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Subject: Re: [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple
 modules share objects
To: Masahiro Yamada <yamada.masahiro@socionext.com>,
        <linux-kbuild@vger.kernel.org>
CC: Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Govind Singh <govinds@codeaurora.org>,
        Kalle Valo <kvalo@codeaurora.org>, <linux-kernel@vger.kernel.org>
References: <1520471103-10089-1-git-send-email-yamada.masahiro@socionext.com>
 <1520471103-10089-3-git-send-email-yamada.masahiro@socionext.com>
From: Cao jin <caoj.fnst@cn.fujitsu.com>
Message-ID: <4022257e-9ab0-b038-df0e-b15b98cb999f@cn.fujitsu.com>
Date: Thu, 8 Mar 2018 18:11:39 +0800
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On 03/08/2018 09:05 AM, Masahiro Yamada wrote:
> Currently, KBUILD_MODNAME is defined only when $(modname) contains
> just one word.  If an object is shared among multiple modules,
> undefined KBUILD_MODNAME could cause a build error.  For example,
> if CONFIG_DYNAMIC_DEBUG is enabled, any call of printk() populates
> .modname, then fails to build due to undefined KBUILD_MODNAME.
> 
> Take the following code as an example:
> 
>   obj-m += foo.o
>   obj-m += bar.o
>   foo-objs := foo-bar-common.o foo-main.o
>   bar-objs := foo-bar-common.o bar-main.o
> 
> In this case, there is room for argument what to define for
> KBUILD_MODNAME when foo-bar-common.o is being compiled.
> "foo", "bar", or what else?
> 
> One idea is to define colon-separated modules that share the object,
> in this case, "bar:foo" (modules are sorted alphabetically by
> $(sort ...).
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  scripts/Makefile.lib | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index a7e315f..a1fbd6a 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -92,8 +92,7 @@ subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
>  #       differ in different configs.
>  name-fix = $(squote)$(quote)$(subst $(comma),_,$(subst -,_,$1))$(quote)$(squote)
>  basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
> -modname_flags  = $(if $(filter 1,$(words $(modname))),\
> -                 -DKBUILD_MODNAME=$(call name-fix,$(modname)))
> +modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname))
>  

I guess there is comment also need to be modified above this code hunk:

Note: Files that end up in two or more modules are compiled without the
      KBUILD_MODNAME definition. The reason is that any made-up name
      would differ in different configs.
-- 
Sincerely,
Cao jin