Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932283AbWB1R55 (ORCPT ); Tue, 28 Feb 2006 12:57:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932293AbWB1R55 (ORCPT ); Tue, 28 Feb 2006 12:57:57 -0500 Received: from mx.pathscale.com ([64.160.42.68]:24532 "EHLO mx.pathscale.com") by vger.kernel.org with ESMTP id S932283AbWB1R54 (ORCPT ); Tue, 28 Feb 2006 12:57:56 -0500 Subject: Re: [PATCH] Define wc_wmb, a write barrier for PCI write combining From: "Bryan O'Sullivan" To: Jes Sorensen Cc: Andrew Morton , Andi Kleen , linux-kernel In-Reply-To: References: <1140841250.2587.33.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 28 Feb 2006 09:57:55 -0800 Message-Id: <1141149475.24103.18.camel@camp4.serpentine.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 701 Lines: 20 On Tue, 2006-02-28 at 05:01 -0500, Jes Sorensen wrote: > Could you explain why the current mmiowb() API won't suffice for this? > It seems that this is basically trying to achieve the same thing. It's a no-op on every arch I care about: #define mmiowb() Which makes it useless. Also, based on the comments in the qla driver, mmiowb() seems to have inter-CPU ordering semantics that I don't want. I'm thus hesitant to appropriate it for my needs.