1639 lines
75 KiB
XML
1639 lines
75 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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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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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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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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<para>
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The operators "_append" and "_prepend" differ from
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the operators ".=" and "=." in that they are deferred
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until after parsing completes rather than being immediately
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applied.
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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 "abc456".
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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 becoming the current date.
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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></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></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>
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In this case, after all the parsing is complete, and
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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
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set to "Y" before the expansion, to become "X".
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</para>
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</section>
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<section id='variable-interaction-worked-examples'>
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<title>Examples</title>
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<para>
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Despite the previous explanations that show the different forms of
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variable definitions, it can be hard to work
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out exactly what happens when variable operators, conditional
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overrides, and unconditional overrides are combined.
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This section presents some common scenarios along
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with explanations for variable interactions that
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typically confuse users.
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</para>
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<para>
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There is often confusion concerning the order in which
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overrides and various "append" operators take effect.
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Recall that an append or prepend operation using "_append"
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and "_prepend" does not result in an immediate assignment
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as would "+=", ".=", "=+", or "=.".
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Consider the following example:
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<literallayout class='monospaced'>
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OVERRIDES = "foo"
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A = "Z"
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A_foo_append = "X"
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</literallayout>
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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>.
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Because overrides have not been applied yet,
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<filename>A_foo</filename> is set to "X" due to the append
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and <filename>A</filename> simply equals "Z".
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</para>
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<para>
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Applying overrides, however, changes things.
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Since "foo" is listed in <filename>OVERRIDES</filename>,
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the conditional variable <filename>A</filename> is replaced
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with the "foo" version, which is equal to "X".
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So effectively, <filename>A_foo</filename> replaces <filename>A</filename>.
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</para>
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<para>
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This next example changes the order of the override and
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the append:
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<literallayout class='monospaced'>
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OVERRIDES = "foo"
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A = "Z"
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A_append_foo = "X"
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</literallayout>
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For this case, before overrides are handled,
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<filename>A</filename> is set to "Z" and <filename>A_append_foo</filename>
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is set to "X".
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Once the override for "foo" is applied, however,
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<filename>A</filename> gets appended with "X".
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Consequently, <filename>A</filename> becomes "ZX".
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Notice that spaces are not appended.
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</para>
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<para>
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This next example has the order of the appends and overrides reversed
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back as in the first example:
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<literallayout class='monospaced'>
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OVERRIDES = "foo"
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A = "Y"
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A_foo_append = "Z"
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A_foo_append += "X"
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</literallayout>
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For this case, before any overrides are resolved,
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<filename>A</filename> is set to "Y" using an immediate assignment.
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After this immediate assignment, <filename>A_foo</filename> is set
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to "Z", and then further appended with
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"X" leaving the variable set to "Z X".
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Finally, applying the override for "foo" results in the conditional
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variable <filename>A</filename> becoming "Z X" (i.e.
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<filename>A</filename> is replaced with <filename>A_foo</filename>).
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</para>
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<para>
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This final example mixes in some varying operators:
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<literallayout class='monospaced'>
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A = "1"
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A_append = "2"
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A_append = "3"
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A += "4"
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A .= "5"
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</literallayout>
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For this case, the type of append operators are affecting the
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order of assignments as BitBake passes through the code
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multiple times.
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Initially, <filename>A</filename> is set to "1 45" because
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of the three statements that use immediate operators.
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After these assignments are made, BitBake applies the
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<filename>_append</filename> operations.
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Those operations result in <filename>A</filename> becoming "1 4523".
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</para>
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</section>
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</section>
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<section id='sharing-functionality'>
|
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<title>Sharing Functionality</title>
|
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|
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<para>
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BitBake allows for metadata sharing through include files
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(<filename>.inc</filename>) and class files
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(<filename>.bbclass</filename>).
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For example, suppose you have a piece of common functionality
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such as a task definition that you want to share between
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more than one recipe.
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In this case, creating a <filename>.bbclass</filename>
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file that contains the common functionality and then using
|
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the <filename>inherit</filename> directive in your recipes to
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inherit the class would be a common way to share the task.
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</para>
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<para>
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This section presents the mechanisms BitBake provides to
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allow you to share functionality between recipes.
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Specifically, the mechanisms include <filename>include</filename>,
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<filename>inherit</filename>, <filename>INHERIT</filename>, and
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<filename>require</filename> directives.
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</para>
|
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|
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<section id='locating-include-and-class-files'>
|
|
<title>Locating Include and Class Files</title>
|
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|
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<para>
|
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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 three 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>
|
|
</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='automatically-mapping-functions-within-the-context-of-a-class'>
|
|
<title>Automatically Mapping Functions Within the Context of a Class</title>
|
|
|
|
<para>
|
|
Through coding techniques and the use of
|
|
<filename>EXPORT_FUNCTIONS</filename>, BitBake supports
|
|
automatic mapping for functions within the context of
|
|
a class.
|
|
</para>
|
|
|
|
<para>
|
|
To understand the benefits of this feature, consider the basic scenario
|
|
where a class defines a function and your recipe inherits the class.
|
|
In this basic scenario, your recipe has access to the function in the
|
|
class by way of inheritance and can freely call and use the function
|
|
as defined in the class.
|
|
However, if you need to have a modified version of that function
|
|
in your recipe you are limited to using either your modified version
|
|
of the function or using "prepend_" or "_append" operators to add
|
|
code to be executed before or after the original function in the
|
|
class.
|
|
Your recipe cannot use both versions of the fucntion.
|
|
</para>
|
|
|
|
<para>
|
|
Function mapping allows you to access both your custom function
|
|
function that is defined in the recipe and the original function that
|
|
is defined in the class.
|
|
You have this access all from within your recipe.
|
|
To accomplish this, you need some things in place:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
The class needs to define the function as follows:
|
|
<literallayout class='monospaced'>
|
|
<classname>_<functionname>
|
|
</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 <functionname>
|
|
</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,
|
|
your recipe would call the <filename>do_foo</filename> function
|
|
from the recipe by referring to it as
|
|
<filename>bar_do_foo</filename>.
|
|
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, tasks can also be deleted.
|
|
This is done simply with <filename>deltask</filename> command.
|
|
For example, to delete the example task used in the previous
|
|
sections, you would use:
|
|
<literallayout class='monospaced'>
|
|
deltask printdate
|
|
</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()</filename>.
|
|
The datastore object is useful, for example, to find the original
|
|
<filename>DISPLAY</filename> variable.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
BB_ORIGENV - add example?
|
|
|
|
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'>
|
|
<variable> = d.getVarFlags("<variable>")
|
|
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>dirs:</emphasis>
|
|
Directories that should be created before the task runs.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>cleandirs:</emphasis>
|
|
Empty directories that should created before the task runs.
|
|
</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>fakeroot:</emphasis>
|
|
Causes a task to be run in a fakeroot environment,
|
|
obtained by adding the variables in
|
|
<link linkend='var-FAKEROOTENV'><filename>FAKEROOTENV</filename></link>
|
|
to the environment.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>umask:</emphasis>
|
|
The umask to run the task under.
|
|
</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>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>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>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>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>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>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>
|
|
</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>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>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>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 operation against a given
|
|
<filename>.bb</filename>, 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>
|
|
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_staging"
|
|
</literallayout>
|
|
In this example, the <filename>do_populate_staging</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_write[rdeptask] = "do_package"
|
|
</literallayout>
|
|
In the previous example, the <filename>do_package</filename>
|
|
task of each item in <filename>RDEPENDS</filename> must have
|
|
completed before <filename>do_package_write</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_staging"
|
|
</literallayout>
|
|
In this example, the <filename>do_populate_staging</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>
|