On Sat, Oct 18, 2014 at 12:13:23AM +0300, Jani Nikula wrote:
Documentation/kbuild/kconfig-language.txt warns to use select with care, and in general use select only for non-visible symbols and for symbols with no dependencies, because select will force a symbol to a value without visiting the dependencies.
Select has become particularly problematic, interdependently, with the BACKLIGHT_CLASS_DEVICE and ACPI_VIDEO configs. For example:
scripts/kconfig/conf --randconfig Kconfig KCONFIG_SEED=0x48312B00 warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT) warning: (DRM_RADEON && DRM_NOUVEAU && DRM_I915 && DRM_GMA500 && DRM_SHMOBILE && DRM_TILCDC && FB_BACKLIGHT && FB_MX3 && USB_APPLEDISPLAY && FB_OLPC_DCON && ASUS_LAPTOP && SONY_LAPTOP && THINKPAD_ACPI && EEEPC_LAPTOP && ACPI_CMPC && SAMSUNG_Q10) selects BACKLIGHT_CLASS_DEVICE which has unmet direct dependencies (HAS_IOMEM && BACKLIGHT_LCD_SUPPORT)
With tristates it's possible to end up selecting FOO=y depending on BAR=m in the config, which gets discovered at build time, not config time, like reported in the thread referenced below.
Do the following to fix the dependencies:
Depend on instead of select BACKLIGHT_CLASS_DEVICE everywhere. Drop select BACKLIGHT_LCD_SUPPORT in such cases, as it's a dependency of BACKLIGHT_CLASS_DEVICE.
Remove config FB_BACKLIGHT altogether, and replace it with a dependency on BACKLIGHT_CLASS_DEVICE. All configs selecting FB_BACKLIGHT select or depend on FB anyway, so we can simplify.
Depend on (ACPI && ACPI_VIDEO) || ACPI=n in several places instead of selecting ACPI_VIDEO and a number of its dependencies if ACPI is enabled. This is tied to backlight, as ACPI_VIDEO depends on BACKLIGHT_CLASS_DEVICE.
Replace a couple of select INPUT/VT with depends as it seemed to be necessary.
Reference: http://lkml.kernel.org/r/CA+r1ZhhmT4DrWtf6MbRQo5EqXwx+LxCqh15Vsu_d9WpftLhnxw... Reported-by: Jim Davis jim.epost@gmail.com Cc: Randy Dunlap rdunlap@infradead.org Cc: David Airlie airlied@linux.ie Cc: Daniel Vetter daniel.vetter@intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Darren Hart dvhart@infradead.org Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Jens Frederich jfrederich@gmail.com Cc: Daniel Drake dsd@laptop.org Cc: Jon Nettleton jon.nettleton@gmail.com Cc: Jean-Christophe Plagniol-Villard plagnioj@jcrosoft.com Cc: Tomi Valkeinen tomi.valkeinen@ti.com Signed-off-by: Jani Nikula jani.nikula@intel.com
As for the drivers/platform/x86/Kconfig:
Acked-by: Darren Hart dvhart@linux.intel.com
Thanks,