linux-kernel - Re: [PATCH 3/6] kconfig: do not call conf_set_all_new

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Date:   Fri, 12 Jan 2018 15:28:41 +0100
From:   Ulf Magnusson <ulfalizer@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Marc Herbert <marc.herbert@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] kconfig: do not call conf_set_all_new_symbols() for (all)defconfig

On Wed, Jan 10, 2018 at 7:56 AM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> (all)defconfig does not need to call conf_set_all_new_symbols() because
> conf_write() calculates all symbols based on their default unless they
> have been user-defined.
>
> conf_set_all_new_symbols(def_default) is no-op except for "choice".
> It calls sym_cal_value() for "choice", but the SYMBOL_VALID is cleared
> by set_all_choice_values() later on.  So, conf_write() will re-calculate
> it, which is just a wasteful computation.  The only difference I see
> is SYMBOL_DEF_USER flag for "choice", but it gives no difference to the
> resulted .config file.
>
> I confirmed this change still produced the same .config for all ARCH.
>
> I also moved savedefconfig to collect the no-op cases at the end of
> the switch statement.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
>  scripts/kconfig/conf.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
> index 52cbe5d..8364811 100644
> --- a/scripts/kconfig/conf.c
> +++ b/scripts/kconfig/conf.c
> @@ -655,18 +655,10 @@ int main(int ac, char **av)
>         case allmodconfig:
>                 conf_set_all_new_symbols(def_mod);
>                 break;
> -       case alldefconfig:
> -               conf_set_all_new_symbols(def_default);
> -               break;
>         case randconfig:
>                 /* Really nothing to do in this loop */
>                 while (conf_set_all_new_symbols(def_random)) ;
>                 break;
> -       case defconfig:
> -               conf_set_all_new_symbols(def_default);
> -               break;
> -       case savedefconfig:
> -               break;
>         case oldaskconfig:
>                 rootEntry = &rootmenu;
>                 conf(&rootmenu);
> @@ -681,7 +673,10 @@ int main(int ac, char **av)
>                         check_conf(&rootmenu);
>                 } while (conf_cnt && input_mode != listnewconfig);
>                 break;
> +       case alldefconfig:
> +       case defconfig:
>         case olddefconfig:
> +       case savedefconfig:
>         default:
>                 break;
>         }
> --
> 2.7.4
>

Another side effect of conf_set_all_new_symbols(def_default) is that
SYMBOL_NEED_SET_CHOICE_VALUES is set on all choice values. Might want
to check fbe98bb9ed3d ("kconfig: Fix defconfig when one choice menu
selects options that another choice menu depends on") to make sure
nothing breaks related to that.

Cheers,
Ulf