Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030282AbWILQrz (ORCPT ); Tue, 12 Sep 2006 12:47:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030284AbWILQrz (ORCPT ); Tue, 12 Sep 2006 12:47:55 -0400 Received: from mail-in-01.arcor-online.net ([151.189.21.41]:63427 "EHLO mail-in-01.arcor-online.net") by vger.kernel.org with ESMTP id S1030282AbWILQry (ORCPT ); Tue, 12 Sep 2006 12:47:54 -0400 In-Reply-To: <1158022147.15465.29.camel@localhost.localdomain> References: <20060911.062144.74719116.davem@davemloft.net> <8DA3BCBF-0F19-4CF0-B22E-91E57E7CB033@kernel.crashing.org> <20060911.173208.74750403.davem@davemloft.net> <1158022147.15465.29.camel@localhost.localdomain> Mime-Version: 1.0 (Apple Message framework v750) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <5488ABE0-92BB-4DCA-9D31-1928B8432D68@kernel.crashing.org> Cc: David Miller , jbarnes@virtuousgeek.org, jeff@garzik.org, paulus@samba.org, torvalds@osdl.org, linux-kernel@vger.kernel.org, akpm@osdl.org Content-Transfer-Encoding: 7bit From: Segher Boessenkool Subject: Re: Opinion on ordering of writel vs. stores to RAM Date: Tue, 12 Sep 2006 18:47:29 +0200 To: Benjamin Herrenschmidt X-Mailer: Apple Mail (2.750) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1088 Lines: 27 > As Paulus also pointed out, having writel() behave differently > based on > some magic done earlier at map time makes it harder to understand what > happens when reading the code, and thus harder to audit drivers for > missing barriers etc... since it's not obvious at first sight wether a > driver is using ordered or relaxed semantics. I do not buy this argument because I do not believe you can "audit" a driver at "first sight". You'll have to look at the mapping call anyway, something might be wrong there (playing evil __ioremap() tricks, mapping the wrong size, whatever). I do see your point, I don't believe the ramifications are as severe as you make them to be though, esp. when compared to all the (readability, auditing!) problems that having more different interfaces for basically the same thing will bring us. Segher - 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/