linux-kernel - Re: Yet more ARM breakage in linux-next

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Date:	Wed, 03 Dec 2008 15:37:44 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <rmk+lkml@....linux.org.uk>,
	linux-kernel@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: Yet more ARM breakage in linux-next

Rusty Russell wrote:
> On Thursday 04 December 2008 07:11:09 Andrew Morton wrote:
>> On Wed, 3 Dec 2008 19:29:05 +0000
>>
>> Russell King <rmk+lkml@....linux.org.uk> wrote:
>>> This seems to be causing lots of ARM breakage:
>>>
>>> lib/find_next_bit.c:183: error: implicit declaration of function '__fls'
>>>
>>> Whoever's responsible,
>> git-blame?
> 
> It's me.  Turns out sparc, avr32 and arm all don't define __fls in their
> asm/bitops.h, and I'm the first one to use it in generic code.
> 
> But as I prepared this patch, I note that the armv5 __fls/fls is wrong:
> 
>   /* Implement fls() in C so that 64-bit args are suitably truncated */
>   static inline int fls(int x)
>   {
>       return __fls(x);
>   }
> 
> __fls(x) returns a bit number (0-31).  fls() returns 0 or bitnumber+1.
> 
> (Yes, classic useless kerneldoc documentation doesn't actually *say* 
> this clearly).
 
oh fud.  That's not a fault of kernel-doc, just of whoever wrote it.
It's only as good as someone makes it.


> But here's the linux-next fix:
> 
> arm: define __fls for pre v5 ARM
> 
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> 
> diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h
> --- a/arch/arm/include/asm/bitops.h
> +++ b/arch/arm/include/asm/bitops.h
> @@ -239,6 +239,7 @@ extern int _find_next_bit_be(const unsig
>  #include <asm-generic/bitops/ffz.h>
>  #include <asm-generic/bitops/__ffs.h>
>  #include <asm-generic/bitops/fls.h>
> +#include <asm-generic/bitops/__fls.h>
>  #include <asm-generic/bitops/ffs.h>
>  
>  #else

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