Subject: Re: randconfig build error with next-20141001, in drivers/gpu/drm/i915

From: Randy Dunlap <[email-masked]>
Date: Thu, 02 Oct 2014 09:56:27 -0700

On 10/02/14 00:46, Jani Nikula wrote:
> On Wed, 01 Oct 2014, Randy Dunlap <[email-masked]> wrote:
>> On 10/01/14 10:57, Jani Nikula wrote:
>>> On Wed, 01 Oct 2014, Jim Davis <[email-masked]> wrote:
>>>> Building with the attached random configuration file,
>>>>
>>>> warning: (VIDEO_TIMBERDALE) selects TIMB_DMA which has unmet direct
>>>> dependencies (DMADEVICES && MFD_TIMBERDALE)
>>>> warning: (USB_OTG_FSM && FSL_USB2_OTG && USB_MV_OTG) selects USB_OTG
>>>> which has unmet direct dependencies (USB_SUPPORT && USB && PM_RUNTIME)
>>>>
>>>> drivers/built-in.o: In function `intel_panel_setup_backlight':
>>>> (.text+0x11855d): undefined reference to `backlight_device_register'
>>>> drivers/built-in.o: In function `intel_panel_destroy_backlight':
>>>> (.text+0x118624): undefined reference to `backlight_device_unregister'
>>>> make: *** [vmlinux] Error 1
>>>
>>> It's the combination:
>>>
>>>> CONFIG_DRM_I915=y
>>>> CONFIG_BACKLIGHT_CLASS_DEVICE=m
>>>
>>> Not sure what the Kconfig magic spell needs to be when we don't want to
>>> depend on CONFIG_BACKLIGHT_CLASS_DEVICE but we'll use it if it's enabled
>>> (y or m).
>>
>> Something like:
>>
>> 	depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n
>>
>> is what we usually use.
> 
> Oh boy this gets ugly. Trying
> 
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index 4e39ab34eb1c..daa453c62aa6 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -3,6 +3,7 @@ config DRM_I915
>  	depends on DRM
>  	depends on X86 && PCI
>  	depends on (AGP || AGP=n)
> +	depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>  	select INTEL_GTT
>  	select AGP_INTEL if AGP
>  	select INTERVAL_TREE
> 
> leads to
> 
> scripts/kconfig/conf --olddefconfig Kconfig
> drivers/gpu/drm/i915/Kconfig:1:error: recursive dependency detected!
> drivers/gpu/drm/i915/Kconfig:1:	symbol DRM_I915 depends on BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:156:	symbol BACKLIGHT_CLASS_DEVICE is selected by DRM_I915
> 
> because we depend on ACPI_VIDEO when ACPI is enabled, originally done in
> 
> commit ecb4aed78dcf09e48c8c34c8c2fa7f5c69344be6
> Author: Len Brown <[email-masked]>
> Date:   Fri Apr 24 11:33:47 2009 -0400
> 
>     ACPI, i915: build fix
> 
> Now, trying to fix that with what seems to me like the obvious
> dependency, conveying what we really want
> 
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index 4e39ab34eb1c..f5a1ee37603e 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -3,6 +3,7 @@ config DRM_I915
>  	depends on DRM
>  	depends on X86 && PCI
>  	depends on (AGP || AGP=n)
> +	depends on ((ACPI && ACPI_VIDEO) || ACPI=n)
>  	select INTEL_GTT
>  	select AGP_INTEL if AGP
>  	select INTERVAL_TREE
> @@ -11,13 +12,6 @@ config DRM_I915
>  	select SHMEM
>  	select TMPFS
>  	select DRM_KMS_HELPER
> -	# i915 depends on ACPI_VIDEO when ACPI is enabled
> -	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
> -	select BACKLIGHT_LCD_SUPPORT if ACPI
> -	select BACKLIGHT_CLASS_DEVICE if ACPI
> -	select INPUT if ACPI
> -	select ACPI_VIDEO if ACPI
> -	select ACPI_BUTTON if ACPI
>  	help
>  	  Choose this option if you have a system that has "Intel Graphics
>  	  Media Accelerator" or "HD Graphics" integrated graphics,
> 
> leads to more fun
> 
> scripts/kconfig/conf --olddefconfig Kconfig
> drivers/video/fbdev/Kconfig:5:error: recursive dependency detected!
> drivers/video/fbdev/Kconfig:5:	symbol FB is selected by DRM_KMS_FB_HELPER
> drivers/gpu/drm/Kconfig:34:	symbol DRM_KMS_FB_HELPER is selected by DRM_I915_FBDEV
> drivers/gpu/drm/i915/Kconfig:40:	symbol DRM_I915_FBDEV depends on DRM_I915
> drivers/gpu/drm/i915/Kconfig:1:	symbol DRM_I915 depends on ACPI_VIDEO
> drivers/acpi/Kconfig:130:	symbol ACPI_VIDEO is selected by BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:156:	symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT
> drivers/video/fbdev/Kconfig:188:	symbol FB_BACKLIGHT is selected by PMAC_BACKLIGHT
> drivers/macintosh/Kconfig:135:	symbol PMAC_BACKLIGHT depends on FB
> 
> and the rabbit hole gets deeper than I thought. I guess it always does.
> 
> At this point the question is whether "depends on ((ACPI && ACPI_VIDEO)
> || ACPI=n)" is worth pursuing and makes more sense than the "select foo
> if ACPI" lines, or do we need to build hacks upon hacks to get this
> fixed.

I certainly prefer the depends that you added to all of those selects.

I'm afraid that I can't help you much here other than to say that if you
can express the driver needs with depends instead of select, you should
come out ahead by removing some of the depth of the rabbit hole.

-- 
~Randy