From owner-freebsd-hackers@FreeBSD.ORG Thu Aug 7 07:22:45 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4E74D37B401 for ; Thu, 7 Aug 2003 07:22:45 -0700 (PDT) Received: from mail.speakeasy.net (mail12.speakeasy.net [216.254.0.212]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9AA4E43F85 for ; Thu, 7 Aug 2003 07:22:44 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: (qmail 26870 invoked from network); 7 Aug 2003 14:22:43 -0000 Received: from unknown (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender )encrypted SMTP for ; 7 Aug 2003 14:22:43 -0000 Received: from laptop.baldwin.cx (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.12.9/8.12.9) with ESMTP id h77EMf9s031106; Thu, 7 Aug 2003 10:22:42 -0400 (EDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.5.4 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <20030806.192742.85412759.imp@bsdimp.com> Date: Thu, 07 Aug 2003 10:23:03 -0400 (EDT) From: John Baldwin To: "M. Warner Losh" cc: ticso@cicely12.cicely.de cc: freebsd-hackers@freebsd.org cc: phk@phk.freebsd.dk cc: ticso@cicely.de Subject: Re: How to get a device_t X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Aug 2003 14:22:45 -0000 On 07-Aug-2003 M. Warner Losh wrote: > In message: <20030807005810.GG35859@cicely12.cicely.de> > Bernd Walter writes: >: The host bridge is not available yet at probing time of the host bridge. >: What we have is the host bridges parent (nexus) in the calling function. >: Either we hand out the parents device_t to nexus_pcib_is_host_bridge, or >: we find it out later. > > Don't you mean legacy_pcib_is_host_bridge? That's where the matching > is done in current right now (well, at least as of my last sync) If > so, passing the host bridge's device down to it would be trivial to > add. It would also allow other CPUs with builtin host bridges to do > similar tricks to the one that is done for the ELAN. These sorts of > features have been very common in other CPU families, and there's no > reason to think that there won't be more of them in the x86 family as > time goes on. > > I'm not sure that adding it to nexus at this stage of the boot would > truly work. Since the legacy device has decided to attach, the nexus > bus is already walking through its children. Adding a child during > that walk strikes me as dangerous, since we have no locking on the > children element of the device_t. Hmmm, looks I just found a source > of problems in my newbus locking code that might explain some weird > things happening when I enable it.... Thanks for making me go look :-) You would add it to legacy, not nexus. What you probably really want to do is to write a host-PCI bridge driver that attaches to the actual PCI device like 'hostb' and 'agp' do that creates a suitable child bus for the MMCR stuff. This works for both ACPI and non-ACPI and doesn't require hacking the legacy_pcib stuff. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/