Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751362AbYAMGnq (ORCPT ); Sun, 13 Jan 2008 01:43:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750796AbYAMGni (ORCPT ); Sun, 13 Jan 2008 01:43:38 -0500 Received: from srv5.dvmed.net ([207.36.208.214]:51398 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbYAMGnh (ORCPT ); Sun, 13 Jan 2008 01:43:37 -0500 Message-ID: <4789B2F8.5010800@garzik.org> Date: Sun, 13 Jan 2008 01:43:04 -0500 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Matthew Wilcox CC: Arjan van de Ven , tcamuso@redhat.com, Ivan Kokshaysky , Greg KH , Linus Torvalds , Greg KH , linux-kernel@vger.kernel.org, linux-pci@atrey.karlin.mff.cuni.cz, Benjamin Herrenschmidt , Martin Mares , Loic Prylli , Prarit Bhargava , "Chumbalkar, Nagananda" , "Schoeller, Patrick (Linux - Houston, TX)" , Bhavana Nagendra Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in References: <20080111235856.GA16079@jurassic.park.msu.ru> <20080112002638.GA18710@kroah.com> <20080112144030.GA19279@jurassic.park.msu.ru> <20080112094557.71f5382a@laptopd505.fenrus.org> <20080112214911.GA20102@jurassic.park.msu.ru> <20080112150120.05f93768@laptopd505.fenrus.org> <47895767.3090503@redhat.com> <20080112164006.6f6f7bc2@laptopd505.fenrus.org> <47896B3B.2000108@redhat.com> <20080112204248.29abb1dd@laptopd505.fenrus.org> <20080113044748.GY18741@parisc-linux.org> In-Reply-To: <20080113044748.GY18741@parisc-linux.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.2.3 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 992 Lines: 24 Matthew Wilcox wrote: > On Sat, Jan 12, 2008 at 08:42:48PM -0800, Arjan van de Ven wrote: >> Wanne bet there'll be devices that screw this up? THere's devices that even screwed >> up the 64-256 region after all. > > I don't know if they 'screwed it up'. There are devices that misbehave > when registers are read from pci config space. But this was never > guaranteed to be a safe thing to do; it gradualy became clear that > people expected to be able to read random registers and manufacturers > responded accordingly, but I don't think you were ever guaranteed to be > able to peek at bits of config space arbitrarily. Quite correct... Reading registers can have all sorts of side effects, for example clearing chip conditions. Jeff -- 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/