Commit c0ea806f authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

kbuild: doc: document subdir-y syntax 



There is no explanation about subdir-y.

Let's document it.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: default avatarRandy Dunlap <rdunlap@infradead.org>
parent d0e628cd

Documentation/kbuild/makefiles.rst

+15 −0
Original line number Diff line number Diff line
@@ -319,6 +319,21 @@ more details, with real examples. 
	that directory specifies obj-y, those objects will be left orphan.

	It is very likely a bug of the Makefile or of dependencies in Kconfig.



	Kbuild also supports dedicated syntax, subdir-y and subdir-m, for

	descending into subdirectories. It is a good fit when you know they

	do not contain kernel-space objects at all. A typical usage is to let

	Kbuild descend into subdirectories to build tools.



	Examples::



		# scripts/Makefile

		subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins

		subdir-$(CONFIG_MODVERSIONS) += genksyms

		subdir-$(CONFIG_SECURITY_SELINUX) += selinux



	Unlike obj-y/m, subdir-y/m does not need the trailing slash since this

	syntax is always used for directories.



	It is good practice to use a `CONFIG_` variable when assigning directory

	names. This allows kbuild to totally skip the directory if the

	corresponding `CONFIG_` option is neither 'y' nor 'm'.