From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from de01egw02.freescale.net (de01egw02.freescale.net [192.88.165.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "de01egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 3F045DDE1F for ; Fri, 18 May 2007 02:55:10 +1000 (EST) Message-ID: <464C871C.4090300@freescale.com> Date: Thu, 17 May 2007 11:47:24 -0500 From: Scott Wood MIME-Version: 1.0 To: Kumar Gala Subject: Re: [PATCH 3/5] powerpc: Document device nodes for I2C devices. References: <20070517143846.GC29795@ld0162-tx32.am.freescale.net> <464C800C.20400@freescale.com> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Cc: linuxppc-dev@ozlabs.org, i2c@lm-sensors.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Kumar Gala wrote: > On May 17, 2007, at 11:17 AM, Scott Wood wrote: >> Kumar Gala wrote: >>> As I've stated before, we need a bus number as well so we can >>> handle things like I2C switches and muxes. >> >> Is this something we handle now? If not, then it's really not within >> the scope of this patchset. If so, how am I breaking it? > > We don't handle i2c devices in the dev tree today. If you are going to > propose a solution it should work for all cases that people are aware > of even if linux doesn't support the functionality. But we do handle i2c *controllers* in the device tree, and that's where a bus number property would go. Given that we don't have a binding for non-toplevel i2c buses, and I'm not adding one, I don't see the relevance. Note that adding a bus number property makes zero sense for toplevel buses, as at that level the bus number is just a fiction maintained by Linux for user API and device preregistration purposes. It's not a matter of the binding only covering some cases; it's a matter of the binding being for one thing (i2c devices) and not another (multiplexed i2c buses). > If only some subset of cases are handled what good is the device tree > to a user? They will just have to figure out if their usage is > supported or not and if not find some other solution that works for them. ...just as they'll have to figure out if a binding exists for device type $FOO. -Scott