simpledrm problem: Kconfig:error: recursive dependency detected!

simpledrm problem: Kconfig:error: recursive dependency detected!

[Noralf Trønnes]

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?

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


Noralf.

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Re: simpledrm problem: Kconfig:error: recursive dependency detected!

[Jani Nikula]

On Wed, 03 Aug 2016, Noralf Trønnes <noralf@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
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Re: simpledrm problem: Kconfig:error: recursive dependency detected!

[David Herrmann]

Hey

On Thu, Aug 4, 2016 at 9:04 AM, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Wed, 03 Aug 2016, Noralf Trønnes <noralf@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.

As a workaround, just drop the FB_SIMPLE dependency. It was really
just meant as a safety net in my original code. Nothing bad happens if
both are enabled. The first to be loaded wins, the other one will very
likely print a confusing error message and exit.

Thanks
David
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Re: simpledrm problem: Kconfig:error: recursive dependency detected!

[Jani Nikula]

On Thu, 04 Aug 2016, David Herrmann <dh.herrmann@gmail.com> wrote:
> Hey
>
> On Thu, Aug 4, 2016 at 9:04 AM, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> On Wed, 03 Aug 2016, Noralf Trønnes <noralf@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.
>
> As a workaround, just drop the FB_SIMPLE dependency. It was really
> just meant as a safety net in my original code. Nothing bad happens if
> both are enabled. The first to be loaded wins, the other one will very
> likely print a confusing error message and exit.

Thanks David, and sorry about derailing into a non-helpful rant about
kconfig. :/

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center
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