Re: [PATCH] drm/i915: Fix Kconfig error for CONFIG_DRM_I915

[Wang Jinchao]

On Mon, Aug 14, 2023 at 03:13:32PM +0300, Jani Nikula wrote:
> On Mon, 14 Aug 2023, Wang Jinchao <wangjinchao@xxxxxxxxxxx> wrote:
> > On Mon, Aug 14, 2023 at 10:26:45AM +0300, Jani Nikula wrote:
> >> 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
> > it works.
> >> 
> >> but in order to do that, you need to change a lot of places to depend
> > Why, what are the other places?
> 
> Generally when you have a mixture of depends on and select on a kconfig
> symbol, you'll eventually end up with dependency problems.
> 
> BR,
> Jani.
> 
Now that I understand what you said, I will make an effort to correct it.

      GEN     Makefile
    drivers/gpu/drm/i915/Kconfig:2:error: recursive dependency detected!
    drivers/gpu/drm/i915/Kconfig:2: symbol DRM_I915 depends on BACKLIGHT_CLASS_DEVICE
    drivers/video/backlight/Kconfig:136:    symbol BACKLIGHT_CLASS_DEVICE is selected by DRM_FSL_DCU
    drivers/gpu/drm/fsl-dcu/Kconfig:2:      symbol DRM_FSL_DCU depends on COMMON_CLK
    drivers/clk/Kconfig:21: symbol COMMON_CLK is selected by X86_INTEL_QUARK
    arch/x86/Kconfig:627:   symbol X86_INTEL_QUARK depends on X86_PLATFORM_DEVICES
    drivers/platform/x86/Kconfig:6: symbol X86_PLATFORM_DEVICES is selected by DRM_I915
    For a resolution refer to Documentation/kbuild/kconfig-language.rst
    subsection "Kconfig recursive dependency limitations"
> 
> >> on, not select BACKLIGHT_CLASS_DEVICE, because otherwise you end up with
> > got it.
> >> 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
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center