From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755699Ab1LVSLb (ORCPT ); Thu, 22 Dec 2011 13:11:31 -0500 Received: from cantor2.suse.de ([195.135.220.15]:39459 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753459Ab1LVSL2 (ORCPT ); Thu, 22 Dec 2011 13:11:28 -0500 Date: Thu, 22 Dec 2011 10:10:52 -0800 From: Greg KH To: "Moffett, Kyle D" , Magnus Damm Cc: "linux-kernel@vger.kernel.org" , Grant Likely , Rob Herring , Benjamin Herrenschmidt Subject: Re: Driver core support for early platform devices Message-ID: <20111222181052.GA30259@suse.de> References: <0282FD61-7E73-45CE-8EC8-32BF411C7619@boeing.com> <20111222174521.GA29144@suse.de> <99F3E881-FB9E-4D49-9A91-793FDD04795D@boeing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <99F3E881-FB9E-4D49-9A91-793FDD04795D@boeing.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 22, 2011 at 11:55:56AM -0600, Moffett, Kyle D wrote: > On Dec 22, 2011, at 12:45, Greg KH wrote: > > On Thu, Dec 22, 2011 at 11:15:06AM -0600, Moffett, Kyle D wrote: > >> Hi, > >> > >> I'm tinkering with some improvements to the way that OpenPIC/MPIC are > >> detected and loaded on PowerPC platforms, and it seems like I am trying > >> to use the driver model before it is fully initialized. > >> > >> In particular, it seems like it should be possible to simply declare an > >> OpenPIC in the device-tree and have it automatically bound to a platform > >> driver declaring the right OpenFirmware match strings. > >> > >> Unfortunately, it needs to be bound by init_IRQ() time, while the driver > >> model does not get initialized until much later (after the scheduler is > >> up and running). > >> > >> As far as I can tell, there seem to be 2 possible approaches to making > >> that possible: > >> > >> (1) Split the driver-model initialization into "early" and "late" phases > >> so that drivers can be registered and devices probed very early on > >> and then replay the necessary scheduler-dependent things after the > >> system is mostly started up (IE: devtmpfs, etc). > > > > We already have that today with the "early_platform*" functions, right? > > Will those work for you, or do you need this for a bus you are creating > > and not using the platform bus? > > Well, I can't figure out how "early_platform" is actually supposed to > integrate with the platform bus itself. It seems designed mostly for > drivers like "earlyprintk" et. al. for which loading is controlled by > a kernel parameter. > > Specifically, I don't see any "early_platform" logic to match devices in > the OF device-tree based on the driver "of_match" parameters, just based > on text strings in early_param(). > > Furthermore, if I register an "early_platform" device, it seems to get > unregistered when the normal driver model is brought up, instead of > being sucked in and promoted to a normal platform_device. That code is > pretty poorly documented and only used in a couple places right now, > though, so it's possible I am misreading it. I think Magnus wrote this code, as he was having the same issues you were, so he should be able to answer these questions better than I, as I do not know this code at all, sorry. greg k-h