From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760024AbYGQPrX (ORCPT ); Thu, 17 Jul 2008 11:47:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754793AbYGQPrP (ORCPT ); Thu, 17 Jul 2008 11:47:15 -0400 Received: from wa-out-1112.google.com ([209.85.146.182]:62508 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754603AbYGQPrO convert rfc822-to-8bit (ORCPT ); Thu, 17 Jul 2008 11:47:14 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=WwSy5s21XCE+dV8hh2Lku/V7RSgDsFLIETjdTj7ce/pRYFioDuAzz2xSUUBC83dOdD TY9DTXeiFgCvTrs9hyO0cNnpffHblkKE/56WFwaklACjvEK+izlEoSbiUzYJIuotqeD7 1eAhGV+gMd/mjMTF/Jsz9rHuOwYAL7P/ipcK8= Message-ID: Date: Thu, 17 Jul 2008 16:47:13 +0100 From: "Robert Lougher" To: "Geert Uytterhoeven" Subject: Re: [Squashfs-devel] Squashfs mainlining status? Cc: "Peter Korsgaard" , "Phillip Lougher" , squashfs-devel@lists.sourceforge.net, "Linux Kernel Development" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline References: <48460906.2080205@lougher.demon.co.uk> <87od6h7d7l.fsf@macbook.be.48ers.dk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 17, 2008 at 4:35 PM, Geert Uytterhoeven wrote: > Hi Peter, > > On Wed, 4 Jun 2008, Peter Korsgaard wrote: >> >>>>> "Phillip" == Phillip Lougher writes: >> Phillip> The major work of course is the move to a little endian >> Phillip> layout without any bit fields in the structures to make it >> Phillip> easier to swap member fields on big-endian architectures. >> Phillip> I'm currently working on this on a non-CVS branch. >> Phillip> Most of the work till now has been without any attempt to >> Phillip> retain backwards compatibility with the current 3.3 >> Phillip> little-endian filesystem layout. After your private email >> Phillip> regarding retaining backwards compatibility I will look >> Phillip> again at this issue, it may well be that I will abandon my >> Phillip> current layout changes that I have so far made. >> >> What private mail? Anything of interest to the rest of the group? As I > > Oops, I've just returned from holidays, and realize I never actually responded > to this question. So here is the gist of it: > > | I had a closer look at the structures and bitfields, and I still think it's > | possible to stay compatible with the current little endian layout: > | 1. About half of the bitfields are actually bytes or 16-bit words. Hence > | these can easily be converted to __u8 or __le16. > | 2. Most of the remaining bitfields sit in an 8, 16, or 32 bit integer. > | Hence these can be converted to such an integer (or an array of bytes, > | cfr. 3 below), and accessed using get_unaligned_le{16,32}() and a > | shift/mask operation. > | 3. There are a few bitfields that sit in an `odd' number of bytes. These > | can be converted to an array of bytes, and accessed using > | get_unaligned_le{16,32}() and a shift/mask operation. > | 4. The integral fields in the structs should be accessed using > | get_unaligned_le{8,16,32}(), too. > > I noticed the squashfs CVS repository is getting a new (incompatible) 4.0 > layout now? > > What do people think? > Last time I looked you were not the maintainer of squashfs. Phillip spent a long time examining the possibility of maintaining compatibility but decided asthat there were sufficient advantages in a new layout to warrant the change. Rob. > With kind regards, > > Geert Uytterhoeven > Software Architect > > Sony Techsoft Centre Europe > The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium > > Phone: +32 (0)2 700 8453 > Fax: +32 (0)2 700 8622 > E-mail: Geert.Uytterhoeven@eu.sony.com > Internet: http://www.sony-europe.com/ > > A division of Sony Europe (Belgium) N.V. > VAT BE 0413.825.160 · RPR Brussels > Fortis 293-0376800-10 GEBA-BE-BB > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Squashfs-devel mailing list > Squashfs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/squashfs-devel > >