mirror of
https://git.yoctoproject.org/poky
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69b6919341
Rather than just use d.getVar(X), use the more explict d.getVar(X, False) since at some point in the future, having the default of expansion would be nice. This is the first step towards that. This patch was mostly made using the command: sed -e 's:\(getVar([^,()]*\)\s*):\1, False):g' -i `grep -ril getVar *` (Bitbake rev: 659ef95c9b8aced3c4ded81c48bcc0fbde4d429f) Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
1831 lines
84 KiB
XML
1831 lines
84 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<chapter id="bitbake-user-manual-metadata">
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<title>Syntax and Operators</title>
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<para>
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Bitbake files have their own syntax.
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The syntax has similarities to several
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other languages but also has some unique features.
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This section describes the available syntax and operators
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as well as provides examples.
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</para>
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<section id='basic-syntax'>
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<title>Basic Syntax</title>
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<para>
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This section provides some basic syntax examples.
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</para>
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<section id='basic-variable-setting'>
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<title>Basic Variable Setting</title>
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<para>
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The following example sets <filename>VARIABLE</filename> to
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"value".
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This assignment occurs immediately as the statement is parsed.
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It is a "hard" assignment.
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<literallayout class='monospaced'>
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VARIABLE = "value"
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</literallayout>
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As expected, if you include leading or trailing spaces as part of
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an assignment, the spaces are retained:
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<literallayout class='monospaced'>
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VARIABLE = " value"
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VARIABLE = "value "
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</literallayout>
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Setting <filename>VARIABLE</filename> to "" sets it to an empty string,
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while setting the variable to " " sets it to a blank space
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(i.e. these are not the same values).
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<literallayout class='monospaced'>
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VARIABLE = ""
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VARIABLE = " "
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</literallayout>
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</para>
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</section>
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<section id='variable-expansion'>
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<title>Variable Expansion</title>
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<para>
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BitBake supports variables referencing one another's
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contents using a syntax that is similar to shell scripting.
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Following is an example that results in <filename>A</filename>
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containing "aval" and <filename>B</filename> evaluating to
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"preavalpost" based on that current value of
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<filename>A</filename>.
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<literallayout class='monospaced'>
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A = "aval"
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B = "pre${A}post"
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</literallayout>
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You should realize that whenever <filename>B</filename> is
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referenced, its evaluation will depend on the state of
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<filename>A</filename> at that time.
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Thus, later evaluations of <filename>B</filename> in the
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previous example could result in different values
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depending on the value of <filename>A</filename>.
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</para>
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</section>
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<section id='setting-a-default-value'>
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<title>Setting a default value (?=)</title>
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<para>
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You can use the "?=" operator to achieve a "softer" assignment
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for a variable.
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This type of assignment allows you to define a variable if it
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is undefined when the statement is parsed, but to leave the
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value alone if the variable has a value.
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Here is an example:
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<literallayout class='monospaced'>
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A ?= "aval"
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</literallayout>
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If <filename>A</filename> is set at the time this statement is parsed,
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the variable retains its value.
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However, if <filename>A</filename> is not set,
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the variable is set to "aval".
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<note>
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This assignment is immediate.
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Consequently, if multiple "?=" assignments
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to a single variable exist, the first of those ends up getting
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used.
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</note>
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</para>
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</section>
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<section id='setting-a-weak-default-value'>
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<title>Setting a weak default value (??=)</title>
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<para>
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It is possible to use a "weaker" assignment than in the
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previous section by using the "??=" operator.
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This assignment behaves identical to "?=" except that the
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assignment is made at the end of the parsing process rather
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than immediately.
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Consequently, when multiple "??=" assignments exist, the last
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one is used.
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Also, any "=" or "?=" assignment will override the value set with
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"??=".
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Here is an example:
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<literallayout class='monospaced'>
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A ??= "somevalue"
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A ??= "someothervalue"
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</literallayout>
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If <filename>A</filename> is set before the above statements are parsed,
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the variable retains its value.
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If <filename>A</filename> is not set,
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the variable is set to "someothervalue".
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</para>
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<para>
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Again, this assignment is a "lazy" or "weak" assignment
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because it does not occur until the end
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of the parsing process.
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</para>
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</section>
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<section id='immediate-variable-expansion'>
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<title>Immediate variable expansion (:=)</title>
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<para>
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The ":=" operator results in a variable's
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contents being expanded immediately,
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rather than when the variable is actually used:
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<literallayout class='monospaced'>
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T = "123"
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A := "${B} ${A} test ${T}"
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T = "456"
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B = "${T} bval"
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C = "cval"
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C := "${C}append"
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</literallayout>
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In this example, <filename>A</filename> contains
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"test 123" because <filename>${B}</filename> and
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<filename>${A}</filename> at the time of parsing are undefined,
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which leaves "test 123".
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And, the variable <filename>C</filename>
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contains "cvalappend" since <filename>${C}</filename> immediately
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expands to "cval".
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</para>
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</section>
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<section id='appending-and-prepending'>
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<title>Appending (+=) and prepending (=+) With Spaces</title>
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<para>
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Appending and prepending values is common and can be accomplished
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using the "+=" and "=+" operators.
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These operators insert a space between the current
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value and prepended or appended value.
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</para>
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<para>
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These operators take immediate effect during parsing.
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Here are some examples:
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<literallayout class='monospaced'>
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B = "bval"
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B += "additionaldata"
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C = "cval"
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C =+ "test"
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</literallayout>
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The variable <filename>B</filename> contains
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"bval additionaldata" and <filename>C</filename>
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contains "test cval".
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</para>
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</section>
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<section id='appending-and-prepending-without-spaces'>
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<title>Appending (.=) and Prepending (=.) Without Spaces</title>
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<para>
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If you want to append or prepend values without an
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inserted space, use the ".=" and "=." operators.
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</para>
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<para>
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These operators take immediate effect during parsing.
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Here are some examples:
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<literallayout class='monospaced'>
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B = "bval"
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B .= "additionaldata"
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C = "cval"
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C =. "test"
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</literallayout>
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The variable <filename>B</filename> contains
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"bvaladditionaldata" and
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<filename>C</filename> contains "testcval".
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</para>
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</section>
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<section id='appending-and-prepending-override-style-syntax'>
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<title>Appending and Prepending (Override Style Syntax)</title>
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<para>
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You can also append and prepend a variable's value
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using an override style syntax.
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When you use this syntax, no spaces are inserted.
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</para>
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<para>
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These operators differ from the ":=", ".=", "=.", "+=", and "=+"
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operators in that their effects are deferred
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until after parsing completes rather than being immediately
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applied.
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Here are some examples:
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<literallayout class='monospaced'>
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B = "bval"
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B_append = " additional data"
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C = "cval"
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C_prepend = "additional data "
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D = "dval"
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D_append = "additional data"
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</literallayout>
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The variable <filename>B</filename> becomes
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"bval additional data" and <filename>C</filename> becomes
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"additional data cval".
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The variable <filename>D</filename> becomes
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"dvaladditional data".
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<note>
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You must control all spacing when you use the
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override syntax.
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</note>
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</para>
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</section>
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<section id='removing-override-style-syntax'>
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<title>Removal (Override Style Syntax)</title>
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<para>
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You can remove values from lists using the removal
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override style syntax.
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Specifying a value for removal causes all occurrences of that
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value to be removed from the variable.
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</para>
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<para>
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When you use this syntax, BitBake expects one or more strings.
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Surrounding spaces are removed as well.
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Here is an example:
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<literallayout class='monospaced'>
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FOO = "123 456 789 123456 123 456 123 456"
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FOO_remove = "123"
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FOO_remove = "456"
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FOO2 = "abc def ghi abcdef abc def abc def"
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FOO2_remove = "abc def"
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</literallayout>
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The variable <filename>FOO</filename> becomes
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"789 123456" and <filename>FOO2</filename> becomes
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"ghi abcdef".
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</para>
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</section>
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<section id='variable-flag-syntax'>
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<title>Variable Flag Syntax</title>
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<para>
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Variable flags are BitBake's implementation of variable properties
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or attributes.
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It is a way of tagging extra information onto a variable.
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You can find more out about variable flags in general in the
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"<link linkend='variable-flags'>Variable Flags</link>"
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section.
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</para>
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<para>
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You can define, append, and prepend values to variable flags.
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All the standard syntax operations previously mentioned work
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for variable flags except for override style syntax
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(i.e. <filename>_prepend</filename>, <filename>_append</filename>,
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and <filename>_remove</filename>).
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</para>
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<para>
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Here are some examples showing how to set variable flags:
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<literallayout class='monospaced'>
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FOO[a] = "abc"
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FOO[b] = "123"
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FOO[a] += "456"
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</literallayout>
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The variable <filename>FOO</filename> has two flags:
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<filename>a</filename> and <filename>b</filename>.
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The flags are immediately set to "abc" and "123", respectively.
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The <filename>a</filename> flag becomes "abc 456".
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</para>
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<para>
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No need exists to pre-define variable flags.
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You can simply start using them.
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One extremely common application
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is to attach some brief documentation to a BitBake variable as
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follows:
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<literallayout class='monospaced'>
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CACHE[doc] = "The directory holding the cache of the metadata."
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</literallayout>
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</para>
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</section>
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<section id='inline-python-variable-expansion'>
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<title>Inline Python Variable Expansion</title>
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<para>
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You can use inline Python variable expansion to
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set variables.
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Here is an example:
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<literallayout class='monospaced'>
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DATE = "${@time.strftime('%Y%m%d',time.gmtime())}"
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</literallayout>
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This example results in the <filename>DATE</filename>
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variable being set to the current date.
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</para>
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<para>
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Probably the most common use of this feature is to extract
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the value of variables from BitBake's internal data dictionary,
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<filename>d</filename>.
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The following lines select the values of a package name
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and its version number, respectively:
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<literallayout class='monospaced'>
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PN = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[0] or 'defaultpkgname'}"
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PV = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE', False),d)[1] or '1.0'}"
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</literallayout>
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</para>
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</section>
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<section id='providing-pathnames'>
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<title>Providing Pathnames</title>
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<para>
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When specifying pathnames for use with BitBake,
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do not use the tilde ("~") character as a shortcut
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for your home directory.
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Doing so might cause BitBake to not recognize the
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path since BitBake does not expand this character in
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the same way a shell would.
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</para>
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<para>
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Instead, provide a fuller path as the following
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example illustrates:
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<literallayout class='monospaced'>
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BBLAYERS ?= " \
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/home/scott-lenovo/LayerA \
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"
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</literallayout>
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</para>
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</section>
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</section>
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<section id='conditional-syntax-overrides'>
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<title>Conditional Syntax (Overrides)</title>
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<para>
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BitBake uses
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<link linkend='var-OVERRIDES'><filename>OVERRIDES</filename></link>
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to control what variables are overridden after BitBake
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parses recipes and configuration files.
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This section describes how you can use
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<filename>OVERRIDES</filename> as conditional metadata,
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talks about key expansion in relationship to
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<filename>OVERRIDES</filename>, and provides some examples
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to help with understanding.
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</para>
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<section id='conditional-metadata'>
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<title>Conditional Metadata</title>
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<para>
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You can use <filename>OVERRIDES</filename> to conditionally select
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a specific version of a variable and to conditionally
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append or prepend the value of a variable.
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<itemizedlist>
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<listitem><para><emphasis>Selecting a Variable:</emphasis>
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The <filename>OVERRIDES</filename> variable is
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a colon-character-separated list that contains items
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for which you want to satisfy conditions.
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Thus, if you have a variable that is conditional on “arm”, and “arm”
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is in <filename>OVERRIDES</filename>, then the “arm”-specific
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version of the variable is used rather than the non-conditional
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version.
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Here is an example:
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<literallayout class='monospaced'>
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OVERRIDES = "architecture:os:machine"
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TEST = "default"
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TEST_os = "osspecific"
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TEST_nooverride = "othercondvalue"
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</literallayout>
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In this example, the <filename>OVERRIDES</filename>
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variable lists three overrides:
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"architecture", "os", and "machine".
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The variable <filename>TEST</filename> by itself has a default
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value of "default".
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You select the os-specific version of the <filename>TEST</filename>
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variable by appending the "os" override to the variable
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(i.e.<filename>TEST_os</filename>).
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</para>
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<para>
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To better understand this, consider a practical example
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that assumes an OpenEmbedded metadata-based Linux
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kernel recipe file.
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The following lines from the recipe file first set
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the kernel branch variable <filename>KBRANCH</filename>
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to a default value, then conditionally override that
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value based on the architecture of the build:
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<literallayout class='monospaced'>
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KBRANCH = "standard/base"
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KBRANCH_qemuarm = "standard/arm-versatile-926ejs"
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KBRANCH_qemumips = "standard/mti-malta32"
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KBRANCH_qemuppc = "standard/qemuppc"
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KBRANCH_qemux86 = "standard/common-pc/base"
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KBRANCH_qemux86-64 = "standard/common-pc-64/base"
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KBRANCH_qemumips64 = "standard/mti-malta64"
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</literallayout>
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</para></listitem>
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<listitem><para><emphasis>Appending and Prepending:</emphasis>
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BitBake also supports append and prepend operations to
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variable values based on whether a specific item is
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listed in <filename>OVERRIDES</filename>.
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Here is an example:
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<literallayout class='monospaced'>
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DEPENDS = "glibc ncurses"
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OVERRIDES = "machine:local"
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DEPENDS_append_machine = "libmad"
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</literallayout>
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In this example, <filename>DEPENDS</filename> becomes
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"glibc ncurses libmad".
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</para>
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<para>
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Again, using an OpenEmbedded metadata-based
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kernel recipe file as an example, the
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following lines will conditionally append to the
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<filename>KERNEL_FEATURES</filename> variable based
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on the architecture:
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<literallayout class='monospaced'>
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KERNEL_FEATURES_append = " ${KERNEL_EXTRA_FEATURES}"
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KERNEL_FEATURES_append_qemux86=" cfg/sound.scc cfg/paravirt_kvm.scc"
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KERNEL_FEATURES_append_qemux86-64=" cfg/sound.scc cfg/paravirt_kvm.scc"
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</literallayout>
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
|
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|
|
<section id='key-expansion'>
|
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<title>Key Expansion</title>
|
|
|
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<para>
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Key expansion happens when the BitBake datastore is finalized
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|
just before BitBake expands overrides.
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|
To better understand this, consider the following example:
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|
<literallayout class='monospaced'>
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A${B} = "X"
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B = "2"
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A2 = "Y"
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</literallayout>
|
|
In this case, after all the parsing is complete, and
|
|
before any overrides are handled, BitBake expands
|
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<filename>${B}</filename> into "2".
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|
This expansion causes <filename>A2</filename>, which was
|
|
set to "Y" before the expansion, to become "X".
|
|
</para>
|
|
</section>
|
|
|
|
<section id='variable-interaction-worked-examples'>
|
|
<title>Examples</title>
|
|
|
|
<para>
|
|
Despite the previous explanations that show the different forms of
|
|
variable definitions, it can be hard to work
|
|
out exactly what happens when variable operators, conditional
|
|
overrides, and unconditional overrides are combined.
|
|
This section presents some common scenarios along
|
|
with explanations for variable interactions that
|
|
typically confuse users.
|
|
</para>
|
|
|
|
<para>
|
|
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"
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|
and "_prepend" does not result in an immediate assignment
|
|
as would "+=", ".=", "=+", or "=.".
|
|
Consider the following example:
|
|
<literallayout class='monospaced'>
|
|
OVERRIDES = "foo"
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A = "Z"
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A_foo_append = "X"
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|
</literallayout>
|
|
For this case, <filename>A</filename> is
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|
unconditionally set to "Z" and "X" is
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|
unconditionally and immediately appended to the variable
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<filename>A_foo</filename>.
|
|
Because overrides have not been applied yet,
|
|
<filename>A_foo</filename> is set to "X" due to the append
|
|
and <filename>A</filename> simply equals "Z".
|
|
</para>
|
|
|
|
<para>
|
|
Applying overrides, however, changes things.
|
|
Since "foo" is listed in <filename>OVERRIDES</filename>,
|
|
the conditional variable <filename>A</filename> is replaced
|
|
with the "foo" version, which is equal to "X".
|
|
So effectively, <filename>A_foo</filename> replaces <filename>A</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
This next example changes the order of the override and
|
|
the append:
|
|
<literallayout class='monospaced'>
|
|
OVERRIDES = "foo"
|
|
A = "Z"
|
|
A_append_foo = "X"
|
|
</literallayout>
|
|
For this case, before overrides are handled,
|
|
<filename>A</filename> is set to "Z" and <filename>A_append_foo</filename>
|
|
is set to "X".
|
|
Once the override for "foo" is applied, however,
|
|
<filename>A</filename> gets appended with "X".
|
|
Consequently, <filename>A</filename> becomes "ZX".
|
|
Notice that spaces are not appended.
|
|
</para>
|
|
|
|
<para>
|
|
This next example has the order of the appends and overrides reversed
|
|
back as in the first example:
|
|
<literallayout class='monospaced'>
|
|
OVERRIDES = "foo"
|
|
A = "Y"
|
|
A_foo_append = "Z"
|
|
A_foo_append += "X"
|
|
</literallayout>
|
|
For this case, before any overrides are resolved,
|
|
<filename>A</filename> is set to "Y" using an immediate assignment.
|
|
After this immediate assignment, <filename>A_foo</filename> is set
|
|
to "Z", and then further appended with
|
|
"X" leaving the variable set to "Z X".
|
|
Finally, applying the override for "foo" results in the conditional
|
|
variable <filename>A</filename> becoming "Z X" (i.e.
|
|
<filename>A</filename> is replaced with <filename>A_foo</filename>).
|
|
</para>
|
|
|
|
<para>
|
|
This final example mixes in some varying operators:
|
|
<literallayout class='monospaced'>
|
|
A = "1"
|
|
A_append = "2"
|
|
A_append = "3"
|
|
A += "4"
|
|
A .= "5"
|
|
</literallayout>
|
|
For this case, the type of append operators are affecting the
|
|
order of assignments as BitBake passes through the code
|
|
multiple times.
|
|
Initially, <filename>A</filename> is set to "1 45" because
|
|
of the three statements that use immediate operators.
|
|
After these assignments are made, BitBake applies the
|
|
<filename>_append</filename> operations.
|
|
Those operations result in <filename>A</filename> becoming "1 4523".
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='sharing-functionality'>
|
|
<title>Sharing Functionality</title>
|
|
|
|
<para>
|
|
BitBake allows for metadata sharing through include files
|
|
(<filename>.inc</filename>) and class files
|
|
(<filename>.bbclass</filename>).
|
|
For example, suppose you have a piece of common functionality
|
|
such as a task definition that you want to share between
|
|
more than one recipe.
|
|
In this case, creating a <filename>.bbclass</filename>
|
|
file that contains the common functionality and then using
|
|
the <filename>inherit</filename> directive in your recipes to
|
|
inherit the class would be a common way to share the task.
|
|
</para>
|
|
|
|
<para>
|
|
This section presents the mechanisms BitBake provides to
|
|
allow you to share functionality between recipes.
|
|
Specifically, the mechanisms include <filename>include</filename>,
|
|
<filename>inherit</filename>, <filename>INHERIT</filename>, and
|
|
<filename>require</filename> directives.
|
|
</para>
|
|
|
|
<section id='locating-include-and-class-files'>
|
|
<title>Locating Include and Class Files</title>
|
|
|
|
<para>
|
|
BitBake uses the
|
|
<link linkend='var-BBPATH'><filename>BBPATH</filename></link>
|
|
variable to locate needed include and class files.
|
|
The <filename>BBPATH</filename> variable is analogous to
|
|
the environment variable <filename>PATH</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
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 <filename>BBPATH</filename>.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='inherit-directive'>
|
|
<title><filename>inherit</filename> Directive</title>
|
|
|
|
<para>
|
|
When writing a recipe or class file, you can use the
|
|
<filename>inherit</filename> directive to inherit the
|
|
functionality of a class (<filename>.bbclass</filename>).
|
|
BitBake only supports this directive when used within recipe
|
|
and class files (i.e. <filename>.bb</filename> and
|
|
<filename>.bbclass</filename>).
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>inherit</filename> directive is a rudimentary
|
|
means of specifying what classes of functionality your
|
|
recipes require.
|
|
For example, you can easily abstract out the tasks involved in
|
|
building a package that uses Autoconf and Automake and put
|
|
those tasks into a class file that can be used by your recipe.
|
|
</para>
|
|
|
|
<para>
|
|
As an example, your recipes could use the following directive
|
|
to inherit an <filename>autotools.bbclass</filename> file.
|
|
The class file would contain common functionality for using
|
|
Autotools that could be shared across recipes:
|
|
<literallayout class='monospaced'>
|
|
inherit autotools
|
|
</literallayout>
|
|
In this case, BitBake would search for the directory
|
|
<filename>classes/autotools.bbclass</filename>
|
|
in <filename>BBPATH</filename>.
|
|
<note>
|
|
You can override any values and functions of the
|
|
inherited class within your recipe by doing so
|
|
after the "inherit" statement.
|
|
</note>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='include-directive'>
|
|
<title><filename>include</filename> Directive</title>
|
|
|
|
<para>
|
|
BitBake understands the <filename>include</filename>
|
|
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 <filename>BBPATH</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
As an example, suppose you needed a recipe to include some
|
|
self-test definitions:
|
|
<literallayout class='monospaced'>
|
|
include test_defs.inc
|
|
</literallayout>
|
|
<note>
|
|
The <filename>include</filename> directive does not
|
|
produce an error when the file cannot be found.
|
|
Consequently, it is recommended that if the file you
|
|
are including is expected to exist, you should use
|
|
<link linkend='require-inclusion'><filename>require</filename></link>
|
|
instead of <filename>include</filename>.
|
|
Doing so makes sure that an error is produced if the
|
|
file cannot be found.
|
|
</note>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='require-inclusion'>
|
|
<title><filename>require</filename> Directive</title>
|
|
|
|
<para>
|
|
BitBake understands the <filename>require</filename>
|
|
directive.
|
|
This directive behaves just like the
|
|
<filename>include</filename> directive with the exception that
|
|
BitBake raises a parsing error if the file to be included cannot
|
|
be found.
|
|
Thus, any file you require is inserted into the file that is
|
|
being parsed at the location of the directive.
|
|
</para>
|
|
|
|
<para>
|
|
Similar to how BitBake handles
|
|
<link linkend='include-directive'><filename>include</filename></link>,
|
|
if the path specified
|
|
on the require line is a relative path, BitBake locates
|
|
the first file it can find within <filename>BBPATH</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
As an example, suppose you have two versions of a recipe
|
|
(e.g. <filename>foo_1.2.2.bb</filename> and
|
|
<filename>foo_2.0.0.bb</filename>) where
|
|
each version contains some identical functionality that could be
|
|
shared.
|
|
You could create an include file named <filename>foo.inc</filename>
|
|
that contains the common definitions needed to build "foo".
|
|
You need to be sure <filename>foo.inc</filename> 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 <filename>require</filename> directive from within each
|
|
recipe:
|
|
<literallayout class='monospaced'>
|
|
require foo.inc
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='inherit-configuration-directive'>
|
|
<title><filename>INHERIT</filename> Configuration Directive</title>
|
|
|
|
<para>
|
|
When creating a configuration file (<filename>.conf</filename>),
|
|
you can use the <filename>INHERIT</filename> directive to
|
|
inherit a class.
|
|
BitBake only supports this directive when used within
|
|
a configuration file.
|
|
</para>
|
|
|
|
<para>
|
|
As an example, suppose you needed to inherit a class
|
|
file called <filename>abc.bbclass</filename> from a
|
|
configuration file as follows:
|
|
<literallayout class='monospaced'>
|
|
INHERIT += "abc"
|
|
</literallayout>
|
|
This configuration directive causes the named
|
|
class to be inherited at the point of the directive
|
|
during parsing.
|
|
As with the <filename>inherit</filename> directive, the
|
|
<filename>.bbclass</filename> file must be located in a
|
|
"classes" subdirectory in one of the directories specified
|
|
in <filename>BBPATH</filename>.
|
|
<note>
|
|
Because <filename>.conf</filename> files are parsed
|
|
first during BitBake's execution, using
|
|
<filename>INHERIT</filename> to inherit a class effectively
|
|
inherits the class globally (i.e. for all recipes).
|
|
</note>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='functions'>
|
|
<title>Functions</title>
|
|
|
|
<para>
|
|
As with most languages, functions are the building blocks that
|
|
are used to build up operations into tasks.
|
|
BitBake supports these types of functions:
|
|
<itemizedlist>
|
|
<listitem><para><emphasis>Shell Functions:</emphasis>
|
|
Functions written in shell script and executed either
|
|
directly as functions, tasks, or both.
|
|
They can also be called by other shell functions.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>BitBake Style Python Functions:</emphasis>
|
|
Functions written in Python and executed by BitBake or other
|
|
Python functions using <filename>bb.build.exec_func()</filename>.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Python Functions:</emphasis>
|
|
Functions written in Python and executed by Python.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Anonymous Python Functions:</emphasis>
|
|
Python functions executed automatically during
|
|
parsing.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
Regardless of the type of function, you can only
|
|
define them in class (<filename>.bbclass</filename>)
|
|
and recipe (<filename>.bb</filename> or <filename>.inc</filename>)
|
|
files.
|
|
</para>
|
|
|
|
<section id='shell-functions'>
|
|
<title>Shell Functions</title>
|
|
|
|
<para>
|
|
Functions written in shell script and executed either
|
|
directly as functions, tasks, or both.
|
|
They can also be called by other shell functions.
|
|
Here is an example shell function definition:
|
|
<literallayout class='monospaced'>
|
|
some_function () {
|
|
echo "Hello World"
|
|
}
|
|
</literallayout>
|
|
When you create these types of functions in your recipe
|
|
or class files, you need to follow the shell programming
|
|
rules.
|
|
The scripts are executed by <filename>/bin/sh</filename>,
|
|
which may not be a bash shell but might be something
|
|
such as <filename>dash</filename>.
|
|
You should not use Bash-specific script (bashisms).
|
|
</para>
|
|
</section>
|
|
|
|
<section id='bitbake-style-python-functions'>
|
|
<title>BitBake Style Python Functions</title>
|
|
|
|
<para>
|
|
These functions are written in Python and executed by
|
|
BitBake or other Python functions using
|
|
<filename>bb.build.exec_func()</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
An example BitBake function is:
|
|
<literallayout class='monospaced'>
|
|
python some_python_function () {
|
|
d.setVar("TEXT", "Hello World")
|
|
print d.getVar("TEXT", True)
|
|
}
|
|
</literallayout>
|
|
Because the Python "bb" and "os" modules are already
|
|
imported, you do not need to import these modules.
|
|
Also in these types of functions, the datastore ("d")
|
|
is a global variable and is always automatically
|
|
available.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='python-functions'>
|
|
<title>Python Functions</title>
|
|
|
|
<para>
|
|
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:
|
|
<literallayout class='monospaced'>
|
|
def get_depends(d):
|
|
if d.getVar('SOMECONDITION', True):
|
|
return "dependencywithcond"
|
|
else:
|
|
return "dependency"
|
|
SOMECONDITION = "1"
|
|
DEPENDS = "${@get_depends(d)}"
|
|
</literallayout>
|
|
This would result in <filename>DEPENDS</filename>
|
|
containing <filename>dependencywithcond</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
Here are some things to know about Python functions:
|
|
<itemizedlist>
|
|
<listitem><para>Python functions can take parameters.
|
|
</para></listitem>
|
|
<listitem><para>The BitBake datastore is not
|
|
automatically available.
|
|
Consequently, you must pass it in as a
|
|
parameter to the function.
|
|
</para></listitem>
|
|
<listitem><para>The "bb" and "os" Python modules are
|
|
automatically available.
|
|
You do not need to import them.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='anonymous-python-functions'>
|
|
<title>Anonymous Python Functions</title>
|
|
|
|
<para>
|
|
Sometimes it is useful to run some code during
|
|
parsing to set variables or to perform other operations
|
|
programmatically.
|
|
To do this, you can define an anonymous Python function.
|
|
Here is an example that conditionally sets a
|
|
variable based on the value of another variable:
|
|
<literallayout class='monospaced'>
|
|
python __anonymous () {
|
|
if d.getVar('SOMEVAR', True) == 'value':
|
|
d.setVar('ANOTHERVAR', 'value2')
|
|
}
|
|
</literallayout>
|
|
The "__anonymous" function name is optional, so the
|
|
following example is functionally equivalent to the above:
|
|
<literallayout class='monospaced'>
|
|
python () {
|
|
if d.getVar('SOMEVAR', True) == 'value':
|
|
d.setVar('ANOTHERVAR', 'value2')
|
|
}
|
|
</literallayout>
|
|
Because unlike other Python functions anonymous
|
|
Python functions are executed during parsing, the
|
|
"d" variable within an anonymous Python function represents
|
|
the datastore for the entire recipe.
|
|
Consequently, you can set variable values here and
|
|
those values can be picked up by other functions.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='flexible-inheritance-for-class-functions'>
|
|
<title>Flexible Inheritance for Class Functions</title>
|
|
|
|
<para>
|
|
Through coding techniques and the use of
|
|
<filename>EXPORT_FUNCTIONS</filename>, BitBake supports
|
|
exporting a function from a class such that the
|
|
class function appears as the default implementation
|
|
of the function, but can still be called if a recipe
|
|
inheriting the class needs to define its own version of
|
|
the function.
|
|
</para>
|
|
|
|
<para>
|
|
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
|
|
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.
|
|
<filename>EXPORT_FUNCTIONS</filename> provides a mechanism
|
|
that enables the recipe's version of the function to call
|
|
the original version of the function.
|
|
</para>
|
|
|
|
<para>
|
|
To make use of this technique, you need the following
|
|
things in place:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
The class needs to define the function as follows:
|
|
<literallayout class='monospaced'>
|
|
<replaceable>classname</replaceable><filename>_</filename><replaceable>functionname</replaceable>
|
|
</literallayout>
|
|
For example, if you have a class file
|
|
<filename>bar.bbclass</filename> and a function named
|
|
<filename>do_foo</filename>, the class must define the function
|
|
as follows:
|
|
<literallayout class='monospaced'>
|
|
bar_do_foo
|
|
</literallayout>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
The class needs to contain the <filename>EXPORT_FUNCTIONS</filename>
|
|
statement as follows:
|
|
<literallayout class='monospaced'>
|
|
EXPORT_FUNCTIONS <replaceable>functionname</replaceable>
|
|
</literallayout>
|
|
For example, continuing with the same example, the
|
|
statement in the <filename>bar.bbclass</filename> would be
|
|
as follows:
|
|
<literallayout class='monospaced'>
|
|
EXPORT_FUNCTIONS do_foo
|
|
</literallayout>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
You need to call the function appropriately from within your
|
|
recipe.
|
|
Continuing with the same example, if your recipe
|
|
needs to call the class version of the function,
|
|
it should call <filename>bar_do_foo</filename>.
|
|
Assuming <filename>do_foo</filename> was a shell function
|
|
and <filename>EXPORT_FUNCTIONS</filename> was used as above,
|
|
the recipe's function could conditionally call the
|
|
class version of the function as follows:
|
|
<literallayout class='monospaced'>
|
|
do_foo() {
|
|
if [ somecondition ] ; then
|
|
bar_do_foo
|
|
else
|
|
# Do something else
|
|
fi
|
|
}
|
|
</literallayout>
|
|
To call your modified version of the function as defined
|
|
in your recipe, call it as <filename>do_foo</filename>.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
With these conditions met, your single recipe
|
|
can freely choose between the original function
|
|
as defined in the class file and the modified function in your recipe.
|
|
If you do not set up these conditions, you are limited to using one function
|
|
or the other.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='tasks'>
|
|
<title>Tasks</title>
|
|
|
|
<para>
|
|
Tasks are BitBake execution units that originate as
|
|
functions and make up the steps that BitBake needs to run
|
|
for given recipe.
|
|
Tasks are only supported in recipe (<filename>.bb</filename>
|
|
or <filename>.inc</filename>) and class
|
|
(<filename>.bbclass</filename>) files.
|
|
By convention, task names begin with the string "do_".
|
|
</para>
|
|
|
|
<para>
|
|
Here is an example of a task that prints out the date:
|
|
<literallayout class='monospaced'>
|
|
python do_printdate () {
|
|
import time
|
|
print time.strftime('%Y%m%d', time.gmtime())
|
|
}
|
|
addtask printdate after do_fetch before do_build
|
|
</literallayout>
|
|
</para>
|
|
|
|
<section id='promoting-a-function-to-a-task'>
|
|
<title>Promoting a Function to a Task</title>
|
|
|
|
<para>
|
|
Any function can be promoted to a task by applying the
|
|
<filename>addtask</filename> command.
|
|
The <filename>addtask</filename> command also describes
|
|
inter-task dependencies.
|
|
Here is the function from the previous section but with the
|
|
<filename>addtask</filename> command promoting it to a task
|
|
and defining some dependencies:
|
|
<literallayout class='monospaced'>
|
|
python do_printdate () {
|
|
import time
|
|
print time.strftime('%Y%m%d', time.gmtime())
|
|
}
|
|
addtask printdate after do_fetch before do_build
|
|
</literallayout>
|
|
In the example, the function is defined and then promoted
|
|
as a task.
|
|
The <filename>do_printdate</filename> task becomes a dependency of
|
|
the <filename>do_build</filename> task, which is the default
|
|
task.
|
|
And, the <filename>do_printdate</filename> task is dependent upon
|
|
the <filename>do_fetch</filename> task.
|
|
Execution of the <filename>do_build</filename> task results
|
|
in the <filename>do_printdate</filename> task running first.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='deleting-a-task'>
|
|
<title>Deleting a Task</title>
|
|
|
|
<para>
|
|
As well as being able to add tasks, you can delete them.
|
|
Simply use the <filename>deltask</filename> command to
|
|
delete a task.
|
|
For example, to delete the example task used in the previous
|
|
sections, you would use:
|
|
<literallayout class='monospaced'>
|
|
deltask printdate
|
|
</literallayout>
|
|
If you delete a task using the <filename>deltask</filename>
|
|
command and the task has dependencies, the dependencies are
|
|
not reconnected.
|
|
For example, suppose you have three tasks named
|
|
<filename>do_a</filename>, <filename>do_b</filename>, and
|
|
<filename>do_c</filename>.
|
|
Furthermore, <filename>do_c</filename> is dependent on
|
|
<filename>do_b</filename>, which in turn is dependent on
|
|
<filename>do_a</filename>.
|
|
Given this scenario, if you use <filename>deltask</filename>
|
|
to delete <filename>do_b</filename>, the implicit dependency
|
|
relationship between <filename>do_c</filename> and
|
|
<filename>do_a</filename> through <filename>do_b</filename>
|
|
no longer exists, and <filename>do_c</filename> dependencies
|
|
are not updated to include <filename>do_a</filename>.
|
|
Thus, <filename>do_c</filename> is free to run before
|
|
<filename>do_a</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
If you want dependencies such as these to remain intact, use
|
|
the <filename>noexec</filename> varflag to disable the task
|
|
instead of using the <filename>deltask</filename> command to
|
|
delete it:
|
|
<literallayout class='monospaced'>
|
|
do_b[noexec] = "1"
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='passing-information-into-the-build-task-environment'>
|
|
<title>Passing Information Into the Build Task Environment</title>
|
|
|
|
<para>
|
|
When running a task, BitBake tightly controls the execution
|
|
environment of the build tasks to make
|
|
sure unwanted contamination from the build machine cannot
|
|
influence the build.
|
|
Consequently, if you do want something to get passed into the
|
|
build task environment, you must take these two steps:
|
|
<orderedlist>
|
|
<listitem><para>
|
|
Tell BitBake to load what you want from the environment
|
|
into the datastore.
|
|
You can do so through the
|
|
<link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link>
|
|
variable.
|
|
For example, assume you want to prevent the build system from
|
|
accessing your <filename>$HOME/.ccache</filename>
|
|
directory.
|
|
The following command tells BitBake to load
|
|
<filename>CCACHE_DIR</filename> from the environment into
|
|
the datastore:
|
|
<literallayout class='monospaced'>
|
|
export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR"
|
|
</literallayout></para></listitem>
|
|
<listitem><para>
|
|
Tell BitBake to export what you have loaded into the
|
|
datastore to the task environment of every running task.
|
|
Loading something from the environment into the datastore
|
|
(previous step) only makes it 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 <filename>local.conf</filename> or your
|
|
distribution configuration file:
|
|
<literallayout class='monospaced'>
|
|
export CCACHE_DIR
|
|
</literallayout>
|
|
<note>
|
|
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
|
|
ignores the dependency when it creates checksums.
|
|
</note></para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
|
|
<para>
|
|
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
|
|
<link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link>.
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>BB_ORIGENV</filename> variable returns a datastore
|
|
object that can be queried using the standard datastore operators
|
|
such as <filename>getVar(, False)</filename>.
|
|
The datastore object is useful, for example, to find the original
|
|
<filename>DISPLAY</filename> variable.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
origenv = d.getVar("BB_ORIGENV", False)
|
|
bar = origenv.getVar("BAR", False)
|
|
</literallayout>
|
|
The previous example returns <filename>BAR</filename> from the original
|
|
execution environment.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='variable-flags'>
|
|
<title>Variable Flags</title>
|
|
|
|
<para>
|
|
Variable flags (varflags) help control a task's functionality
|
|
and dependencies.
|
|
BitBake reads and writes varflags to the datastore using the following
|
|
command forms:
|
|
<literallayout class='monospaced'>
|
|
<replaceable>variable</replaceable> = d.getVarFlags("<replaceable>variable</replaceable>")
|
|
self.d.setVarFlags("FOO", {"func": True})
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
When working with varflags, the same syntax, with the exception of
|
|
overrides, applies.
|
|
In other words, you can set, append, and prepend varflags just like
|
|
variables.
|
|
See the
|
|
"<link linkend='variable-flag-syntax'>Variable Flag Syntax</link>"
|
|
section for details.
|
|
</para>
|
|
|
|
<para>
|
|
BitBake has a defined set of varflags available for recipes and
|
|
classes.
|
|
Tasks support a number of these flags which control various
|
|
functionality of the task:
|
|
<itemizedlist>
|
|
<listitem><para><emphasis>cleandirs:</emphasis>
|
|
Empty directories that should created before the task runs.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>depends:</emphasis>
|
|
Controls inter-task dependencies.
|
|
See the
|
|
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
|
|
variable and the
|
|
"<link linkend='inter-task-dependencies'>Inter-Task Dependencies</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>deptask:</emphasis>
|
|
Controls task build-time dependencies.
|
|
See the
|
|
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
|
|
variable and the
|
|
"<link linkend='build-dependencies'>Build Dependencies</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>dirs:</emphasis>
|
|
Directories that should be created before the task runs.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>lockfiles:</emphasis>
|
|
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.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>noexec:</emphasis>
|
|
Marks the tasks as being empty and no execution required.
|
|
The <filename>noexec</filename> flag can be used to set up
|
|
tasks as dependency placeholders, or to disable tasks defined
|
|
elsewhere that are not needed in a particular recipe.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>nostamp:</emphasis>
|
|
Tells BitBake to not generate a stamp file for a task,
|
|
which implies the task should always be executed.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>postfuncs:</emphasis>
|
|
List of functions to call after the completion of the task.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>prefuncs:</emphasis>
|
|
List of functions to call before the task executes.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>rdepends:</emphasis>
|
|
Controls inter-task runtime dependencies.
|
|
See the
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>
|
|
variable, the
|
|
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>
|
|
variable, and the
|
|
"<link linkend='inter-task-dependencies'>Inter-Task Dependencies</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>rdeptask:</emphasis>
|
|
Controls task runtime dependencies.
|
|
See the
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>
|
|
variable, the
|
|
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>
|
|
variable, and the
|
|
"<link linkend='runtime-dependencies'>Runtime Dependencies</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>recideptask:</emphasis>
|
|
When set in conjunction with
|
|
<filename>recrdeptask</filename>, specifies a task that
|
|
should be inspected for additional dependencies.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>recrdeptask:</emphasis>
|
|
Controls task recursive runtime dependencies.
|
|
See the
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>
|
|
variable, the
|
|
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>
|
|
variable, and the
|
|
"<link linkend='recursive-dependencies'>Recursive Dependencies</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>stamp-extra-info:</emphasis>
|
|
Extra stamp information to append to the task's stamp.
|
|
As an example, OpenEmbedded uses this flag to allow
|
|
machine-specific tasks.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>umask:</emphasis>
|
|
The umask to run the task under.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
Several varflags are useful for controlling how signatures are
|
|
calculated for variables.
|
|
For more information on this process, see the
|
|
"<link linkend='checksums'>Checksums (Signatures)</link>"
|
|
section.
|
|
<itemizedlist>
|
|
<listitem><para><emphasis>vardeps:</emphasis>
|
|
Specifies a space-separated list of additional
|
|
variables to add to a variable's dependencies
|
|
for the purposes of calculating its signature.
|
|
Adding variables to this list is useful, for example, when
|
|
a function refers to a variable in a manner that
|
|
does not allow BitBake to automatically determine
|
|
that the variable is referred to.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>vardepsexclude:</emphasis>
|
|
Specifies a space-separated list of variables
|
|
that should be excluded from a variable's dependencies
|
|
for the purposes of calculating its signature.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>vardepvalue:</emphasis>
|
|
If set, instructs BitBake to ignore the actual
|
|
value of the variable and instead use the specified
|
|
value when calculating the variable's signature.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>vardepvalueexclude:</emphasis>
|
|
Specifies a pipe-separated list of strings to exclude
|
|
from the variable's value when calculating the
|
|
variable's signature.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='events'>
|
|
<title>Events</title>
|
|
|
|
<para>
|
|
BitBake allows installation of event handlers within
|
|
recipe and class files.
|
|
Events are triggered at certain points during operation,
|
|
such as the beginning of an operation against a given recipe
|
|
(<filename>*.bb</filename> file), the start of a given task,
|
|
task failure, task success, and so forth.
|
|
The intent is to make it easy to do things like email
|
|
notification on build failure.
|
|
</para>
|
|
|
|
<para>
|
|
Following is an example event handler that
|
|
prints the name of the event and the content of
|
|
the <filename>FILE</filename> variable:
|
|
<literallayout class='monospaced'>
|
|
addhandler myclass_eventhandler
|
|
python myclass_eventhandler() {
|
|
from bb.event import getName
|
|
from bb import data
|
|
print("The name of the Event is %s" % getName(e))
|
|
print("The file we run for is %s" % data.getVar('FILE', e.data, True))
|
|
}
|
|
</literallayout>
|
|
This event handler gets called every time an event is
|
|
triggered.
|
|
A global variable "<filename>e</filename>" is defined and
|
|
"<filename>e.data</filename>" contains an instance of
|
|
"<filename>bb.data</filename>".
|
|
With the <filename>getName(e)</filename> method, one can get
|
|
the name of the triggered event.
|
|
</para>
|
|
|
|
<para>
|
|
Because you probably are only interested in a subset of events,
|
|
you would likely use the <filename>[eventmask]</filename> flag
|
|
for your event handler to be sure that only certain events
|
|
trigger the handler.
|
|
Given the previous example, suppose you only wanted the
|
|
<filename>bb.build.TaskFailed</filename> event to trigger that
|
|
event handler.
|
|
Use the flag as follows:
|
|
<literallayout class='monospaced'>
|
|
addhandler myclass_eventhandler
|
|
myclass_eventhandler[eventmask] = "bb.build.TaskFailed"
|
|
python myclass_eventhandler() {
|
|
from bb.event import getName
|
|
from bb import data
|
|
print("The name of the Event is %s" % getName(e))
|
|
print("The file we run for is %s" % data.getVar('FILE', e.data, True))
|
|
}
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
During a standard build, the following common events might occur:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
<filename>bb.event.ConfigParsed()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.ParseStarted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.ParseProgress()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.ParseCompleted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.BuildStarted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.build.TaskStarted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.build.TaskInvalid()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.build.TaskFailedSilent()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.build.TaskFailed()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.build.TaskSucceeded()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.BuildCompleted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.cooker.CookerExit()</filename>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
Here is a list of other events that occur based on specific requests
|
|
to the server:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
<filename>bb.event.TreeDataPreparationStarted()</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.TreeDataPreparationProgress</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.TreeDataPreparationCompleted</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.DepTreeGenerated</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.CoreBaseFilesFound</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.ConfigFilePathFound</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.FilesMatchingFound</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.ConfigFilesFound</filename>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>bb.event.TargetsTreeGenerated</filename>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='variants-class-extension-mechanism'>
|
|
<title>Variants - Class Extension Mechanism</title>
|
|
|
|
<para>
|
|
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
|
|
<link linkend='var-BBCLASSEXTEND'><filename>BBCLASSEXTEND</filename></link>
|
|
and
|
|
<link linkend='var-BBVERSIONS'><filename>BBVERSIONS</filename></link>
|
|
variables.
|
|
<note>
|
|
The mechanism for this class extension is extremely
|
|
specific to the implementation.
|
|
Usually, the recipe's
|
|
<link linkend='var-PROVIDES'><filename>PROVIDES</filename></link>,
|
|
<link linkend='var-PN'><filename>PN</filename></link>, and
|
|
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
|
|
variables would need to be modified by the extension class.
|
|
For specific examples, see the OE-Core
|
|
<filename>native</filename>, <filename>nativesdk</filename>,
|
|
and <filename>multilib</filename> classes.
|
|
</note>
|
|
<itemizedlist>
|
|
<listitem><para><emphasis><filename>BBCLASSEXTEND</filename>:</emphasis>
|
|
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.
|
|
<literallayout class='monospaced'>
|
|
BBCLASSEXTEND = "native"
|
|
</literallayout></para></listitem>
|
|
<listitem><para><emphasis><filename>BBVERSIONS</filename>:</emphasis>
|
|
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
|
|
<link linkend='var-OVERRIDES'><filename>OVERRIDES</filename></link>
|
|
mechanism) for a single version, or an optionally named range of versions.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
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"
|
|
</literallayout>
|
|
The name of the range defaults to the original version of the
|
|
recipe.
|
|
For example, in OpenEmbedded, the recipe file
|
|
<filename>foo_1.0.0+.bb</filename> creates a default name range
|
|
of <filename>1.0.0+</filename>.
|
|
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
|
|
<filename>file://</filename> search paths
|
|
(<link linkend='var-FILESPATH'><filename>FILESPATH</filename></link>).
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='dependencies'>
|
|
<title>Dependencies</title>
|
|
|
|
<para>
|
|
To allow for efficient operation given multiple processes
|
|
executing in parallel, BitBake handles dependencies at
|
|
the task level.
|
|
BitBake supports a robust method to handle these dependencies.
|
|
</para>
|
|
|
|
<para>
|
|
This section describes several types of dependency mechanisms.
|
|
</para>
|
|
|
|
<section id='dependencies-internal-to-the-bb-file'>
|
|
<title>Dependencies Internal to the <filename>.bb</filename> File</title>
|
|
|
|
<para>
|
|
BitBake uses the <filename>addtask</filename> directive
|
|
to manage dependencies that are internal to a given recipe
|
|
file.
|
|
You can use the <filename>addtask</filename> directive to
|
|
indicate when a task is dependent on other tasks or when
|
|
other tasks depend on that recipe.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
addtask printdate after do_fetch before do_build
|
|
</literallayout>
|
|
In this example, the <filename>printdate</filename> task is
|
|
depends on the completion of the <filename>do_fetch</filename>
|
|
task.
|
|
And, the <filename>do_build</filename> depends on the completion
|
|
of the <filename>printdate</filename> task.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='build-dependencies'>
|
|
<title>Build Dependencies</title>
|
|
|
|
<para>
|
|
BitBake uses the
|
|
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
|
|
variable to manage build time dependencies.
|
|
The "deptask" varflag for tasks signifies the task of each
|
|
item listed in <filename>DEPENDS</filename> that must
|
|
complete before that task can be executed.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
do_configure[deptask] = "do_populate_sysroot"
|
|
</literallayout>
|
|
In this example, the <filename>do_populate_sysroot</filename>
|
|
task of each item in <filename>DEPENDS</filename> must complete before
|
|
<filename>do_configure</filename> can execute.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='runtime-dependencies'>
|
|
<title>Runtime Dependencies</title>
|
|
|
|
<para>
|
|
BitBake uses the
|
|
<link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>,
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>, and
|
|
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>
|
|
variables to manage runtime dependencies.
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>PACKAGES</filename> variable lists runtime
|
|
packages.
|
|
Each of those packages can have <filename>RDEPENDS</filename> and
|
|
<filename>RRECOMMENDS</filename> 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.
|
|
<literallayout class='monospaced'>
|
|
do_package_qa[rdeptask] = "do_packagedata"
|
|
</literallayout>
|
|
In the previous example, the <filename>do_packagedata</filename>
|
|
task of each item in <filename>RDEPENDS</filename> must have
|
|
completed before <filename>do_package_qa</filename> can execute.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='recursive-dependencies'>
|
|
<title>Recursive Dependencies</title>
|
|
|
|
<para>
|
|
BitBake uses the "recrdeptask" flag to manage
|
|
recursive task dependencies.
|
|
BitBake looks through the build-time and runtime
|
|
dependencies of the current recipe, looks through
|
|
the task's inter-task
|
|
dependencies, and then adds dependencies for the
|
|
listed task.
|
|
Once BitBake has accomplished this, it recursively works through
|
|
the dependencies of those tasks.
|
|
Iterative passes continue until all dependencies are discovered
|
|
and added.
|
|
</para>
|
|
|
|
<para>
|
|
You might want to not only have BitBake look for
|
|
dependencies of those tasks, but also have BitBake look
|
|
for build-time and runtime dependencies of the dependent
|
|
tasks as well.
|
|
If that is the case, you need to reference the task name
|
|
itself in the task list:
|
|
<literallayout class='monospaced'>
|
|
do_a[recrdeptask] = "do_a do_b"
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='inter-task-dependencies'>
|
|
<title>Inter-Task Dependencies</title>
|
|
|
|
<para>
|
|
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 <filename>DEPENDS</filename>.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
do_patch[depends] = "quilt-native:do_populate_sysroot"
|
|
</literallayout>
|
|
In this example, the <filename>do_populate_sysroot</filename>
|
|
task of the target <filename>quilt-native</filename>
|
|
must have completed before the
|
|
<filename>do_patch</filename> task can execute.
|
|
</para>
|
|
|
|
<para>
|
|
The "rdepends" flag works in a similar way but takes targets
|
|
in the runtime namespace instead of the build-time dependency
|
|
namespace.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='accessing-datastore-variables-using-python'>
|
|
<title>Accessing Datastore Variables Using Python</title>
|
|
|
|
<para>
|
|
It is often necessary to access variables in the
|
|
BitBake datastore using Python functions.
|
|
The Bitbake datastore has an API that allows you this
|
|
access.
|
|
Here is a list of available operations:
|
|
</para>
|
|
|
|
<para>
|
|
<informaltable frame='none'>
|
|
<tgroup cols='2' align='left' colsep='1' rowsep='1'>
|
|
<colspec colname='c1' colwidth='1*'/>
|
|
<colspec colname='c2' colwidth='1*'/>
|
|
<thead>
|
|
<row>
|
|
<entry align="left"><emphasis>Operation</emphasis></entry>
|
|
<entry align="left"><emphasis>Description</emphasis></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry align="left"><filename>d.getVar("X", expand=False)</filename></entry>
|
|
<entry align="left">Returns the value of variable "X".
|
|
Using "expand=True" expands the value.</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.setVar("X", "value")</filename></entry>
|
|
<entry align="left">Sets the variable "X" to "value".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.appendVar("X", "value")</filename></entry>
|
|
<entry align="left">Adds "value" to the end of the variable "X".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.prependVar("X", "value")</filename></entry>
|
|
<entry align="left">Adds "value" to the start of the variable "X".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.delVar("X")</filename></entry>
|
|
<entry align="left">Deletes the variable "X" from the datastore.</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.renameVar("X", "Y")</filename></entry>
|
|
<entry align="left">Renames the variable "X" to "Y".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.getVarFlag("X", flag, expand=False)</filename></entry>
|
|
<entry align="left">Gets then named flag from the variable "X".
|
|
Using "expand=True" expands the named flag.</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.setVarFlag("X", flag, "value")</filename></entry>
|
|
<entry align="left">Sets the named flag for variable "X" to "value".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.appendVarFlag("X", flag, "value")</filename></entry>
|
|
<entry align="left">Appends "value" to the named flag on the
|
|
variable "X".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.prependVarFlag("X", flag, "value")</filename></entry>
|
|
<entry align="left">Prepends "value" to the named flag on
|
|
the variable "X".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.delVarFlag("X", flag)</filename></entry>
|
|
<entry align="left">Deletes the named flag on the variable
|
|
"X" from the datastore.</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.setVarFlags("X", flagsdict)</filename></entry>
|
|
<entry align="left">Sets the flags specified in
|
|
the <filename>flagsdict()</filename> parameter.
|
|
<filename>setVarFlags</filename> does not clear previous flags.
|
|
Think of this operation as <filename>addVarFlags</filename>.</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.getVarFlags("X")</filename></entry>
|
|
<entry align="left">Returns a <filename>flagsdict</filename> of the flags for
|
|
the variable "X".</entry>
|
|
</row>
|
|
<row>
|
|
<entry align="left"><filename>d.delVarFlags("X")</filename></entry>
|
|
<entry align="left">Deletes all the flags for the variable "X".</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='task-checksums-and-setscene'>
|
|
<title>Task Checksums and Setscene</title>
|
|
|
|
<para>
|
|
BitBake uses checksums (or signatures) along with the setscene
|
|
to determine if a task needs to be run.
|
|
This section describes the process.
|
|
To help understand how BitBake does this, the section assumes an
|
|
OpenEmbedded metadata-based example.
|
|
</para>
|
|
|
|
<para>
|
|
This list is a place holder of content existed from previous work
|
|
on the manual.
|
|
Some or all of it probably needs integrated into the subsections
|
|
that make up this section.
|
|
For now, I have just provided a short glossary-like description
|
|
for each variable.
|
|
Ultimately, this list goes away.
|
|
<itemizedlist>
|
|
<listitem><para><filename>STAMP</filename>:
|
|
The base path to create stamp files.</para></listitem>
|
|
<listitem><para><filename>STAMPCLEAN</filename>
|
|
Again, the base path to create stamp files but can use wildcards
|
|
for matching a range of files for clean operations.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_STAMP_WHITELIST</filename>
|
|
Lists stamp files that are looked at when the stamp policy
|
|
is "whitelist".
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_STAMP_POLICY</filename>
|
|
Defines the mode for comparing timestamps of stamp files.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_HASHCHECK_FUNCTION</filename>
|
|
Specifies the name of the function to call during
|
|
the "setscene" part of the task's execution in order
|
|
to validate the list of task hashes.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_SETSCENE_VERIFY_FUNCTION</filename>
|
|
Specifies a function to call that verifies the list of
|
|
planned task execution before the main task execution
|
|
happens.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_SETSCENE_DEPVALID</filename>
|
|
Specifies a function BitBake calls that determines
|
|
whether BitBake requires a setscene dependency to
|
|
be met.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_TASKHASH</filename>
|
|
Within an executing task, this variable holds the hash
|
|
of the task as returned by the currently enabled
|
|
signature generator.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
</chapter>
|