From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frank Rowand Subject: Re: [RFC PATCH 0/1] Portable Device Tree Connector -- conceptual Date: Mon, 4 Jul 2016 11:15:44 -0700 Message-ID: <577AA7D0.7050402@gmail.com> References: <1467503750-31703-1-git-send-email-frowand.list@gmail.com> <20160704152226.GJ6247@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160704152226.GJ6247@sirena.org.uk> Sender: linux-i2c-owner@vger.kernel.org To: Mark Brown 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 List-Id: devicetree@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