netdev - Re: [PATCH] kconfig: forbid symbols that end with '

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Message-ID: <CAK7LNATDMzR1DnwwAcQFHaKZeGVYDZ1oDKL-QOe_7DaB_yByAA@mail.gmail.com>
Date:   Thu, 26 Aug 2021 11:28:24 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Péter Ujfalusi <peter.ujfalusi@...il.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Kalle Valo <kvalo@...eaurora.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-wireless@...r.kernel.org, Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH] kconfig: forbid symbols that end with '_MODULE'

On Wed, Aug 25, 2021 at 8:59 PM Péter Ujfalusi <peter.ujfalusi@...il.com> wrote:
>
> Hi,
>
> On 25/08/2021 07:16, Masahiro Yamada wrote:
> > Kconfig (syncconfig) generates include/generated/autoconf.h to make
> > CONFIG options available to the pre-processor.
> >
> > The macros are suffixed with '_MODULE' for symbols with the value 'm'.
> >
> > Here is a conflict; CONFIG_FOO=m results in '#define CONFIG_FOO_MODULE 1',
> > but CONFIG_FOO_MODULE=y also results in the same define.
> >
> > fixdep always assumes CONFIG_FOO_MODULE comes from CONFIG_FOO=m, so the
> > dependency is not properly tracked for symbols that end with '_MODULE'.
> >
> > This commit makes Kconfig error out if it finds a symbol suffixed with
> > '_MODULE'. This restriction does not exist if the module feature is not
> > supported (at least from the Kconfig perspective).
> >
> > It detected one error:
> >   error: SND_SOC_DM365_VOICE_CODEC_MODULE: symbol name must not end with '_MODULE'
> >
> > Rename it to SND_SOC_DM365_VOICE_CODEC_MODULAR. Commit 147162f57515
> > ("ASoC: ti: fix SND_SOC_DM365_VOICE_CODEC dependencies") added it for
> > internal use. So, this renaming has no impact on users.
> >
> > Remove a comment from drivers/net/wireless/intel/iwlwifi/Kconfig since
> > this is a hard error now.
> >
> > Add a comment to include/linux/kconfig.h in order not to worry observant
> > developers.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
> >
> >  drivers/net/wireless/intel/iwlwifi/Kconfig |  1 -
> >  include/linux/kconfig.h                    |  3 ++
> >  scripts/kconfig/parser.y                   | 40 +++++++++++++++++++++-
> >  sound/soc/ti/Kconfig                       |  2 +-
> >  4 files changed, 43 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/wireless/intel/iwlwifi/Kconfig b/drivers/net/wireless/intel/iwlwifi/Kconfig
> > index 1085afbefba8..5b238243617c 100644
> > --- a/drivers/net/wireless/intel/iwlwifi/Kconfig
> > +++ b/drivers/net/wireless/intel/iwlwifi/Kconfig
> > @@ -70,7 +70,6 @@ config IWLMVM
> >         of the devices that use this firmware is available here:
> >         https://wireless.wiki.kernel.org/en/users/drivers/iwlwifi#firmware
> >
> > -# don't call it _MODULE -- will confuse Kconfig/fixdep/...
> >  config IWLWIFI_OPMODE_MODULAR
> >       bool
> >       default y if IWLDVM=m
> > diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
> > index 20d1079e92b4..54f677e742fe 100644
> > --- a/include/linux/kconfig.h
> > +++ b/include/linux/kconfig.h
> > @@ -53,6 +53,9 @@
> >   * IS_MODULE(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'm', 0
> >   * otherwise.  CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1" in
> >   * autoconf.h.
> > + * CONFIG_FOO_MODULE=y would also result in "#define CONFIG_FOO_MODULE 1",
> > + * but Kconfig forbids symbol names that end with '_MODULE', so that would
> > + * not happen.
> >   */
> >  #define IS_MODULE(option) __is_defined(option##_MODULE)
> >
> > diff --git a/scripts/kconfig/parser.y b/scripts/kconfig/parser.y
> > index 2af7ce4e1531..b0f73f74ccd3 100644
> > --- a/scripts/kconfig/parser.y
> > +++ b/scripts/kconfig/parser.y
> > @@ -475,6 +475,37 @@ assign_val:
> >
> >  %%
> >
> > +/*
> > + * Symbols suffixed with '_MODULE' would cause a macro conflict in autoconf.h,
> > + * and also confuse the interaction between syncconfig and fixdep.
> > + * Error out if a symbol with the '_MODULE' suffix is found.
> > + */
> > +static int sym_check_name(struct symbol *sym)
> > +{
> > +     static const char *suffix = "_MODULE";
> > +     static const size_t suffix_len = strlen("_MODULE");
> > +     char *name;
> > +     size_t len;
> > +
> > +     name = sym->name;
> > +
> > +     if (!name)
> > +             return 0;
> > +
> > +     len = strlen(name);
> > +
> > +     if (len < suffix_len)
> > +             return 0;
> > +
> > +     if (strcmp(name + len - suffix_len, suffix))
> > +             return 0;
> > +
> > +     fprintf(stderr, "error: %s: symbol name must not end with '%s'\n",
> > +             name, suffix);
> > +
> > +     return -1;
> > +}
> > +
> >  void conf_parse(const char *name)
> >  {
> >       struct symbol *sym;
> > @@ -493,8 +524,15 @@ void conf_parse(const char *name)
> >
> >       if (yynerrs)
> >               exit(1);
> > -     if (!modules_sym)
> > +
> > +     if (modules_sym) {
> > +             for_all_symbols(i, sym) {
> > +                     if (sym_check_name(sym))
> > +                             yynerrs++;
> > +             }
> > +     } else {
> >               modules_sym = sym_find( "n" );
> > +     }
> >
> >       if (!menu_has_prompt(&rootmenu)) {
> >               current_entry = &rootmenu;
> > diff --git a/sound/soc/ti/Kconfig b/sound/soc/ti/Kconfig
> > index 698d7bc84dcf..c56a5789056f 100644
> > --- a/sound/soc/ti/Kconfig
> > +++ b/sound/soc/ti/Kconfig
> > @@ -211,7 +211,7 @@ config SND_SOC_DM365_VOICE_CODEC
> >         Say Y if you want to add support for SoC On-chip voice codec
> >  endchoice
> >
> > -config SND_SOC_DM365_VOICE_CODEC_MODULE
> > +config SND_SOC_DM365_VOICE_CODEC_MODULAR
>
> This Kconfig option is only used to select the codecs needed for the
> voice mode, I think it would be better to use something like
>
> SND_SOC_DM365_SELECT_VOICE_CODECS ?


I do not have a strong opinion.
I am fine with any name unless it ends with _MODULE.


The sound subsystem maintainers and Arnd,
author of 147162f575152db800 are CC'ed.

If they suggest a better name, I'd be happy to adopt it.



-- 
Best Regards
Masahiro Yamada