Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756602Ab2ECOEu (ORCPT ); Thu, 3 May 2012 10:04:50 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:37656 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755120Ab2ECOEq (ORCPT ); Thu, 3 May 2012 10:04:46 -0400 Date: Thu, 3 May 2012 15:04:28 +0100 From: Russell King - ARM Linux To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, Jean-Christophe PLAGNIOL-VILLARD , Deepak Saxena , Tony Lindgren , Linus Walleij , shawn.guo@linaro.org, Sascha Hauer , Magnus Damm , Kukjin Kim , Olof Johansson , David Brown , Nicolas Pitre , Haojian Zhuang , Jason Cooper , Nicolas Ferre Subject: Re: Making ARM multiplatform kernels DT-only? Message-ID: <20120503140428.GB897@n2100.arm.linux.org.uk> References: <201205031350.35476.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201205031350.35476.arnd@arndb.de> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2708 Lines: 57 On Thu, May 03, 2012 at 01:50:35PM +0000, Arnd Bergmann wrote: > Hi everyone, > > I've been discussing multiplatform kernels with a few people recently, > and we will have a lot of discussion sessions about this at Linaro > Connect in Hong Kong. > > One question that came up repeatedly is whether we should support all > possible board files for each platform in a multiplatform kernel, > or just the ones that are already using DT probing. I would like > to get a quick poll of opinions on that and I've tried to put those > people on Cc that would be most impacted by this, i.e. the maintainers > for platforms that have both DT and non-DT board files at the moment. > > My feeling is that we should just mandate DT booting for multiplatform > kernels, because it significantly reduces the combinatorial space > at compile time, avoids a lot of legacy board files that we cannot > test anyway, reduces the total kernel size and gives an incentive > for people to move forward to DT with their existing boards. > > The counterargument is that we won't be able to support all the > boards we currently do when the user switches on multiplatform, > but I think that is acceptable. > Note that I would still want to allow users to build platforms > separately in order to enable the ATAG style board files, even > for platforms that are not multiplatform capable. I'm basing my comments off mach-zynq. How about we take the following steps towards it? 1. create arch/arm/include/mach/ which contains standardized headers for DT based implementations. This must include all headers included by asm/ or linux/ includes. This will also be the only mach/ header directory included for code outside of arch/arm/mach-*. This also acts as the 'default' set of mach/* includes for stuff like timex.h and the empty hardware.h 2. DT based mach-* directories do not have an include directory; their include files must be located in the main include/ heirarchy if shared with other parts of the kernel, otherwise they must be in the mach-* directory. 3. Allow build multiple mach-* directories (which we already do... see the samsung stuff.) We still have irqs.h being SoC dependent, and we still haven't taken debug-macros.S far enough along to get rid of that. Then there's also the problem of uncompress.h. The last piece of the puzzle is the common clock stuff. So, I think we're still a way off it yet - maybe six months or so. -- 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/