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-rw-r--r--Documentation/kbuild/kconfig-language.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index c4a293a03c33..f5b9493f04ad 100644
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -77,6 +77,27 @@ applicable everywhere (see syntax).
Optionally, dependencies only for this default value can be added with
"if".
+ The default value deliberately defaults to 'n' in order to avoid bloating the
+ build. With few exceptions, new config options should not change this. The
+ intent is for "make oldconfig" to add as little as possible to the config from
+ release to release.
+
+ Note:
+ Things that merit "default y/m" include:
+
+ a) A new Kconfig option for something that used to always be built
+ should be "default y".
+
+ b) A new gatekeeping Kconfig option that hides/shows other Kconfig
+ options (but does not generate any code of its own), should be
+ "default y" so people will see those other options.
+
+ c) Sub-driver behavior or similar options for a driver that is
+ "default n". This allows you to provide sane defaults.
+
+ d) Hardware or infrastructure that everybody expects, such as CONFIG_NET
+ or CONFIG_BLOCK. These are rare exceptions.
+
- type definition + default value:
"def_bool"/"def_tristate" <expr> ["if" <expr>]
This is a shorthand notation for a type definition plus a value.