From owner-freebsd-arch@FreeBSD.ORG Thu Sep 11 01:46:06 2003 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4191116A4BF; Thu, 11 Sep 2003 01:46:06 -0700 (PDT) Received: from herring.nlsystems.com (mailgate.nlsystems.com [80.177.232.242]) by mx1.FreeBSD.org (Postfix) with ESMTP id 288AD43FF7; Thu, 11 Sep 2003 01:46:00 -0700 (PDT) (envelope-from dfr@nlsystems.com) Received: from [10.0.0.2] (herring.nlsystems.com [10.0.0.2]) by herring.nlsystems.com (8.12.9/8.12.8) with ESMTP id h8B8Tfgs059465; Thu, 11 Sep 2003 09:29:41 +0100 (BST) (envelope-from dfr@nlsystems.com) From: Doug Rabson To: John Baldwin In-Reply-To: References: Content-Type: text/plain Message-Id: <1063268981.55877.9.camel@herring.nlsystems.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.0 Date: 11 Sep 2003 09:29:41 +0100 Content-Transfer-Encoding: 7bit X-Spam-Status: No, hits=-4.9 required=5.0 tests=EMAIL_ATTRIBUTION,IN_REP_TO,QUOTED_EMAIL_TEXT,REFERENCES, REPLY_WITH_QUOTES,USER_AGENT_XIMIAN version=2.55 X-Spam-Checker-Version: SpamAssassin 2.55 (1.174.2.19-2003-05-19-exp) cc: arch@FreeBSD.org Subject: RE: When to burn those bridges X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Sep 2003 08:46:06 -0000 On Wed, 2003-09-10 at 23:39, John Baldwin wrote: > On 10-Sep-2003 Doug Rabson wrote: > > > > My feeling about that was always that the hostb driver provides > > absolutely no added value in the system. When I was developing agp > > originally, I just nuked it and kldloading agp.ko worked just fine. > > I don't mind if hostb were to die, but it does serve somewhat of a > purpose. A dummy vga driver might also be useful with Warner's PCI > power management stuff as well. A long time ago, I was thinking about a scheme where newbus would detach a driver which had attached to a device at a very low priority if a new driver was added via kldload. The way it might work is that a 'placeholder' driver like hostb would mark the device with a flag, e.g. device_set_placeholder. When a new driver is loaded, devices set as placeholders would be re-probed in bus_generic_driver_added as well as devices with no drivers at all. If the new driver probed with a higher value than the current placeholder driver, in device_probe_and_attach, the old driver would be detached and the new one attached.