Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760105Ab3CZSeB (ORCPT ); Tue, 26 Mar 2013 14:34:01 -0400 Received: from mail-we0-f171.google.com ([74.125.82.171]:45105 "EHLO mail-we0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754365Ab3CZSdm (ORCPT ); Tue, 26 Mar 2013 14:33:42 -0400 From: Grant Likely Subject: Re: [PATCH 1/5] capemgr: Beaglebone DT overlay based cape manager To: Pantelis Antoniou , Lee Jones Cc: Arnd Bergmann , Tony Lindgren , Rob Herring , Rob Landley , Jon Loeliger , Stephen Warren , David Gibson , Benoit Cousson , Mitch Bradley , Alan Tull , Greg Kroah-Hartman , linux-omap@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Matt Porter , Russ Dill , Koen Kooi , Joel A Fernandes , Rob Clark , Jason Kridner , Matt Ranostay , Sascha Hauer , Linus Walleij , Guennadi Liakhovetski In-Reply-To: <21E7B891-269B-422D-9038-381FAA15B59B@antoniou-consulting.com> References: <1357584666-17374-1-git-send-email-panto@antoniou-consulting.com> <93BF5C62-ADE8-4EFC-9175-C2D7E43300E3@antoniou-consulting.com> <20130107210551.GL14149@atomide.com> <201301072135.05166.arnd@arndb.de> <89A7A8FD-935E-4225-8C7B-EA1DBA0C2780@antoniou-consulting.com> <20130108100042.GD21994@gmail.com> <21E7B891-269B-422D-9038-381FAA15B59B@antoniou-consulting.com> Date: Tue, 26 Mar 2013 16:16:10 +0000 Message-Id: <20130326161610.804983E2499@localhost> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3203 Lines: 65 On Tue, 8 Jan 2013 12:10:20 +0200, Pantelis Antoniou wrote: > Hi Lee, > > On Jan 8, 2013, at 12:00 PM, Lee Jones wrote: > > >>>>> At the end of the line, some kind of hardware glue is going to be needed. > >>>>> > >>>>> I just feel that drawing from a sample size of 1 (maybe 2 if I get to throw > >>>>> in the beagleboard), it is a bit premature to think about making it overly > >>>>> general, besides the part that are obviously part of the infrastructure > >>>>> (like the DT overlay stuff). > >>>>> > >>>>> What I'm getting at, is that we need some user experience about this, before > >>>>> going away and creating structure out of possible misconception about the uses. > >>>> > >>>> IMHO stuff like this will be needed by many SoCs. Some examples of similar > >>>> things for omaps that have eventually become generic frameworks have been > >>>> the clock framework, USB OTG support, runtime PM, pinmux framework and > >>>> so on. > >>>> > >>>> So I suggest a minimal generic API from the start as that will make things > >>>> a lot easier in the long run. > >>> > >>> I agree. The ux500 platform already has the concept of "user interface boards", > >>> which currently is not well integrated into devicetree. I believe Sascha > >>> mentioned that Pengutronix had been shipping some other systems with add-on > >>> boards and generating device tree binaries from source for each combination. > >>> > >>> Ideally, both of the above should be able to use the same DT overlay logic > >>> as BeagleBone, and I'm sure there are more of those. > >> > >> Hmm, I see. > >> > >> I will need some more information about the interface of the 'user interface boards'. > >> I.e. how is the board identified, what is typically present on those boards, etc. > > > > User Interface Boards are mearly removable PCBs which are interchangeable > > amongst various hardware platforms. They are connected via numerous > > connectors which carry all sorts of different data links; i2c, spi, rs232, > > etc. The UIB I'm looking at right now has a touchscreen, speakers, a key > > pad, leds, jumpers, switches and a bunch of sensors. > > > > You can find a small example of how we interface to these by viewing > > 'arch/arm/boot/dts/stuib.dtsi'. To add a UIB to a particular build, we > > currently include it as a *.dtsi from a platform's dts file. > > I see. What I'm asking about is whether there's a method where you can read > an EEPROM, or some GPIO code combination where I can find out what kind of board > is plugged each time. > > If there is not, there is no way to automatically load the overlays; you can always > use the kernel command line, or have the a user space application to request the loading > of a specific board's overlay. > In this case the best thing to do is announce the availability of the expansion via a request_firmware() call and let udev handle supplying the correct overlay file. g. -- 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/