From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: Randy Dunlap <rdunlap@infradead.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Michal Marek <michal.lkml@markovi.net>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 7/7] kbuild: doc: document subdir-y syntax
Date: Mon, 23 Nov 2020 13:54:03 +0900 [thread overview]
Message-ID: <20201123045403.63402-7-masahiroy@kernel.org> (raw)
In-Reply-To: <20201123045403.63402-1-masahiroy@kernel.org>
There is no explanation about subdir-y.
Let's document it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
Documentation/kbuild/makefiles.rst | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
index 159e470f2616..6332b9ca7942 100644
--- a/Documentation/kbuild/makefiles.rst
+++ b/Documentation/kbuild/makefiles.rst
@@ -319,6 +319,20 @@ 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::
+
+ subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
+ subdir-$(CONFIG_MODVERSIONS) += genksyms
+ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
+
+ Unlike obj-y/m, subdir-y/m does not need the trailing slash since this
+ syntax is always used for directories.
+
It is good practice to use a `CONFIG_` variable when assigning directory
names. This allows kbuild to totally skip the directory if the
corresponding `CONFIG_` option is neither 'y' nor 'm'.
--
2.25.1
next prev parent reply other threads:[~2020-11-23 4:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-23 4:53 [PATCH 1/7] kbuild: doc: update the description about kbuild Makefiles Masahiro Yamada
2020-11-23 4:53 ` [PATCH 2/7] kbuild: doc: replace arch/$(ARCH)/ with arch/$(SRCARCH)/ Masahiro Yamada
2020-11-23 17:39 ` Randy Dunlap
2020-11-23 4:53 ` [PATCH 3/7] kbuild: doc: fix 'List directories to visit when descending' section Masahiro Yamada
2020-11-23 4:57 ` Masahiro Yamada
2020-11-23 4:54 ` [PATCH 4/7] kbuild: doc: merge 'Special Rules' and 'Custom kbuild commands' sections Masahiro Yamada
2020-11-23 4:54 ` [PATCH 5/7] kbuild: doc: split if_changed explanation to a separate section Masahiro Yamada
2020-11-23 17:51 ` Randy Dunlap
2020-11-23 4:54 ` [PATCH 6/7] kbuild: doc: clarify the difference between extra-y and always-y Masahiro Yamada
2020-11-23 18:00 ` Randy Dunlap
2020-11-23 4:54 ` Masahiro Yamada [this message]
2020-11-23 18:03 ` [PATCH 7/7] kbuild: doc: document subdir-y syntax Randy Dunlap
2020-11-28 8:58 ` Masahiro Yamada
2020-11-28 16:56 ` Randy Dunlap
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