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Subject: Re: [PATCH] kconfig: forbid symbols that end with '_MODULE'
To:     Masahiro Yamada <masahiroy@kernel.org>,
        linux-kbuild@vger.kernel.org, arnd@arndb.de
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Kalle Valo <kvalo@codeaurora.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Mark Brown <broonie@kernel.org>, Takashi Iwai <tiwai@suse.com>,
        alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org
References: <20210825041637.365171-1-masahiroy@kernel.org>
From:   =?UTF-8?Q?P=c3=a9ter_Ujfalusi?= <peter.ujfalusi@gmail.com>
Message-ID: <9df591f6-53fc-4567-8758-0eb1be4eade5@gmail.com>
Date:   Wed, 25 Aug 2021 14:59:44 +0300
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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@kernel.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 ?

>  	def_tristate y
>  	depends on SND_SOC_DM365_VOICE_CODEC && SND_SOC
>  	select MFD_DAVINCI_VOICECODEC
> 

-- 
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