linux-kernel - Re: [PATCH] drm/i915: Fix Kconfig error for CONFIG_DRM

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Date:   Mon, 14 Aug 2023 15:13:32 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Wang Jinchao <wangjinchao@...sion.com>
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, stone.xulei@...sion.com
Subject: Re: [PATCH] drm/i915: Fix Kconfig error for CONFIG_DRM_I915

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

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.


>> 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@...sion.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

-- 
Jani Nikula, Intel Open Source Graphics Center