules through ``npm``:: $ devtool add "npm://registry.npmjs.org;name=forever;version=0.15.1" 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:: - You must use quotes around the URL. The ``devtool add`` does not require the quotes, but the shell considers ";" as a splitter between multiple commands. Thus, without the quotes, ``devtool add`` does not receive the other parts, which results in several "command not found" errors. - In order to support adding Node.js modules, a ``nodejs`` recipe must be part of your SDK. As mentioned earlier, you can also add Node.js modules directly from a repository or local source tree. To add modules this way, use ``devtool add`` in the following form:: $ devtool add https://github.com/diversario/node-ssdp In this example, ``devtool`` fetches the specified Git repository, detects the code as Node.js code, fetches dependencies using ``npm``, and sets :term:`SRC_URI` accordingly. Working With Recipes ==================== When building a recipe using the ``devtool build`` command, the typical build progresses as follows: 1. Fetch the source 2. Unpack the source 3. Configure the source 4. Compile the source 5. Install the build output 6. Package the installed output 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. :ref:`ref-tasks-fetch`, :ref:`ref-tasks-unpack`, and so forth). These functions are typically shell scripts but can instead be written in Python. 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 ``inherit`` directive. This technique leaves the recipe to describe just the things that are specific to the software being built. There is a :ref:`base ` class that is implicitly inherited by all recipes and provides the functionality that most recipes typically need. The remainder of this section presents information useful when working with recipes. Finding Logs and Work Files --------------------------- After the first run of the ``devtool build`` command, recipes that were previously created using the ``devtool add`` command or whose sources were modified using the ``devtool modify`` command contain symbolic links created within the source tree: - ``oe-logs``: This link points to the directory in which log files and run scripts for each build step are created. - ``oe-workdir``: This link points to the temporary work area for the recipe. The following locations under ``oe-workdir`` are particularly useful: - ``image/``: Contains all of the files installed during the :ref:`ref-tasks-install` stage. Within a recipe, this directory is referred to by the expression ``${``\ :term:`D`\ ``}``. - ``sysroot-destdir/``: Contains a subset of files installed within :ref:`ref-tasks-install` that have been put into the shared sysroot. For more information, see the ":ref:`dev-manual/common-tasks:sharing files between recipes`" section. - ``packages-split/``: Contains subdirectories for each package produced by the recipe. For more information, see the ":ref:`sdk-manual/extensible:packaging`" section. You can use these links to get more information on what is happening at each build step. Setting Configure Arguments --------------------------- 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 :term:`EXTRA_OECONF` or :term:`PACKAGECONFIG_CONFARGS` set within the recipe. If you wish to pass additional options, add them to :term:`EXTRA_OECONF` or :term:`PACKAGECONFIG_CONFARGS`. Other supported build tools have similar variables (e.g. :term:`EXTRA_OECMAKE` for CMake, :term:`EXTRA_OESCONS` for Scons, and so forth). If you need to pass anything on the ``make`` command line, you can use :term:`EXTRA_OEMAKE` or the :term:`PACKAGECONFIG_CONFARGS` variables to do so. You can use the ``devtool configure-help`` 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 :term:`EXTRA_OECONF` or :term:`PACKAGECONFIG_CONFARGS`. If applicable, the command also shows you the output of the configure script's "--help" option as a reference. Sharing Files Between Recipes ----------------------------- Recipes often need to use files provided by other recipes on the :term:`Build Host`. For example, an application linking to a common library needs access to the library itself and its associated headers. The way this access is accomplished within the extensible SDK is through the sysroot. There is one sysroot per "machine" for which the SDK is being built. In practical terms, this means there is a sysroot for the target machine, and a sysroot for the build host. Recipes should never write files directly into the sysroot. Instead, files should be installed into standard locations during the :ref:`ref-tasks-install` task within the ``${``\ :term:`D`\ ``}`` 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. Packaging --------- 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. During the :ref:`ref-tasks-package` task, files installed during the :ref:`ref-tasks-install` 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 ``-doc`` package. Recipes that package software containing optional modules or plugins might undergo additional package splitting as well. After building a recipe, you can see where files have gone by looking in the ``oe-workdir/packages-split`` directory, which contains a subdirectory for each package. Apart from some advanced cases, the :term:`PACKAGES` and :term:`FILES` variables controls splitting. The :term:`PACKAGES` variable lists all of the packages to be produced, while the :term:`FILES` variable specifies which files to include in each package by using an override to specify the package. For example, ``FILES:${PN}`` specifies the files to go into the main package (i.e. the main package has the same name as the recipe and ``${``\ :term:`PN`\ ``}`` evaluates to the recipe name). The order of the :term:`PACKAGES` value is significant. For each installed file, the first package whose :term:`FILES` value matches the file is the package into which the file goes. Both the :term:`PACKAGES` and :term:`FILES` variables have default values. 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. Restoring the Target Device to its Original State ================================================= If you use the ``devtool deploy-target`` 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 ``devtool deploy-target`` command. Because the ``devtool deploy-target`` command backs up any files it overwrites, you can use the ``devtool undeploy-target`` command to restore those files and remove any other files the recipe deployed. Consider the following example:: $ devtool undeploy-target lighttpd root@192.168.7.2 If you have deployed multiple applications, you can remove them all using the "-a" option thus restoring the target device to its original state:: $ devtool undeploy-target -a root@192.168.7.2 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 devtool deploy-target and devtool undeploy-target commands do not currently interact with any package management system on the target device (e.g. RPM or OPKG). Consequently, you should not intermingle devtool deploy-target and package manager operations on the target device. Doing so could result in a conflicting set of files. Installing Additional Items Into the Extensible SDK =================================================== 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 ``devtool search`` 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:: $ devtool search libGL mesa A free implementation of the OpenGL API Once you know the recipe (i.e. ``mesa`` in this example), you can install it. When using the extensible SDK directly in a Yocto build ------------------------------------------------------- In this scenario, the Yocto build tooling, e.g. ``bitbake`` is directly accessible to build additional items, and it can simply be executed directly: $ bitbake mesa $ bitbake build-sysroots When using a standalone installer for the Extensible SDK -------------------------------------------------------- $ devtool sdk-install mesa By default, the ``devtool sdk-install`` 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:: $ devtool sdk-install -s mesa It is important to remember that building the item from source takes significantly longer than installing the pre-built artifact. Also, if there is no recipe for the item you want to add to the SDK, you must instead add the item using the ``devtool add`` command. Applying Updates to an Installed Extensible SDK =============================================== If you are working with an installed extensible SDK that gets occasionally updated (e.g. a third-party SDK), then you will need to manually "pull down" the updates into the installed SDK. To update your installed SDK, use ``devtool`` as follows:: $ devtool sdk-update The previous command assumes your SDK provider has set the default update URL for you through the :term:`SDK_UPDATE_URL` variable as described in the ":ref:`sdk-manual/appendix-customizing:Providing Updates to the Extensible SDK After Installation`" section. If the SDK provider has not set that default URL, you need to specify it yourself in the command as follows: $ devtool sdk-update path_to_update_directory .. note:: The URL needs to point specifically to a published SDK and not to an SDK installer that you would download and install. Creating a Derivative SDK With Additional Components ==================================================== 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: 1. If necessary, install an extensible SDK that you want to use as a base for your derivative SDK. 2. Source the environment script for the SDK. 3. Add the extra libraries or other components you want by using the ``devtool add`` command. 4. Run the ``devtool build-sdk`` command. 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.