On Fri, Nov 19, 2021 at 11:07:16AM -0800, Brian Norris wrote: > Hi Daniel, > > On Fri, Nov 19, 2021 at 11:01:18AM +0100, Daniel Vetter wrote: > > On Thu, Nov 18, 2021 at 11:30:43AM -0800, Brian Norris wrote: > > > On Thu, Nov 18, 2021 at 10:05:11AM +0100, Daniel Vetter wrote: > > > > On Wed, Nov 17, 2021 at 02:48:40PM -0800, Brian Norris wrote: > > > > > --- a/drivers/gpu/drm/Kconfig > > > > > +++ b/drivers/gpu/drm/Kconfig > > > > > @@ -79,9 +79,15 @@ config DRM_DEBUG_SELFTEST > > > > > > > > > > If in doubt, say "N". > > > > > > > > > > +config DRM_INPUT_HELPER > > > > > + def_bool y > > > > > + depends on DRM_KMS_HELPER > > > > > + depends on INPUT > > > > > > > > Uh please no configs for each thing, it just makes everything more > > > > complex. Do we _really_ need this? > > > > > > First, it's not a configurable option (a user will never see this nor > > > have to answer Y/N to it); it only serves as an intermediary to express > > > the CONFIG_INPUT dependency (which is necessary) without making > > > DRM_KMS_HELPER fully depend on CONFIG_INPUT. (We should be able to run > > > display stacks without the input subsystem.) > > > > I'm not so much worried about the user cost, but the maintenance cost. > > Kbuild config complexity is ridiculous, anything that adds even a bit is > > really silly. > > > > > The closest alternative I can think of with fewer Kconfig symbols is to > > > just use CONFIG_INPUT directly in the code, to decide whether to provide > > > the helpers or else just stub them out. But that has a problem of not > > > properly expressing the =m vs. =y necessity: if, for example, > > > CONFIG_DRM_KMS_HELPER=y and CONFIG_INPUT=m, then we'll have linker > > > issues. > > > > Usually this is done by providing static inline dummy implementations in > > the headers. That avoids having to sprinkle new Kconfig symbols all over. > > Right, I already did that, and I'm not sprinkling > CONFIG_DRM_INPUT_HELPER much. (I do include one around the module > parameter, because it doesn't make much sense to have the module > parameter even exist, if the underlying feature is stubbed out.) > > But that doesn't solve the problem in my last sentence, involving > tristates. The "stub inline" approach only works well for boolean > features -- either built-in, or disabled. Once your feature is in a > module, you need to ensure that no built-in code depends on it. > > Do you want DRM_KMS_HELPER to unconditionally depend on CONFIG_INPUT? If > so, I can just add a 'select' or 'depend' and drop this intermediate > symbol. > If not, then what do you expect to happen with DRM_KMS_HELPER=y and > CONFIG_INPUT=m? Yeah just add the dependency. If you still want to keep it optional the way to do it is to add depends on FOO || FOO=n And then just have #if IS_ENABLED(FOO) around your inline wrappers. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
