Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758951Ab3GZNlU (ORCPT ); Fri, 26 Jul 2013 09:41:20 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39219 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755189Ab3GZNlR (ORCPT ); Fri, 26 Jul 2013 09:41:17 -0400 Message-ID: <1374846070.14574.92.camel@i7.infradead.org> Subject: Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?] From: David Woodhouse To: Jason Cooper Cc: Richard Cochran , Mark Rutland , "devicetree@vger.kernel.org" , "ksummit-2013-discuss@lists.linuxfoundation.org" , Russell King - ARM Linux , Ian Campbell , Pawel Moll , Stephen Warren , Domenico Andreoli , "rob.herring@calxeda.com" , "linux-kernel@vger.kernel.org" , Jason Gunthorpe , Dave P Martin , "linux-arm-kernel@lists.infradead.org" Date: Fri, 26 Jul 2013 14:41:10 +0100 In-Reply-To: <20130726132709.GH29916@titan.lakedaemon.net> References: <20130725175702.GC22291@e106331-lin.cambridge.arm.com> <51F168FC.9070906@wwwdotorg.org> <20130725182920.GA24955@e106331-lin.cambridge.arm.com> <20130725184834.GA8296@netboy> <20130725213753.GC17616@obsidianresearch.com> <20130726080115.GA5436@netboy> <1374831744.2923.42.camel@shinybook.infradead.org> <20130726130927.GC4219@netboy> <20130726132709.GH29916@titan.lakedaemon.net> Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-mfZdylPhIVoL/a2UuclL" X-Mailer: Evolution 3.8.3 (3.8.3-2.fc19) Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by merlin.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9396 Lines: 147 --=-mfZdylPhIVoL/a2UuclL Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2013-07-26 at 09:27 -0400, Jason Cooper wrote: >=20 > The other dynamic change that bears mentioning here is attributes which > have been configured by the bootloader. For example, in mvebu, we have > the Schrodinger's Cat register. It allows you to reconfigure the base > address of the registers from *within* that register range. If the > bootloader does this, the DT needs to be updated to reflect the current > hardware configuration. Otherwise, the kernel is stuck poking around at > memory addresses hoping to find something sane. >=20 > But this falls into the same category as you mentioned, but outside of > chosen {};. Yeah, /chosen was given as an example of stuff that's almost *exclusively* "configuration" stuff. But there's plenty outside there that can reasonably change. It's OK to change the data, and of *course* the base address reported in the DT should actually match reality *today*, if it changes on the fly. It's not OK to change the *schema* in which those data are expressed. 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