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Date: Mon, 2 Feb 2015 14:27:32 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Christoph Jaeger <cj@...ux.com>
Cc: linux-kernel@...r.kernel.org,
Yalin Wang <yalin.wang@...ymobile.com>,
Will Deacon <will.deacon@....com>,
Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH linux-next] lib: Kconfig: use bool instead of boolean
On Mon, 2 Feb 2015 09:59:16 -0500 Christoph Jaeger <cj@...ux.com> wrote:
> Keyword 'boolean' for type definition attributes is considered
> deprecated and, therefore, should not be used anymore.
>
> See http://lkml.kernel.org/r/cover.1418003065.git.cj@linux.com
> See http://lkml.kernel.org/r/1419108071-11607-1-git-send-email-cj@linux.com
>
> ...
>
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -14,7 +14,7 @@ config BITREVERSE
> tristate
>
> config HAVE_ARCH_BITREVERSE
> - boolean
> + bool
> default n
> depends on BITREVERSE
> help
Your patch patches 556d2f055bf6d ("ARM: 8187/1: add
CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction") which appears
in linux-next via the ARM tree.
There are many uses of "boolean" in lib/Kconfig. Converting just one
of them is inefficient and odd.
556d2f055bf6d is a bit of a surprise. It looks good to me from a
non-ARM perspective - the __builtin_constant_p() optimisation is
sensible, although bitrev on a constant probably isn't very common.
I'm not sure about the ARM part though! __bitrev8() is pretty damn
fast. Presumably an inlined rbit instruction is faster still, but not
very much?
The Kconfig help text in 556d2f055bf6d rather needs some caring for.
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