Re: [PATCH] platform/x86: dell: Fix ALIENWARE_WMI dependencies

[Ilpo Järvinen]

Hi Kbuild/config people,

Could you please take a look at this select problem.

I attempted to solve this kconfig select logic problem a few years back 
but IIRC, my solution leaked memory or had some other problem I could not 
find solution to (and now the code has changed enough I couldn't even get 
my buggy solution easily forward-ported so I just dropped the solution and 
left just the test case into the patch).

As the Kconfig problem back then got resolved through other means, I never 
mentioned this back then but seems the same problem likely happens here
in some other form (bool selecting tristate that ends up getting only =m).

On Mon, 10 Mar 2025, Kurt Borja wrote:
> On Mon Mar 10, 2025 at 9:29 AM -05, Ilpo Järvinen wrote:
> > On Sun, 9 Mar 2025, Kurt Borja wrote:
> >
> >> If ACPI_PLATFORM_PROFILE is selected by ALIENWARE_WMI_WMAX, the former
> >> is forced to be at least =m, because the latter is a bool.
> >> 
> >> This allows the following config:
> >> 
> >> 	CONFIG_ALIENWARE_WMI=y
> >> 	CONFIG_ACPI_PLATFORM_PROFILE=m
> >
> > Hi,
> >
> > selecting from =y should not result in =m for the other symbol. This is 
> > a bug in Kconfig infrastructure.
> >
> > I ran across this a few years back and even had a test case to prove the 
> > select bug but back then the original problem eventually was solved in a 
> > different way which no longer hit the problem. I never could figure out
> > how to fix the kconfig logic though without breaking something and it 
> > ended up into low priority bin and never got solved.
> >
> > Sadly, it seems I've lost the test case patch that exhibits the bug 
> > somewhere... I'll try to look for it from my archived files.
> 
> That's funny.
> 
> I thought this was a Kconfig quirk, that resulted from the following
> hierarchy:
> 
> Type		0	1	2
> =============== ======= ======= =======
> Bool		n	y

I think y should be 2 in both cases so select should cause the selected 
symbol to becomes =y but there's a logic problem deep in select logic in 
the kconfig code.

I've attached the multi-select based reproducer test case. make 
testconfig runs kconfig selftests and results in CONFIG_A3=m despite 
CONFIG_C3=y selecting it.

Please do not apply the test case before the problem is fixed.

> Tristate	n	m	y
> 
> So a <bool> selecting the <tristate> would force it to be at least =m.
> 
> The same thing happens with depend, where a dependecy would be fulfilled
> for a <bool> if a <tristate> was at least =m. That's why in the kernel
> robot report the linking error was also due to the HWMON dependency.
> 
> Anyway, this patch could serve as a workaround if you feel it's
> necessary. I'm going to put the HWMON dependecy in the ALIENWARE_WMI
> symbol for my other series.
> 
> 

-- 
 i.From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Subject: [PATCH] kconfig: Test that the largest of selects is taken

DO NOT APPLY WITHOUT FIXING KCONFIG CODE FIRST!!!

With dual select, the largest selection should be taken. Test with
indepedent selectors and ones which depends on each other.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>

---
 scripts/kconfig/tests/dual_select/Kconfig         | 40 +++++++++++++++++++++++
 scripts/kconfig/tests/dual_select/__init__.py     |  8 +++++
 scripts/kconfig/tests/dual_select/defconfig       |  7 ++++
 scripts/kconfig/tests/dual_select/expected_config | 10 ++++++
 4 files changed, 65 insertions(+)
 create mode 100644 scripts/kconfig/tests/dual_select/Kconfig
 create mode 100644 scripts/kconfig/tests/dual_select/__init__.py
 create mode 100644 scripts/kconfig/tests/dual_select/defconfig
 create mode 100644 scripts/kconfig/tests/dual_select/expected_config

diff --git a/scripts/kconfig/tests/dual_select/Kconfig b/scripts/kconfig/tests/dual_select/Kconfig
new file mode 100644
index 000000000000..776ddc4e8bf9
--- /dev/null
+++ b/scripts/kconfig/tests/dual_select/Kconfig
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config MODULES
+	bool "Enable loadable module support"
+	modules
+	default y
+
+config A1
+	tristate "A1"
+# indepedendent tristate selects tristate
+config B1
+	tristate "B1"
+	select A1
+# bool selects lib
+config C1
+	bool "C1"
+	select A1
+
+config A2
+	tristate "A2"
+config B2
+	tristate "B2"
+	select A2
+# tristate depends on tristate and selects tristate
+config C2
+	tristate "C2"
+	depends on B2
+	select A2
+
+
+config A3
+	tristate "A3"
+config B3
+	tristate "B3"
+	select A3
+# bool depends on tristate and selects tristate
+config C3
+	bool "C3"
+	depends on B3
+	select A3
diff --git a/scripts/kconfig/tests/dual_select/__init__.py b/scripts/kconfig/tests/dual_select/__init__.py
new file mode 100644
index 000000000000..613d801014e8
--- /dev/null
+++ b/scripts/kconfig/tests/dual_select/__init__.py
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+"""
+Test dual select should select the largest selection.
+"""
+
+def test(conf):
+    assert conf.defconfig('defconfig') == 0
+    assert conf.config_contains('expected_config')
diff --git a/scripts/kconfig/tests/dual_select/defconfig b/scripts/kconfig/tests/dual_select/defconfig
new file mode 100644
index 000000000000..fa0475fa74ab
--- /dev/null
+++ b/scripts/kconfig/tests/dual_select/defconfig
@@ -0,0 +1,7 @@
+CONFIG_MODULES=y
+CONFIG_B1=m
+CONFIG_C1=y
+CONFIG_B2=y
+CONFIG_C2=m
+CONFIG_B3=m
+CONFIG_C3=y
diff --git a/scripts/kconfig/tests/dual_select/expected_config b/scripts/kconfig/tests/dual_select/expected_config
new file mode 100644
index 000000000000..1c06356d8b1c
--- /dev/null
+++ b/scripts/kconfig/tests/dual_select/expected_config
@@ -0,0 +1,10 @@
+CONFIG_MODULES=y
+CONFIG_A1=y
+CONFIG_B1=m
+CONFIG_C1=y
+CONFIG_A2=y
+CONFIG_B2=y
+CONFIG_C2=m
+CONFIG_A3=y
+CONFIG_B3=m
+CONFIG_C3=y

-- 
tg: (80e54e84911a..) kconfig/dual-select-case (depends on: master)