From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261734AbVFFXdz (ORCPT ); Mon, 6 Jun 2005 19:33:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261269AbVFFXSo (ORCPT ); Mon, 6 Jun 2005 19:18:44 -0400 Received: from dsl027-180-168.sfo1.dsl.speakeasy.net ([216.27.180.168]:56790 "EHLO sunset.davemloft.net") by vger.kernel.org with ESMTP id S261720AbVFFXAN (ORCPT ); Mon, 6 Jun 2005 19:00:13 -0400 Date: Mon, 06 Jun 2005 15:59:54 -0700 (PDT) Message-Id: <20050606.155954.59466251.davem@davemloft.net> To: gregkh@suse.de Cc: tom.l.nguyen@intel.com, linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org, roland@topspin.com Subject: Re: pci_enable_msi() for everyone? From: "David S. Miller" In-Reply-To: <20050606225548.GA11184@suse.de> References: <20050603224551.GA10014@kroah.com> <20050605.124612.63111065.davem@davemloft.net> <20050606225548.GA11184@suse.de> X-Mailer: Mew version 3.3 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 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 From: Greg KH Date: Mon, 6 Jun 2005 15:55:49 -0700 > Why would it matter? The driver shouldn't care if the interrupts come > in via the standard interrupt way, or through MSI, right? And if it > does, it could always use a function like the one I proposed to set up a > different irq handler. It matters because MSI totally changes the DMA vs. interrupt delivery guarentees. With MSI, you can be assured that any DMA sent from the device, before the interrupt, has reached global visibility before the MSI arrives at the cpu. There is no such guarentee with pre-MSI interrupt delivery. Drivers optimize this, so they have to know if MSI is being used or not.