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

[Wang Jinchao <wangjinchao@xfusion.com>]

On Mon, Aug 14, 2023 at 10:26:45AM +0300, Jani Nikula wrote:
> On Sat, 12 Aug 2023, Wang Jinchao <wangjinchao@xfusion.com> 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?
> 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@xfusion.com>
> > ---
> >  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