From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965046AbcEXSMV (ORCPT ); Tue, 24 May 2016 14:12:21 -0400 Received: from 37-46-169-123.customers.ownit.se ([37.46.169.123]:50372 "EHLO zoo.weinigel.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752702AbcEXSMQ (ORCPT ); Tue, 24 May 2016 14:12:16 -0400 X-Greylist: delayed 505 seconds by postgrey-1.27 at vger.kernel.org; Tue, 24 May 2016 14:12:15 EDT Subject: Re: [PATCH] devicetree - document using aliases to set spi bus number. To: Mark Brown References: <1464107960-10775-1-git-send-email-christer@weinigel.se> <20160524172045.GN8206@sirena.org.uk> Cc: linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, devicetree@vger.kernel.org From: Christer Weinigel X-Enigmail-Draft-Status: N1110 Message-ID: <57449784.4070108@weinigel.se> Date: Tue, 24 May 2016 20:03:48 +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: <20160524172045.GN8206@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 05/24/2016 07:20 PM, Mark Brown wrote: >> Not having used devicetree that much it was surprisingly hard to >> figure out how to assign a stable bus number to a spi bus. Add >> a simple example that shows how to do that. > > I'm not sure this is something we want to support at all, I can't > immediately see anything that does this deliberately in the SPI > code and obviously the "bus number" is something of a Linux > specific concept which would need some explanation if we were going > to document it. It's something I'm struggling a bit to see a > robust use case for that isn't better served by parsing sysfs, > what's the goal here? Well, that's how it works right now: commit bb29785e0d6d150181704be2efcc3141044625e2 Author: Grant Likely Date: Fri Dec 21 19:32:09 2012 +0000 spi/of: Use DT aliases for assigning bus number > + if ((master->bus_num < 0) && master->dev.of_node) + > master->bus_num = of_alias_get_id(master->dev.of_node, "spi"); If this isn't something that should be in the Documentation/devicetree because it's not generig enough, where should Linux-specific interpretations such as this be documented? /Christer