From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753505AbcGDSQA (ORCPT ); Mon, 4 Jul 2016 14:16:00 -0400 Received: from mail-pa0-f67.google.com ([209.85.220.67]:33911 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750713AbcGDSP4 (ORCPT ); Mon, 4 Jul 2016 14:15:56 -0400 Subject: Re: [RFC PATCH 0/1] Portable Device Tree Connector -- conceptual To: Mark Brown References: <1467503750-31703-1-git-send-email-frowand.list@gmail.com> <20160704152226.GJ6247@sirena.org.uk> Cc: robh+dt@kernel.org, david@gibson.dropbear.id.au, pantelis.antoniou@konsulko.com, stephen.boyd@linaro.org, grant.likely@secretlab.ca, mark.rutland@arm.com, mporter@konsulko.com, koen@dominion.thruhere.net, linux@roeck-us.net, marex@denx.de, wsa@the-dreams.de, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, panto@antoniou-consulting.com From: Frank Rowand Message-ID: <577AA7D0.7050402@gmail.com> Date: Mon, 4 Jul 2016 11:15:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20160704152226.GJ6247@sirena.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/16 08:22, Mark Brown wrote: > On Sat, Jul 02, 2016 at 04:55:49PM -0700, frowand.list@gmail.com wrote: > >> This is an extremely simple example to illustrate the concepts. It is not >> meant to represent the complexity of a real board. >> >> To start with, assume that the device that will eventually be on a daughter >> board is first soldered onto the mother board. The mother board contains >> two devices connected via bus spi_1. One device is described in the .dts >> file, the other is described in an included .dtsi file. >> Then the device tree files will look like: > > Can I suggest not using SPI as an example here? It's particularly > messy since addresses are essentially just a random signal that can be > totally separate to the controller hardware which might be adding more > complexity early on in building up your model than is really desirable. > It will need to be dealt with but perhaps not right now. I2C might be > easier. > > The initial issue with SPI is that you really need to do something like > bring out individual slots on the bus rather than the bus as a whole > since you're going to need a remapping layer to map chip selects on the > module to chip selects on the host board. > Yes, thank you for pointing that out. For the purposes of the mental model, when thinking about what I wrote, just change SPI to I2C everywhere. -Frank