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

From: Jani Nikula <[email-masked]>
Date: Thu, 02 Oct 2014 10:46:52 +0300

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.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center