On 18/01/2019 16:00, Andrew Murray wrote: > A common pattern found in header files is a function declaration dependent > on a CONFIG_ option being enabled, followed by an empty function for when > that option isn't enabled. This can often take up a lot of space and impact > code readability. > > Let's introduce the following STUB_UNLESS macro: > > STUB_UNLESS(CONFIG_FOO, [body], prototype) > > This evaluates to 'prototype' prepended with 'extern' if CONFIG_FOO is set > to 'y'. Otherwise it will evaluate to 'prototype' prepended with 'static > inline' followed by an empty function body. Where optional argument 'body' > then 'body' will be used as the function body, intended to allow for simple > return statements. > > Signed-off-by: Andrew Murray <[email protected]>
Seems like it should remove a lot of boilerplate code, so looks good to me. Reviewed-by: Steven Price <[email protected]> > --- > include/linux/kconfig.h | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h > index cc8fa10..216a27f 100644 > --- a/include/linux/kconfig.h > +++ b/include/linux/kconfig.h > @@ -12,6 +12,7 @@ > > #define __ARG_PLACEHOLDER_1 0, > #define __take_second_arg(__ignored, val, ...) val > +#define __take_fourth_arg(__ignored, __ignored2, __ignored3, val, ...) val > > /* > * The use of "&&" / "||" is limited in certain expressions. > @@ -70,4 +71,34 @@ > */ > #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option)) > > + > + > +/* > + * Allow for __stub to be overloaded by making the second argument optional > + */ > +#define __stub_overload(...) __take_fourth_arg(__VA_ARGS__, \ > + __stub_body, __stub_void)(__VA_ARGS__) > +#define __stub_body(option, body, ptype) __stub(option, body, ptype) > +#define __stub_void(option, ptype) __stub(option, , ptype) > + > +/* > + * Using the same trick as __defined we use the config option to > conditionally > + * expand to an extern function declaration or a static stub function. > + */ > +#define __stub(option, body, ptype) ___stub( \ > + __ARG_PLACEHOLDER_##option, body, ptype) > +#define ___stub(arg1_or_junk, body, ptype) __take_second_arg( \ > + arg1_or_junk __extern_ptype(ptype), __static_ptype(body, ptype)) > +#define __static_ptype(body, ptype) static inline ptype { body; } > +#define __extern_ptype(ptype) extern ptype > + > +/* > + * STUB_UNLESS(CONFIG_FOO, [body], prototype) evaluates to 'prototype' > prepended > + * with 'extern' if CONFIG_FOO is set to 'y'. Otherwise it will evaluate to > + * 'prototype' prepended with 'static inline' followed by an empty function > + * body. Where optional argument 'body' is present then 'body' will be used > + * as the function body, intended to allow for simple return statements. > + */ > +#define STUB_UNLESS(...) __stub_overload(__VA_ARGS__) > + > #endif /* __LINUX_KCONFIG_H */ >
