Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754169AbXLWFEx (ORCPT ); Sun, 23 Dec 2007 00:04:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750835AbXLWFEq (ORCPT ); Sun, 23 Dec 2007 00:04:46 -0500 Received: from srv5.dvmed.net ([207.36.208.214]:48570 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750785AbXLWFEq (ORCPT ); Sun, 23 Dec 2007 00:04:46 -0500 Message-ID: <476DEC66.9050701@garzik.org> Date: Sun, 23 Dec 2007 00:04:38 -0500 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Linus Torvalds CC: Arjan van de Ven , linux-kernel@vger.kernel.org, gregkh@suse.de, linux-pci@atrey.karlin.mff.cuni.cz, Benjamin Herrenschmidt Subject: Re: [patch] Make MMCONFIG space (extended PCI config space) a driver opt-in issue References: <20071222043139.0cd59804@laptopd505.fenrus.org> <476D1D16.5090703@garzik.org> <20071222064719.73fdd9a4@laptopd505.fenrus.org> <476DB95F.3090801@garzik.org> <476DE07A.4000204@garzik.org> <476DE19F.5040702@garzik.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.1.9 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: 1542 Lines: 37 Linus Torvalds wrote: > I want to limit that downside. Right now, the easiest way to limit it > seems to be to say that those (very very few) drivers that actually care > could enable it. That way, we automatically limit it to only those > machines that have hardware that cares. Then let's do it right: disable mmconfig by default on x86, and enable it when passed "pci=mmconfig". For the rare -- you and I agree its very rare -- case where it is REQUIRED, the user can pass pci=mmconfig as instructed by driver documentation somewhere. Let's not bend over backwards and introduce an API for these presently-theoretical cases. Given the complete lack of hw vendor testing and potential to confuse userspace, the two choices for a computer should be "mmconfig off" or "mmconfig on." Kernel hackers developing drivers and code for new machines will know enough to pass pci=mmconfig if they NEED it. That practice will only become annoying when x86 hardware actually starts to NEED extended config space -- at which future time we can revisit, as you describe. > And yes, if you want the capability following to notice automatically when > capabilities really do go into the 0x100+ range, that's fine. I suspect Yes, we /must/ do this checking, if we don't already. 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/