From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LXSm0-00078S-E0 for qemu-devel@nongnu.org; Wed, 11 Feb 2009 23:02:00 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LXSlx-00078G-U6 for qemu-devel@nongnu.org; Wed, 11 Feb 2009 23:01:59 -0500 Received: from [199.232.76.173] (port=41964 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LXSlx-00078D-OJ for qemu-devel@nongnu.org; Wed, 11 Feb 2009 23:01:57 -0500 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:57017) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LXSlw-0004fw-M4 for qemu-devel@nongnu.org; Wed, 11 Feb 2009 23:01:57 -0500 Received: from d23relay02.au.ibm.com (d23relay02.au.ibm.com [202.81.31.244]) by e23smtp08.au.ibm.com (8.13.1/8.13.1) with ESMTP id n1C41nlt006852 for ; Thu, 12 Feb 2009 15:01:49 +1100 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay02.au.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id n1C427U5954452 for ; Thu, 12 Feb 2009 15:02:07 +1100 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n1C41nKZ020735 for ; Thu, 12 Feb 2009 15:01:49 +1100 Date: Thu, 12 Feb 2009 15:01:38 +1100 From: David Gibson Subject: Re: [Qemu-devel] [RFC] Machine description as data Message-ID: <20090212040138.GD31142@yookeroo.seuss> References: <87iqnh6kyv.fsf@pike.pond.sub.org> <1234378228.28751.79.camel@slate.austin.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1234378228.28751.79.camel@slate.austin.ibm.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hollis Blanchard Cc: devicetree-discuss@ozlabs.org, qemu-devel@nongnu.org On Wed, Feb 11, 2009 at 12:50:28PM -0600, Hollis Blanchard wrote: > On Wed, 2009-02-11 at 16:40 +0100, Markus Armbruster wrote: [snip] > > I briefly examined the DT source format and the tree structure it > > describes for the purpose of QEMU configuration. I decided against > > using it in my prototype because I found it awfully low-level and > > verbose for that purpose (I'm sure it serves the purpose it was designed > > for just fine). Issues include: > > > > * Since the DT is designed for booting kernels, not configuring QEMU, > > there's information that has no place in QEMU configuration, and > > required QEMU configuration isn't there. > > What's needed is a "binding" in IEEE1275-speak: a document that > describes qemu-specific nodes/properties and how they are to be > interpreted. > > As an example, you could require that block devices contain properties > named "qemu,path", "qemu,backend", etc. Yes, it shouldn't be hard to annotate an IEEE1275 style tree with extra information for qemu's use. As for the other direction, in some cases it may be appropriate for qemu's device tree code to fill in missing device tree properties, based on what the device emulation code knows about itself. > > * Redundancy between node name and its device_type property. Note that "device_type" may not mean what you think. It describes what methods the device support within the OF client interface. New device trees that aren't linked to a full OF implementation with client interface should generally omit device_type in most places (there are a few special cases for compatibility with OSes that expect device_type properties in certain places). > > * Property "reg", which encodes address ranges, does so in terms of > > "cells": #address-cells 32-bit words (big endian) for the address, > > followed by #size-cells words for the size, where #address-cells and > > #size-cells are properties of the enclosing bus. If this sounds > > like gibberish to you, well, that's my point. #address-cells and #size-cells takes a little getting used to, but it's really not that bad. It's just a way of representing the fact that different busses have different sized address encodings. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson