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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-01 13:48:46 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-01 13:48:46 -0700 |
| commit | e81a2dabc3f3faa0d96808708a8dc2025f2bdde3 (patch) | |
| tree | b82c05de6c0b8769215ac0daeccd622810d9135d /Documentation | |
| parent | d2c5231581d636af8d5af888ee13048dfbb438c7 (diff) | |
| parent | 2d7d1bc119a4d7f54cfe0b1be480c34e8c712d06 (diff) | |
Merge tag 'kbuild-fixes-v6.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild fixes from Masahiro Yamada:
- Fix the module compression with xz so the in-kernel decompressor
works
- Document a kconfig idiom to express an optional dependency between
modules
- Make modpost, when W=1 is given, detect broken drivers that reference
.exit.* sections
- Remove unused code
* tag 'kbuild-fixes-v6.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kbuild: remove stale code for 'source' symlink in packaging scripts
modpost: Don't let "driver"s reference .exit.*
vmlinux.lds.h: remove unused CPU_KEEP and CPU_DISCARD macros
modpost: add missing else to the "of" check
Documentation: kbuild: explain handling optional dependencies
kbuild: Use CRC32 and a 1MiB dictionary for XZ compressed modules
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/kbuild/kconfig-language.rst | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst index 858ed5d80def..0135905c0aa3 100644 --- a/Documentation/kbuild/kconfig-language.rst +++ b/Documentation/kbuild/kconfig-language.rst @@ -573,6 +573,32 @@ above, leading to: bool "Support for foo hardware" depends on ARCH_FOO_VENDOR || COMPILE_TEST +Optional dependencies +~~~~~~~~~~~~~~~~~~~~~ + +Some drivers are able to optionally use a feature from another module +or build cleanly with that module disabled, but cause a link failure +when trying to use that loadable module from a built-in driver. + +The most common way to express this optional dependency in Kconfig logic +uses the slightly counterintuitive:: + + config FOO + tristate "Support for foo hardware" + depends on BAR || !BAR + +This means that there is either a dependency on BAR that disallows +the combination of FOO=y with BAR=m, or BAR is completely disabled. +For a more formalized approach if there are multiple drivers that have +the same dependency, a helper symbol can be used, like:: + + config FOO + tristate "Support for foo hardware" + depends on BAR_OPTIONAL + + config BAR_OPTIONAL + def_tristate BAR || !BAR + Kconfig recursive dependency limitations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |