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diff --git a/poky/documentation/migration-guides/migration-3.4.rst b/poky/documentation/migration-guides/migration-3.4.rst new file mode 100644 index 000000000..e83e936b7 --- /dev/null +++ b/poky/documentation/migration-guides/migration-3.4.rst @@ -0,0 +1,83 @@ +Release 3.4 (honister) +====================== + +This section provides migration information for moving to the Yocto +Project 3.4 Release (codename "honister") from the prior release. + +Override syntax changes +----------------------- + +This release requires changes to the metadata to indicate where overrides are +being used in variable key names. This is done with the ``:`` character replacing +the use of ``_`` previously. This means that an entry like:: + + SRC_URI_qemux86 = "file://somefile" + +becomes:: + + SRC_URI:qemux86 = "file://somefile" + +since ``qemux86`` is an override. This applies to any use of override syntax so:: + + SRC_URI_append = " file://somefile" + SRC_URI_append_qemux86 = " file://somefile2" + SRC_URI_remove_qemux86-64 = " file://somefile3" + SRC_URI_prepend_qemuarm = "file://somefile4 " + FILES_${PN}-ptest = "${bindir}/xyz" + IMAGE_CMD_tar = "tar" + BASE_LIB_tune-cortexa76 = "lib" + SRCREV_pn-bash = "abc" + BB_TASK_NICE_LEVEL_task-testimage = '0' + +becomes:: + + SRC_URI:append = " file://somefile" + SRC_URI:append:qemux86 = " file://somefile2" + SRC_URI:remove:qemux86-64 = " file://somefile3" + SRC_URI:prepend:qemuarm = "file://somefile4 " + FILES:${PN}-ptest = "${bindir}/xyz" + IMAGE_CMD:tar = "tar" + BASE_LIB:tune-cortexa76 = "lib" + SRCREV:pn-bash = "abc" + BB_TASK_NICE_LEVEL:task-testimage = '0' + +This also applies to +:ref:`variable queries to the datastore <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:functions for accessing datastore variables>`, +for example using ``getVar`` and similar so ``d.getVar("RDEPENDS_${PN}")`` +becomes ``d.getVar("RDEPENDS:${PN}")``. + +Whilst some of these are fairly obvious such as :term:`MACHINE` and :term:`DISTRO` +overrides, some are less obvious, for example the packaging variables such as +:term:`RDEPENDS`, :term:`FILES` and so on taking package names (e.g. ``${PN}``, +``${PN}-ptest``) as overrides. These overrides are not always in +:term:`OVERRIDES` but applied conditionally in specific contexts +such as packaging. ``task-<taskname>`` is another context specific override, the +context being specific tasks in that case. Tune overrides are another special +case where some code does use them as overrides but some does not. We plan to try +and make the tune code use overrides more consistently in the future. + +There are some variables which do not use override syntax which include the +suffix to variables in ``layer.conf`` files such as :term:`BBFILE_PATTERN`, +:term:`SRCREV`\ ``_xxx`` where ``xxx`` is a name from :term:`SRC_URI` and +:term:`PREFERRED_VERSION`\ ``_xxx``. In particular, ``layer.conf`` suffixes +may be the same as a :term:`DISTRO` override causing some confusion. We do +plan to try and improve consistency as these issues are identified. + +To help with migration of layers there is a script in OE-Core. Once configured +with the overrides used by a layer, this can be run as:: + + <oe-core>/scripts/contrib/convert-overrides.py <layerdir> + +.. note:: + + Please read the notes in the script as it isn't entirely automatic and it isn't + expected to handle every case. In particular, it needs to be told which overrides + the layer uses (usually machine and distro names/overrides) and the result should + be carefully checked since it can be a little enthusiastic and will convert + references to ``_append``, ``_remove`` and ``_prepend`` in function and variables names. + +For reference, this conversion is important as it allows BitBake to know what is +an override and what is not. This should allow us to proceed with other syntax +improvements and simplifications for usability. It also means bitbake no longer +has to guess and maintain large lookup lists just in case ``functionname`` in +``my_functionname`` is an override and this should improve efficiency. |