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From: Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: linux-kernel@vger.kernel.org, Tom Gundersen <teg@jklm.no>,
	Kay Sievers <kay@vrfy.org>, Rusty Russell <rusty@rustcorp.com.au>,
	akpm@linux-foundation.org, backports@vger.kernel.org
Subject: Re: [RFC PATCH 2/5] Add CONFIG symbol to module as compilation parameter
Date: Sat, 20 Aug 2016 17:11:37 +0200
Message-ID: <CAGZ2q2yt1NYshNpm5ZCmPXfYxPynttEU7KiiL3RALegGD04nug@mail.gmail.com> (raw)
In-Reply-To: <20160818181007.GN3296@wotan.suse.de>

2016-08-18 20:10 GMT+02:00 Luis R. Rodriguez <mcgrof@kernel.org>:
> On Wed, Aug 17, 2016 at 09:27:00PM +0200, Cristina Moraru wrote:
>> Add  CONFIG symbol to kernel modules as a define via -D
>
> Perhaps better worded as:
>
> When modules have a direct Kconfig CONFIG_ symbol associated with
> we want to be able to make it available to the build system when we
> are building the module.
>
> You can then describe you do this with -D.
>
>> compilation parameter. The CONFIG_FOO symbol for each
>> module is determined by the module name, using the
>> associations from Module.ksymb. This file is loaded
>> using the 'include' directive, thus run like a regular
>> makefile. The format of the content of the file is the
>> following:
>>
>> foo_KCONF=CONFIG_FOO
>>
>> creating a set of Makefile variables foo_KCONF with the
>> CONFIG_FOO as values.
>>
>> The Makefile then adds this value in the compilation
>> command with -DKBUILD_KCONF='"CONFIG_FOO"'.
>
> Very nice. What would it mean if it lacks this ?
> This should be explained on the commit log.
>

If we lack it then KBUILD_KCONF="" and in /sys the module has the
kconfig_symbol attribute but with the empty string as content:

prompt:/sys$ cat ./module/mptbase/kconfig_symbol

prompt:/sys$

I will add it into the commit log.

>> This patch is part of a research project within
>> Google Summer of Code of porting 'make localmodconfig'
>> for backported drivers. The goal is to enable each
>> module to expose in /sys its corresponding CONFIG_* option.
>> The value of this attribute will be dynamically pegged by
>> modpost without requiring extra work from the driver developers.
>> Further, this information will be used by a hardware interogation
>> tool to extract build information about the existing devices.
>
> You can leave this out as its part of the cover letter and
> not relevant to the patch. You can however mention you will
> use this later to make the define more useful in userspace.
>
>> Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
>> ---
>>  scripts/Makefile.lib | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
>> index e7df0f5..8ae9b7f 100644
>> --- a/scripts/Makefile.lib
>> +++ b/scripts/Makefile.lib
>> @@ -89,6 +89,10 @@ multi-objs-m       := $(addprefix $(obj)/,$(multi-objs-m))
>>  subdir-ym    := $(addprefix $(obj)/,$(subdir-ym))
>>  obj-dirs     := $(addprefix $(obj)/,$(obj-dirs))
>>
>> +# Include Module.ksymb which contains the associations of modules' names
>> +# and corresponding CONFIG_* options
>> +include Module.ksymb
>
> Is this file always generated? If not prefixing the include call with - would
> be better. If we are going to make this optional, then an ifdef wrapper would
> suffice as we know it'd be expected only if the new feature was enabled.

Yes. This file is always generated. In case a 'git pull' happened
between two 'make' commands, the associations should be updated. Ok. I
will add a ifdef.

>
>> +
>>  # These flags are needed for modversions and compiling, so we define them here
>>  # already
>>  # $(modname_flags) #defines KBUILD_MODNAME as the name of the module it will
>> @@ -100,6 +104,9 @@ 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)))
>> +ksym-fix = $(squote)$(quote)$($(subst $(comma),_,$(subst -,_,$1))_KCONF)$(quote)$(squote)
>> +ksymb_flags = $(if $(filter 1,$(words $(modname))),\
>> +                 -DKBUILD_KSYMB=$(call ksym-fix, $(modname)))
>
> Are clashes possible with this formula? Can we end up with two results for instance?
> If not what prevents current konfig logic and namespace from a clash ? If we do
> not have anything to prevent a clash, what can we do to help make such clash not
> possible ?

I think the fact that modname is unique prevents from having clashes.
KBUILD_KSYMB is found according to modname.
Currently there is no clash because I enforced the Module.ksymb to
have 1-to-1 mapping.
The only potential clash I can imagine right now it having the same
module name but architecture specific CONFIG_* symbol. If there is a
1-to-1 mapping in Module.ksymb there should be no clash in the
makefile.

>
>>  orig_c_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \
>>                   $(ccflags-y) $(CFLAGS_$(basetarget).o)
>> @@ -162,7 +169,7 @@ endif
>>
>>  c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
>>                $(__c_flags) $(modkern_cflags)                           \
>> -              $(basename_flags) $(modname_flags)
>> +              $(basename_flags) $(modname_flags) $(ksymb_flags)
>>
>>  a_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
>>                $(__a_flags) $(modkern_aflags)
>> --
>
> Other than that looks good!
>
>   Luis
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Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1471462023-119645-1-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 17:55 ` [RFC PATCH 0/5] Add CONFIG symbol as module attribute Luis R. Rodriguez
2016-08-19  9:07   ` Michal Marek
2016-08-22 19:48     ` Cristina-Gabriela Moraru
2016-08-23 21:32     ` Luis R. Rodriguez
2016-08-24 11:05       ` Michal Marek
2016-08-24 16:33         ` Luis R. Rodriguez
2016-08-24 17:31           ` Naveen Kumar
2016-08-22 19:35   ` Cristina-Gabriela Moraru
2016-08-23 19:17     ` Luis R. Rodriguez
2016-08-25  7:43   ` Christoph Hellwig
2016-08-25  8:00     ` Johannes Berg
2016-08-25 19:51       ` Luis R. Rodriguez
2016-08-25  8:41     ` Michal Marek
2016-08-25 20:19     ` Luis R. Rodriguez
2019-02-05 22:07       ` Luis Chamberlain
2019-06-26 22:21         ` Luis Chamberlain
2019-06-27  4:50           ` Christoph Hellwig
2019-06-28 18:40             ` Luis Chamberlain
2019-06-29  8:42               ` Greg Kroah-Hartman
2019-07-02 20:51                 ` Luis Chamberlain
2019-07-03  7:40                   ` Greg Kroah-Hartman
2019-07-03 16:50                     ` Luis Chamberlain
2019-07-03 18:57                       ` Greg Kroah-Hartman
2019-07-03 22:25                         ` Luis Chamberlain
2019-07-11 23:07                           ` Brendan Higgins
2019-07-11 23:22                             ` Luis Chamberlain
2019-07-03 12:16               ` Enrico Weigelt, metux IT consult
2019-07-03 17:35                 ` Luis Chamberlain
2019-07-03 19:31                   ` Enrico Weigelt, metux IT consult
2019-07-03 22:42                     ` Luis Chamberlain
2019-07-11 23:27                       ` Brendan Higgins
2019-07-13 14:44                         ` Enrico Weigelt, metux IT consult
     [not found] ` <1471462023-119645-3-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 18:10   ` [RFC PATCH 2/5] Add CONFIG symbol to module as compilation parameter Luis R. Rodriguez
2016-08-18 18:55     ` Luis R. Rodriguez
2016-08-20 15:11     ` Cristina-Gabriela Moraru [this message]
2016-08-23 19:07       ` Luis R. Rodriguez
     [not found] ` <1471462023-119645-2-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 18:22   ` [RFC PATCH 1/5] Add generation of Module.symb in streamline_config Luis R. Rodriguez
2016-08-18 18:32     ` Luis R. Rodriguez
     [not found]     ` <CAGZ2q2xi9Uy-ye387=mWhy_fOEJBC593Nos7fH027m-_ZdoOXA@mail.gmail.com>
2016-08-20 14:49       ` Cristina-Gabriela Moraru
2016-08-23 19:00       ` Luis R. Rodriguez
     [not found] ` <1471462023-119645-4-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 18:30   ` [RFC PATCH 3/5] Trigger Module.ksymb generation in Makefile Luis R. Rodriguez
     [not found] ` <1471462023-119645-5-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 18:59   ` [RFC PATCH 4/5] Set KCONFIG_KSYMB as value for kconfig_ksymb module attribute Luis R. Rodriguez
2016-08-20 15:16     ` Cristina-Gabriela Moraru
2016-08-23 19:10       ` Luis R. Rodriguez
     [not found] ` <1471462023-119645-6-git-send-email-cristina.moraru09@gmail.com>
2016-08-18 19:02   ` [RFC PATCH 5/5] Add kconf_symb as kernel " Luis R. Rodriguez

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