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Date: Mon, 11 Dec 2023 08:18:35 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Samuel Holland <samuel.holland@sifive.com>
Cc: linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
	linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
	linux-riscv@lists.infradead.org,
	Christoph Hellwig <hch@infradead.org>, linux-kernel@vger.kernel.org,
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	Masahiro Yamada <masahiroy@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>, linux-kbuild@vger.kernel.org
Subject: Re: [RFC PATCH 11/12] selftests/fpu: Move FP code to a separate
 translation unit
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 <20231208055501.2916202-12-samuel.holland@sifive.com>
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>  obj-$(CONFIG_TEST_FPU) += test_fpu.o
> -CFLAGS_test_fpu.o += $(FPU_CFLAGS)
> +test_fpu-y := test_fpu_glue.o test_fpu_impl.o
> +CFLAGS_test_fpu_impl.o += $(FPU_CFLAGS)

Btw, I really wonder if having a

modname-fpu += foo.o

syntax in kbuild wouldn't be preferable to this.  Of coure that requires
someone who understands kbuild inside out.

> +int test_fpu(void);

This needs to go into a header.

And I think I underatand your way to enforce the use of a separate
compilation unit in the riscv patch now.

Can we just make that generic, e.g. have a <linux/fpu.h> that wraps
<asm/fpu.h> that does the guard based on a
-D_LINUX_FPU_COMPILATION_UNIT=1 on the command line so that all the
code becomes fully portable?  Any legacy arch specific fpu users not
using <linux/fpu.h> would not be affected by it, although it would be
great to eventually migrate them to the common scheme.