Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762382AbXEYUJe (ORCPT ); Fri, 25 May 2007 16:09:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753433AbXEYUJ1 (ORCPT ); Fri, 25 May 2007 16:09:27 -0400 Received: from mail1.webmaster.com ([216.152.64.169]:2552 "EHLO mail1.webmaster.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753048AbXEYUJ0 (ORCPT ); Fri, 25 May 2007 16:09:26 -0400 From: "David Schwartz" To: "Linux-Kernel@Vger. Kernel. Org" Subject: RE: [PATCH 1/2] msi: Invert the sense of the MSI enables. Date: Fri, 25 May 2007 13:09:31 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) In-Reply-To: Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Authenticated-Sender: joelkatz@webmaster.com X-Spam-Processed: mail1.webmaster.com, Fri, 25 May 2007 14:09:48 -0700 (not processed: message from trusted or authenticated source) X-MDRemoteIP: 206.171.168.138 X-Return-Path: davids@webmaster.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org Reply-To: davids@webmaster.com X-MDAV-Processed: mail1.webmaster.com, Fri, 25 May 2007 14:09:48 -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1758 Lines: 47 > Hmm... > I find in section 6.1: > > In addition to PCI INTx compatible interrupt emulation, PCI Express > > requires support of MSI or MSI-X or both. > Which suggests that INTx support is required. Unfortunately, this can be equally well read to suggest that MSI/MSI-X is not required, but that MSI/MSI-x is required in addition if you choose to support PCI INTx. Section 6.1 is ambiguous and you have to look elsewhere to figure out if PCI INTx is required or not. I think the most natural reading of this is that if you choose to support PCI INTx compatible interrupt emulation, PCI Express requires support of MSI or MSI-X or both in addition. However, other sections are not ambiguous: "For legacy compatibility, PCI Express provides a PCI INTx emulation mechanism to signal interrupts to the system interrupt controller (typically part of the Root Complex). This mechanism is compatible with existing PCI software, and provides the same level and type service as corresponding PCI interrupt signaling mechanism and is independent of system interrupt controller specifics. This legacy compatibility mechanism allows boot device support without requiring complex BIOS-level interrupt configuration/control service stacks. It virtualizes PCI physical interrupt signals by using an in-band signaling mechanism." This seems to make it pretty clear that if a device requires MSI/MSI-X, it is broken. Devices are supposed to work even with PCI drivers that are not smart enough to support MSI/MSI-X. DS - 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/