linux-kernel - Re: [v2, 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn

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Message-Id: <401RHF2pwPz9sCS@ozlabs.org>
Date:   Wed, 14 Mar 2018 20:28:25 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Mathieu Malaterre <malat@...ian.org>
Cc:     Mathieu Malaterre <malat@...ian.org>,
        open list <linux-kernel@...r.kernel.org>,
        Paul Mackerras <paulus@...ba.org>,
        "open list:LINUX FOR POWERPC 32-BIT AND 64-BIT" 
        <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [v2, 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid

On Wed, 2018-03-07 at 20:34:35 UTC, Mathieu Malaterre wrote:
> Rewrite comparison since all values compared are of type `unsigned long`.
> 
> Instead of using unsigned properties and rewriting the original code as:
> (originally suggested by Segher Boessenkool <segher@...nel.crashing.org>)
> 
>   #define pfn_valid(pfn) \
>                (((pfn) - ARCH_PFN_OFFSET) < (max_mapnr - ARCH_PFN_OFFSET))
> 
> Prefer a static inline function to make code as readable as possible.
> 
> Fix a warning (treated as error in W=1):
> 
>   CC      arch/powerpc/kernel/irq.o
> In file included from ./include/linux/bug.h:5:0,
>                  from ./include/linux/cpumask.h:13,
>                  from ./include/linux/smp.h:13,
>                  from ./include/linux/kernel_stat.h:5,
>                  from arch/powerpc/kernel/irq.c:35:
> ./include/linux/dma-mapping.h: In function ‘dma_map_resource’:
> ./arch/powerpc/include/asm/page.h:129:32: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
>  #define pfn_valid(pfn)  ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr)
>                                 ^
> Suggested-by: Christophe Leroy <christophe.leroy@....fr>
> Signed-off-by: Mathieu Malaterre <malat@...ian.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/603b892200e653dd7e86a0e4a31556

cheers