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ref-manual: Clarified the OVERRIDES glossary description. 

Fixes [YOCTO #10173]

I provided a more detailed description of how this variable
works.  Also provided a cross-reference link back to the
variable at the end of the PREFERRED_VERSION variable.

(From yocto-docs rev: 679b205eea541b89e220656f7aa304d0f343c8a6)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2016-09-01 10:57:39 -07:00 committed by Richard Purdie
parent f1879193b9
commit e0347ec2dc
1 changed files with 56 additions and 7 deletions
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63
documentation/ref-manual/ref-variables.xml
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@ -8420,18 +8420,60 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
<glossentry id='var-OVERRIDES'><glossterm>OVERRIDES</glossterm>
<info>
OVERRIDES[doc] = "BitBake uses OVERRIDES to control what variables are overridden after BitBake parses recipes and configuration files."
OVERRIDES[doc] = "A colon-separated list of overrides that currently apply."
</info>
<glossdef>
<para role="glossdeffirst">
<!-- <para role="glossdeffirst"><imagedata fileref="figures/define-generic.png" /> -->
BitBake uses <filename>OVERRIDES</filename> to control
what variables are overridden after BitBake parses
recipes and configuration files.
You can find more information on how overrides are handled
in the
A colon-separated list of overrides that currently apply.
Overrides are a BitBake mechanism that allows variables to
be selectively overridden at the end of parsing.
The set of overrides in <filename>OVERRIDES</filename>
represents the "state" during building, which includes
the current recipe being built, the machine for which
is being built, and so forth.
</para>
<para>
As an example, if the string "an-override" appears as an
element in the colon-separated list in
<filename>OVERRIDES</filename>, then the following
assignment will override <filename>FOO</filename> with the
value "overridden" at the end of parsing:
<literallayout class='monospaced'>
FOO_an-override = "overridden"
</literallayout>
See the
"<ulink url='&YOCTO_DOCS_BB_URL;#conditional-syntax-overrides'>Conditional Syntax (Overrides)</ulink>"
section of the BitBake User Manual.
section in the BitBake User Manual for more information on
the overrides mechanism.
</para>
<para>
The default value of <filename>OVERRIDES</filename>
includes the values of the
<link linkend='var-CLASSOVERRIDE'><filename>CLASSOVERRIDE</filename></link>,
<link linkend='var-MACHINEOVERRIDES'><filename>MACHINEOVERRIDES</filename></link>,
and
<link linkend='var-DISTROOVERRIDES'><filename>DISTROOVERRIDES</filename></link>
variables.
Another important override included by default is
<filename>pn-${PN}</filename>.
This override allows variables to be set for a single
recipe within configuration (<filename>.conf</filename>)
files.
Here is an example:
<literallayout class='monospaced'>
FOO_pn-myrecipe = "myrecipe-specific value"
</literallayout>
<note><title>Tip</title>
An easy way to see what overrides apply is to search for
<filename>OVERRIDES</filename> in the output of the
<filename>bitbake -e</filename> command.
See the
"<link linkend='usingpoky-debugging-viewing-variable-values'>Viewing Variable Values</link>"
section for more information.
</note>
</para>
</glossdef>
</glossentry>
@ -9830,6 +9872,13 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
<literallayout class='monospaced'>
PREFERRED_VERSION_linux-yocto_forcevariable = "3.4%"
</literallayout>
<note>
The <filename>_forcevariable</filename> override is
not handled specially.
This override only works because the default value of
<link linkend='var-OVERRIDES'><filename>OVERRIDES</filename></link>
includes "forcevariable".
</note>
</para>
</glossdef>
</glossentry>