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From: Masahiro Yamada <yamada.masahiro@socionext.com>
Date: Wed, 17 Jan 2018 01:47:58 +0900
Message-ID: <CAK7LNAR-qJqgSTa53iDTH0VwRR9b8cfbQtN8qzSJG8kkUnYfrg@mail.gmail.com>
Subject: Re: [PATCH 3/6] kconfig: do not call conf_set_all_new_symbols() for (all)defconfig
To: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Marc Herbert <marc.herbert@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org

Hi Ulf,

2018-01-12 23:28 GMT+09:00 Ulf Magnusson <ulfalizer@gmail.com>:
> On Wed, Jan 10, 2018 at 7:56 AM, Masahiro Yamada
> <yamada.masahiro@socionext.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@socionext.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
> --

Thanks for your comments!

>From a quick test, this patch seems OK,
but I need to take a closer look at this.


-- 
Best Regards
Masahiro Yamada