From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id C39DFDDDF0 for ; Tue, 12 May 2009 08:29:29 +1000 (EST) Subject: Re: device trees. From: Benjamin Herrenschmidt To: "David H. Lynch Jr." In-Reply-To: <4A089AC8.9080704@dlasys.net> References: <4A0457BC.3040408@dlasys.net> <1242007203.7767.28.camel@concordia> <4A07C664.6040609@dlasys.net> <4A085612.9050602@dlasys.net> <4A089AC8.9080704@dlasys.net> Content-Type: text/plain Date: Tue, 12 May 2009 08:29:22 +1000 Message-Id: <1242080962.304.10.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2009-05-11 at 17:38 -0400, David H. Lynch Jr. wrote: > Not only is the device tree expected to pass static hardware > configuration information, but it is the sole means of passing > anything. > As an example Command lines are to be in the device tree. > Everything is supposed to be in the device tree, whether that > information is static or dynamic, whether it is hardware information, > or user choices. > > That means that whether you are in a Sun or Apple Desktop or a > system with the no flash and barely enough resources to run Linux, > you still may have to manipulate the device tree. To some extend, but the user choice information is well isolated, it's all in /chosen, so it's really only that node that needs to be modified or created from scratch by the bootloader. Thus, your bootloader can pick the right static dtb for a given bitfile, and then just use libfdt to generate the right /chosen node with other informations. Ben.