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-rw-r--r--Documentation/kbuild/kconfig-language.txt32
1 files changed, 31 insertions, 1 deletions
diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index b507d61fd41..44e2649fbb2 100644
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -113,6 +113,13 @@ applicable everywhere (see syntax).
That will limit the usefulness but on the other hand avoid
the illegal configurations all over.
+- limiting menu display: "visible if" <expr>
+ This attribute is only applicable to menu blocks, if the condition is
+ false, the menu block is not displayed to the user (the symbols
+ contained there can still be selected by other symbols, though). It is
+ similar to a conditional "prompt" attribude for individual menu
+ entries. Default value of "visible" is true.
+
- numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
This allows to limit the range of possible input values for int
and hex symbols. The user can only input a value which is larger than
@@ -303,7 +310,8 @@ menu:
"endmenu"
This defines a menu block, see "Menu structure" above for more
-information. The only possible options are dependencies.
+information. The only possible options are dependencies and "visible"
+attributes.
if:
@@ -381,3 +389,25 @@ config FOO
limits FOO to module (=m) or disabled (=n).
+Kconfig symbol existence
+~~~~~~~~~~~~~~~~~~~~~~~~
+The following two methods produce the same kconfig symbol dependencies
+but differ greatly in kconfig symbol existence (production) in the
+generated config file.
+
+case 1:
+
+config FOO
+ tristate "about foo"
+ depends on BAR
+
+vs. case 2:
+
+if BAR
+config FOO
+ tristate "about foo"
+endif
+
+In case 1, the symbol FOO will always exist in the config file (given
+no other dependencies). In case 2, the symbol FOO will only exist in
+the config file if BAR is enabled.