Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753604Ab3G1NkE (ORCPT ); Sun, 28 Jul 2013 09:40:04 -0400 Received: from mail-bk0-f51.google.com ([209.85.214.51]:40664 "EHLO mail-bk0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753480Ab3G1NkC (ORCPT ); Sun, 28 Jul 2013 09:40:02 -0400 From: Tomasz Figa To: Richard Cochran Cc: Arend van Spriel , Olof Johansson , Mark Brown , 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" Subject: Re: [Ksummit-2013-discuss] DT bindings as ABI [was: Do we have people interested in device tree janitoring / cleanup?] Date: Sun, 28 Jul 2013 15:39:56 +0200 Message-ID: <2529481.u8xHuXumcd@flatron> User-Agent: KMail/4.10.5 (Linux/3.10.1-gentoo; KDE/4.10.5; x86_64; ; ) In-Reply-To: <20130728131901.GA8864@netboy> References: <20130725175702.GC22291@e106331-lin.cambridge.arm.com> <1416484.XDfk5G56BI@flatron> <20130728131901.GA8864@netboy> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2191 Lines: 56 On Sunday 28 of July 2013 15:19:03 Richard Cochran wrote: > On Sun, Jul 28, 2013 at 11:12:53AM +0200, Tomasz Figa wrote: > > I'm not really sure what effect on users this has. Maybe you should > > define "users". > > ... > > > Care to explain this reasoning? > > Use Case > ~~~~~~~~ > > User acquires a machine running ARM Linux version 3.x, with u-boot > and dtb in a read only flash partition. The board boots and works just > fine. However, for his application, the user requires a new kernel > feature that appeared in version 3.y where y > x. He compiles the new > kernel, and it also works. Generally the user does not care where the dtb is stored. He just want to upgrade the kernel without thinking about internals. There are many possible options: a) The BSP packaging script he received from board vendor, or even kernel build system, builds dtb from kernel sources and appends it to built zImage. He just flashes the zImage and everything is working correctly. This is pretty common case today, as many boards still use legacy bootloaders without native support for DT. See the analogy to board files, being compiled as a part of kernel sources. b) The user always compiles the kernel and dtb and flashes both at the same time. This does not differ at all to flashing the kernel alone, except two files, not one, need to be flashed. By the way, in use case you are describing, changes that dtb wouldn't have to be updated are very low, unless the one present in read only memory of the board is complete, i.e. fully describes all the available hardware, which is unlikely for a dtb built at time of 3.x availability, whenever the feature showed up in 3.y (y > x). The user will most likely have to update the dtb anyway. Please note, though, I'm _not_ trying to convince you that this kind of solutions is good, as I'm not convinced either. That's why we are discussing this. Best regards, Tomasz -- 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/