From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH RFC v2 3/5] spmi: add generic SPMI controller binding documentation Date: Fri, 23 Aug 2013 15:58:36 -0600 Message-ID: <5217DB0C.7000101@wwwdotorg.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from avon.wwwdotorg.org ([70.85.31.133]:33366 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754105Ab3HWV6l (ORCPT ); Fri, 23 Aug 2013 17:58:41 -0400 In-Reply-To: Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Josh Cartwright Cc: Grant Likely , Rob Herring , Greg Kroah-Hartman , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Sagar Dharia , Gilad Avidov , Michael Bohan , devicetree@vger.kernel.org On 08/22/2013 01:59 PM, Josh Cartwright wrote: > Signed-off-by: Josh Cartwright > --- > I'm introducing this as an RFC, because there are set of assumptions > made in this binding spec, that currently hold true for the supported > controller/addressing scheme for the Snapdragon 800 series, but don't > necessarily hold true for SPMI in general. > > 1. No use of Group Slave Identifiers (GSIDs) > (SPMI allows for a slave to belong to zero or more groups specified > by GSID, however this feature isn't currently implemented) > > 2. No specification of Master Identifier (MID) > (A "system integrator" allocates to each master a 2-bit MID, this > currently isn't being specified, as it isn't needed by software for > the PMIC Arb; not sure if this is of use to other SPMI controllers) > > 3. Single SPMI master per controller > > Effectively, only a subset of possible SPMI configurations are specified > in this document. > > So, if it's considered necessary to provide a generic SPMI binding > specification, is it acceptable to only define a subset at this time, > expanding only when necessary, or shall I expand the definition to at > least address 1 & 2, even though they are of no use in the current > implementation? It's best to define the whole thing from the start if possible. It's easier to ensure the whole binding is consistent, and nothing has been left out. However, it's probably OK to define a subset binding initially and then expand it later, as long as some thought it put into how it can be expanded in a way that is 100% compatible: old DTs will still operate with new kernels and perhaps even new DTs will still operate with old kernels. That said, if the thought is put in to ensure that's possible, it's probably just as easy to define the whole binding from the start.