bitbake.conf: Fix up OVERRIDES documentation (some bits from OE) and also add forcevariable OVERRIDE

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index 5a4013d2f..2aaa5116f 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -597,16 +597,20 @@ AUTO_LIBNAME_PKGS = "${PACKAGES}"
 ### Config file processing
 ###
 
+# Overrides are processed left to right, so the ones that are named later take precedence.
+# You generally want them to go from least to most specific.
+# 
 # This means that an envionment variable named '<foo>_arm' overrides an
-# environment variable '<foo>' (when ${TARGET_ARCH} is arm). And the same: an
-# environment variable '<foo>_ramses' overrides both '<foo>' and '<foo>_arm
-# when ${MACHINE} is 'ramses'. And finally '<foo>_local' overrides anything.
+# environment variable '<foo>' (when ${TARGET_ARCH} is arm).
+# An environment variable '<foo>_ramses' overrides '<foo>' but doesn't override
+# '<foo>_arm' when ${MACHINE} is 'ramses'. 
+# If you use combination ie '<foo>_arm_ramses', then '<foo>_arm_ramses' will override 
+# '<foo>_arm' and then '<foo>' will be overriden with that value from '<foo>_arm'.
+# And finally '<foo>_local' overrides any standard variable, but with lowest priority.
 #
 # This works for  functions as well, they are really just environment variables.
 # Default OVERRIDES to make compilation fail fast in case of build system misconfiguration.
-OVERRIDES = "local:${MACHINE}:${DISTRO}:${TARGET_OS}:${TARGET_ARCH}:build-${BUILD_OS}:fail-fast:pn-${PN}"
-# Alternative OVERRIDES definition without "fail fast", usually only for native building and Scratchbox toolchains.
-#OVERRIDES = "local:${MACHINE}:${DISTRO}:${TARGET_OS}:${TARGET_ARCH}:build-${BUILD_OS}:pn-${PN}"
+OVERRIDES = "local:${MACHINE}:${DISTRO}:${TARGET_OS}:${TARGET_ARCH}:build-${BUILD_OS}:fail-fast:pn-${PN}:forcevariable"
 
 CPU_FEATURES ?= ""
 CPU_FEATURES_arm ?= "vfp"