Documentation: kconfig: add recommended way to describe compiler support

It would be nice if the source code is written in the same style.
This proposes the convention for describing the compiler capability
in Kconfig.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index 0e966e8f9ec72f20df4c9b5b8db737e1d3ca50a0..a4eb01843c0413e96422d4e873fb54b0855ec142 100644 (file)
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -473,6 +473,24 @@ config option to 'y' no matter the dependencies.
 The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the
 situation where select forces a symbol equals to 'y'.
 
+Adding features that need compiler support
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are several features that need compiler support. The recommended way
+to describe the dependency on the compiler feature is to use "depends on"
+followed by a test macro.
+
+config CC_STACKPROTECTOR
+       bool "Stack Protector buffer overflow detection"
+       depends on $(cc-option,-fstack-protector)
+       ...
+
+If you need to expose a compiler capability to makefiles and/or C source files,
+CC_HAS_ is the recommended prefix for the config option.
+
+config CC_HAS_STACKPROTECTOR_NONE
+       def_bool $(cc-option,-fno-stack-protector)
+
 Build as module only
 ~~~~~~~~~~~~~~~~~~~~
 To restrict a component build to module-only, qualify its config symbol