From 64b81ed7fb1e45c914317b20316f32827bc6444b Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Thu, 28 Apr 2011 10:58:52 -0700 Subject: kconfig-language: add to hints Explain a little about kconfig symbol dependencies and symbol existence given optional kconfig language scenarios. Yes, I was bitten by this. Signed-off-by: Randy Dunlap Signed-off-by: Michal Marek --- Documentation/kbuild/kconfig-language.txt | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt index 48a3981c717b..44e2649fbb29 100644 --- a/Documentation/kbuild/kconfig-language.txt +++ b/Documentation/kbuild/kconfig-language.txt @@ -389,3 +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. -- cgit v1.2.3