linux-kernel - Re: [PATCH v2] kconfig: Add transitional symbol attribute for migration support

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Message-ID: <18c2c59e-edae-4281-ac7c-8524d9cde1c5@oracle.com>
Date: Thu, 4 Sep 2025 19:10:14 +0200
From: Vegard Nossum <vegard.nossum@...cle.com>
To: Kees Cook <kees@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>,
        Nicolas Schier <nicolas.schier@...ux.dev>,
        Jonathan Corbet <corbet@....net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Randy Dunlap
 <rdunlap@...radead.org>, Arnd Bergmann <arnd@...db.de>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-kbuild@...r.kernel.org, linux-doc@...r.kernel.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Stephen Brennan <stephen.s.brennan@...cle.com>,
        Marco Bonelli <marco@...eim.net>, Petr Vorel <pvorel@...e.cz>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] kconfig: Add transitional symbol attribute for
 migration support

On 04/09/2025 19:03, Vegard Nossum wrote:
> @@ -214,6 +214,11 @@ static void sym_calc_visibility(struct symbol *sym)
>          struct property *prop;
>          tristate tri;
> 
> +       if (sym->flags & SYMBOL_HIDDEN) {
> +               sym->visible = yes;

...I just saw the irony here after having already pressed "Send".

Let me explain:

SYMBOL_HIDDEN is your new flag that indicates that somebody used
"transitional" on the config entry.

sym->visible is tristate value that gives you the condition for whether
a symbol can take on a value -- y/m means the option is visible to the
user (hence the name) and thus eligible to have a value assigned to it.
In this case you've explicitly hidden the symbol from the user but you
_want_ it to be able to take on a value from the .config that was read in.

If we want to be perfectly clear, we'd rename SYMBOL_HIDDEN to
SYMBOL_TRANSITIONAL and rename sym->visible to sym->assignable or
something like that. Then the logic would be:

if (sym->flags & SYMBOL_TRANSITIONAL)
     sym->assignable = yes;

which is much more intuitive.

Vegard