From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753446Ab3KGJrI (ORCPT ); Thu, 7 Nov 2013 04:47:08 -0500 Received: from demumfd002.nsn-inter.net ([93.183.12.31]:11592 "EHLO demumfd002.nsn-inter.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752769Ab3KGJrB (ORCPT ); Thu, 7 Nov 2013 04:47:01 -0500 Message-ID: <527B6156.1080000@nsn.com> Date: Thu, 07 Nov 2013 10:45:58 +0100 From: Alexander Sverdlin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: ext Pantelis Antoniou , Sebastian Andrzej Siewior CC: Grant Likely , Rob Herring , Stephen Warren , Matt Porter , Koen Kooi , Alison Chaiken , Dinh Nguyen , Jan Lubbe , Michael Stickel , Guenter Roeck , Dirk Behme , Alan Tull , Sascha Hauer , Michael Bohan , Ionut Nicu , Michal Simek , Matt Ranostay , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3 - V2] Introducing Device Tree Overlays References: <1383676898-29819-1-git-send-email-panto@antoniou-consulting.com> <20131106190152.GA8662@breakpoint.cc> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-type: clean X-purgate-Ad: Categorized by eleven eXpurgate (R) http://www.eleven.de X-purgate: clean X-purgate: This mail is considered clean (visit http://www.eleven.de for further information) X-purgate-size: 1637 X-purgate-ID: 151667::1383817568-00005753-70980A87/0-0/0-0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! On 06/11/13 20:08, ext Pantelis Antoniou wrote: >>> The following patchset introduces Device Tree overlays, a method >>> of dynamically altering the kernel's live Device Tree, along with >>> a generic interface to use it in a board agnostic manner. >> >> In case this has been discussed and I missed it: Why are we doing this? >> Isn't it possible to d o the overlay thingy in u-boot and pass a >> complete device tree to the kernel? >> Are you trying to do something like hotplug-PCI where the PCI card can >> be replaced at runtime? >> > > It has been discussed. > > We are doing it because > > a) We tried to do it in u-boot and it has been a complete disaster. > Regular users just can't handle bootloader updates. There are buses we simply do not want to deal with in uboot, like SRIO, PCIe, everything-over-ethernet. All of them are hot-pluggable. And yeah, device-tree processing in uboot is possible, but in Linux it's way easier... > b) It is similar to that. It was originally created for the beaglebone, > which has a concept of capes (similar to Arduino shields). > http://circuitco.com/support/index.php?title=BeagleBone_Capes > Turns out it's really useful to anyone doing reconfigurable hardware too, > so that's why FPGA people are thinking of using it. > > c) There are people that want to tinker with Linux based hardware boards > but are not kernel developers. This gives them a way to do so without > having to recompile the kernel and/or reboot while tinkering. > >> Sebastian > > Regards > > -- Pantelis > > > -- Best regards, Alexander Sverdlin.