Messages in this thread | | | From | Masahiro Yamada <> | Date | Tue, 27 Aug 2019 14:14:59 +0900 | Subject | Re: [PATCH] riscv: add arch/riscv/Kbuild |
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On Mon, Aug 26, 2019 at 8:35 PM Christoph Hellwig <hch@infradead.org> wrote: > > On Wed, Aug 21, 2019 at 06:26:58PM +0900, Masahiro Yamada wrote: > > Use the standard obj-y form to specify the sub-directories under > > arch/riscv/. No functional change intended. > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > Do you have a document what the grand scheme here is?
There is a small documentation about "Makefile" vs "Kbuild" in Documentation/kbuild/modules.rst section 3.2
It is talking about external modules, but the benefit applies to arch/$(SRCARCH)/Kbuild as well.
arch/$(SRCARCH)/Makefile is included by the top Makefile to specify arch-specific compiler flags, etc.
On the other hand, arch/$(SRCARCH)/Kbuild, if exists, is included when Kbuild actually descends into arch/$(SRCARCH)/.
This allows you to hierarchize the sub-directories to visit instead of specifying everything in flat in arch/$(SRCARCH)/Makefile.
Major architectures are already doing this.
See arch/x86/Kbuild arch/sparc/Kbuild arch/powerpc/Kbuild etc.
(and arm64 also adopted this recently)
The trick is "Kbuild" has precedence over "Makefile".
If you are interested in the actual code, see line 41 of scripts/Makefile.build
> Less of the magic > in arch/$(ARCH)/Makefile sounds like a good idea, but unless we have > a very specific split between the kbuild makefile and various override > I fear just splitting things up into two files doesn't really help much.
Why not?
-- Best Regards Masahiro Yamada
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