linux-kernel - Re: [PATCH] arch/powerpc: provide zero

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Date:	Thu, 08 Oct 2015 14:39:35 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Michal Sojka <sojkam1@....cvut.cz>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Philippe Bergheaud <felix@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Anton Blanchard <anton@...ba.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arch/powerpc: provide zero_bytemask() for big-endian

On Wed, 2015-10-07 at 10:46 -0400, Chris Metcalf wrote:
> For some reason, only the little-endian flavor of
> powerpc provided the zero_bytemask() implementation.

Because previously it was optional unless DCACHE_WORD_ACCESS was enabled.

> Reported-by: Michal Sojka <sojkam1@....cvut.cz>
> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
> ---
>  arch/powerpc/include/asm/word-at-a-time.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/word-at-a-time.h b/arch/powerpc/include/asm/word-at-a-time.h
> index 5b3a903adae6..e4396a7d0f7c 100644
> --- a/arch/powerpc/include/asm/word-at-a-time.h
> +++ b/arch/powerpc/include/asm/word-at-a-time.h
> @@ -40,6 +40,11 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct
>  	return (val + c->high_bits) & ~rhs;
>  }
>  
> +static inline unsigned long zero_bytemask(unsigned long mask)
> +{
> +	return ~1ul << __fls(mask);
> +}
> +
>  #else
>  
>  #ifdef CONFIG_64BIT


This looks right, and I tested it too so have an ack if you want it:

Acked-by: Michael Ellerman <mpe@...erman.id.au>


If you can CC linuxppc-dev@...ts.ozlabs.org in future on powerpc patches I'll
notice them quicker, I know I was CC'ed on this but because it also went to
LKML it got put in my lkml folder.

cheers



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