On Thu, Sep 14, 2023 at 5:34 AM Nicolas Schier <nicolas@xxxxxxxxx> wrote: > > On Wed, Sep 13, 2023 at 09:55:36PM +0200 Arnd Bergmann wrote: > > On Wed, Sep 13, 2023, at 21:48, Nicolas Schier wrote: > > > On Wed, Sep 13, 2023 at 01:37:52PM +0200 Arnd Bergmann wrote: > > > > > >> Documentation/kbuild/kconfig-language.rst | 26 +++++++++++++++++++++++ > > >> 1 file changed, 26 insertions(+) > > >> > > >> diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst > > >> index 858ed5d80defe..89dea587a469a 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 slighly counterintuitive > > > > > > slighly -> slightly > > > > Fixed, thanks > > > > > For better RST compliance: could you explicitly start the code block e.g. by > > > appending '::' as in "... counterintuitive::"? > > > > Ok, done. > > > > >> + > > >> + config FOO > > >> + bool "Support for foo hardware" > > >> + depends on BAR || !BAR > > > > > > are you sure that this is enough? While testing, I needed to explicitly use > > > =y|=n: > > > > > > depends on BAR=y || BAR=n > > > > > > to prevent FOO to be selectable iff BAR=m. > > > > I see my problem, I made a different mistake here. Your version > > is correct for a 'bool' symbol as I had here, but the intention > > of this was to make it work for tristate symbols, which are the > > interesting case. I've fixed it up this way now, hope it now makes > > sense to you: > > > > --- a/Documentation/kbuild/kconfig-language.rst > > +++ b/Documentation/kbuild/kconfig-language.rst > > @@ -581,19 +581,19 @@ 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 slighly counterintuitive > > +uses the slightly counterintuitive:: > > > > config FOO > > - bool "Support for foo hardware" > > + tristate "Support for foo hardware" > > depends on BAR || !BAR > > ah, thanks, tristate kconfig symbols are really more interesting. Both FOO and BAR MUST be tristate to make this documentation sensible. If FOO is bool type, "depends on BAR || !BAR" becomes a no-op. As you notice, FOO and BAR become independent of each other. You may wonder why. Here, another unclear rule applies: 'depends on m' for a bool option is promoted to 'depends on y'. https://github.com/torvalds/linux/blob/v6.5/scripts/kconfig/symbol.c#L214 -- Best Regards Masahiro Yamada
