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-rw-r--r--documentation/ref-manual/ref-variables.xml28
1 files changed, 28 insertions, 0 deletions
diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 1181d64576..4316ea5dc6 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -9951,6 +9951,34 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
9951 The <filename>PROVIDES</filename> statement results in 9951 The <filename>PROVIDES</filename> statement results in
9952 the "libav" recipe also being known as "libpostproc". 9952 the "libav" recipe also being known as "libpostproc".
9953 </para> 9953 </para>
9954
9955 <para>
9956 In addition to providing recipes under alternate names,
9957 the <filename>PROVIDES</filename> mechanism is also used
9958 to implement virtual targets.
9959 A virtual target is a name that corresponds to some
9960 particular functionality (e.g. a Linux kernel).
9961 Recipes that provide the functionality in question list the
9962 virtual target in <filename>PROVIDES</filename>.
9963 Recipes that depend on the functionality in question can
9964 include the virtual target in
9965 <link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
9966 to leave the choice of provider open.
9967 </para>
9968
9969 <para>
9970 Conventionally, virtual targets have names on the form
9971 "virtual/function" (e.g. "virtual/kernel").
9972 The slash is simply part of the name and has no
9973 syntactical significance.
9974 </para>
9975
9976 <para>
9977 The
9978 <link linkend='var-PREFERRED_PROVIDER'><filename>PREFERRED_PROVIDER</filename></link>
9979 variable is used to select which particular recipe
9980 provides a virtual target.
9981 </para>
9954 </glossdef> 9982 </glossdef>
9955 </glossentry> 9983 </glossentry>
9956 9984