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Date: Wed, 24 Apr 2024 14:24:03 +0200
From: Nicolas Schier <n.schier@avm.de>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-sh@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	Nathan Chancellor <nathan@kernel.org>, linux-doc@vger.kernel.org
Subject: Re: [PATCH v2 2/2] kconfig: remove 'optional' property support
Message-ID: <Zij545f6JVmmbcoj@buildd.core.avm.de>
References: <20240422164104.2869507-1-masahiroy@kernel.org>
 <20240422164104.2869507-3-masahiroy@kernel.org>
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In-Reply-To: <20240422164104.2869507-3-masahiroy@kernel.org>

On Tue, Apr 23, 2024 at 01:41:04AM +0900, Masahiro Yamada wrote:
> The 'choice' statement is primarily used to exclusively select one
> option, but the 'optional' property allows all entries to be disabled.
> 
> In the following example, both A and B can be disabled simultaneously:
> 
>     choice
>             prompt "choose A, B, or nothing"
>             optional
> 
>     config A
>             bool "A"
> 
>     config B
>             bool "B"
> 
>     endchoice
> 
> You can achieve the equivalent outcome by other means.
> 
> A common solution is to add another option to guard the choice block.
> In the following example, you can set ENABLE_A_B_CHOICE=n to disable
> the entire choice block:
> 
>     choice
>             prompt "choose A or B"
>             depends on ENABLE_A_B_CHOICE
> 
>     config A
>             bool "A"
> 
>     config B
>             bool "B"
> 
>     endchoice
> 
> Another approach is to insert one more entry as a place-holder:
> 
>     choice
>             prompt "choose A, B, or disable both"
> 
>     config A
>             bool "A"
> 
>     config B
>             bool "B"
> 
>     config DISABLE_A_AND_B
>             bool "choose this to disable both A and B"
> 
>     endchoice
> 
> Some real examples are DEBUG_INFO_NONE, INITRAMFS_COMPRESSION_NONE,
> LTO_NONE, etc.
> 
> The 'optional' property is even more unnecessary for a tristate choice.
> 
> Without the 'optional' property, you can disable A and B; you can set
> 'm' in the choice prompt, and disable A and B individually:
> 
>     choice
>             prompt "choose one built-in or make them modular"
> 
>     config A
>             tristate "A"
> 
>     config B
>             tristate "B"
> 
>     endchoice
> 
> In conclusion, the 'optional' property was unneeded.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> (no changes since v1)

thanks for the patch!

I found just one small remnant that probably should be removed as well:

diff --git a/scripts/kconfig/tests/choice/__init__.py b/scripts/kconfig/tests/choice/__init__.py
index 4318fce05912f..05e162220085c 100644
--- a/scripts/kconfig/tests/choice/__init__.py
+++ b/scripts/kconfig/tests/choice/__init__.py
@@ -8,4 +8,2 @@ The behavior of 'y' choice is intuitive.  If choice values are tristate,
 the choice can be 'm' where each value can be enabled independently.
-Also, if a choice is marked as 'optional', the whole choice can be
-invisible.
 """

Reviewed-by: Nicolas Schier <n.schier@avm.de>

Kind regards,
Nicolas


PS: For other reviewers, this patch (set) depends on
https://lore.kernel.org/linux-kbuild/20240422161054.2867285-1-masahiroy@kernel.org/