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Date:   Tue, 06 Jun 2023 09:43:15 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Zhangjin Wu" <falcon@tinylab.org>, "Willy Tarreau" <w@1wt.eu>
Cc:     linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-riscv@lists.infradead.org,
        =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= <thomas@t-8ch.de>
Subject: Re: [PATCH v3 3/3] selftests/nolibc: riscv: customize makefile for rv32
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On Sat, Jun 3, 2023, at 11:05, Zhangjin Wu wrote:
> Both riscv64 and riscv32 have:
>
> * the same ARCH value, it is riscv
> * the same arch/riscv source code tree
>
> The only differences are:
>
> * riscv64 uses defconfig, riscv32 uses rv32_defconfig
> * riscv64 uses qemu-system-riscv64, riscv32 uses qemu-system-riscv32
> * riscv32 has different compiler options (-march= and -mabi=)
>
> So, riscv32 can share most of the settings with riscv64, there is no
> need to add it as a whole new architecture but just need a flag to
> record and reflect the difference.
>
> The 32bit mips and loongarch may be able to use the same method, so,
> let's use a meaningful flag: CONFIG_32BIT. If required in the future,
> this flag can also be automatically loaded from
> include/config/auto.conf.

If we use a CONFIG_* symbol, I think it should be the other way
round, for consistency with the kernel, which uses CONFIG_64BIT
on all architectures, but only uses CONFIG_32BIT on mips, loongarch
powerpc and riscv.


>  # kernel image names by architecture
>  IMAGE_i386       = arch/x86/boot/bzImage
>  IMAGE_x86_64     = arch/x86/boot/bzImage
> @@ -34,7 +40,7 @@ DEFCONFIG_x86        = defconfig
>  DEFCONFIG_arm64      = defconfig
>  DEFCONFIG_arm        = multi_v7_defconfig
>  DEFCONFIG_mips       = malta_defconfig
> -DEFCONFIG_riscv      = defconfig
> +DEFCONFIG_riscv      = $(if $(CONFIG_32BIT),rv32_defconfig,defconfig)
>  DEFCONFIG_s390       = defconfig
>  DEFCONFIG_loongarch  = defconfig
>  DEFCONFIG            = $(DEFCONFIG_$(ARCH))

This feels slightly odd, as we otherwise have a fixed defconfig
per target, so doing

DEFCONFIG_riscv      = defconfig
DEFCONFIG_riscv64    = defconfig
DEFCONFIG_riscv32    = rv32_defconfig

would seem more consistent with how x86 is handled, and would
probably be more easily extensible if we want to also make
this work with other sub-targets like mipseb, armv5 or ppc32
in the future.

     Arnd