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author | Paul Eggleton <paul.eggleton@linux.intel.com> | 2012-10-10 14:38:35 -0700 |
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committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2012-10-15 14:45:12 +0100 |
commit | 88924d6deae40513354919eae60d32a0c173bb7f (patch) | |
tree | 3ddb500d352d24cdba7cda34f669cd383adfc79c /documentation/poky-ref-manual/ref-features.xml | |
parent | 5abdefd89c5e4a999ccbd55a516b9267412a2719 (diff) | |
download | poky-88924d6deae40513354919eae60d32a0c173bb7f.tar.gz |
documentation: poky-ref-manual - New backfill variables and section.
Document DISTRO_FEATURES_BACKFILL and MACHINE_FEATURES_BACKFILL. We may
wish to expand upon this in future, but at least this explains what
these variables are for and how to use them.
Also add a link from the DISTRO_FEATURES entry to the section that lists
valid DISTRO_FEATURES items.
(From yocto-docs rev: 018af5c28b44464ae66646780ade910bdcab2bef)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'documentation/poky-ref-manual/ref-features.xml')
-rw-r--r-- | documentation/poky-ref-manual/ref-features.xml | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/documentation/poky-ref-manual/ref-features.xml b/documentation/poky-ref-manual/ref-features.xml index 159d56dabc..c42a4fd807 100644 --- a/documentation/poky-ref-manual/ref-features.xml +++ b/documentation/poky-ref-manual/ref-features.xml | |||
@@ -171,6 +171,61 @@ | |||
171 | </itemizedlist> | 171 | </itemizedlist> |
172 | </para> | 172 | </para> |
173 | </section> | 173 | </section> |
174 | |||
175 | <section id='ref-features-backfill'> | ||
176 | <title>Feature Backfilling</title> | ||
177 | |||
178 | <para> | ||
179 | Sometimes, it is necessary for a new feature to be added to control existing | ||
180 | functionality that was previously enabled by default and not able to be disabled. | ||
181 | In order to ensure that the feature remains enabled for users with existing | ||
182 | configurations that upgrade to a new version of the core metadata without that | ||
183 | configuration having to be changed, while still allowing others who want to turn | ||
184 | the feature off to do so, the backfilling mechanism was introduced. | ||
185 | This | ||
186 | functionality is available for <filename><link linkend='var-DISTRO_FEATURES'>DISTRO_FEATURES</link></filename> | ||
187 | and <filename><link linkend='var-MACHINE_FEATURES'>MACHINE_FEATURES</link></filename>. | ||
188 | </para> | ||
189 | |||
190 | <para> | ||
191 | An example is the "pulseaudio" distro feature. | ||
192 | Previously, PulseAudio support | ||
193 | was enabled within the Qt and GStreamer frameworks. | ||
194 | However some users desired | ||
195 | to be able to disable this. | ||
196 | To allow this to be disabled without affecting | ||
197 | existing configurations in which PulseAudio support should remain enabled, | ||
198 | "pulseaudio" was added to | ||
199 | <filename><link linkend='var-DISTRO_FEATURES_BACKFILL'>DISTRO_FEATURES_BACKFILL</link></filename> | ||
200 | within <filename>meta/conf/bitbake.conf</filename>. | ||
201 | This means that "pulseaudio" | ||
202 | is automatically added to <filename>DISTRO_FEATURES</filename> without the distro | ||
203 | configuration needing to be updated to do so itself. | ||
204 | Those who do not want PulseAudio support can add "pulseaudio" to | ||
205 | <filename><link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'>DISTRO_FEATURES_BACKFILL_CONSIDERED</link></filename> | ||
206 | in their distro <filename>.conf</filename> file and this will disable adding "pulseaudio" to | ||
207 | <filename>DISTRO_FEATURES</filename>. | ||
208 | </para> | ||
209 | |||
210 | <para> | ||
211 | Another example is the "rtc" machine feature. | ||
212 | Previously, real time clock (RTC) | ||
213 | support was enabled for all target devices. | ||
214 | However certain targets do not have | ||
215 | this capability. | ||
216 | To allow this to be disabled by such machines without affecting | ||
217 | other machines in which RTC support should remain enabled, "rtc" was added to | ||
218 | <filename><link linkend='var-MACHINE_FEATURES_BACKFILL'>MACHINE_FEATURES_BACKFILL</link></filename> | ||
219 | within <filename>meta/conf/bitbake.conf</filename>. | ||
220 | This means that "rtc" | ||
221 | is automatically added to <filename>MACHINE_FEATURES</filename> without the | ||
222 | machine configuration needing to be updated to do so itself. | ||
223 | For machines that not need RTC support can add "rtc" to | ||
224 | <filename><link linkend='var-MACHINE_FEATURES_BACKFILL_CONSIDERED'>MACHINE_FEATURES_BACKFILL_CONSIDERED</link></filename> | ||
225 | in their machine <filename>.conf</filename> file and this will disable adding "rtc" to | ||
226 | <filename>MACHINE_FEATURES</filename>. | ||
227 | </para> | ||
228 | </section> | ||
174 | </chapter> | 229 | </chapter> |
175 | 230 | ||
176 | <!-- | 231 | <!-- |