4.9 Moving to the Yocto Project 2.1 Release

This section provides migration information for moving to the Yocto Project 2.1 Release from the prior release.

4.9.1 Variable Expansion in Python Functions

Variable expressions, such as ${VARNAME} no longer expand automatically within Python functions. Suppressing expansion was done to allow Python functions to construct shell scripts or other code for situations in which you do not want such expressions expanded. For any existing code that relies on these expansions, you need to change the expansions to expand the value of individual variables through d.getVar(). To alternatively expand more complex expressions, use d.expand().

4.9.2 Overrides Must Now be Lower-Case

The convention for overrides has always been for them to be lower-case characters. This practice is now a requirement as BitBake’s datastore now assumes lower-case characters in order to give a slight performance boost during parsing. In practical terms, this requirement means that anything that ends up in OVERRIDES must now appear in lower-case characters (e.g. values for MACHINE, TARGET_ARCH, DISTRO, and also recipe names if _pn-recipename overrides are to be effective).

4.9.3 Expand Parameter to getVar() and getVarFlag() is Now Mandatory

The expand parameter to getVar() and getVarFlag() previously defaulted to False if not specified. Now, however, no default exists so one must be specified. You must change any getVar() calls that do not specify the final expand parameter to calls that do specify the parameter. You can run the following sed command at the base of a layer to make this change:

sed -e 's:\(\.getVar([^,()]*\)):\1, False):g' -i `grep -ril getVar *`
sed -e 's:\(\.getVarFlag([^,()]*,[^,()]*\)):\1, False):g' -i `grep -ril getVarFlag *`

Note

The reason for this change is that it prepares the way for changing the default to True in a future Yocto Project release. This future change is a much more sensible default than False. However, the change needs to be made gradually as a sudden change of the default would potentially cause side-effects that would be difficult to detect.

4.9.4 Makefile Environment Changes

EXTRA_OEMAKE now defaults to “” instead of “-e MAKEFLAGS=”. Setting EXTRA_OEMAKE to “-e MAKEFLAGS=” by default was a historical accident that has required many classes (e.g. autotools, module) and recipes to override this default in order to work with sensible build systems. When upgrading to the release, you must edit any recipe that relies upon this old default by either setting EXTRA_OEMAKE back to “-e MAKEFLAGS=” or by explicitly setting any required variable value overrides using EXTRA_OEMAKE, which is typically only needed when a Makefile sets a default value for a variable that is inappropriate for cross-compilation using the “=” operator rather than the “?=” operator.

4.9.5 libexecdir Reverted to ${prefix}/libexec

The use of ${libdir}/${BPN} as libexecdir is different as compared to all other mainstream distributions, which either uses ${prefix}/libexec or ${libdir}. The use is also contrary to the GNU Coding Standards (i.e. https://www.gnu.org/prep/standards/html_node/Directory-Variables.html) that suggest ${prefix}/libexec and also notes that any package-specific nesting should be done by the package itself. Finally, having libexecdir change between recipes makes it very difficult for different recipes to invoke binaries that have been installed into libexecdir. The Filesystem Hierarchy Standard (i.e. https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s07.html) now recognizes the use of ${prefix}/libexec/, giving distributions the choice between ${prefix}/lib or ${prefix}/libexec without breaking FHS.

4.9.6 ac_cv_sizeof_off_t is No Longer Cached in Site Files

For recipes inheriting the autotools class, ac_cv_sizeof_off_t is no longer cached in the site files for autoconf. The reason for this change is because the ac_cv_sizeof_off_t value is not necessarily static per architecture as was previously assumed. Rather, the value changes based on whether large file support is enabled. For most software that uses autoconf, this change should not be a problem. However, if you have a recipe that bypasses the standard do_configure task from the autotools class and the software the recipe is building uses a very old version of autoconf, the recipe might be incapable of determining the correct size of off_t during do_configure.

The best course of action is to patch the software as necessary to allow the default implementation from the autotools class to work such that autoreconf succeeds and produces a working configure script, and to remove the overridden do_configure task such that the default implementation does get used.

4.9.7 Image Generation is Now Split Out from Filesystem Generation

Previously, for image recipes the do_rootfs task assembled the filesystem and then from that filesystem generated images. With this Yocto Project release, image generation is split into separate do_image tasks for clarity both in operation and in the code.

For most cases, this change does not present any problems. However, if you have made customizations that directly modify the do_rootfs task or that mention do_rootfs, you might need to update those changes. In particular, if you had added any tasks after do_rootfs, you should make edits so that those tasks are after the do_image_complete task rather than after do_rootfs so that the your added tasks run at the correct time.

A minor part of this restructuring is that the post-processing definitions and functions have been moved from the image class to the rootfs-postcommands class. Functionally, however, they remain unchanged.

4.9.8 Removed Recipes

The following recipes have been removed in the 2.1 release:

  • gcc version 4.8: Versions 4.9 and 5.3 remain.

  • qt4: All support for Qt 4.x has been moved out to a separate meta-qt4 layer because Qt 4 is no longer supported upstream.

  • x11vnc: Moved to the meta-oe layer.

  • linux-yocto-3.14: No longer supported.

  • linux-yocto-3.19: No longer supported.

  • libjpeg: Replaced by the libjpeg-turbo recipe.

  • pth: Became obsolete.

  • liboil: Recipe is no longer needed and has been moved to the meta-multimedia layer.

  • gtk-theme-torturer: Recipe is no longer needed and has been moved to the meta-gnome layer.

  • gnome-mime-data: Recipe is no longer needed and has been moved to the meta-gnome layer.

  • udev: Replaced by the eudev recipe for compatibility when using sysvinit with newer kernels.

  • python-pygtk: Recipe became obsolete.

  • adt-installer: Recipe became obsolete. See the “ADT Removed” section for more information.

4.9.9 Class Changes

The following classes have changed:

  • autotools_stage: Removed because the autotools class now provides its functionality. Recipes that inherited from autotools_stage should now inherit from autotools instead.

  • boot-directdisk: Merged into the image-vm class. The boot-directdisk class was rarely directly used. Consequently, this change should not cause any issues.

  • bootimg: Merged into the image-live class. The bootimg class was rarely directly used. Consequently, this change should not cause any issues.

  • packageinfo: Removed due to its limited use by the Hob UI, which has itself been removed.

4.9.10 Build System User Interface Changes

The following changes have been made to the build system user interface:

  • Hob GTK+-based UI: Removed because it is unmaintained and based on the outdated GTK+ 2 library. The Toaster web-based UI is much more capable and is actively maintained. See the “Using the Toaster Web Interface” section in the Toaster User Manual for more information on this interface.

  • “puccho” BitBake UI: Removed because is unmaintained and no longer useful.

4.9.11 ADT Removed

The Application Development Toolkit (ADT) has been removed because its functionality almost completely overlapped with the standard SDK and the extensible SDK. For information on these SDKs and how to build and use them, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

Note

The Yocto Project Eclipse IDE Plug-in is still supported and is not affected by this change.

4.9.12 Poky Reference Distribution Changes

The following changes have been made for the Poky distribution:

  • The meta-yocto layer has been renamed to meta-poky to better match its purpose, which is to provide the Poky reference distribution. The meta-yocto-bsp layer retains its original name since it provides reference machines for the Yocto Project and it is otherwise unrelated to Poky. References to meta-yocto in your conf/bblayers.conf should automatically be updated, so you should not need to change anything unless you are relying on this naming elsewhere.

  • The uninative class is now enabled by default in Poky. This class attempts to isolate the build system from the host distribution’s C library and makes re-use of native shared state artifacts across different host distributions practical. With this class enabled, a tarball containing a pre-built C library is downloaded at the start of the build.

    The uninative class is enabled through the meta/conf/distro/include/yocto-uninative.inc file, which for those not using the Poky distribution, can include to easily enable the same functionality.

    Alternatively, if you wish to build your own uninative tarball, you can do so by building the uninative-tarball recipe, making it available to your build machines (e.g. over HTTP/HTTPS) and setting a similar configuration as the one set by yocto-uninative.inc.

  • Static library generation, for most cases, is now disabled by default in the Poky distribution. Disabling this generation saves some build time as well as the size used for build output artifacts.

    Disabling this library generation is accomplished through a meta/conf/distro/include/no-static-libs.inc, which for those not using the Poky distribution can easily include to enable the same functionality.

    Any recipe that needs to opt-out of having the “–disable-static” option specified on the configure command line either because it is not a supported option for the configure script or because static libraries are needed should set the following variable:

    DISABLE_STATIC = ""
    
  • The separate poky-tiny distribution now uses the musl C library instead of a heavily pared down glibc. Using musl results in a smaller distribution and facilitates much greater maintainability because musl is designed to have a small footprint.

    If you have used poky-tiny and have customized the glibc configuration you will need to redo those customizations with musl when upgrading to the new release.

4.9.13 Packaging Changes

The following changes have been made to packaging:

  • The runuser and mountpoint binaries, which were previously in the main util-linux package, have been split out into the util-linux-runuser and util-linux-mountpoint packages, respectively.

  • The python-elementtree package has been merged into the python-xml package.

4.9.14 Tuning File Changes

The following changes have been made to the tuning files:

  • The “no-thumb-interwork” tuning feature has been dropped from the ARM tune include files. Because interworking is required for ARM EABI, attempting to disable it through a tuning feature no longer makes sense.

    Note

    Support for ARM OABI was deprecated in gcc 4.7.

  • The tune-cortexm*.inc and tune-cortexr4.inc files have been removed because they are poorly tested. Until the OpenEmbedded build system officially gains support for CPUs without an MMU, these tuning files would probably be better maintained in a separate layer if needed.

4.9.15 Supporting GObject Introspection

This release supports generation of GLib Introspective Repository (GIR) files through GObject introspection, which is the standard mechanism for accessing GObject-based software from runtime environments. You can enable, disable, and test the generation of this data. See the “Enabling GObject Introspection Support” section in the Yocto Project Development Tasks Manual for more information.

4.9.16 Miscellaneous Changes

These additional changes exist:

  • The minimum Git version has been increased to 1.8.3.1. If your host distribution does not provide a sufficiently recent version, you can install the buildtools, which will provide it. See the Required Git, tar, Python and gcc Versions section for more information on the buildtools tarball.

  • The buggy and incomplete support for the RPM version 4 package manager has been removed. The well-tested and maintained support for RPM version 5 remains.

  • Previously, the following list of packages were removed if package-management was not in IMAGE_FEATURES, regardless of any dependencies:

    update-rc.d
    base-passwd
    shadow
    update-alternatives
    run-postinsts
    

    With the Yocto Project 2.1 release, these packages are only removed if “read-only-rootfs” is in IMAGE_FEATURES, since they might still be needed for a read-write image even in the absence of a package manager (e.g. if users need to be added, modified, or removed at runtime).

  • The devtool modify command now defaults to extracting the source since that is most commonly expected. The “-x” or “–extract” options are now no-ops. If you wish to provide your own existing source tree, you will now need to specify either the “-n” or “–no-extract” options when running devtool modify.

  • If the formfactor for a machine is either not supplied or does not specify whether a keyboard is attached, then the default is to assume a keyboard is attached rather than assume no keyboard. This change primarily affects the Sato UI.

  • The .debug directory packaging is now automatic. If your recipe builds software that installs binaries into directories other than the standard ones, you no longer need to take care of setting FILES_${PN}-dbg to pick up the resulting .debug directories as these directories are automatically found and added.

  • Inaccurate disk and CPU percentage data has been dropped from buildstats output. This data has been replaced with getrusage() data and corrected IO statistics. You will probably need to update any custom code that reads the buildstats data.

  • The meta/conf/distro/include/package_regex.inc is now deprecated. The contents of this file have been moved to individual recipes.

    Note

    Because this file will likely be removed in a future Yocto Project release, it is suggested that you remove any references to the file that might be in your configuration.

  • The v86d/uvesafb has been removed from the genericx86 and genericx86-64 reference machines, which are provided by the meta-yocto-bsp layer. Most modern x86 boards do not rely on this file and it only adds kernel error messages during startup. If you do still need to support uvesafb, you can simply add v86d to your image.

  • Build sysroot paths are now removed from debug symbol files. Removing these paths means that remote GDB using an unstripped build system sysroot will no longer work (although this was never documented to work). The supported method to accomplish something similar is to set IMAGE_GEN_DEBUGFS to “1”, which will generate a companion debug image containing unstripped binaries and associated debug sources alongside the image.