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 \#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) and #endif directives. 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. v2: Add a line starting with # 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 -- 2.40.0
