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--- oe_yp_backfill [2020/04/11 11:37] – created rpjday
+++ oe_yp_backfill [2020/04/11 12:06] (current) – rpjday
@@ Line 2: / Line 2: @@
 How backfilling works.
+===== Files =====
+==== documentation.conf ====
+<code>
+DISTRO_FEATURES[doc] = "The features enabled for the distribution."
+DISTRO_FEATURES_BACKFILL[doc] = "Features to be added to DISTRO_FEATURES if not also present in DISTRO_FEATURES_BACKFILL_CONSIDERED. This variable is set in the meta/conf/bitbake.conf file and it is not intended to be user-configurable."
+DISTRO_FEATURES_BACKFILL_CONSIDERED[doc] = "Features from DISTRO_FEATURES_BACKFILL that should not be backfilled (i.e. added to DISTRO_FEATURES) during the build."
+MACHINE_FEATURES[doc] = "Specifies the list of hardware features the MACHINE supports."
+MACHINE_FEATURES_BACKFILL[doc] = "Features to be added to MACHINE_FEATURES if not also present in MACHINE_FEATURES_BACKFILL_CONSIDERED. This variable is set in the meta/conf/bitbake.conf file and is not intended to be user-configurable."
+MACHINE_FEATURES_BACKFILL_CONSIDERED[doc] = "Features from MACHINE_FEATURES_BACKFILL that should not be backfilled (i.e. added to MACHINE_FEATURES) during the build."
+</code>
+==== bitbake.conf ====
+<code>
+DISTRO_FEATURES_BACKFILL = "pulseaudio sysvinit gobject-introspection-data ldconfig"
+MACHINE_FEATURES_BACKFILL = "rtc qemu-usermode"
+</code>
+==== meta/lib/oe/utils.py ====
+<code>
+def features_backfill(var,d):
+    # This construct allows the addition of new features to variable specified
+    # as var
+    # Example for var = "DISTRO_FEATURES"
+    # This construct allows the addition of new features to DISTRO_FEATURES
+    # that if not present would disable existing functionality, without
+    # disturbing distributions that have already set DISTRO_FEATURES.
+    # Distributions wanting to elide a value in DISTRO_FEATURES_BACKFILL should
+    # add the feature to DISTRO_FEATURES_BACKFILL_CONSIDERED
+    features = (d.getVar(var) or "").split()
+    backfill = (d.getVar(var+"_BACKFILL") or "").split()
+    considered = (d.getVar(var+"_BACKFILL_CONSIDERED") or "").split()
+    addfeatures = []
+    for feature in backfill:
+        if feature not in features and feature not in considered:
+            addfeatures.append(feature)
+    if addfeatures:
+        d.appendVar(var, " " + " ".join(addfeatures))
+</code>
+===== Examples =====
+You can prevent the SysVinit distribution feature from being automatically enabled with one of:
+<code>
+DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
+DISTRO_FEATURES_BACKFILL_CONSIDERED_append = " sysvinit"
+</code>