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

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

[Wang Jinchao]

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.

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
-- 
2.40.0

[PATCH v2] drm/i915: Fix Kconfig error for CONFIG_DRM_I915

[Wang Jinchao]

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@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
-- 
2.40.0

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

[Jani Nikula]

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

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@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

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

[Wang Jinchao]

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

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

[Jani Nikula]

On Mon, 14 Aug 2023, Wang Jinchao <wangjinchao@xfusion.com> wrote:
> 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?

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@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

-- 
Jani Nikula, Intel Open Source Graphics Center

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@xfusion.com> wrote:
> > 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?
> 
> Generally when you have a mixture of depends on and select on a kconfig
> symbol, you'll eventually end up with dependency problems.
> 
Using A to represent DRM_I915 and B to represent BACKLIGHT_CLASS_DEVICE, 
as both A and B are tristate options, all the possibilities include:

1. A=n, B=n
2. A=m, B=n
3. A=y, B=n
4. A=n, B=m
5. A=m, B=m
6. A=y, B=m
7. A=n, B=y
8. A=m, B=y
9. A=y, B=y
Among them, only the 6th case (A=y, B=m) would lead to a compilation failure.

Based on your suggestion, I tested the following configuration:

    config A
        tristate "A Option"
        depends on B || B=n
    
    config B
        tristate "B Option"

I tested it using menuconfig, and found that the 6th combination (A=y, B=m) 
cannot be manually selected.

Specifically, if B=m, A can only be selected as either n or m.
If A=y and B is set to m, A automatically changes to m as well.

I believe there is no issue with the solution you provided.
Is there something that I might have overlooked?

> 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@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
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

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@xfusion.com> wrote:
> > 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?
> 
> 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@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
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center