diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml index 1f4b2171a9..df1631df83 100644 --- a/documentation/ref-manual/ref-variables.xml +++ b/documentation/ref-manual/ref-variables.xml @@ -8420,18 +8420,60 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3" OVERRIDES - OVERRIDES[doc] = "BitBake uses OVERRIDES to control what variables are overridden after BitBake parses recipes and configuration files." + OVERRIDES[doc] = "A colon-separated list of overrides that currently apply." - BitBake uses OVERRIDES to control - what variables are overridden after BitBake parses - recipes and configuration files. - You can find more information on how overrides are handled - in the + A colon-separated list of overrides that currently apply. + Overrides are a BitBake mechanism that allows variables to + be selectively overridden at the end of parsing. + The set of overrides in OVERRIDES + represents the "state" during building, which includes + the current recipe being built, the machine for which + is being built, and so forth. + + + + As an example, if the string "an-override" appears as an + element in the colon-separated list in + OVERRIDES, then the following + assignment will override FOO with the + value "overridden" at the end of parsing: + + FOO_an-override = "overridden" + + See the "Conditional Syntax (Overrides)" - section of the BitBake User Manual. + section in the BitBake User Manual for more information on + the overrides mechanism. + + + + The default value of OVERRIDES + includes the values of the + CLASSOVERRIDE, + MACHINEOVERRIDES, + and + DISTROOVERRIDES + variables. + Another important override included by default is + pn-${PN}. + This override allows variables to be set for a single + recipe within configuration (.conf) + files. + Here is an example: + + FOO_pn-myrecipe = "myrecipe-specific value" + + Tip + An easy way to see what overrides apply is to search for + OVERRIDES in the output of the + bitbake -e command. + See the + "Viewing Variable Values" + section for more information. + @@ -9830,6 +9872,13 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3" PREFERRED_VERSION_linux-yocto_forcevariable = "3.4%" + + The _forcevariable override is + not handled specially. + This override only works because the default value of + OVERRIDES + includes "forcevariable". +