Messages in this thread | | | From | Masahiro Yamada <> | Date | Mon, 21 Nov 2022 08:45:14 +0900 | Subject | Re: [PATCH 11/18] platform/x86: int3472: fix object shared between several modules |
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On Mon, Nov 21, 2022 at 5:55 AM Hans de Goede <hdegoede@redhat.com> wrote: > > 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.
This does have a value.
This clarifies the ownership of the common.o, in other words, makes KBUILD_MODNAME deterministic.
If an object belongs to a module, KBUILD_MODNAME is defined as the module name.
If an object is always built-in, KBUILD_MODNAME is defined as the basename of the object.
Here is a question: if common.o is shared by two modules intel_skl_int3472_discrete and intel_skl_int3472_tps68470, what should KBUILD_MODNAME be?
I see some patch submissions relying on the assumption that KBUILD_MODNAME is unique. We cannot determine KBUILD_MODNAME correctly if an object is shared by multiple modules.
BTW, this patch is not the way I suggested. The Suggested-by should not have been there (or at least Reported-by)
You argued "common.o is tiny", so I would vote for making them inline functions, like
https://lore.kernel.org/linux-kbuild/20221119225650.1044591-2-alobakin@pm.me/T/#u
> 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. > > >
-- Best Regards Masahiro Yamada
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