From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Cameron Subject: Re: [PATCH 13/18] iio: adc: mcp320x: Set struct spi_driver .of_match_table Date: Sat, 22 Aug 2015 18:48:53 +0100 Message-ID: <55D8B605.4040302@kernel.org> 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=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55D65937.6070909-JPH+aEBZ4P+UEJcrhfAQsw@public.gmane.org> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Javier Martinez Canillas , Michael Welling Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrea Galbusera , linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Peter Meerwald , Lars-Peter Clausen , Manfred Schlaegl , =?UTF-8?Q?S=c3=b8ren_Andersen?= , Hartmut Knaack , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On 20/08/15 23:48, 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. Take the view the old version is wrong but needs to be supported and add also the corrected strings + document them. cc'd The device tree list for any more comments on this. > > 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. > > [0]: https://www.power.org/documentation/epapr-version-1-1/ > > Best regards, >