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| author | Masahiro Yamada <masahiroy@kernel.org> | 2020-11-28 12:51:08 +0100 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2020-12-21 05:57:07 +0100 |
| commit | c0ea806f874eb32894249b4a67c2f2452881b775 (patch) | |
| tree | 0db0a94c9a5897cc2d8dd6abb679b79ce085178e /Documentation/kbuild | |
| parent | kbuild: doc: clarify the difference between extra-y and always-y (diff) | |
| download | linux-c0ea806f874eb32894249b4a67c2f2452881b775.tar.xz linux-c0ea806f874eb32894249b4a67c2f2452881b775.zip | |
kbuild: doc: document subdir-y syntax
There is no explanation about subdir-y.
Let's document it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Diffstat (limited to 'Documentation/kbuild')
| -rw-r--r-- | Documentation/kbuild/makefiles.rst | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index 3f1697ce1cd4..d36768cf1250 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'. |