linux-kernel - Re: [PATCH v8 01/14] Consolidate IO memcpy/memset into iomap

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Message-Id: <a9fa56b4-b00c-4941-8c8c-1d3b58b573e2@app.fastmail.com>
Date: Tue, 08 Oct 2024 09:27:20 +0000
From: "Arnd Bergmann" <arnd@...db.de>
To: "Julian Vetter" <jvetter@...rayinc.com>,
 "Russell King" <linux@...linux.org.uk>,
 "Catalin Marinas" <catalin.marinas@....com>,
 "Will Deacon" <will@...nel.org>, guoren <guoren@...nel.org>,
 "Huacai Chen" <chenhuacai@...nel.org>, "WANG Xuerui" <kernel@...0n.name>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Geert Uytterhoeven" <geert@...ux-m68k.org>,
 "Richard Henderson" <richard.henderson@...aro.org>,
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 "Matt Turner" <mattst88@...il.com>,
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 "Helge Deller" <deller@....de>,
 "Yoshinori Sato" <ysato@...rs.sourceforge.jp>,
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Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH v8 01/14] Consolidate IO memcpy/memset into iomap_copy.c

On Tue, Oct 8, 2024, at 07:50, Julian Vetter wrote:
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 80de699bf6af..f14655ed4d9d 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -102,6 +102,12 @@ static inline void log_post_read_mmio(u64 val, u8 
> width, const volatile void __i
> 
>  #endif /* CONFIG_TRACE_MMIO_ACCESS */
> 
> +extern void memcpy_fromio(void *to, const volatile void __iomem *from,
> +			  size_t count);
> +extern void memcpy_toio(volatile void __iomem *to, const void *from,
> +			size_t count);
> +extern void memset_io(volatile void __iomem *dst, int c, size_t count);
> +

I think having this globally visible is the reason you are running
into the mismatched prototypes. The patches to change the architecture
specific implementations are all good, but I would instead add
#ifdef checks around the prototypes the same way you do for the
implementation, to make the series bisectible and shorter.

 include/asm-generic/io.h |  58 ++----------------
 lib/iomap_copy.c         | 127 +++++++++++++++++++++++++++++++++++++++

Along the same lines, I would change lib/Makefile to build
this file unconditionally even on architectures that don't
set CONFIG_HAS_IOMEM. Again, strengthening the driver dependencies
is good, but it feels like a distraction here when we just need the
common implementation to be available.

       Arnd