linux-kernel - Re: [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple modules share objects

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Date:   Thu, 8 Mar 2018 19:29:38 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Cao jin <caoj.fnst@...fujitsu.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Govind Singh <govinds@...eaurora.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple
 modules share objects

2018-03-08 19:25 GMT+09:00 Cao jin <caoj.fnst@...fujitsu.com>:
> Masahiro-san
>
> On 03/08/2018 06:21 PM, Masahiro Yamada wrote:
>> 2018-03-08 19:11 GMT+09:00 Cao jin <caoj.fnst@...fujitsu.com>:
>>>
>>>
>>> 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@...ionext.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.
>>
>>
>> Why do I have to add lying comments here?
>>
>> The commit subject/log claims KBUILD_MODNAME should be _always_ defined.
>>
>
> I feel you misunderstand my intention, the comment I mentioned is
> already there, so they should be modified according to your patch.
>

Ugh.  Sorry I missed your intention.

I will remove the comment.  Thanks!



-- 
Best Regards
Masahiro Yamada