Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752871AbbHTXxx (ORCPT ); Thu, 20 Aug 2015 19:53:53 -0400 Received: from mail-ig0-f170.google.com ([209.85.213.170]:33869 "EHLO mail-ig0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751699AbbHTXxv (ORCPT ); Thu, 20 Aug 2015 19:53:51 -0400 Date: Thu, 20 Aug 2015 18:53:41 -0500 From: Michael Welling To: Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Andrea Galbusera , linux-iio@vger.kernel.org, Peter Meerwald , Lars-Peter Clausen , Manfred Schlaegl , =?iso-8859-1?Q?S=F8ren?= Andersen , Jonathan Cameron , Hartmut Knaack Subject: Re: [PATCH 13/18] iio: adc: mcp320x: Set struct spi_driver .of_match_table Message-ID: <20150820235340.GA31967@deathstar> References: <1440054451-1223-1-git-send-email-javier@osg.samsung.com> <1440054451-1223-14-git-send-email-javier@osg.samsung.com> <20150820200912.GA2866@deathstar> <55D64E80.4050502@osg.samsung.com> <20150820222906.GB28249@deathstar> <55D65937.6070909@osg.samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55D65937.6070909@osg.samsung.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2940 Lines: 81 On Fri, Aug 21, 2015 at 12:48:23AM +0200, Javier Martinez Canillas wrote: > Hello Michael, > > On 08/21/2015 12:29 AM, Michael Welling wrote: > > On Fri, Aug 21, 2015 at 12:02:40AM +0200, Javier Martinez Canillas wrote: > >> Hello Michael, > >> > >> On 08/20/2015 10:09 PM, Michael Welling wrote: > >>> On Thu, Aug 20, 2015 at 09:07:26AM +0200, Javier Martinez Canillas wrote: > >>>> The driver has an OF id table but the .of_match_table is not set so > >>>> the SPI core can't do an OF style match and the table was unused. > >>>> > >>> > >>> Is an OF style match necessary? > >>> > >> > >> Did you read the cover letter [0] on which I explain why is needed to > >> avoid breaking module autoloading in the future? Once the SPI core is > >> changed by RFC patch 18/18? (you were cc'ed in the cover letter BTW). > > > > Well I have read it now. :) > > > > Great :) > > >> > >>> I have been using devicetree and it matches based on the .id_table. > >>> > >> > >> Yes it fallbacks to the .id_table or the driver name but the correct > >> thing to do for devices registered by OF, is to match using the > >> compatible string. > >> > >>> Couldn't we just remove the mcp320x_dt_ids table instead? > >>> > >> > >> No, that is the wrong thing to do IMHO since the compatible string > >> contains both vendor and device name whle the .id_table only contains > >> a device name. > >> > >> So it makes sense to match using the compatible string and also report > >> the OF modalias information to user-space. > >> > >> Otherwise what's the point of the vendor in the compatible string for > >> SPI devices? You can just use "bar" instead of "foo,bar" as a string. > >> > > > > Well then shouldn't the patch include adding the vendor to the compatible > > string? > > > > Well, I was talking in general. You are right that this specific driver does > not have a vendor prefix for the compatible strings. This is incorrect > according to the ePAPR document [0]. > > However, these compatible strings are already documented as a DT binding doc > in Documentation/devicetree/bindings/iio/adc/mcp320x.txt so I don't know > what is the correct thing to do in this situation. > > Changing the compatible string will break old DTB with newer kernels and that > is a no go. But that doesn't invalidate what I said since once the SPI core > is changed and report OF modalias, you will need a MODULE_DEVICE_TABLE(of,...) > regardless if the compatible string has a vendor prefix or not. > Okay. Acked-by: Michael Welling > [0]: https://www.power.org/documentation/epapr-version-1-1/ > > Best regards, > -- > Javier Martinez Canillas > Open Source Group > Samsung Research America -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/