Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965537Ab3E2J6t (ORCPT ); Wed, 29 May 2013 05:58:49 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:45816 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965205Ab3E2J6p (ORCPT ); Wed, 29 May 2013 05:58:45 -0400 From: "Mohammed, Afzal" To: "Cousson, Benoit" CC: Stephen Warren , Jon Hunter , Russell King , "linux-doc@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , Rob Herring , "Grant Likely" , Benoit Cousson , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: RE: [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer Thread-Topic: [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer Thread-Index: AQHOWufOwwwB7s/tqE2Htmmr900F0pkal7yAgAALLwCAAST2AP//jDYAgACKqgA= Date: Wed, 29 May 2013 09:58:06 +0000 Message-ID: References: <223d90dc9eeab13d8496690d336cdf0f7d27cd22.1369658705.git.afzal@ti.com> <51A520B5.8040803@gmail.com> <51A52A16.1040204@wwwdotorg.org> <51A5BEB6.6070809@ti.com> In-Reply-To: <51A5BEB6.6070809@ti.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.24.170.142] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id r4T9wult008466 Content-Length: 3357 Lines: 69 Hi Benoit, On Wed, May 29, 2013 at 14:09:18, Cousson, Benoit wrote: > On 05/29/2013 10:06 AM, Mohammed, Afzal wrote: > > On Wed, May 29, 2013 at 03:35:10, Stephen Warren wrote: > >> On 05/28/2013 03:25 PM, Jon Hunter wrote: > >>> If you are adding more compatibility strings, then this implies that the > >>> AM43x timers are not 100% compatible with any other device listed (such > >>> as am335x or any omap device). That's fine but you should state that in > >>> the changelog. If the AM43x timer registers are 100% compatible with > >>> existing devices you should not add these. > >> > >> I'm not sure that's true; .dts files should always include a compatible > >> value that describes the most specific model of the HW, plus any > >> baseline compatible value that the HW is compatible with. This allows > >> any required quirks/fixes/... to be applied for the specific HW model > >> later even if nobody knows right now they'll be needed. Hence, defining > >> new compatible values doesn't necessarily mean incompatible HW. > > > > Stephen took words out of my finger ;) > > > > Some explanations,I don;t > > > > 1. first compatible should be exact device [A], followed by compatible > > model (if one) > > 2. Minor effort in getting DT right the first time may help prevent > > difficult effort later modifying it (if a necessity comes), considering > > the fact that DT sources has to move out of Kernel at some point of > > time. And DT is not supposed to be modified, which may cause difficulty > > for the users (I had been a minor victim of this during rebase). > > > > As we both were in GPMC land earlier, an example, > > > > If my memory is right, GPMC IP in am335x is rev 6, and IP has 8 chip > > select, but one is not pinned out. Now assume that same IP is integrated > > in another SoC (probably OMAP4 has rev 6). Here if we use same compatible > > for both, driver cannot handle it properly (w/o knowledge about platform). > > But if exact compatible is mentioned, without modifying DT (which should > > be considered as a firmware) just by modifying Kernel, deciding based on > > compatible would help achieve what is required. > > That's true for the DTS itself, but here your are changing the binding > documentation which is supposed to reflect the driver "interface" in the > Device Tree model description. > > Since the driver does not support any new compatible string, you should > not update the binding. I have a different opinion: Binding documentation is to be considered an entity that is not a part of the Kernel, but currently is a part of the Kernel for want of a better place. And binding is to be considered OS agnostic being ignorant of any piece of software (driver here). Binding has the authority to allow its usage in DT sources. > The driver and the binding will have to be changed the day you will have > to update the driver to handle a bug / feature specific to that revision > (ti,am4372-timer). > > Since this series does not seems to update the driver, you should not > update the bindings. I believe that updating binding is a prerequisite for making a new DTS change, hence binding was updated first, then DTS. Regards Afzal ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?