Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbaLESYz (ORCPT ); Fri, 5 Dec 2014 13:24:55 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:39756 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750862AbaLESYy (ORCPT ); Fri, 5 Dec 2014 13:24:54 -0500 Date: Fri, 5 Dec 2014 18:24:43 +0000 From: Russell King - ARM Linux To: Catalin Marinas Cc: Arnd Bergmann , linux-wireless , "brcm80211-dev-list@broadcom.com" , "linux-kernel@vger.kernel.org" , Arend van Spriel , David Miller , "linux-arm-kernel@lists.infradead.org" Subject: Re: using DMA-API on ARM Message-ID: <20141205182443.GX11285@n2100.arm.linux.org.uk> References: <5481794E.4050406@broadcom.com> <4565667.WCBuNmaazQ@wuerfel> <20141205111114.GQ11285@n2100.arm.linux.org.uk> <20141205173839.GB31222@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141205173839.GB31222@e104818-lin.cambridge.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 05, 2014 at 05:38:39PM +0000, Catalin Marinas wrote: > On Fri, Dec 05, 2014 at 11:11:14AM +0000, Russell King - ARM Linux wrote: > > In any case, wouldn't using a u64 type for "address" be better - isn't > > "long long" 128-bit on 64-bit architectures? > > No, it's still 64-bit. There is no 128-bit integer in the C standard. Actually, that's a fallicy. The C99 standard (like previous versions) does not define exactly the number of bits in each type. It defines ranks of type, and says that lower ranks are a subrange of integers with higher ranks (for the same signed-ness.) See section 6.2.5. So, it merely states that: range(char) <= range(short) <= range(int) <= range(long) <= range(long long) So, an implementation could have: char: 8 short: 16 int: 16 long: 32 long long: 64 char: 8 short: 16 int: 32 long: 32 long long: 64 char: 8 short: 16 int: 32 long: 64 long long: 64 char: 8 short: 16 int: 64 long: 64 long long: 64 or even: char: 8 short: 16 int: 32 long: 64 long long: 128 and that would still be compliant with C99, since it continues to meet the criteria about the required data types specified in the standard. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/