On Thu, Sep 14, 2023, at 15:42, Jani Nikula wrote: > On Wed, 13 Sep 2023, Arnd Bergmann <arnd@xxxxxxxxxx> wrote: >> From: Arnd Bergmann <arnd@xxxxxxxx> >> >> +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 >> + >> + config FOO >> + bool "Support for foo hardware" >> + depends on BAR || !BAR > > depends on BAR || BAR=n > > seems to be an alternative that's about as common: > > $ git grep "depends on \([A-Z0-9_]\+\) || \!\1" | wc -l > 109 > $ git grep "depends on \([A-Z0-9_]\+\) || \1=n" | wc -l > 107 > > Maybe worth mentioning both? I fear that would add more confusion than it avoids: "!BAR" is actually different from "BAR=n", but "BAR || !BAR" is the same as "BAR || BAR=n" here, and trying to explain this in the documentation would either make it incorrect or unhelpfully complicated. Arnd