simpledrm problem: Kconfig:error: recursive dependency detected!

[Jani Nikula]

On Wed, 03 Aug 2016, Noralf Trønnes <noralf at tronnes.org> wrote:
> Hi,
>
> I have changed simpledrm to use drm_simple_kms_helper and now I'm
> facing this:
>
> drivers/video/fbdev/Kconfig:5:error: recursive dependency detected!
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
>
> drivers/video/fbdev/Kconfig:5:  symbol FB is selected by DRM_KMS_FB_HELPER
>
> drivers/gpu/drm/Kconfig:42:     symbol DRM_KMS_FB_HELPER depends on 
> DRM_KMS_HELPER
>
> drivers/gpu/drm/Kconfig:36:     symbol DRM_KMS_HELPER is selected by 
> DRM_SIMPLEDRM
>
> drivers/gpu/drm/simpledrm/Kconfig:1:    symbol DRM_SIMPLEDRM depends on 
> FB_SIMPLE
>
> drivers/video/fbdev/Kconfig:2428:       symbol FB_SIMPLE depends on FB
>
>
> Using this Kconfig:
>
> config DRM_SIMPLEDRM
>      tristate "Simple firmware framebuffer DRM driver"
>      depends on DRM && (FB_SIMPLE = n)
>      select DRM_KMS_HELPER
>
>
> Is there a solution to this apart from depending on DRM_KMS_HELPER or
> removing the FB_SIMPLE dependency?

I think the underlying problem is the overuse of "select" all around. I
think people use it for convenience because unsatisfied "depends" hides
a menu option in menuconfig while "select" does not, and it's sometimes
hard to find all the dependencies of an option just to *show* it in
menuconfig.

I don't know what the exact cause here is, but having hunted these down
before, it's often a rabbit hole where you end up having to change a ton
of config options to make it robust, and those changes get rejected
because the menuconfig convenience is lost, and I've given up. :/

Would be great to have a menuconfig feature to recursively enable and
option and all dependencies. Perhaps we could then be more strict about
using "select" for stuff with dependencies.

BR,
Jani.


> video/ is before gpu/ in drivers/Makefile, so having both simpledrm and
> simplefb selected, I guess simplefb will be the one that's used?




-- 
Jani Nikula, Intel Open Source Technology Center