linux-kernel - Re: [PATCH 2/5] [RESEND] x86: avoid unneeded __div64

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Message-ID: <20230801170315.GGZMk60zojZOeuUwX7@fat_crate.local>
Date:   Tue, 1 Aug 2023 19:03:15 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/5] [RESEND] x86: avoid unneeded __div64_32 function
 definition

On Tue, Jul 25, 2023 at 03:48:34PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The __div64_32() function is provided for 32-bit architectures that
> don't have a custom do_div() implementation. x86_32 has one, and
> does not use the header file that declares the function prototype,
> so the definition causes a W=1 warning:
> 
> lib/math/div64.c:31:32: error: no previous prototype for '__div64_32' [-Werror=missing-prototypes]
> 
> Define an empty macro to prevent the function definition from getting
> built, which avoids the warning and saves a little .text space.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/x86/include/asm/div64.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h
> index b8f1dc0761e4b..9826d5fc12e34 100644
> --- a/arch/x86/include/asm/div64.h
> +++ b/arch/x86/include/asm/div64.h
> @@ -71,6 +71,8 @@ static inline u64 mul_u32_u32(u32 a, u32 b)
>  }
>  #define mul_u32_u32 mul_u32_u32
>  
> +#define __div64_32 /* not needed */

This comment, *after* having read the commit message makes sense.

When you look at it alone, after having opened the file, makes me
scratch my head and wonder what is that thing supposed to mean. Please
extend it.

And put the comment ontop, not sideways.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette