linux-kernel - Re: roundup_pow_of_two() may not handle 64-bit integers

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Message-ID: <29314.1400166189@warthog.procyon.org.uk>
Date:	Thu, 15 May 2014 16:03:09 +0100
From:	David Howells <dhowells@...hat.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	dhowells@...hat.com, Linux Kernel <linux-kernel@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	linuxppc-dev@...ts.ozlabs.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: roundup_pow_of_two() may not handle 64-bit integers

Brian Norris <computersforpeace@...il.com> wrote:

> I'm looking to use roundup_pow_of_two() (actually, order_base_2())
> from <linux/log2.h>, but it seems that it only supports 64-bit integers
> if your toolchain uses a 64-bit 'unsigned long' type. This is strange,
> considering that ilog2() is explicitly designed for 32-bit or 64-bit
> compatibility.

ilog2() was explicitly designed for use with 'unsigned long'.  See the commit
description (f0d1b0b30d250a07627ad8b9fbbb5c7cc08422e8).  It may work with
unsigned long long, however...

David


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