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

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Message-Id: <200812040952.44957.rusty@rustcorp.com.au>
Date:	Thu, 4 Dec 2008 09:52:44 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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

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).

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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