Re: [PATCH 11/18] platform/x86: int3472: fix object shared between several modules

From: Hans de Goede <hdegoede@redhat.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Alexander Lobakin <alobakin@pm.me>
Cc: linux-kbuild@vger.kernel.org,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nicolas Schier <nicolas@fjasle.eu>, Jens Axboe <axboe@kernel.dk>,
	Boris Brezillon <bbrezillon@kernel.org>,
	Borislav Petkov <bp@alien8.de>, Tony Luck <tony.luck@intel.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Vladimir Oltean <vladimir.oltean@nxp.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Derek Chickles <dchickles@marvell.com>,
	Ioana Ciornei <ioana.ciornei@nxp.com>,
	Salil Mehta <salil.mehta@huawei.com>,
	Sunil Goutham <sgoutham@marvell.com>,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	Daniel Scally <djrscally@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	NXP Linux Team <linux-imx@nxp.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 11/18] platform/x86: int3472: fix object shared between several modules
Date: Sun, 20 Nov 2022 21:54:51 +0100	[thread overview]
Message-ID: <961a7d7e-c917-86a8-097b-5961428e9ddc@redhat.com> (raw)
In-Reply-To: <Y3oxyUx0UkWVjGvn@smile.fi.intel.com>

Hi,

On 11/20/22 14:55, Andy Shevchenko wrote:
> On Sat, Nov 19, 2022 at 11:08:17PM +0000, Alexander Lobakin wrote:
>> common.o is linked to both intel_skl_int3472_{discrete,tps68470}:
>>
>>> scripts/Makefile.build:252: ./drivers/platform/x86/intel/int3472/Makefile:
>>> common.o is added to multiple modules: intel_skl_int3472_discrete
>>> intel_skl_int3472_tps68470
>>
>> Although both drivers share one Kconfig option
>> (CONFIG_INTEL_SKL_INT3472), it's better to not link one object file
>> into several modules (and/or vmlinux).
>> Under certain circumstances, such can lead to the situation fixed by
>> commit 637a642f5ca5 ("zstd: Fixing mixed module-builtin objects").
>>
>> Introduce the new module, intel_skl_int3472_common, to provide the
>> functions from common.o to both discrete and tps68470 drivers. This
>> adds only 3 exports and doesn't provide any changes to the actual
>> code.

Replying to Andy's reply here since I never saw the original submission
which was not Cc-ed to platform-driver-x86@vger.kernel.org .

As you mention already in the commit msg, the issue from:

commit 637a642f5ca5 ("zstd: Fixing mixed module-builtin objects")

is not an issue here since both modules sharing the .o file are
behind the same Kconfig option.

So there is not really an issue here and common.o is tiny, so
small chances are it does not ever increase the .ko size
when looking a the .ko size rounded up to a multiple of
the filesystem size.

At the same time adding an extra module does come with significant
costs, it will eat up at least 1 possibly more then 1 fs blocks
(I don't know what the module header size overhead is).

And it needs to be loaded separately and module loading is slow;
and it will grow the /lib/modules/<kver>/modules.* sizes.

So nack from me for this patch, since I really don't see
it adding any value.

Regards,

Hans

> 
> ...
> 
>> +MODULE_IMPORT_NS(INTEL_SKL_INT3472);
>> +
> 
> Redundant blank line. You may put it to be last MODULE_*() in the file, if you
> think it would be more visible.
> 
>>  MODULE_DESCRIPTION("Intel SkyLake INT3472 ACPI Discrete Device Driver");
>>  MODULE_AUTHOR("Daniel Scally <djrscally@gmail.com>");
>>  MODULE_LICENSE("GPL v2");
> 
> ...
> 
>> +MODULE_IMPORT_NS(INTEL_SKL_INT3472);
>> +
>>  MODULE_DESCRIPTION("Intel SkyLake INT3472 ACPI TPS68470 Device Driver");
>>  MODULE_AUTHOR("Daniel Scally <djrscally@gmail.com>");
>>  MODULE_LICENSE("GPL v2");
> 
> Ditto. And the same to all your patches.
> 