Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762444AbWLJW7Y (ORCPT ); Sun, 10 Dec 2006 17:59:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762424AbWLJW7Y (ORCPT ); Sun, 10 Dec 2006 17:59:24 -0500 Received: from einhorn.in-berlin.de ([192.109.42.8]:47769 "EHLO einhorn.in-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762384AbWLJW7X (ORCPT ); Sun, 10 Dec 2006 17:59:23 -0500 X-Envelope-From: stefanr@s5r6.in-berlin.de Message-ID: <457C913A.20600@s5r6.in-berlin.de> Date: Sun, 10 Dec 2006 23:59:06 +0100 From: Stefan Richter User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061202 SeaMonkey/1.0.6 MIME-Version: 1.0 To: =?ISO-8859-1?Q?Kristian_H=F8gsberg?= CC: Jeff Garzik , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] Import fw-ohci driver. References: <20061205052229.7213.38194.stgit@dinky.boston.redhat.com> <20061205052245.7213.39098.stgit@dinky.boston.redhat.com> <45750A89.7000802@garzik.org> <457A1A93.5090707@redhat.com> <457A663A.5080308@s5r6.in-berlin.de> <457C8075.4030000@redhat.com> In-Reply-To: <457C8075.4030000@redhat.com> X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1360 Lines: 32 Kristian H?gsberg wrote: > Stefan Richter wrote: >> Kristian H?gsberg wrote: >>> Yup, I've done away with the bitfields and switched to a mix of __le16 >>> and __le32 struct fields. >> >> I suppose the struct should get __attribute__((packed)) then. > > I guess it wouldn't harm, but is it really necessary? Would gcc ever > insert padding here, all the 32 bit fields a 32 bit aligned, and so are > the 16 bit fields. Is 2-byte alignment of 16bit struct members guaranteed on all platforms? A related question: If I specify a struct which, among else, contains 32bit quantities, then any variable of this struct type is supposed to be at least 4-byte-aligned. No if I specifiy this struct as packed, will variables of this type still be aligned on 4 byte boundaries or will the compiler assume no alignment? In other words, should it be __attribute__((packed,aligned(4))) then? I'm speaking about situations where I not only wish to avoid unnecessarily bad machine code due to unaligned access but where the device requires 4-byte alignment too. -- Stefan Richter -=====-=-==- ==-- -=-=- http://arcgraph.de/sr/ - 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/