drm/stub/Kconfig: fix Kconfig for stub driver.

* Dave Airlie <airlied@linux.ie> wrote:

> > Lee, Chun-Yi (1):
> >       gpu: Add Intel GMA500(Poulsbo) Stub Driver

Today's -tip fails to build due to upstream commit e26fd119 ("gpu: Add Intel
GMA500(Poulsbo) Stub Driver"), committed two days ago and merged yesterday, on
x86 allmodconfig with BACKLIGHT_CLASS_DEVICE disabled:

 drivers/built-in.o: In function `acpi_video_bus_put_one_device':
 video.c:(.text+0x7d26f): undefined reference to `backlight_device_unregister'
 drivers/built-in.o: In function `acpi_video_switch_brightness':
 video.c:(.text+0x7d6f5): undefined reference to `backlight_force_update'
 drivers/built-in.o: In function `acpi_video_device_find_cap':
 video.c:(.text+0x7dfdb): undefined reference to `backlight_device_register'

drivers/gpu/stub/Kconfig selects ACPI_VIDEO, but ACPI_VIDEO is a complex interactive
Kconfig option with a lot of dependencies:

 config ACPI_VIDEO
	tristate "Video"
	depends on X86 && BACKLIGHT_CLASS_DEVICE && VIDEO_OUTPUT_CONTROL
	depends on INPUT
	select THERMAL
	help
	  This driver implements the ACPI Extensions For Display Adapters

and if any of its dependencies are not met, we get a build failure. This problem was
apparently realized in the driver at a certain stage:

 config STUB_POULSBO
        tristate "Intel GMA500 Stub Driver"
        depends on PCI
        # Poulsbo stub depends on ACPI_VIDEO when ACPI is enabled
        # but for select to work, need to select ACPI_VIDEO's dependencies, ick
        select ACPI_VIDEO if ACPI

but not fully understood and not fully fixed.

As a quick fix select these secondary dependencies, like drivers/gpu/drm/Kconfig
does:

 config DRM_I915
	tristate "i915 driver"
	depends on AGP_INTEL
	select SHMEM
	select DRM_KMS_HELPER
	select FB_CFB_FILLRECT
	select FB_CFB_COPYAREA
	select FB_CFB_IMAGEBLIT
	# i915 depends on ACPI_VIDEO when ACPI is enabled
	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
	select VIDEO_OUTPUT_CONTROL 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 830M, 845G,
	  852GM, 855GM 865G or 915G integrated graphics.  If M is selected, the

But it's arguably not particularly nice looking, so maybe this area of code is ripe
for a Kconfig restructuring/cleanup.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dave Airlie <airlied@redhat.com>