Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757494Ab1FUUmG (ORCPT ); Tue, 21 Jun 2011 16:42:06 -0400 Received: from relais.videotron.ca ([24.201.245.36]:53938 "EHLO relais.videotron.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753791Ab1FUUmB (ORCPT ); Tue, 21 Jun 2011 16:42:01 -0400 MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: TEXT/PLAIN; charset=US-ASCII Date: Tue, 21 Jun 2011 16:41:59 -0400 (EDT) From: Nicolas Pitre X-X-Sender: nico@xanadu.home To: Alan Stern Cc: Alexander Holler , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-usb@vger.kernel.org, gregkh@suse.de, lkml , Rabin Vincent Subject: Re: [PATCH] USB: ehci: use packed,aligned(4) instead of removing the packed attribute In-reply-to: Message-id: References: User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1700 Lines: 43 On Tue, 21 Jun 2011, Alan Stern wrote: > On Mon, 20 Jun 2011, Nicolas Pitre wrote: > > > > We don't fall into any of these cases, and therefore as you say, we > > > don't need packed. Arnd and I have both explained this. So why do you > > > keep arguing that we do need it? > > > > Please show me where I keep arguing that you need it? > > Not explicitly perhaps. But you did write: > > > Doesn't mean that because it used to work that it is strictly correct. > > Wouldn't be the first time that a GCC upgrade broke the kernel because > > the kernel wasn't describing things properly enough. > > which strongly implies that "packed" is needed. You also wrote: In this case ... > > Yes, but that's a consequence of not being able to access those fields > > in their naturally aligned position anymore. Hence the addition of the > > align attribute to tell the compiler that we know that the structure is > > still aligned to a certain degree letting the compiler to avoid > > byte-oriented instructions when possible. > > which is predicated on the assumption that "packed" is needed. ... and also in this case, I was talking about proper use of the packed attribute in general, not at all about a specific case. I wanted to provide a broader view to some people who expressed doubts and misunderstanding in the hope that the archive could keep this knowledge base available. I apologize if that wasn't clear to you. Nicolas -- 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/