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author | Scott Rifenbark <scott.m.rifenbark@intel.com> | 2012-10-19 06:28:12 -0700 |
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committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2012-10-19 17:38:52 +0100 |
commit | 014f91cb3f596cc32e67855bc0451fed3087a887 (patch) | |
tree | 32e45c4a01847a0d25293d1fef2c150744607a8a /documentation | |
parent | c6ce06b172ca25f8a016758bdec67f1840c96fca (diff) | |
download | ast2050-yocto-poky-014f91cb3f596cc32e67855bc0451fed3087a887.zip ast2050-yocto-poky-014f91cb3f596cc32e67855bc0451fed3087a887.tar.gz |
documentation: poky-ref-manual - Edits to feature backfill
Final edits (I think) to this section from Paul Eggleton.
(From yocto-docs rev: 95fd830ffb668109631205df4538454ccf023b20)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'documentation')
-rw-r--r-- | documentation/poky-ref-manual/ref-features.xml | 51 |
1 files changed, 24 insertions, 27 deletions
diff --git a/documentation/poky-ref-manual/ref-features.xml b/documentation/poky-ref-manual/ref-features.xml index 7d98464..063eaad 100644 --- a/documentation/poky-ref-manual/ref-features.xml +++ b/documentation/poky-ref-manual/ref-features.xml @@ -178,38 +178,35 @@ <title>Feature Backfilling</title> <para> - Sometimes it is necessary to control functionality enabled by features - that are listed with + Sometimes it is necessary in the OpenEmbedded build system to extend <link linkend='var-MACHINE_FEATURES'><filename>MACHINE_FEATURES</filename></link> - and <link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>. - For example, some functionality exists that is enabled - by default for all configurations. - For these cases, the metadata, as shipped with the Yocto Project, ensures - the feature is "backfilled" into all the specific distro - and machine configurations. - You can see how this is done by finding the + or <link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link> + to control functionality that was previously enabled and not able + to be disabled. + For these cases, we need to add an + additional feature item to appear in one of these variables, + but we do not want to force developers who have existing values + of the variables in their configuration to add the new feature + in order to retain the same overall level of functionality. + Thus, the OpenEmbedded build system has a mechanism to + automatically "backfill" these added features into existing + distro or machine configurations. + You can see the list of features for which this is done by + finding the <link linkend='var-DISTRO_FEATURES_BACKFILL'><filename>DISTRO_FEATURES_BACKFILL</filename></link> and <link linkend='var-MACHINE_FEATURES_BACKFILL'><filename>MACHINE_FEATURES_BACKFILL</filename></link> variables in the <filename>meta/conf/bitbake.conf</filename> file. </para> <para> - Because certain functionality is enabled across all configurations as - described in the previous paragraph, it also becomes necessary - to give the developer the ability to disable (remove) a feature - from a particular configuration. - For example, suppose you have a machine feature that needs to be - disabled but the metadata has backfilled it across all configurations as enabled. - You need to be able to remove the feature from your configuration's - <filename>MACHINE_FEATURES</filename> - without disturbing existing configurations that still - might need the functionality? - </para> - - <para> - Feature backfilling allows you to selectively prevent a feature from - being backfilled to <filename>MACHINE_FEATURES</filename>, - <filename>DISTRO_FEATURES</filename>, or both. + Because such features are backfilled by default into all + configurations as described in the previous paragraph, developers + who wish to disable the new features need to be able to selectively + prevent the backfilling from occurring. + They can do this by adding the undesired feature or features to the + <link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'><filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename></link> + or <link linkend='var-MACHINE_FEATURES_BACKFILL_CONSIDERED'><filename>MACHINE_FEATURES_BACKFILL_CONSIDERED</filename></link> + variables for distro features and machine features respectively. </para> <para> @@ -226,7 +223,7 @@ You can disable the feature without affecting other existing distro configurations that need PulseAudio support by adding "pulseaudio" to - <link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'><filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename></link> + DISTRO_FEATURES_BACKFILL_CONSIDERED in your distro's <filename>.conf</filename> file. Adding the feature to this variable when it also exists in the <filename>DISTRO_FEATURES_BACKFILL</filename> @@ -243,7 +240,7 @@ You can disable RTC support for your device without affecting other machines that need RTC support by adding the feature to your machine's - <link linkend='var-MACHINE_FEATURES_BACKFILL_CONSIDERED'><filename>MACHINE_FEATURES_BACKFILL_CONSIDERED</filename></link> + MACHINE_FEATURES_BACKFILL_CONSIDERED list in the machine's <filename>.conf</filename> file. Adding the feature to this variable when it also exists in the <filename>MACHINE_FEATURES_BACKFILL</filename> |