Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965103Ab1CaS4F (ORCPT ); Thu, 31 Mar 2011 14:56:05 -0400 Received: from www.linutronix.de ([62.245.132.108]:39027 "EHLO linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759072Ab1CaS4C (ORCPT ); Thu, 31 Mar 2011 14:56:02 -0400 Date: Thu, 31 Mar 2011 20:55:44 +0200 (CEST) From: Thomas Gleixner To: Nicolas Pitre cc: Arnd Bergmann , Kevin Hilman , Russell King - ARM Linux , Ingo Molnar , david@lang.hm, Linus Torvalds , Tony Lindgren , David Brown , lkml , linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, Catalin Marinas , "H. Peter Anvin" Subject: Re: [GIT PULL] omap changes for v2.6.39 merge window In-Reply-To: Message-ID: References: <201103301906.42429.arnd@arndb.de> <87d3l7jqpr.fsf@ti.com> <201103311723.02301.arnd@arndb.de> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2235 Lines: 51 On Thu, 31 Mar 2011, Nicolas Pitre wrote: > On Thu, 31 Mar 2011, Thomas Gleixner wrote: > > > Start off with such a trivial, but immense effective cleanup and see > > what it helps to share code even accross SoC vendors. They all glue > > together random IP blocks from the market and there are not soo many > > sources which are relevant. This makes sense in all aspects: > > > > 1) less and better code > > 2) faster setup for new SoCs > > 3) shared benefit for all vendors > > If this was always true. Someone commented on the fact that the IP > block providing USB on OMAP is shared with a couple other platforms. > But about 2600 lines of pure glue is still necessary around the common > driver to make it work for everyone. I'm not saying that separate > drivers are called for here, simply that hardware people _will_ screw it > up, especially when they are hooking it up to a non-standard > SOC-specific bus. Right. That's a problem, but we should not ignore the places where reusing stuff is easy possible. And making good examples out of it. And it really _IS_ worth the trouble. Look at the git log of drivers/spi/pxa2xx* . We could have slapped the other "x86" driver into spi, but that does not make any sense from a software engineering and maintainability POV. And it would have been more work in the end to cleanup the separate driver than isolating the existing one and reuse it. This is a sustainability issue. And we need to become more clever about identifying the places where we can abstract stuff into shared drivers and infrastructure when we want to sustain Linux for another few decades. > And what would the hardware guys tell you? That software is cheap. If you can prove with simple examples that using existing software removes 6 month of useless reinventing the wheel and another 6 month of testing plus the fight with the kernel folks, then eventually they start to listen as you can express this in $$$. Thanks, tglx -- 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/