kconfig: remove tristate choice support

I previously submitted a fix for a bug in the choice feature [1], where
I mentioned, "Another (much cleaner) approach would be to remove the
tristate choice support entirely".

There are more issues in the tristate choice feature. For example, you
can observe a couple of bugs in the following test code.

[Test Code]

    config MODULES
            def_bool y
            modules

    choice
            prompt "tristate choice"
            default A

    config A
            tristate "A"

    config B
            tristate "B"

    endchoice

Bug 1: the 'default' property is not correctly processed

'make alldefconfig' produces:

    CONFIG_MODULES=y
    # CONFIG_A is not set
    # CONFIG_B is not set

However, the correct output should be:

    CONFIG_MODULES=y
    CONFIG_A=y
    # CONFIG_B is not set

The unit test file, scripts/kconfig/tests/choice/alldef_expected_config,
is wrong as well.

Bug 2: choice members never get 'y' with randconfig

For the test code above, the following combinations are possible:

               A    B
        (1)    y    n
        (2)    n    y
        (3)    m    m
        (4)    m    n
        (5)    n    m
        (6)    n    n

'make randconfig' never produces (1) or (2).

These bugs are fixable, but a more critical problem is the lack of a
sensible syntax to specify the default for the tristate choice.
The default for the choice must be one of the choice members, which
cannot specify any of the patterns (3) through (6) above.

In addition, I have never seen it being used in a useful way.

The following commits removed unnecessary use of tristate choices:

 - df8df5e4bc37 ("usb: get rid of 'choice' for legacy gadget drivers")
 - bfb57ef0544a ("rapidio: remove choice for enumeration")

This commit removes the tristate choice support entirely, which allows
me to delete a lot of code, making further refactoring easier.

Note:
This includes the revert of commit fa64e5f6a35e ("kconfig/symbol.c:
handle choice_values that depend on 'm' symbols"). It was suspicious
because it did not address the root cause but introduced inconsistency
in visibility between choice members and other symbols.

[1]: https://lore.kernel.org/linux-kbuild/20240427104231.2728905-1-masahiroy@kernel.org/T/#m0a1bb6992581462ceca861b409bb33cb8fd7dbae

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

5 files changed, 0 insertions, 46 deletions

diff --git a/scripts/kconfig/tests/choice_value_with_m_dep/Kconfig b/scripts/kconfig/tests/choice_value_with_m_dep/Kconfig
deleted file mode 100644
index bd970cec07d6..000000000000
--- a/scripts/kconfig/tests/choice_value_with_m_dep/Kconfig
+++ /dev/null
@@ -1,21 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-
-config MODULES
-	def_bool y
-	modules
-
-config DEP
-	tristate
-	default m
-
-choice
-	prompt "Tristate Choice"
-
-config CHOICE0
-	tristate "Choice 0"
-
-config CHOICE1
-	tristate "Choice 1"
-	depends on DEP
-
-endchoice
diff --git a/scripts/kconfig/tests/choice_value_with_m_dep/__init__.py b/scripts/kconfig/tests/choice_value_with_m_dep/__init__.py
deleted file mode 100644
index 075b4e08696e..000000000000
--- a/scripts/kconfig/tests/choice_value_with_m_dep/__init__.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-"""
-Hide tristate choice values with mod dependency in y choice.
-
-If tristate choice values depend on symbols set to 'm', they should be
-hidden when the choice containing them is changed from 'm' to 'y'
-(i.e. exclusive choice).
-
-Related Linux commit: fa64e5f6a35efd5e77d639125d973077ca506074
-"""
-
-
-def test(conf):
-    assert conf.oldaskconfig('config', 'y') == 0
-    assert conf.config_contains('expected_config')
-    assert conf.stdout_contains('expected_stdout')
diff --git a/scripts/kconfig/tests/choice_value_with_m_dep/config b/scripts/kconfig/tests/choice_value_with_m_dep/config
deleted file mode 100644
index 3a126b7a2546..000000000000
--- a/scripts/kconfig/tests/choice_value_with_m_dep/config
+++ /dev/null
@@ -1,2 +0,0 @@
-CONFIG_CHOICE0=m
-CONFIG_CHOICE1=m
diff --git a/scripts/kconfig/tests/choice_value_with_m_dep/expected_config b/scripts/kconfig/tests/choice_value_with_m_dep/expected_config
deleted file mode 100644
index 4d07b449540e..000000000000
--- a/scripts/kconfig/tests/choice_value_with_m_dep/expected_config
+++ /dev/null
@@ -1,3 +0,0 @@
-CONFIG_MODULES=y
-CONFIG_DEP=m
-CONFIG_CHOICE0=y
diff --git a/scripts/kconfig/tests/choice_value_with_m_dep/expected_stdout b/scripts/kconfig/tests/choice_value_with_m_dep/expected_stdout
deleted file mode 100644
index 2b50ab65c86a..000000000000
--- a/scripts/kconfig/tests/choice_value_with_m_dep/expected_stdout
+++ /dev/null
@@ -1,4 +0,0 @@
-Tristate Choice [M/y/?] y
-Tristate Choice
-> 1. Choice 0 (CHOICE0)
-choice[1]: 1