From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wr-out-0506.google.com (wr-out-0506.google.com [64.233.184.225]) by ozlabs.org (Postfix) with ESMTP id D7407DDE16 for ; Tue, 27 Nov 2007 03:40:37 +1100 (EST) Received: by wr-out-0506.google.com with SMTP id 68so537055wri for ; Mon, 26 Nov 2007 08:40:36 -0800 (PST) Message-ID: Date: Mon, 26 Nov 2007 09:30:35 -0700 From: "Grant Likely" Sender: glikely@secretlab.ca To: "Koss, Mike (Mission Systems)" Subject: Re: Xilinx devicetrees In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <47480CF0.7090105@dlasys.net> <47493D4F.4070605@dlasys.net> <4749FD5E.7000408@dlasys.net> <20071125235855.95B9999804D@mail138-cpk.bigfish.com> Cc: Stephen Neuendorffer , linuxppc-embedded List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 11/26/07, Koss, Mike (Mission Systems) wrote: > DL> And once again a plea to ALWAYS make version/capabilities registers > DL> atleast an optional part of every design. > DL> Embeddeding a device tree into a design might be fairly expensive. a > DL> pair of read only 32 bit registers is damn near free - basically the > DL> FPGA equivalent of atmost 64 diodes or resistors. > > SN> Actually, device trees actually seem to be cheaper (in the whole system > sense) than such registers. Unless there is something I don't understand? > > The issue here is that the hardware changed and the driver doesn't support > it. I think this would be fixed by having information passed to the driver > in the platform_device struct to specify information, since its not able to > be discerned by the physical hardware information: version registers, etc. This is exactly the information that should be encoded in the 'compatible' property of the device tree. (instead of platform_data; platform_data is no longer required with the of_platform bus binding) *If* edk is generating our device tree(s) for us, *then* version registers are not needed by Linux. Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. grant.likely@secretlab.ca (403) 399-0195