There is no explanation about subdir-y. Let's document it. Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> --- (no changes since v1) Documentation/kbuild/makefiles.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index 4fd6b327a19f..a276bfa93675 100644 --- a/Documentation/kbuild/makefiles.rst +++ b/Documentation/kbuild/makefiles.rst @@ -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'. -- 2.27.0
