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+Moving to the Yocto Project 3.1 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 3.1 Release from the prior release.
+
+.. _migration-3.1-minimum-system-requirements:
+
+Minimum system requirements
+---------------------------
+
+The following versions / requirements of build host components have been
+updated:
+
+-  gcc 5.0
+
+-  python 3.5
+
+-  tar 1.28
+
+-  ``rpcgen`` is now required on the host (part of the ``libc-dev-bin``
+   package on Ubuntu, Debian and related distributions, and the
+   ``glibc`` package on RPM-based distributions).
+
+Additionally, the ``makeinfo`` and ``pod2man`` tools are *no longer*
+required on the host.
+
+.. _migration-3.1-mpc8315e-rdb-removed:
+
+mpc8315e-rdb machine removed
+----------------------------
+
+The MPC8315E-RDB machine is old/obsolete and unobtainable, thus given
+the maintenance burden the ``mpc8315e-rdb`` machine configuration that
+supported it has been removed in this release. The removal does leave a
+gap in official PowerPC reference hardware support; this may change in
+future if a suitable machine with accompanying support resources is
+found.
+
+.. _migration-3.1-python-2-removed:
+
+Python 2 removed
+----------------
+
+Due to the expiration of upstream support in January 2020, support for
+Python 2 has now been removed; it is recommended that you use Python 3
+instead. If absolutely needed there is a meta-python2 community layer
+containing Python 2, related classes and various Python 2-based modules,
+however it should not be considered as supported.
+
+.. _migration-3.1-reproducible-builds:
+
+Reproducible builds now enabled by default
+------------------------------------------
+
+In order to avoid unnecessary differences in output files (aiding binary
+reproducibility), the Poky distribution configuration
+(``DISTRO = "poky"``) now inherits the ``reproducible_build`` class by
+default.
+
+.. _migration-3.1-ptest-feature-impact:
+
+Impact of ptest feature is now more significant
+-----------------------------------------------
+
+The Poky distribution configuration (``DISTRO = "poky"``) enables ptests
+by default to enable runtime testing of various components. In this
+release, a dependency needed to be added that has resulted in a
+significant increase in the number of components that will be built just
+when building a simple image such as core-image-minimal. If you do not
+need runtime tests enabled for core components, then it is recommended
+that you remove "ptest" from
+:term:`DISTRO_FEATURES` to save a significant
+amount of build time e.g. by adding the following in your configuration:
+::
+
+   DISTRO_FEATURES_remove = "ptest"
+
+.. _migration-3.1-removed-recipes:
+
+Removed recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``chkconfig``: obsolete
+
+-  ``console-tools``: obsolete
+
+-  ``enchant``: replaced by ``enchant2``
+
+-  ``foomatic-filters``: obsolete
+
+-  ``libidn``: no longer needed, moved to meta-oe
+
+-  ``libmodulemd``: replaced by ``libmodulemd-v1``
+
+-  ``linux-yocto``: drop 4.19, 5.2 version recipes (5.4 now provided)
+
+-  ``nspr``: no longer needed, moved to meta-oe
+
+-  ``nss``: no longer needed, moved to meta-oe
+
+-  ``python``: Python 2 removed (Python 3 preferred)
+
+-  ``python-setuptools``: Python 2 version removed (python3-setuptools
+   preferred)
+
+-  ``sysprof``: no longer needed, moved to meta-oe
+
+-  ``texi2html``: obsolete
+
+-  ``u-boot-fw-utils``: functionally replaced by ``libubootenv``
+
+.. _migration-3.1-features-check:
+
+features_check class replaces distro_features_check
+---------------------------------------------------
+
+The ``distro_features_check`` class has had its functionality expanded,
+now supporting ``ANY_OF_MACHINE_FEATURES``,
+``REQUIRED_MACHINE_FEATURES``, ``CONFLICT_MACHINE_FEATURES``,
+``ANY_OF_COMBINED_FEATURES``, ``REQUIRED_COMBINED_FEATURES``,
+``CONFLICT_COMBINED_FEATURES``. As a result the class has now been
+renamed to ``features_check``; the ``distro_features_check`` class still
+exists but generates a warning and redirects to the new class. In
+preparation for a future removal of the old class it is recommended that
+you update recipes currently inheriting ``distro_features_check`` to
+inherit ``features_check`` instead.
+
+.. _migration-3.1-removed-classes:
+
+Removed classes
+---------------
+
+The following classes have been removed:
+
+-  ``distutils-base``: moved to meta-python2
+
+-  ``distutils``: moved to meta-python2
+
+-  ``libc-common``: merged into the glibc recipe as nothing else used
+   it.
+
+-  ``python-dir``: moved to meta-python2
+
+-  ``pythonnative``: moved to meta-python2
+
+-  ``setuptools``: moved to meta-python2
+
+-  ``tinderclient``: dropped as it was obsolete.
+
+.. _migration-3.1-src-uri-checksums:
+
+SRC_URI checksum behaviour
+--------------------------
+
+Previously, recipes by tradition included both SHA256 and MD5 checksums
+for remotely fetched files in :term:`SRC_URI`, even
+though only one is actually mandated. However, the MD5 checksum does not
+add much given its inherent weakness; thus when a checksum fails only
+the SHA256 sum will now be printed. The md5sum will still be verified if
+it is specified.
+
+.. _migration-3.1-npm:
+
+npm fetcher changes
+-------------------
+
+The npm fetcher has been completely reworked in this release. The npm
+fetcher now only fetches the package source itself and no longer the
+dependencies; there is now also an npmsw fetcher which explicitly
+fetches the shrinkwrap file and the dependencies. This removes the
+slightly awkward ``NPM_LOCKDOWN`` and ``NPM_SHRINKWRAP`` variables which
+pointed to local files; the lockdown file is no longer needed at all.
+Additionally, the package name in ``npm://`` entries in
+:term:`SRC_URI` is now specified using a ``package``
+parameter instead of the earlier ``name`` which overlapped with the
+generic ``name`` parameter. All recipes using the npm fetcher will need
+to be changed as a result.
+
+An example of the new scheme: ::
+
+   SRC_URI = "npm://registry.npmjs.org;package=array-flatten;version=1.1.1 \\
+              npmsw://${THISDIR}/npm-shrinkwrap.json"
+
+Another example where the sources are fetched from git rather than an npm repository: ::
+
+   SRC_URI = "git://github.com/foo/bar.git;protocol=https \
+              npmsw://${THISDIR}/npm-shrinkwrap.json"
+
+devtool and recipetool have also been updated to match with the npm
+fetcher changes. Other than producing working and more complete recipes
+for npm sources, there is also a minor change to the command line for
+devtool: the ``--fetch-dev`` option has been renamed to ``--npm-dev`` as
+it is npm-specific.
+
+.. _migration-3.1-packaging-changes:
+
+Packaging changes
+-----------------
+
+-  ``intltool`` has been removed from ``packagegroup-core-sdk`` as it is
+   rarely needed to build modern software - gettext can do most of the
+   things it used to be needed for. ``intltool`` has also been removed
+   from ``packagegroup-core-self-hosted`` as it is not needed to for
+   standard builds.
+
+-  git: ``git-am``, ``git-difftool``, ``git-submodule``, and
+   ``git-request-pull`` are no longer perl-based, so are now installed
+   with the main ``git`` package instead of within ``git-perltools``.
+
+-  The ``ldconfig`` binary built as part of glibc has now been moved to
+   its own ``ldconfig`` package (note no ``glibc-`` prefix). This
+   package is in the :term:`RRECOMMENDS` of the main
+   ``glibc`` package if ``ldconfig`` is present in
+   :term:`DISTRO_FEATURES`.
+
+-  ``libevent`` now splits each shared library into its own package (as
+   Debian does). Since these are shared libraries and will be pulled in
+   through the normal shared library dependency handling, there should
+   be no impact to existing configurations other than less unnecessary
+   libraries being installed in some cases.
+
+-  linux-firmware now has a new package for ``bcm4366c`` and includes
+   available NVRAM config files into the ``bcm43340``, ``bcm43362``,
+   ``bcm43430`` and ``bcm4356-pcie`` packages.
+
+-  ``harfbuzz`` now splits the new ``libharfbuzz-subset.so`` library
+   into its own package to reduce the main package size in cases where
+   ``libharfbuzz-subset.so`` is not needed.
+
+.. _migration-3.1-package-qa-warnings:
+
+Additional warnings
+-------------------
+
+Warnings will now be shown at ``do_package_qa`` time in the following
+circumstances:
+
+-  A recipe installs ``.desktop`` files containing ``MimeType`` keys but
+   does not inherit the new ``mime-xdg`` class
+
+-  A recipe installs ``.xml`` files into ``${datadir}/mime/packages``
+   but does not inherit the ``mime`` class
+
+.. _migration-3.1-x86-live-wic:
+
+``wic`` image type now used instead of ``live`` by default for x86
+------------------------------------------------------------------
+
+``conf/machine/include/x86-base.inc`` (inherited by most x86 machine
+configurations) now specifies ``wic`` instead of ``live`` by default in
+:term:`IMAGE_FSTYPES`. The ``live`` image type will
+likely be removed in a future release so it is recommended that you use
+``wic`` instead.
+
+.. _migration-3.1-misc:
+
+Miscellaneous changes
+---------------------
+
+-  The undocumented ``SRC_DISTRIBUTE_LICENSES`` variable has now been
+   removed in favour of a new ``AVAILABLE_LICENSES`` variable which is
+   dynamically set based upon license files found in
+   ``${COMMON_LICENSE_DIR}`` and ``${LICENSE_PATH}``.
+
+-  The tune definition for big-endian microblaze machines is now
+   ``microblaze`` instead of ``microblazeeb``.
+
+-  ``newlib`` no longer has built-in syscalls. ``libgloss`` should then
+   provide the syscalls, ``crt0.o`` and other functions that are no
+   longer part of ``newlib`` itself. If you are using
+   ``TCLIBC = "newlib"`` this now means that you must link applications
+   with both ``newlib`` and ``libgloss``, whereas before ``newlib``
+   would run in many configurations by itself.