1 files changed, 470 insertions, 261 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 7ea68ade72..f60a9d8312 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
@@ -26,7 +26,7 @@ assignment. ::
    VARIABLE = "value"
 
 As expected, if you include leading or
-trailing spaces as part of an assignment, the spaces are retained: ::
+trailing spaces as part of an assignment, the spaces are retained::
 
    VARIABLE = " value"
    VARIABLE = "value "
@@ -40,7 +40,7 @@ blank space (i.e. these are not the same values). ::
 
 You can use single quotes instead of double quotes when setting a
 variable's value. Doing so allows you to use values that contain the
-double quote character: ::
+double quote character::
 
    VARIABLE = 'I have a " in my value'
 
@@ -77,7 +77,7 @@ occurs, you can use BitBake to check the actual value of the suspect
 variable. You can make these checks for both configuration and recipe
 level changes:
 
--  For configuration changes, use the following: ::
+-  For configuration changes, use the following::
 
       $ bitbake -e
 
@@ -91,9 +91,10 @@ level changes:
       Variables that are exported to the environment are preceded by the
       string "export" in the command's output.
 
--  For recipe changes, use the following: ::
+-  To find changes to a given variable in a specific recipe, use the
+   following::
 
-      $ bitbake recipe -e \| grep VARIABLE="
+      $ bitbake recipename -e | grep VARIABLENAME=\"
 
    This command checks to see if the variable actually makes
    it into a specific recipe.
@@ -103,20 +104,20 @@ 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
-variable assignments over multiple lines, as in the following example: ::
+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``.
 
 Consider this additional example where the two assignments both assign
-"barbaz" to ``FOO``: ::
+"barbaz" to ``FOO``::
 
    FOO = "barbaz"
    FOO = "bar\
@@ -124,7 +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``.
@@ -149,7 +150,7 @@ The "=" operator does not immediately expand variable references in the
 right-hand side. Instead, expansion is deferred until the variable
 assigned to is actually used. The result depends on the current values
 of the referenced variables. The following example should clarify this
-behavior: ::
+behavior::
 
    A = "${B} baz"
    B = "${C} bar"
@@ -158,7 +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
@@ -177,7 +178,7 @@ Setting a default value (?=)
 You can use the "?=" operator to achieve a "softer" assignment for a
 variable. This type of assignment allows you to define a variable if it
 is undefined when the statement is parsed, but to leave the value alone
-if the variable has a value. Here is an example: ::
+if the variable has a value. Here is an example::
 
    A ?= "aval"
 
@@ -194,28 +195,51 @@ 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 (:=)
 ---------------------------------
 
 The ":=" operator results in a variable's contents being expanded
-immediately, rather than when the variable is actually used: ::
+immediately, rather than when the variable is actually used::
 
    T = "123"
    A := "test ${T}"
@@ -225,7 +249,7 @@ immediately, rather than when the variable is actually used: ::
    C := "${C}append"
 
 In this example, ``A`` contains "test 123", even though the final value
-of ``T`` is "456". The variable ``B`` will end up containing "456
+of :term:`T` is "456". The variable :term:`B` will end up containing "456
 cvalappend". This is because references to undefined variables are
 preserved as is during (immediate)expansion. This is in contrast to GNU
 Make, where undefined variables expand to nothing. The variable ``C``
@@ -241,14 +265,14 @@ the "+=" and "=+" operators. These operators insert a space between the
 current value and prepended or appended value.
 
 These operators take immediate effect during parsing. Here are some
-examples: ::
+examples::
 
    B = "bval"
    B += "additionaldata"
    C = "cval"
    C =+ "test"
 
-The variable ``B`` contains "bval additionaldata" and ``C`` contains "test
+The variable :term:`B` contains "bval additionaldata" and ``C`` contains "test
 cval".
 
 .. _appending-and-prepending-without-spaces:
@@ -260,14 +284,14 @@ If you want to append or prepend values without an inserted space, use
 the ".=" and "=." operators.
 
 These operators take immediate effect during parsing. Here are some
-examples: ::
+examples::
 
    B = "bval"
    B .= "additionaldata"
    C = "cval"
    C =. "test"
 
-The variable ``B`` contains "bvaladditionaldata" and ``C`` contains
+The variable :term:`B` contains "bvaladditionaldata" and ``C`` contains
 "testcval".
 
 Appending and Prepending (Override Style Syntax)
@@ -278,16 +302,16 @@ style syntax. When you use this syntax, no spaces are inserted.
 
 These operators differ from the ":=", ".=", "=.", "+=", and "=+"
 operators in that their effects are applied at variable expansion time
-rather than being immediately applied. Here are some examples: ::
+rather than being immediately applied. Here are some examples::
 
    B = "bval"
-   B_append = " additional data"
+   B:append = " additional data"
    C = "cval"
-   C_prepend = "additional data "
+   C:prepend = "additional data "
    D = "dval"
-   D_append = "additional data"
+   D:append = "additional data"
 
-The variable ``B``
+The variable :term:`B`
 becomes "bval additional data" and ``C`` becomes "additional data cval".
 The variable ``D`` becomes "dvaladditional data".
 
@@ -295,6 +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.
@@ -306,16 +334,17 @@ 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: ::
+Surrounding spaces and spacing are preserved. Here is an example::
 
    FOO = "123 456 789 123456 123 456 123 456"
-   FOO_remove = "123"
-   FOO_remove = "456"
+   FOO:remove = "123"
+   FOO:remove = "456"
    FOO2 = " abc def ghi abcdef abc def abc def def"
-   FOO2_remove = "\
+   FOO2:remove = "\
        def \
        abc \
        ghi \
@@ -324,40 +353,62 @@ Surrounding spaces and spacing are preserved. Here is an example: ::
 The variable ``FOO`` becomes
 "  789 123456    " and ``FOO2`` becomes "    abcdef     ".
 
-Like "_append" and "_prepend", "_remove" is applied at variable
+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
 -----------------------------------
 
-An advantage of the override style operations "_append", "_prepend", and
-"_remove" as compared to the "+=" and "=+" operators is that the
+An advantage of the override style operations ":append", ":prepend", and
+":remove" as compared to the "+=" and "=+" operators is that the
 override style operators provide guaranteed operations. For example,
 consider a class ``foo.bbclass`` that needs to add the value "val" to
-the variable ``FOO``, and a recipe that uses ``foo.bbclass`` as follows: ::
+the variable ``FOO``, and a recipe that uses ``foo.bbclass`` as follows::
 
    inherit foo
    FOO = "initial"
 
 If ``foo.bbclass`` uses the "+=" operator,
 as follows, then the final value of ``FOO`` will be "initial", which is
-not what is desired: ::
+not what is desired::
 
    FOO += "val"
 
 If, on the other hand, ``foo.bbclass``
-uses the "_append" operator, then the final value of ``FOO`` will be
-"initial val", as intended: ::
+uses the ":append" operator, then the final value of ``FOO`` will be
+"initial val", as intended::
 
-   FOO_append = " val"
+   FOO:append = " val"
 
 .. note::
 
-   It is never necessary to use "+=" together with "_append". The following
-   sequence of assignments appends "barbaz" to FOO: ::
+   It is never necessary to use "+=" together with ":append". The following
+   sequence of assignments appends "barbaz" to FOO::
 
-       FOO_append = "bar"
-       FOO_append = "baz"
+       FOO:append = "bar"
+       FOO:append = "baz"
 
 
    The only effect of changing the second assignment in the previous
@@ -378,10 +429,10 @@ You can find more out about variable flags in general in the
 
 You can define, append, and prepend values to variable flags. All the
 standard syntax operations previously mentioned work for variable flags
-except for override style syntax (i.e. "_prepend", "_append", and
-"_remove").
+except for override style syntax (i.e. ":prepend", ":append", and
+":remove").
 
-Here are some examples showing how to set variable flags: ::
+Here are some examples showing how to set variable flags::
 
    FOO[a] = "abc"
    FOO[b] = "123"
@@ -393,15 +444,21 @@ respectively. The ``[a]`` flag becomes "abc 456".
 
 No need exists to pre-define variable flags. You can simply start using
 them. One extremely common application is to attach some brief
-documentation to a BitBake variable as follows: ::
+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
 --------------------------------
 
 You can use inline Python variable expansion to set variables. Here is
-an example: ::
+an example::
 
    DATE = "${@time.strftime('%Y%m%d',time.gmtime())}"
 
@@ -410,21 +467,21 @@ This example results in the ``DATE`` variable being set to the current date.
 Probably the most common use of this feature is to extract the value of
 variables from BitBake's internal data dictionary, ``d``. The following
 lines select the values of a package name and its version number,
-respectively: ::
+respectively::
 
-   PN = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[0] or 'defaultpkgname'}"
-   PV = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[1] or '1.0'}"
+   PN = "${@bb.parse.vars_from_file(d.getVar('FILE', False),d)[0] or 'defaultpkgname'}"
+   PV = "${@bb.parse.vars_from_file(d.getVar('FILE', False),d)[1] or '1.0'}"
 
 .. note::
 
    Inline Python expressions work just like variable expansions insofar as the
    "=" and ":=" operators are concerned. Given the following assignment, foo()
-   is called each time FOO is expanded: ::
+   is called each time FOO is expanded::
 
       FOO = "${@foo()}"
 
    Contrast this with the following immediate assignment, where foo() is only
-   called once, while the assignment is parsed: ::
+   called once, while the assignment is parsed::
 
       FOO := "${@foo()}"
 
@@ -437,7 +494,7 @@ Unsetting variables
 
 It is possible to completely remove a variable or a variable flag from
 BitBake's internal data dictionary by using the "unset" keyword. Here is
-an example: ::
+an example::
 
    unset DATE
    unset do_fetch[noexec]
@@ -452,7 +509,7 @@ When specifying pathnames for use with BitBake, do not use the tilde
 cause BitBake to not recognize the path since BitBake does not expand
 this character in the same way a shell would.
 
-Instead, provide a fuller path as the following example illustrates: ::
+Instead, provide a fuller path as the following example illustrates::
 
    BBLAYERS ?= " \
        /home/scott-lenovo/LayerA \
@@ -463,7 +520,7 @@ Exporting Variables to the Environment
 
 You can export variables to the environment of running tasks by using
 the ``export`` keyword. For example, in the following example, the
-``do_foo`` task prints "value from the environment" when run: ::
+``do_foo`` task prints "value from the environment" when run::
 
    export ENV_VARIABLE
    ENV_VARIABLE = "value from the environment"
@@ -481,7 +538,7 @@ It does not matter whether ``export ENV_VARIABLE`` appears before or
 after assignments to ``ENV_VARIABLE``.
 
 It is also possible to combine ``export`` with setting a value for the
-variable. Here is an example: ::
+variable. Here is an example::
 
    export ENV_VARIABLE = "variable-value"
 
@@ -496,78 +553,78 @@ Conditional Syntax (Overrides)
 
 BitBake uses :term:`OVERRIDES` to control what
 variables are overridden after BitBake parses recipes and configuration
-files. This section describes how you can use ``OVERRIDES`` as
+files. This section describes how you can use :term:`OVERRIDES` as
 conditional metadata, talks about key expansion in relationship to
-``OVERRIDES``, and provides some examples to help with understanding.
+:term:`OVERRIDES`, and provides some examples to help with understanding.
 
 Conditional Metadata
 --------------------
 
-You can use ``OVERRIDES`` to conditionally select a specific version of
+You can use :term:`OVERRIDES` to conditionally select a specific version of
 a variable and to conditionally append or prepend the value of a
 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 ``OVERRIDES`` variable is a
+-  *Selecting a Variable:* The :term:`OVERRIDES` variable is a
    colon-character-separated list that contains items for which you want
    to satisfy conditions. Thus, if you have a variable that is
-   conditional on "arm", and "arm" is in ``OVERRIDES``, then the
+   conditional on "arm", and "arm" is in :term:`OVERRIDES`, then the
    "arm"-specific version of the variable is used rather than the
-   non-conditional version. Here is an example: ::
+   non-conditional version. Here is an example::
 
       OVERRIDES = "architecture:os:machine"
       TEST = "default"
-      TEST_os = "osspecific"
-      TEST_nooverride = "othercondvalue"
+      TEST:os = "osspecific"
+      TEST:nooverride = "othercondvalue"
 
-   In this example, the ``OVERRIDES``
+   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
    following lines from the recipe file first set the kernel branch
    variable ``KBRANCH`` to a default value, then conditionally override
-   that value based on the architecture of the build: ::
+   that value based on the architecture of the build::
 
       KBRANCH = "standard/base"
-      KBRANCH_qemuarm = "standard/arm-versatile-926ejs"
-      KBRANCH_qemumips = "standard/mti-malta32"
-      KBRANCH_qemuppc = "standard/qemuppc"
-      KBRANCH_qemux86 = "standard/common-pc/base"
-      KBRANCH_qemux86-64 = "standard/common-pc-64/base"
-      KBRANCH_qemumips64 = "standard/mti-malta64"
+      KBRANCH:qemuarm = "standard/arm-versatile-926ejs"
+      KBRANCH:qemumips = "standard/mti-malta32"
+      KBRANCH:qemuppc = "standard/qemuppc"
+      KBRANCH:qemux86 = "standard/common-pc/base"
+      KBRANCH:qemux86-64 = "standard/common-pc-64/base"
+      KBRANCH:qemumips64 = "standard/mti-malta64"
 
 -  *Appending and Prepending:* BitBake also supports append and prepend
    operations to variable values based on whether a specific item is
-   listed in ``OVERRIDES``. Here is an example: ::
+   listed in :term:`OVERRIDES`. Here is an example::
 
       DEPENDS = "glibc ncurses"
       OVERRIDES = "machine:local"
-      DEPENDS_append_machine = "libmad"
+      DEPENDS:append:machine = "libmad"
 
-   In this example, ``DEPENDS`` becomes "glibc ncurses libmad".
+   In this example, :term:`DEPENDS` becomes "glibc ncurses libmad".
 
    Again, using an OpenEmbedded metadata-based kernel recipe file as an
    example, the following lines will conditionally append to the
-   ``KERNEL_FEATURES`` variable based on the architecture: ::
+   ``KERNEL_FEATURES`` variable based on the architecture::
 
-      KERNEL_FEATURES_append = " ${KERNEL_EXTRA_FEATURES}"
-      KERNEL_FEATURES_append_qemux86=" cfg/sound.scc cfg/paravirt_kvm.scc"
-      KERNEL_FEATURES_append_qemux86-64=" cfg/sound.scc cfg/paravirt_kvm.scc"
+      KERNEL_FEATURES:append = " ${KERNEL_EXTRA_FEATURES}"
+      KERNEL_FEATURES:append:qemux86=" cfg/sound.scc cfg/paravirt_kvm.scc"
+      KERNEL_FEATURES:append:qemux86-64=" cfg/sound.scc cfg/paravirt_kvm.scc"
 
 -  *Setting a Variable for a Single Task:* BitBake supports setting a
-   variable just for the duration of a single task. Here is an example: ::
+   variable just for the duration of a single task. Here is an example::
 
-      FOO_task-configure = "val 1"
-      FOO_task-compile = "val 2"
+      FOO:task-configure = "val 1"
+      FOO:task-compile = "val 2"
 
    In the
    previous example, ``FOO`` has the value "val 1" while the
@@ -580,15 +637,25 @@ variable.
    ``do_compile`` task.
 
    You can also use this syntax with other combinations (e.g.
-   "``_prepend``") as shown in the following example: ::
+   "``:prepend``") as shown in the following example::
+
+      EXTRA_OEMAKE:prepend:task-compile = "${PARALLEL_MAKE} "
+
+.. note::
 
-      EXTRA_OEMAKE_prepend_task-compile = "${PARALLEL_MAKE} "
+   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
 -------------
 
 Key expansion happens when the BitBake datastore is finalized. To better
-understand this, consider the following example: ::
+understand this, consider the following example::
 
    A${B} = "X"
    B = "2"
@@ -612,57 +679,57 @@ users.
 
 There is often confusion concerning the order in which overrides and
 various "append" operators take effect. Recall that an append or prepend
-operation using "_append" and "_prepend" does not result in an immediate
+operation using ":append" and ":prepend" does not result in an immediate
 assignment as would "+=", ".=", "=+", or "=.". Consider the following
-example: ::
+example::
 
    OVERRIDES = "foo"
    A = "Z"
-   A_foo_append = "X"
+   A:foo:append = "X"
 
 For this case,
 ``A`` is unconditionally set to "Z" and "X" is unconditionally and
-immediately appended to the variable ``A_foo``. Because overrides have
-not been applied yet, ``A_foo`` is set to "X" due to the append and
+immediately appended to the variable ``A:foo``. Because overrides have
+not been applied yet, ``A:foo`` is set to "X" due to the append and
 ``A`` simply equals "Z".
 
 Applying overrides, however, changes things. Since "foo" is listed in
-``OVERRIDES``, the conditional variable ``A`` is replaced with the "foo"
-version, which is equal to "X". So effectively, ``A_foo`` replaces
+:term:`OVERRIDES`, the conditional variable ``A`` is replaced with the "foo"
+version, which is equal to "X". So effectively, ``A:foo`` replaces
 ``A``.
 
-This next example changes the order of the override and the append: ::
+This next example changes the order of the override and the append::
 
    OVERRIDES = "foo"
    A = "Z"
-   A_append_foo = "X"
+   A:append:foo = "X"
 
 For this case, before
-overrides are handled, ``A`` is set to "Z" and ``A_append_foo`` is set
+overrides are handled, ``A`` is set to "Z" and ``A:append:foo`` is set
 to "X". Once the override for "foo" is applied, however, ``A`` gets
 appended with "X". Consequently, ``A`` becomes "ZX". Notice that spaces
 are not appended.
 
 This next example has the order of the appends and overrides reversed
-back as in the first example: ::
+back as in the first example::
 
    OVERRIDES = "foo"
    A = "Y"
-   A_foo_append = "Z"
-   A_foo_append = "X"
+   A:foo:append = "Z"
+   A:foo:append = "X"
 
 For this case, before any overrides are resolved,
 ``A`` is set to "Y" using an immediate assignment. After this immediate
-assignment, ``A_foo`` is set to "Z", and then further appended with "X"
+assignment, ``A:foo`` is set to "Z", and then further appended with "X"
 leaving the variable set to "ZX". Finally, applying the override for
 "foo" results in the conditional variable ``A`` becoming "ZX" (i.e.
-``A`` is replaced with ``A_foo``).
+``A`` is replaced with ``A:foo``).
 
-This final example mixes in some varying operators: ::
+This final example mixes in some varying operators::
 
    A = "1"
-   A_append = "2"
-   A_append = "3"
+   A:append = "2"
+   A:append = "3"
    A += "4"
    A .= "5"
 
@@ -670,7 +737,7 @@ For this case, the type of append
 operators are affecting the order of assignments as BitBake passes
 through the code multiple times. Initially, ``A`` is set to "1 45"
 because of the three statements that use immediate operators. After
-these assignments are made, BitBake applies the "_append" operations.
+these assignments are made, BitBake applies the ":append" operations.
 Those operations result in ``A`` becoming "1 4523".
 
 Sharing Functionality
@@ -686,8 +753,10 @@ share the task.
 
 This section presents the mechanisms BitBake provides to allow you to
 share functionality between recipes. Specifically, the mechanisms
-include ``include``, ``inherit``, ``INHERIT``, and ``require``
-directives.
+include ``include``, ``inherit``, :term:`INHERIT`, and ``require``
+directives. There is also a higher-level abstraction called
+``configuration fragments`` that is enabled with ``addfragments``
+directive.
 
 Locating Include and Class Files
 --------------------------------
@@ -702,7 +771,9 @@ current directory for ``include`` and ``require`` directives.
 
 In order for include and class files to be found by BitBake, they need
 to be located in a "classes" subdirectory that can be found in
-``BBPATH``.
+:term:`BBPATH`.
+
+.. _ref-bitbake-user-manual-metadata-inherit:
 
 ``inherit`` Directive
 ---------------------
@@ -720,12 +791,12 @@ file and then have your recipe inherit that class file.
 
 As an example, your recipes could use the following directive to inherit
 an ``autotools.bbclass`` file. The class file would contain common
-functionality for using Autotools that could be shared across recipes: ::
+functionality for using Autotools that could be shared across recipes::
 
    inherit autotools
 
 In this case, BitBake would search for the directory
-``classes/autotools.bbclass`` in ``BBPATH``.
+``classes/autotools.bbclass`` in :term:`BBPATH`.
 
 .. note::
 
@@ -734,7 +805,7 @@ In this case, BitBake would search for the directory
 
 If you want to use the directive to inherit multiple classes, separate
 them with spaces. The following example shows how to inherit both the
-``buildhistory`` and ``rm_work`` classes: ::
+``buildhistory`` and ``rm_work`` classes::
 
    inherit buildhistory rm_work
 
@@ -742,19 +813,43 @@ An advantage with the inherit directive as compared to both the
 :ref:`include <bitbake-user-manual/bitbake-user-manual-metadata:\`\`include\`\` directive>` and :ref:`require <bitbake-user-manual/bitbake-user-manual-metadata:\`\`require\`\` directive>`
 directives is that you can inherit class files conditionally. You can
 accomplish this by using a variable expression after the ``inherit``
-statement. Here is an example: ::
+statement.
+
+For inheriting classes conditionally, using the :ref:`inherit_defer
+<ref-bitbake-user-manual-metadata-inherit-defer>` directive is advised as
+:ref:`inherit_defer <ref-bitbake-user-manual-metadata-inherit-defer>` is
+evaluated at the end of parsing.
+
+.. _ref-bitbake-user-manual-metadata-inherit-defer:
+
+``inherit_defer`` Directive
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The :ref:`inherit_defer <ref-bitbake-user-manual-metadata-inherit-defer>`
+directive works like the :ref:`inherit
+<ref-bitbake-user-manual-metadata-inherit>` directive, except that it is only
+evaluated at the end of parsing. Its usage is recommended when a conditional
+expression is used.
 
-   inherit ${VARNAME}
+This allows conditional expressions to be evaluated "late", meaning changes to
+the variable after the line is parsed will take effect. With the :ref:`inherit
+<ref-bitbake-user-manual-metadata-inherit>` directive this is not the case.
+
+Here is an example::
+
+   inherit_defer ${VARNAME}
 
 If ``VARNAME`` is
-going to be set, it needs to be set before the ``inherit`` statement is
+going to be set, it needs to be set before the ``inherit_defer`` statement is
 parsed. One way to achieve a conditional inherit in this case is to use
-overrides: ::
+overrides::
 
    VARIABLE = ""
-   VARIABLE_someoverride = "myclass"
+   VARIABLE:someoverride = "myclass"
 
-Another method is by using anonymous Python. Here is an example: ::
+Another method is by using :ref:`anonymous Python
+<bitbake-user-manual/bitbake-user-manual-metadata:Anonymous Python Functions>`.
+Here is an example::
 
    python () {
        if condition == value:
@@ -763,11 +858,14 @@ Another method is by using anonymous Python. Here is an example: ::
            d.setVar('VARIABLE', '')
    }
 
-Alternatively, you could use an in-line Python expression in the
-following form: ::
+Alternatively, you could use an inline Python expression in the
+following form::
+
+   inherit_defer ${@'classname' if condition else ''}
 
-   inherit ${@'classname' if condition else ''}
-   inherit ${@functionname(params)}
+Or::
+
+   inherit_defer ${@bb.utils.contains('VARIABLE', 'something', 'classname', '', d)}
 
 In all cases, if the expression evaluates to an
 empty string, the statement does not trigger a syntax error because it
@@ -780,7 +878,7 @@ BitBake understands the ``include`` directive. This directive causes
 BitBake to parse whatever file you specify, and to insert that file at
 that location. The directive is much like its equivalent in Make except
 that if the path specified on the include line is a relative path,
-BitBake locates the first file it can find within ``BBPATH``.
+BitBake locates the first file it can find within :term:`BBPATH`.
 
 The include directive is a more generic method of including
 functionality as compared to the :ref:`inherit <bitbake-user-manual/bitbake-user-manual-metadata:\`\`inherit\`\` directive>`
@@ -790,7 +888,7 @@ encapsulated functionality or configuration that does not suit a
 ``.bbclass`` file.
 
 As an example, suppose you needed a recipe to include some self-test
-definitions: ::
+definitions::
 
    include test_defs.inc
 
@@ -802,6 +900,33 @@ definitions: ::
    of include . Doing so makes sure that an error is produced if the file cannot
    be found.
 
+``include_all`` Directive
+-------------------------
+
+The ``include_all`` directive works like the :ref:`include
+<bitbake-user-manual/bitbake-user-manual-metadata:\`\`include\`\` directive>`
+directive but will include all of the files that match the specified path in
+the enabled layers (layers part of :term:`BBLAYERS`).
+
+For example, let's say a ``maintainers.inc`` file is present in different layers
+and is conventionally placed in the ``conf/distro/include`` directory of each
+layer. In that case the ``include_all`` directive can be used to include
+the ``maintainers.inc`` file for all of these layers::
+
+   include_all conf/distro/include/maintainers.inc
+
+In other words, the ``maintainers.inc`` file for each layer is included through
+the :ref:`include <bitbake-user-manual/bitbake-user-manual-metadata:\`\`include\`\` directive>`
+directive.
+
+BitBake will iterate through the colon-separated :term:`BBPATH` list to look for
+matching files to include, from left to right. As a consequence, matching files
+are included in that order.
+
+As the ``include_all`` directive uses the :ref:`include
+<bitbake-user-manual/bitbake-user-manual-metadata:\`\`include\`\` directive>`
+directive in the background, no error is produced if no files are matched.
+
 .. _require-inclusion:
 
 ``require`` Directive
@@ -822,7 +947,7 @@ does not suit a ``.bbclass`` file.
 
 Similar to how BitBake handles :ref:`include <bitbake-user-manual/bitbake-user-manual-metadata:\`\`include\`\` directive>`, if
 the path specified on the require line is a relative path, BitBake
-locates the first file it can find within ``BBPATH``.
+locates the first file it can find within :term:`BBPATH`.
 
 As an example, suppose you have two versions of a recipe (e.g.
 ``foo_1.2.2.bb`` and ``foo_2.0.0.bb``) where each version contains some
@@ -831,7 +956,7 @@ include file named ``foo.inc`` that contains the common definitions
 needed to build "foo". You need to be sure ``foo.inc`` is located in the
 same directory as your two recipe files as well. Once these conditions
 are set up, you can share the functionality using a ``require``
-directive from within each recipe: ::
+directive from within each recipe::
 
    require foo.inc
 
@@ -844,14 +969,14 @@ class. BitBake only supports this directive when used within a
 configuration file.
 
 As an example, suppose you needed to inherit a class file called
-``abc.bbclass`` from a configuration file as follows: ::
+``abc.bbclass`` from a configuration file as follows::
 
    INHERIT += "abc"
 
 This configuration directive causes the named class to be inherited at
 the point of the directive during parsing. As with the ``inherit``
 directive, the ``.bbclass`` file must be located in a "classes"
-subdirectory in one of the directories specified in ``BBPATH``.
+subdirectory in one of the directories specified in :term:`BBPATH`.
 
 .. note::
 
@@ -862,10 +987,69 @@ subdirectory in one of the directories specified in ``BBPATH``.
 If you want to use the directive to inherit multiple classes, you can
 provide them on the same line in the ``local.conf`` file. Use spaces to
 separate the classes. The following example shows how to inherit both
-the ``autotools`` and ``pkgconfig`` classes: ::
+the ``autotools`` and ``pkgconfig`` classes::
 
    INHERIT += "autotools pkgconfig"
 
+``addfragments`` Directive
+--------------------------
+
+This directive allows fine-tuning local configurations with configuration
+snippets contained in layers in a structured, controlled way. Typically it would
+go into ``bitbake.conf``, for example::
+
+   addfragments conf/fragments OE_FRAGMENTS OE_FRAGMENTS_METADATA_VARS OE_BUILTIN_FRAGMENTS
+
+``addfragments`` takes four parameters:
+
+-  path prefix for fragment files inside the layer file tree that bitbake
+   uses to construct full paths to the fragment files
+
+-  name of variable that holds the list of enabled fragments in an
+   active build
+
+-  name of variable that contains a list of variable names containing
+   fragment-specific metadata (such as descriptions)
+
+-  name of variable that contains definitions for built-in fragments
+
+This allows listing enabled configuration fragments in ``OE_FRAGMENTS``
+variable like this::
+
+   OE_FRAGMENTS = "core/domain/somefragment core/someotherfragment anotherlayer/anotherdomain/anotherfragment"
+
+Fragment names listed in this variable must be prefixed by the layer name
+where a fragment file is located, defined by :term:`BBFILE_COLLECTIONS` in ``layer.conf``.
+
+The implementation then expands this list into
+:ref:`require <bitbake-user-manual/bitbake-user-manual-metadata:\`\`require\`\` directive>`
+directives with full paths to respective layers::
+
+   require /path/to/core-layer/conf/fragments/domain/somefragment.conf
+   require /path/to/core-layer/conf/fragments/someotherfragment.conf
+   require /path/to/another-layer/conf/fragments/anotherdomain/anotherfragment.conf
+
+The variable containing a list of fragment metadata variables could look like this::
+
+   OE_FRAGMENTS_METADATA_VARS = "BB_CONF_FRAGMENT_SUMMARY BB_CONF_FRAGMENT_DESCRIPTION"
+
+The implementation will add a flag containing the fragment name to each of those variables
+when parsing fragments, so that the variables are namespaced by fragment name, and do not override
+each other when several fragments are enabled.
+
+The variable containing a built-in fragment definitions could look like this::
+
+   OE_BUILTIN_FRAGMENTS = "someprefix:SOMEVARIABLE anotherprefix:ANOTHERVARIABLE"
+
+and then if 'someprefix/somevalue' is added to the variable that holds the list
+of enabled fragments:
+
+  OE_FRAGMENTS = "... someprefix/somevalue"
+
+bitbake will treat that as direct value assignment in its configuration::
+
+  SOMEVARIABLE = "somevalue"
+
 Functions
 =========
 
@@ -893,9 +1077,9 @@ 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: ::
+functions. Here is an example shell function definition::
 
    some_function () {
        echo "Hello World"
@@ -907,19 +1091,19 @@ rules. The scripts are executed by ``/bin/sh``, which may not be a bash
 shell but might be something such as ``dash``. You should not use
 Bash-specific script (bashisms).
 
-Overrides and override-style operators like ``_append`` and ``_prepend``
+Overrides and override-style operators like ``:append`` and ``:prepend``
 can also be applied to shell functions. Most commonly, this application
 would be used in a ``.bbappend`` file to modify functions in the main
 recipe. It can also be used to modify functions inherited from classes.
 
-As an example, consider the following: ::
+As an example, consider the following::
 
    do_foo() {
        bbplain first
        fn
    }
 
-   fn_prepend() {
+   fn:prepend() {
        bbplain second
    }
 
@@ -927,11 +1111,11 @@ As an example, consider the following: ::
        bbplain third
    }
 
-   do_foo_append() {
+   do_foo:append() {
        bbplain fourth
    }
 
-Running ``do_foo`` prints the following: ::
+Running ``do_foo`` prints the following::
 
    recipename do_foo: first
    recipename do_foo: second
@@ -943,7 +1127,7 @@ 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
@@ -952,7 +1136,7 @@ BitBake-Style Python Functions
 These functions are written in Python and executed by BitBake or other
 Python functions using ``bb.build.exec_func()``.
 
-An example BitBake function is: ::
+An example BitBake function is::
 
    python some_python_function () {
        d.setVar("TEXT", "Hello World")
@@ -975,9 +1159,9 @@ import these modules. Also in these types of functions, the datastore
 Similar to shell functions, you can also apply overrides and
 override-style operators to BitBake-style Python functions.
 
-As an example, consider the following: ::
+As an example, consider the following::
 
-   python do_foo_prepend() {
+   python do_foo:prepend() {
        bb.plain("first")
    }
 
@@ -985,17 +1169,17 @@ As an example, consider the following: ::
        bb.plain("second")
    }
 
-   python do_foo_append() {
+   python do_foo:append() {
        bb.plain("third")
    }
 
-Running ``do_foo`` prints the following: ::
+Running ``do_foo`` prints the following::
 
    recipename do_foo: first
    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
@@ -1004,7 +1188,7 @@ Python Functions
 These functions are written in Python and are executed by other Python
 code. Examples of Python functions are utility functions that you intend
 to call from in-line Python or from within other Python functions. Here
-is an example: ::
+is an example::
 
    def get_depends(d):
        if d.getVar('SOMECONDITION'):
@@ -1015,7 +1199,7 @@ is an example: ::
    SOMECONDITION = "1"
    DEPENDS = "${@get_depends(d)}"
 
-This would result in ``DEPENDS`` containing ``dependencywithcond``.
+This would result in :term:`DEPENDS` containing ``dependencywithcond``.
 
 Here are some things to know about Python functions:
 
@@ -1056,7 +1240,7 @@ functions and regular Python functions defined with "def":
 -  Regular Python functions are called with the usual Python syntax.
    BitBake-style Python functions are usually tasks and are called
    directly by BitBake, but can also be called manually from Python code
-   by using the ``bb.build.exec_func()`` function. Here is an example: ::
+   by using the ``bb.build.exec_func()`` function. Here is an example::
 
       bb.build.exec_func("my_bitbake_style_function", d)
 
@@ -1094,7 +1278,7 @@ Sometimes it is useful to set variables or perform other operations
 programmatically during parsing. To do this, you can define special
 Python functions, called anonymous Python functions, that run at the end
 of parsing. For example, the following conditionally sets a variable
-based on the value of another variable: ::
+based on the value of another variable::
 
    python () {
        if d.getVar('SOMEVAR') == 'value':
@@ -1107,7 +1291,7 @@ the name "__anonymous", rather than no name.
 Anonymous Python functions always run at the end of parsing, regardless
 of where they are defined. If a recipe contains many anonymous
 functions, they run in the same order as they are defined within the
-recipe. As an example, consider the following snippet: ::
+recipe. As an example, consider the following snippet::
 
    python () {
        d.setVar('FOO', 'foo 2')
@@ -1122,7 +1306,7 @@ recipe. As an example, consider the following snippet: ::
    BAR = "bar 1"
 
 The previous example is conceptually
-equivalent to the following snippet: ::
+equivalent to the following snippet::
 
    FOO = "foo 1"
    BAR = "bar 1"
@@ -1134,12 +1318,12 @@ equivalent to the following snippet: ::
 values set for the variables within the anonymous functions become
 available to tasks, which always run after parsing.
 
-Overrides and override-style operators such as "``_append``" are applied
+Overrides and override-style operators such as "``:append``" are applied
 before anonymous functions run. In the following example, ``FOO`` ends
-up with the value "foo from anonymous": ::
+up with the value "foo from anonymous"::
 
    FOO = "foo"
-   FOO_append = " from outside"
+   FOO:append = " from outside"
 
    python () {
        d.setVar("FOO", "foo from anonymous")
@@ -1164,7 +1348,7 @@ To understand the benefits of this feature, consider the basic scenario
 where a class defines a task function and your recipe inherits the
 class. In this basic scenario, your recipe inherits the task function as
 defined in the class. If desired, your recipe can add to the start and
-end of the function by using the "_prepend" or "_append" operations
+end of the function by using the ":prepend" or ":append" operations
 respectively, or it can redefine the function completely. However, if it
 redefines the function, there is no means for it to call the class
 version of the function. ``EXPORT_FUNCTIONS`` provides a mechanism that
@@ -1173,24 +1357,24 @@ version of the function.
 
 To make use of this technique, you need the following things in place:
 
--  The class needs to define the function as follows: ::
+-  The class needs to define the function as follows::
 
       classname_functionname
 
    For example, if you have a class file
    ``bar.bbclass`` and a function named ``do_foo``, the class must
-   define the function as follows: ::
+   define the function as follows::
 
       bar_do_foo
 
 -  The class needs to contain the ``EXPORT_FUNCTIONS`` statement as
-   follows: ::
+   follows::
 
       EXPORT_FUNCTIONS functionname
 
    For example, continuing with
    the same example, the statement in the ``bar.bbclass`` would be as
-   follows: ::
+   follows::
 
       EXPORT_FUNCTIONS do_foo
 
@@ -1199,7 +1383,7 @@ To make use of this technique, you need the following things in place:
    class version of the function, it should call ``bar_do_foo``.
    Assuming ``do_foo`` was a shell function and ``EXPORT_FUNCTIONS`` was
    used as above, the recipe's function could conditionally call the
-   class version of the function as follows: ::
+   class version of the function as follows::
 
       do_foo() {
           if [ somecondition ] ; then
@@ -1233,11 +1417,11 @@ Tasks are either :ref:`shell functions <bitbake-user-manual/bitbake-user-manual-
 that have been promoted to tasks by using the ``addtask`` command. The
 ``addtask`` command can also optionally describe dependencies between
 the task and other tasks. Here is an example that shows how to define a
-task and declare some dependencies: ::
+task and declare some dependencies::
 
    python do_printdate () {
-       import time
-       print time.strftime('%Y%m%d', time.gmtime())
+       import datetime
+       bb.plain('Date: %s' % (datetime.date.today()))
    }
    addtask printdate after do_fetch before do_build
 
@@ -1264,12 +1448,12 @@ Additionally, the ``do_printdate`` task becomes dependent upon the
    rerun for experimentation purposes, you can make BitBake always
    consider the task "out-of-date" by using the
    :ref:`[nostamp] <bitbake-user-manual/bitbake-user-manual-metadata:Variable Flags>`
-   variable flag, as follows: ::
+   variable flag, as follows::
 
       do_printdate[nostamp] = "1"
 
    You can also explicitly run the task and provide the
-   -f option as follows: ::
+   -f option as follows::
 
       $ bitbake recipe -c printdate -f
 
@@ -1278,7 +1462,7 @@ Additionally, the ``do_printdate`` task becomes dependent upon the
    name.
 
 You might wonder about the practical effects of using ``addtask``
-without specifying any dependencies as is done in the following example: ::
+without specifying any dependencies as is done in the following example::
 
    addtask printdate
 
@@ -1286,7 +1470,7 @@ In this example, assuming dependencies have not been
 added through some other means, the only way to run the task is by
 explicitly selecting it with ``bitbake`` recipe ``-c printdate``. You
 can use the ``do_listtasks`` task to list all tasks defined in a recipe
-as shown in the following example: ::
+as shown in the following example::
 
    $ bitbake recipe -c listtasks
 
@@ -1296,12 +1480,23 @@ For more information on task dependencies, see the
 See the ":ref:`bitbake-user-manual/bitbake-user-manual-metadata:variable flags`" section for information
 on variable flags you can use with tasks.
 
+.. note::
+
+   While it's infrequent, it's possible to define multiple tasks as
+   dependencies when calling ``addtask``. For example, here's a snippet
+   from the OpenEmbedded class file ``package_tar.bbclass``::
+
+     addtask package_write_tar before do_build after do_packagedata do_package
+
+   Note how the ``package_write_tar`` task has to wait until both of
+   ``do_packagedata`` and ``do_package`` complete.
+
 Deleting a Task
 ---------------
 
 As well as being able to add tasks, you can delete them. Simply use the
 ``deltask`` command to delete a task. For example, to delete the example
-task used in the previous sections, you would use: ::
+task used in the previous sections, you would use::
 
    deltask printdate
 
@@ -1317,7 +1512,7 @@ to run before ``do_a``.
 
 If you want dependencies such as these to remain intact, use the
 ``[noexec]`` varflag to disable the task instead of using the
-``deltask`` command to delete it: ::
+``deltask`` command to delete it::
 
    do_b[noexec] = "1"
 
@@ -1331,8 +1526,8 @@ 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
@@ -1340,14 +1535,14 @@ 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
@@ -1355,7 +1550,7 @@ environment, you must take these two steps:
    available in the datastore. To export it to the task environment of
    every running task, use a command similar to the following in your
    local configuration file ``local.conf`` or your distribution
-   configuration file: ::
+   configuration file::
 
       export CCACHE_DIR
 
@@ -1364,17 +1559,17 @@ 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
 original execution environment. BitBake saves a copy of the original
 environment into a special variable named :term:`BB_ORIGENV`.
 
-The ``BB_ORIGENV`` variable returns a datastore object that can be
+The :term:`BB_ORIGENV` variable returns a datastore object that can be
 queried using the standard datastore operators such as
 ``getVar(, False)``. The datastore object is useful, for example, to
-find the original ``DISPLAY`` variable. Here is an example: ::
+find the original ``DISPLAY`` variable. Here is an example::
 
    origenv = d.getVar("BB_ORIGENV", False)
    bar = origenv.getVar("BAR", False)
@@ -1387,7 +1582,7 @@ Variable Flags
 
 Variable flags (varflags) help control a task's functionality and
 dependencies. BitBake reads and writes varflags to the datastore using
-the following command forms: ::
+the following command forms::
 
    variable = d.getVarFlags("variable")
    self.d.setVarFlags("FOO", {"func": True})
@@ -1418,12 +1613,35 @@ 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
@@ -1456,7 +1674,7 @@ functionality of the task:
          can result in unpredictable behavior.
 
       -  Setting the varflag to a value greater than the value used in
-         the ``BB_NUMBER_THREADS`` variable causes ``number_threads`` to
+         the :term:`BB_NUMBER_THREADS` variable causes ``number_threads`` to
          have no effect.
 
 -  ``[postfuncs]``: List of functions to call after the completion of
@@ -1526,7 +1744,7 @@ intent is to make it easy to do things like email notification on build
 failures.
 
 Following is an example event handler that prints the name of the event
-and the content of the ``FILE`` variable: ::
+and the content of the :term:`FILE` variable::
 
    addhandler myclass_eventhandler
    python myclass_eventhandler() {
@@ -1565,11 +1783,11 @@ might have an interest in viewing:
 
 -  ``bb.event.ConfigParsed()``: Fired when the base configuration; which
    consists of ``bitbake.conf``, ``base.bbclass`` and any global
-   ``INHERIT`` statements; has been parsed. You can see multiple such
+   :term:`INHERIT` statements; has been parsed. You can see multiple such
    events when each of the workers parse the base configuration or if
    the server changes configuration and reparses. Any given datastore
    only has one such event executed against it, however. If
-   ```BB_INVALIDCONF`` <#>`__ is set in the datastore by the event
+   :term:`BB_INVALIDCONF` is set in the datastore by the event
    handler, the configuration is reparsed and a new event triggered,
    allowing the metadata to update configuration.
 
@@ -1636,13 +1854,18 @@ 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.
+
+The :term:`BBCLASSEXTEND` variable is a space separated list of classes used
+to "extend" the recipe for each variant. Here is an example that results in a
+second incarnation of the current recipe being available. This second
+incarnation will have the "native" class inherited. ::
 
-BitBake supports two features that facilitate creating from a single
-recipe file multiple incarnations of that recipe file where all
-incarnations are buildable. These features are enabled through the
-:term:`BBCLASSEXTEND` and :term:`BBVERSIONS` variables.
+      BBCLASSEXTEND = "native"
 
 .. note::
 
@@ -1652,34 +1875,6 @@ incarnations are buildable. These features are enabled through the
    class. For specific examples, see the OE-Core native , nativesdk , and
    multilib classes.
 
--  ``BBCLASSEXTEND``: This variable is a space separated list of
-   classes used to "extend" the recipe for each variant. Here is an
-   example that results in a second incarnation of the current recipe
-   being available. This second incarnation will have the "native" class
-   inherited. ::
-
-      BBCLASSEXTEND = "native"
-
--  ``BBVERSIONS``: This variable allows a single recipe to build
-   multiple versions of a project from a single recipe file. You can
-   also specify conditional metadata (using the
-   :term:`OVERRIDES` mechanism) for a single
-   version, or an optionally named range of versions. Here is an
-   example: ::
-
-      BBVERSIONS = "1.0 2.0 git"
-      SRC_URI_git = "git://someurl/somepath.git"
-
-      BBVERSIONS = "1.0.[0-6]:1.0.0+ 1.0.[7-9]:1.0.7+"
-      SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;patch=1"
-
-   The name of the range defaults to the original version of the recipe. For
-   example, in OpenEmbedded, the recipe file ``foo_1.0.0+.bb`` creates a default
-   name range of ``1.0.0+``. This is useful because the range name is not only
-   placed into overrides, but it is also made available for the metadata to use
-   in the variable that defines the base recipe versions for use in ``file://``
-   search paths (:term:`FILESPATH`).
-
 Dependencies
 ============
 
@@ -1708,7 +1903,7 @@ Dependencies Internal to the ``.bb`` File
 BitBake uses the ``addtask`` directive to manage dependencies that are
 internal to a given recipe file. You can use the ``addtask`` directive
 to indicate when a task is dependent on other tasks or when other tasks
-depend on that recipe. Here is an example: ::
+depend on that recipe. Here is an example::
 
    addtask printdate after do_fetch before do_build
 
@@ -1732,7 +1927,7 @@ task depends on the completion of the ``do_printdate`` task.
 
    -  The directive ``addtask mytask after do_configure`` by itself
       never causes ``do_mytask`` to run. ``do_mytask`` can still be run
-      manually as follows: ::
+      manually as follows::
 
          $ bitbake recipe -c mytask
 
@@ -1745,13 +1940,13 @@ Build Dependencies
 
 BitBake uses the :term:`DEPENDS` variable to manage
 build time dependencies. The ``[deptask]`` varflag for tasks signifies
-the task of each item listed in ``DEPENDS`` that must complete before
-that task can be executed. Here is an example: ::
+the task of each item listed in :term:`DEPENDS` that must complete before
+that task can be executed. Here is an example::
 
    do_configure[deptask] = "do_populate_sysroot"
 
 In this example, the ``do_populate_sysroot`` task
-of each item in ``DEPENDS`` must complete before ``do_configure`` can
+of each item in :term:`DEPENDS` must complete before ``do_configure`` can
 execute.
 
 Runtime Dependencies
@@ -1760,8 +1955,8 @@ Runtime Dependencies
 BitBake uses the :term:`PACKAGES`, :term:`RDEPENDS`, and :term:`RRECOMMENDS`
 variables to manage runtime dependencies.
 
-The ``PACKAGES`` variable lists runtime packages. Each of those packages
-can have ``RDEPENDS`` and ``RRECOMMENDS`` runtime dependencies. The
+The :term:`PACKAGES` variable lists runtime packages. Each of those packages
+can have :term:`RDEPENDS` and :term:`RRECOMMENDS` runtime dependencies. The
 ``[rdeptask]`` flag for tasks is used to signify the task of each item
 runtime dependency which must have completed before that task can be
 executed. ::
@@ -1769,9 +1964,9 @@ executed. ::
    do_package_qa[rdeptask] = "do_packagedata"
 
 In the previous
-example, the ``do_packagedata`` task of each item in ``RDEPENDS`` must
+example, the ``do_packagedata`` task of each item in :term:`RDEPENDS` must
 have completed before ``do_package_qa`` can execute.
-Although ``RDEPENDS`` contains entries from the
+Although :term:`RDEPENDS` contains entries from the
 runtime dependency namespace, BitBake knows how to map them back
 to the build-time dependency namespace, in which the tasks are defined.
 
@@ -1788,7 +1983,7 @@ dependencies are discovered and added.
 
 The ``[recrdeptask]`` flag is most commonly used in high-level recipes
 that need to wait for some task to finish "globally". For example,
-``image.bbclass`` has the following: ::
+``image.bbclass`` has the following::
 
    do_rootfs[recrdeptask] += "do_packagedata"
 
@@ -1797,7 +1992,7 @@ the current recipe and all recipes reachable (by way of dependencies)
 from the image recipe must run before the ``do_rootfs`` task can run.
 
 BitBake allows a task to recursively depend on itself by
-referencing itself in the task list: ::
+referencing itself in the task list::
 
    do_a[recrdeptask] = "do_a do_b"
 
@@ -1814,7 +2009,7 @@ Inter-Task Dependencies
 BitBake uses the ``[depends]`` flag in a more generic form to manage
 inter-task dependencies. This more generic form allows for
 inter-dependency checks for specific tasks rather than checks for the
-data in ``DEPENDS``. Here is an example: ::
+data in :term:`DEPENDS`. Here is an example::
 
    do_patch[depends] = "quilt-native:do_populate_sysroot"
 
@@ -1894,11 +2089,35 @@ access. Here is a list of available operations:
 Other Functions
 ---------------
 
-You can find many other functions that can be called from Python by
-looking at the source code of the ``bb`` module, which is in
-``bitbake/lib/bb``. For example, ``bitbake/lib/bb/utils.py`` includes
-the commonly used functions ``bb.utils.contains()`` and
-``bb.utils.mkdirhier()``, which come with docstrings.
+Other functions are documented in the
+:doc:`/bitbake-user-manual/bitbake-user-manual-library-functions` document.
+
+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
 ===========================
@@ -1909,7 +2128,7 @@ To help understand how BitBake does this, the section assumes an
 OpenEmbedded metadata-based example.
 
 These checksums are stored in :term:`STAMP`. You can
-examine the checksums using the following BitBake command: ::
+examine the checksums using the following BitBake command::
 
    $ bitbake-dumpsigs
 
@@ -1932,16 +2151,6 @@ The following list describes related variables:
    Specifies a function BitBake calls that determines whether BitBake
    requires a setscene dependency to be met.
 
--  :term:`BB_SETSCENE_VERIFY_FUNCTION2`:
-   Specifies a function to call that verifies the list of planned task
-   execution before the main task execution happens.
-
--  :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.
@@ -1956,7 +2165,7 @@ Wildcard Support in Variables
 =============================
 
 Support for wildcard use in variables varies depending on the context in
-which it is used. For example, some variables and file names allow
+which it is used. For example, some variables and filenames allow
 limited use of wildcards through the "``%``" and "``*``" characters.
 Other variables or names support Python's
 `glob <https://docs.python.org/3/library/glob.html>`_ syntax,