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    SubjectRe: Yet more ARM breakage in linux-next
    On Thu, 4 Dec 2008, Russell King wrote:

    > On Thu, Dec 04, 2008 at 09:52:44AM +1030, 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@arm.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:
    >
    > __fls is wrong.

    __fls used to _not_ exist at all on ARM until commit 0c65f459ce.

    > > /* 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.
    >
    > The 'clz' instruction returns 32 for a zero input, or (31 - most significant
    > set bit) - which seems to work for fls() but not __fls().

    ... and it looks like the person who introduced the commit above didn't
    take into account the fact that __fls() already had another semantic in
    the kernel.

    > Sending to Nicolas.

    I queued a fix addressing both issues for RMK to merge:

    http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=5339/1


    Nicolas


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