On Sat, 12 Aug 2023, Wang Jinchao <wangjinchao@xxxxxxxxxxx> wrote: > When CONFIG_DRM_I915 is set to 'y' and CONFIG_BACKLIGHT_CLASS_DEVICE > is set to 'm', we encountered an ld.lld error during the build process: > > ld.lld: error: undefined symbol: backlight_device_get_by_name > >>> referenced by intel_backlight.c:955 > >>> vmlinux.o:(intel_backlight_device_register) > > ld.lld: error: undefined symbol: backlight_device_register > >>> referenced by intel_backlight.c:971 > >>> vmlinux.o:(intel_backlight_device_register) > > ld.lld: error: undefined symbol: backlight_device_unregister > >>> referenced by intel_backlight.c:999 > >>> vmlinux.o:(intel_backlight_device_unregister) > > This issue occurred because intel_backlight_device_register and > intel_backlight_device_unregister were enclosed within > However, according to Kconfig, CONFIG_DRM_I915 will select > BACKLIGHT_CLASS_DEVICE only if ACPI is enabled. > This led to an error, which can be resolved by removing the > conditional statements related to ACPI. The real fix is to use depends on BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n but in order to do that, you need to change a lot of places to depend on, not select BACKLIGHT_CLASS_DEVICE, because otherwise you end up with other dependency issues. BR, Jani. > > Signed-off-by: Wang Jinchao <wangjinchao@xxxxxxxxxxx> > --- > drivers/gpu/drm/i915/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig > index 01b5a8272a27..5003de921bf7 100644 > --- a/drivers/gpu/drm/i915/Kconfig > +++ b/drivers/gpu/drm/i915/Kconfig > @@ -24,7 +24,7 @@ config DRM_I915 > select IRQ_WORK > # i915 depends on ACPI_VIDEO when ACPI is enabled > # but for select to work, need to select ACPI_VIDEO's dependencies, ick > - select BACKLIGHT_CLASS_DEVICE if ACPI > + select BACKLIGHT_CLASS_DEVICE > select INPUT if ACPI > select X86_PLATFORM_DEVICES if ACPI > select ACPI_WMI if ACPI -- Jani Nikula, Intel Open Source Graphics Center
