From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ag-out-0708.google.com (ag-out-0708.google.com [72.14.246.247]) by ozlabs.org (Postfix) with ESMTP id 82F9ADDEEF for ; Tue, 8 Jul 2008 00:12:13 +1000 (EST) Received: by ag-out-0708.google.com with SMTP id 8so13122686agc.0 for ; Mon, 07 Jul 2008 07:12:12 -0700 (PDT) Message-ID: Date: Mon, 7 Jul 2008 08:12:11 -0600 From: "Grant Likely" Sender: glikely@secretlab.ca To: "Andre Schwarz" , "David Gibson" , "Segher Boessenkool" , "Benjamin Herrenschmidt" Subject: Re: [PATCH] Add MPC5200B base board mvBC-P In-Reply-To: <4871CA6E.9080805@matrix-vision.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <486E515B.80508@matrix-vision.de> <20080706235046.GA6267@yookeroo.seuss> <4871CA6E.9080805@matrix-vision.de> Cc: linux-ppc list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Jul 7, 2008 at 1:49 AM, Andre Schwarz wrote: > David, > > thanks - removed "device_type" from the DMA controller. > > Which nodes actually require "device_type" and which don't ? > > Is there some general rule ? Segher, David; In OF, what is the purpose of device_type? From what I understand right now, each value of device_type claims a software interface that the device supports. So for example, device_type = "serial" means that firmware supports using the device as a serial port, correct? So, similarly, if OF did not have a driver for the device, then the presence a device_type property would be a bug, right? Does device_type indicated any other information other than firmware driver interface? I had an epiphany about device_type this weekend (and by epiphany, I mean realizing my own stupidity). If I'm correct about the above questions, then that would mean it is *always* a bug to have a device_type property in .dts file because there is no firmware interface. So, it seems to me that we shouldn't just be eliminating undefined device_type values, but also eliminate the ones that are defined in OF because .dts users do not support the firmware driver interface. Am I correct? The only situation where I can see it being appropriate to specify device_type is to work around older bindings that are ambiguous with their other properties. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.