From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261763AbVFGARZ (ORCPT ); Mon, 6 Jun 2005 20:17:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261788AbVFGAOs (ORCPT ); Mon, 6 Jun 2005 20:14:48 -0400 Received: from mail.dvmed.net ([216.237.124.58]:54474 "EHLO mail.dvmed.net") by vger.kernel.org with ESMTP id S261763AbVFFXyE (ORCPT ); Mon, 6 Jun 2005 19:54:04 -0400 Message-ID: <42A4E213.8050102@pobox.com> Date: Mon, 06 Jun 2005 19:53:55 -0400 From: Jeff Garzik User-Agent: Mozilla Thunderbird 1.0.2-6 (X11/20050513) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Greg KH CC: "David S. Miller" , 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? References: <20050603224551.GA10014@kroah.com> <20050605.124612.63111065.davem@davemloft.net> <20050606225548.GA11184@suse.de> <42A4D771.7080400@pobox.com> <20050606231325.GA11610@suse.de> In-Reply-To: <20050606231325.GA11610@suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Greg KH wrote: > On Mon, Jun 06, 2005 at 07:08:33PM -0400, Jeff Garzik wrote: > >>Greg KH wrote: >> >>>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 >> >>It matters. >> >>Not only the differences DaveM mentioned, but also simply that you may >>assume your interrupt is not shared with anyone else. > > > Ok, and again, how would the call, pci_in_msi_mode(struct pci_dev *dev) > not allow for the driver to determine this? Let me see if I understand this correctly :) A technology (MSI) allows one to more efficiently call interrupt handlers, with fewer bus reads... and you want to add a test to each interrupt handler -- a test which adds several bus reads to the hot path of every MSI driver? We want to -decrease- the overhead involved with an interrupt, but pci_in_msi_mode() increases it. Jeff