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Diffstat (limited to 'Documentation/kbuild/makefiles.rst')
| -rw-r--r-- | Documentation/kbuild/makefiles.rst | 33 |
1 files changed, 13 insertions, 20 deletions
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index b89c88168d6a..d7e6534a8505 100644 --- a/Documentation/kbuild/makefiles.rst +++ b/Documentation/kbuild/makefiles.rst @@ -297,9 +297,19 @@ more details, with real examples. If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular) the corresponding obj- variable will be set, and kbuild will descend down in the ext2 directory. - Kbuild only uses this information to decide that it needs to visit - the directory, it is the Makefile in the subdirectory that - specifies what is modular and what is built-in. + + Kbuild uses this information not only to decide that it needs to visit + the directory, but also to decide whether or not to link objects from + the directory into vmlinux. + + When Kbuild descends into the directory with 'y', all built-in objects + from that directory are combined into the built-in.a, which will be + eventually linked into vmlinux. + + When Kbuild descends into the directory with 'm', in contrast, nothing + from that directory will be linked into vmlinux. If the Makefile in + 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. It is good practice to use a `CONFIG_` variable when assigning directory names. This allows kbuild to totally skip the directory if the @@ -1115,23 +1125,6 @@ When kbuild executes, the following steps are followed (roughly): In this example, extra-y is used to list object files that shall be built, but shall not be linked as part of built-in.a. - header-test-y - - header-test-y specifies headers (`*.h`) in the current directory that - should be compile tested to ensure they are self-contained, - i.e. compilable as standalone units. If CONFIG_HEADER_TEST is enabled, - this builds them as part of extra-y. - - header-test-pattern-y - - This works as a weaker version of header-test-y, and accepts wildcard - patterns. The typical usage is:: - - header-test-pattern-y += *.h - - This specifies all the files that matches to `*.h` in the current - directory, but the files in 'header-test-' are excluded. - 6.7 Commands useful for building a boot image --------------------------------------------- |