From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753687AbcEZK6d (ORCPT ); Thu, 26 May 2016 06:58:33 -0400 Received: from 37-46-169-123.customers.ownit.se ([37.46.169.123]:43067 "EHLO zoo.weinigel.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751431AbcEZK6b (ORCPT ); Thu, 26 May 2016 06:58:31 -0400 Subject: Re: [PATCH] devicetree - document using aliases to set spi bus number. To: Mark Brown References: <20160524172045.GN8206@sirena.org.uk> <57449784.4070108@weinigel.se> <20160524183256.GP8206@sirena.org.uk> <5744E51A.1040506@gmail.com> <20160525174932.GA10753@rob-hp-laptop> <5745E9B6.5090204@gmail.com> <20160525184442.GE8206@sirena.org.uk> <57464D0A.1030706@weinigel.se> <574657BB.6070300@weinigel.se> <20160526100753.GB16172@sirena.org.uk> Cc: Rob Herring , Frank Rowand , "linux-kernel@vger.kernel.org" , "linux-spi@vger.kernel.org" , "devicetree@vger.kernel.org" From: Christer Weinigel X-Enigmail-Draft-Status: N1110 Message-ID: <5746D6CE.5020605@weinigel.se> Date: Thu, 26 May 2016 12:58:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <20160526100753.GB16172@sirena.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/26/2016 12:07 PM, Mark Brown wrote: > I think Rob's referring to the fact that there are no in tree DTs > that use this feature - all the aliases for SPI controllers in > mainline are string based. One of the main drivers behind devicetree was that Linus got fed up with the churn for all platform device changes in arch/arm. I faintly recall him writing that he would be rather unhappy if that just got replaced with churn for devicetree dts files. It makes sense to include dts files for reference boards in the mainline kernel. To include dts files for every vendors variant of a design would add just as much churn and be rather pointless. My guess is that the dts file for most platforms are kept private. For platforms based on a FPGA such as the Xilinx Zync it's even more pointless to submit dts files to mainline. When you have "hardware" that can be reconfigured the device tree files can't be set in stone. If I use Xilinx tools [1] to add one more UART I have just added new hardware this needs to be reflected in the devicetree for the devices to be usable in Linux. And something like aliases which provides a stable device name can be very useful here. /Christer [1] http://www.wiki.xilinx.com/Build+Device+Tree+Blob