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Diffstat (limited to 'bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst')
| -rw-r--r-- | bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst | 200 |
1 files changed, 155 insertions, 45 deletions
diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst index 119720d527..58975f4c88 100644 --- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst +++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst @@ -104,15 +104,15 @@ Line Joining Outside of :ref:`functions <bitbake-user-manual/bitbake-user-manual-metadata:functions>`, BitBake joins any line ending in -a backslash character ("\") with the following line before parsing -statements. The most common use for the "\" character is to split +a backslash character ("\\") with the following line before parsing +statements. The most common use for the "\\" character is to split variable assignments over multiple lines, as in the following example:: FOO = "bar \ baz \ qaz" -Both the "\" character and the newline +Both the "\\" character and the newline character that follow it are removed when joining lines. Thus, no newline characters end up in the value of ``FOO``. @@ -125,7 +125,7 @@ Consider this additional example where the two assignments both assign .. note:: - BitBake does not interpret escape sequences like "\n" in variable + BitBake does not interpret escape sequences like "\\n" in variable values. For these to have an effect, the value must be passed to some utility that interprets escape sequences, such as ``printf`` or ``echo -n``. @@ -159,7 +159,7 @@ behavior:: C = "qux" *At this point, ${A} equals "qux bar baz"* B = "norf" - *At this point, ${A} equals "norf baz"\* + *At this point, ${A} equals "norf baz"* Contrast this behavior with the :ref:`bitbake-user-manual/bitbake-user-manual-metadata:immediate variable @@ -195,22 +195,45 @@ value. However, if ``A`` is not set, the variable is set to "aval". Setting a weak default value (??=) ---------------------------------- -It is possible to use a "weaker" assignment than in the previous section -by using the "??=" operator. This assignment behaves identical to "?=" -except that the assignment is made at the end of the parsing process -rather than immediately. Consequently, when multiple "??=" assignments -exist, the last one is used. Also, any "=" or "?=" assignment will -override the value set with "??=". Here is an example:: +The weak default value of a variable is the value which that variable +will expand to if no value has been assigned to it via any of the other +assignment operators. The "??=" operator takes effect immediately, replacing +any previously defined weak default value. Here is an example:: - A ??= "somevalue" - A ??= "someothervalue" + W ??= "x" + A := "${W}" # Immediate variable expansion + W ??= "y" + B := "${W}" # Immediate variable expansion + W ??= "z" + C = "${W}" + W ?= "i" -If ``A`` is set before the above statements are -parsed, the variable retains its value. If ``A`` is not set, the -variable is set to "someothervalue". +After parsing we will have:: -Again, this assignment is a "lazy" or "weak" assignment because it does -not occur until the end of the parsing process. + A = "x" + B = "y" + C = "i" + W = "i" + +Appending and prepending non-override style will not substitute the weak +default value, which means that after parsing:: + + W ??= "x" + W += "y" + +we will have:: + + W = " y" + +On the other hand, override-style appends/prepends/removes are applied after +any active weak default value has been substituted:: + + W ??= "x" + W:append = "y" + +After parsing we will have:: + + W = "xy" Immediate variable expansion (:=) --------------------------------- @@ -296,6 +319,10 @@ The variable ``D`` becomes "dvaladditional data". You must control all spacing when you use the override syntax. +.. note:: + + The overrides are applied in this order, ":append", ":prepend", ":remove". + It is also possible to append and prepend to shell functions and BitBake-style Python functions. See the ":ref:`bitbake-user-manual/bitbake-user-manual-metadata:shell functions`" and ":ref:`bitbake-user-manual/bitbake-user-manual-metadata:bitbake-style python functions`" sections for examples. @@ -307,7 +334,8 @@ Removal (Override Style Syntax) You can remove values from lists using the removal override style syntax. Specifying a value for removal causes all occurrences of that -value to be removed from the variable. +value to be removed from the variable. Unlike ":append" and ":prepend", +there is no need to add a leading or trailing space to the value. When you use this syntax, BitBake expects one or more strings. Surrounding spaces and spacing are preserved. Here is an example:: @@ -328,6 +356,28 @@ The variable ``FOO`` becomes Like ":append" and ":prepend", ":remove" is applied at variable expansion time. +.. note:: + + The overrides are applied in this order, ":append", ":prepend", ":remove". + This implies it is not possible to re-append previously removed strings. + However, one can undo a ":remove" by using an intermediate variable whose + content is passed to the ":remove" so that modifying the intermediate + variable equals to keeping the string in:: + + FOOREMOVE = "123 456 789" + FOO:remove = "${FOOREMOVE}" + ... + FOOREMOVE = "123 789" + + This expands to ``FOO:remove = "123 789"``. + +.. note:: + + Override application order may not match variable parse history, i.e. + the output of ``bitbake -e`` may contain ":remove" before ":append", + but the result will be removed string, because ":remove" is handled + last. + Override Style Operation Advantages ----------------------------------- @@ -398,6 +448,12 @@ documentation to a BitBake variable as follows:: CACHE[doc] = "The directory holding the cache of the metadata." +.. note:: + + Variable flag names starting with an underscore (``_``) character + are allowed but are ignored by ``d.getVarFlags("VAR")`` + in Python code. Such flag names are used internally by BitBake. + Inline Python Variable Expansion -------------------------------- @@ -510,8 +566,8 @@ variable. .. note:: - Overrides can only use lower-case characters. Additionally, - underscores are not permitted in override names as they are used to + Overrides can only use lower-case characters, digits and dashes. + In particular, colons are not permitted in override names as they are used to separate overrides from each other and from the variable name. - *Selecting a Variable:* The :term:`OVERRIDES` variable is a @@ -523,14 +579,14 @@ variable. OVERRIDES = "architecture:os:machine" TEST = "default" - TEST_os = "osspecific" - TEST_nooverride = "othercondvalue" + TEST:os = "osspecific" + TEST:nooverride = "othercondvalue" In this example, the :term:`OVERRIDES` variable lists three overrides: "architecture", "os", and "machine". The variable ``TEST`` by itself has a default value of "default". You select the os-specific version of the ``TEST`` variable by appending - the "os" override to the variable (i.e. ``TEST_os``). + the "os" override to the variable (i.e. ``TEST:os``). To better understand this, consider a practical example that assumes an OpenEmbedded metadata-based Linux kernel recipe file. The @@ -567,7 +623,7 @@ variable. - *Setting a Variable for a Single Task:* BitBake supports setting a variable just for the duration of a single task. Here is an example:: - FOO_task-configure = "val 1" + FOO:task-configure = "val 1" FOO:task-compile = "val 2" In the @@ -585,6 +641,16 @@ variable. EXTRA_OEMAKE:prepend:task-compile = "${PARALLEL_MAKE} " +.. note:: + + Before BitBake 1.52 (Honister 3.4), the syntax for :term:`OVERRIDES` + used ``_`` instead of ``:``, so you will still find a lot of documentation + using ``_append``, ``_prepend``, and ``_remove``, for example. + + For details, see the + :yocto_docs:`Overrides Syntax Changes </migration-guides/migration-3.4.html#override-syntax-changes>` + section in the Yocto Project manual migration notes. + Key Expansion ------------- @@ -894,7 +960,7 @@ Regardless of the type of function, you can only define them in class Shell Functions --------------- -Functions written in shell script and executed either directly as +Functions written in shell script are executed either directly as functions, tasks, or both. They can also be called by other shell functions. Here is an example shell function definition:: @@ -944,7 +1010,7 @@ Running ``do_foo`` prints the following:: Overrides and override-style operators can be applied to any shell function, not just :ref:`tasks <bitbake-user-manual/bitbake-user-manual-metadata:tasks>`. -You can use the ``bitbake -e`` recipename command to view the final +You can use the ``bitbake -e recipename`` command to view the final assembled function after all overrides have been applied. BitBake-Style Python Functions @@ -996,7 +1062,7 @@ Running ``do_foo`` prints the following:: recipename do_foo: second recipename do_foo: third -You can use the ``bitbake -e`` recipename command to view +You can use the ``bitbake -e recipename`` command to view the final assembled function after all overrides have been applied. Python Functions @@ -1343,8 +1409,8 @@ the build machine cannot influence the build. .. note:: By default, BitBake cleans the environment to include only those - things exported or listed in its whitelist to ensure that the build - environment is reproducible and consistent. You can prevent this + things exported or listed in its passthrough list to ensure that the + build environment is reproducible and consistent. You can prevent this "cleaning" by setting the :term:`BB_PRESERVE_ENV` variable. Consequently, if you do want something to get passed into the build task @@ -1352,14 +1418,14 @@ environment, you must take these two steps: #. Tell BitBake to load what you want from the environment into the datastore. You can do so through the - :term:`BB_ENV_WHITELIST` and - :term:`BB_ENV_EXTRAWHITE` variables. For + :term:`BB_ENV_PASSTHROUGH` and + :term:`BB_ENV_PASSTHROUGH_ADDITIONS` variables. For example, assume you want to prevent the build system from accessing - your ``$HOME/.ccache`` directory. The following command "whitelists" - the environment variable ``CCACHE_DIR`` causing BitBake to allow that - variable into the datastore:: + your ``$HOME/.ccache`` directory. The following command adds the + the environment variable ``CCACHE_DIR`` to BitBake's passthrough + list to allow that variable into the datastore:: - export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR" + export BB_ENV_PASSTHROUGH_ADDITIONS="$BB_ENV_PASSTHROUGH_ADDITIONS CCACHE_DIR" #. Tell BitBake to export what you have loaded into the datastore to the task environment of every running task. Loading something from the @@ -1376,7 +1442,7 @@ environment, you must take these two steps: A side effect of the previous steps is that BitBake records the variable as a dependency of the build process in things like the setscene checksums. If doing so results in unnecessary rebuilds of - tasks, you can whitelist the variable so that the setscene code + tasks, you can also flag the variable so that the setscene code ignores the dependency when it creates checksums. Sometimes, it is useful to be able to obtain information from the @@ -1430,12 +1496,35 @@ functionality of the task: directory listed is used as the current working directory for the task. +- ``[file-checksums]``: Controls the file dependencies for a task. The + baseline file list is the set of files associated with + :term:`SRC_URI`. May be used to set additional dependencies on + files not associated with :term:`SRC_URI`. + + The value set to the list is a file-boolean pair where the first + value is the file name and the second is whether or not it + physically exists on the filesystem. :: + + do_configure[file-checksums] += "${MY_DIRPATH}/my-file.txt:True" + + It is important to record any paths which the task looked at and + which didn't exist. This means that if these do exist at a later + time, the task can be rerun with the new additional files. The + "exists" True or False value after the path allows this to be + handled. + - ``[lockfiles]``: Specifies one or more lockfiles to lock while the task executes. Only one task may hold a lockfile, and any task that attempts to lock an already locked file will block until the lock is released. You can use this variable flag to accomplish mutual exclusion. +- ``[network]``: When set to "1", allows a task to access the network. By + default, only the ``do_fetch`` task is granted network access. Recipes + shouldn't access the network outside of ``do_fetch`` as it usually + undermines fetcher source mirroring, image and licence manifests, software + auditing and supply chain security. + - ``[noexec]``: When set to "1", marks the task as being empty, with no execution required. You can use the ``[noexec]`` flag to set up tasks as dependency placeholders, or to disable tasks defined @@ -1648,8 +1737,8 @@ user interfaces: .. _variants-class-extension-mechanism: -Variants - Class Extension Mechanism -==================================== +Variants --- Class Extension Mechanism +====================================== BitBake supports multiple incarnations of a recipe file via the :term:`BBCLASSEXTEND` variable. @@ -1889,6 +1978,33 @@ looking at the source code of the ``bb`` module, which is in the commonly used functions ``bb.utils.contains()`` and ``bb.utils.mkdirhier()``, which come with docstrings. +Extending Python Library Code +----------------------------- + +If you wish to add your own Python library code (e.g. to provide +functions/classes you can use from Python functions in the metadata) +you can do so from any layer using the ``addpylib`` directive. +This directive is typically added to your layer configuration ( +``conf/layer.conf``) although it will be handled in any ``.conf`` file. + +Usage is of the form:: + + addpylib <directory> <namespace> + +Where <directory> specifies the directory to add to the library path. +The specified <namespace> is imported automatically, and if the imported +module specifies an attribute named ``BBIMPORTS``, that list of +sub-modules is iterated and imported too. + +Testing and Debugging BitBake Python code +----------------------------------------- + +The OpenEmbedded build system implements a convenient ``pydevshell`` target which +you can use to access the BitBake datastore and experiment with your own Python +code. See :yocto_docs:`Using a Python Development Shell +</dev-manual/python-development-shell.html#using-a-python-development-shell>` in the Yocto +Project manual for details. + Task Checksums and Setscene =========================== @@ -1921,12 +2037,6 @@ The following list describes related variables: Specifies a function BitBake calls that determines whether BitBake requires a setscene dependency to be met. -- :term:`BB_STAMP_POLICY`: Defines the mode - for comparing timestamps of stamp files. - -- :term:`BB_STAMP_WHITELIST`: Lists stamp - files that are looked at when the stamp policy is "whitelist". - - :term:`BB_TASKHASH`: Within an executing task, this variable holds the hash of the task as returned by the currently enabled signature generator. |