From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 17 Nov 2000 20:50:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 17 Nov 2000 20:50:18 -0500 Received: from cp912944-a.mtgmry1.md.home.com ([24.18.149.178]:40839 "EHLO zalem.puupuu.org") by vger.kernel.org with ESMTP id ; Fri, 17 Nov 2000 20:50:10 -0500 Date: Fri, 17 Nov 2000 20:20:09 -0500 From: Olivier Galibert To: linux-kernel@vger.kernel.org Subject: Re: VGA PCI IO port reservations Message-ID: <20001117202009.B2472@zalem.puupuu.org> Mail-Followup-To: linux-kernel@vger.kernel.org In-Reply-To: <200011172002.UAA01918@raistlin.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i In-Reply-To: ; from root@chaos.analogic.com on Fri, Nov 17, 2000 at 03:27:28PM -0500 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 17, 2000 at 03:27:28PM -0500, Richard B. Johnson wrote: > Then, you read the port as a WORD (16 bits). If nothing responds, > you get the value of 0xffff. If somebody is responding, you will > read something if it's enabled for writes by devices (reads by the CPU). What guarantees you that: 1- No device will respond 0xffff for an address it decodes 2- No device will crap up on you simply because you've read one particular address If any of these if true for any device out there (I think I have one in my computer that does the 1/ part in some cases), your code is unsafe. OG. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/