[oe-commits] [bitbake] branch master updated: bitbake-user-manual: Added section on modifying variables
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Tue Apr 23 15:34:39 UTC 2019
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rpurdie pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
new 5a69795 bitbake-user-manual: Added section on modifying variables
5a69795 is described below
commit 5a697957d7687fe2c730896e178f7e1e054fe724
Author: Scott Rifenbark <srifenbark at gmail.com>
AuthorDate: Thu Apr 18 10:37:07 2019 -0700
bitbake-user-manual: Added section on modifying variables
Fixes [YOCTO #12548]
I created a new section titled "Modifying Variable Values" that
provides instruction on how to use the "bitbake -e" command to
be sure your configuration and variable values are as expected.
Signed-off-by: Scott Rifenbark <srifenbark at gmail.com>
Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
.../bitbake-user-manual-metadata.xml | 72 ++++++++++++++++++++++
1 file changed, 72 insertions(+)
diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
index 199ab23..a125ad3 100644
--- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -61,6 +61,78 @@
</para>
</section>
+ <section id='modifying-existing-variables'>
+ <title>Modifying Existing Variables</title>
+
+ <para>
+ Sometimes you need to modify existing variables.
+ Following are some cases where you might find you want to
+ modify an existing variable:
+ <itemizedlist>
+ <listitem><para>
+ Customize a recipe that uses the variable.
+ </para></listitem>
+ <listitem><para>
+ Change a variable's default value used in a
+ <filename>*.bbclass</filename> file.
+ </para></listitem>
+ <listitem><para>
+ Change the variable in a <filename>*.bbappend</filename>
+ file to override the variable in the original recipe.
+ </para></listitem>
+ <listitem><para>
+ Change the variable in a configuration file so that the
+ value overrides an existing configuration.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ Changing a variable value can sometimes depend on how the
+ value was originally assigned and also on the desired
+ intent of the change.
+ In particular, when you append a value to a variable that
+ has a default value, the resulting value might not be what
+ you expect.
+ In this case, the value you provide might replace the value
+ rather than append to the default value.
+ </para>
+
+ <para>
+ If after you have changed a variable's value and something
+ unexplained occurs, you can use BitBake to check the actual
+ value of the suspect variable.
+ You can make these checks for both configuration and recipe
+ level changes:
+ <itemizedlist>
+ <listitem><para>
+ For configuration changes, use the following:
+ <literallayout class='monospaced'>
+ $ bitbake -e
+ </literallayout>
+ This command displays variable values after the
+ configuration files (i.e. <filename>local.conf</filename>,
+ <filename>bblayers.conf</filename>,
+ <filename>bitbake.conf</filename> and so forth) have
+ been parsed.
+ <note>
+ Variables that are exported to the environment are
+ preceded by the string "export" in the command's
+ output.
+ </note>
+ </para></listitem>
+ <listitem><para>
+ For recipe changes, use the following:
+ <literallayout class='monospaced'>
+ $ bitbake <replaceable>recipe</replaceable> -e | grep VARIABLE="
+ </literallayout>
+ This command checks to see if the variable actually
+ makes it into a specific recipe.
+ </para></listitem>
+ </itemizedlist>
+ </para>
+ </section>
+
<section id='line-joining'>
<title>Line Joining</title>
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