From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 8 Jan 2003 15:32:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 8 Jan 2003 15:32:17 -0500 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:45067 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Wed, 8 Jan 2003 15:32:13 -0500 Message-ID: <3E1C8CD2.4070402@zytor.com> Date: Wed, 08 Jan 2003 12:40:50 -0800 From: "H. Peter Anvin" Organization: Zytor Communications User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020828 X-Accept-Language: en, sv MIME-Version: 1.0 To: "Nakajima, Jun" CC: linux-kernel@vger.kernel.org Subject: Re: PCI code: why need outb (0x01, 0xCFB); ? References: <3014AAAC8E0930438FD38EBF6DCEB5647D0D1C@fmsmsx407.fm.intel.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nakajima, Jun wrote: > > Normally all accesses should be long (0xcf8/0xcfc) but x86 is byte addresseable and some chipsets do support byte accesses. > We do not encourage use of byte accesses as it will not be supported in future platforms. > The PCI standard is quite explicit: byte accesses are permitted to the data window (0xCFC) and not permitted to the address window (0xCF8). Accepting byte accesses to the address window, or not supporting byte accesses to the data window, *will* result in breakage (I can attest to this fact quite well.) -hpa