From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id CDC8CDDF1E for ; Tue, 28 Apr 2009 23:50:20 +1000 (EST) Message-ID: <49F7093F.1000500@freescale.com> Date: Tue, 28 Apr 2009 08:48:47 -0500 From: Timur Tabi MIME-Version: 1.0 To: Kumar Gala , Scott Wood , Linuxppc-dev Development Subject: Re: removing get_immrbase()?? References: <49EF7B11.2000006@freescale.com> <49EF7B1C.2080105@freescale.com> <282847E1-AE1A-44EF-9D18-AF2884105FA5@kernel.crashing.org> <49EF8E3A.4060304@freescale.com> <5D0145E3-0A98-429E-8D53-1A8DF4216462@kernel.crashing.org> <20090423022610.GA19376@yookeroo.seuss> <80CA86D4-3DA5-4C28-AE7A-C03CE5758774@kernel.crashing.org> <20090423040642.GG19376@yookeroo.seuss> <49668C6D-3A6A-499E-A8AD-85B8E808F6CF@kernel.crashing.org> <20090428041257.GC11265@yookeroo.seuss> In-Reply-To: <20090428041257.GC11265@yookeroo.seuss> Content-Type: text/plain; charset=ISO-8859-1 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , David Gibson wrote: > On Wed, Apr 22, 2009 at 11:41:31PM -0500, Kumar Gala wrote: >> Lets say I had an error driver for our MCM (core to soc coherency >> module). It was getting the base address by using get_immrbase(). >> Today I proposed a proper device node for the MCM block as it doesn't >> exist in .dts today. We add such a node into .dts and I can clean up my >> error driver to use proper device node information. However I've just >> broken any old .dts that didn't have this node. You are saying I need to >> add code into the kernel to create this new node and we have to keep that >> code around for ever in the kernel.. why would I ever bother to actually >> changing anything than. > > Well, again. It's a judgement call, balancing the pain of having to > update the dts files (which depends on how widely deployed the > platform is) versus the pain of having to keep the bacwards > compatibility shim in the kernel. I agree with this sentiment. I'm only asking for a reasonable attempt at adding backwards compatibility via an isolated code block. Sprinkle in a few comments, and that should be enough. It won't always be possible to add such code, but at the very least, I expect the driver/kernel to clearly indicate what's missing from the device tree. In Kumar's example above, I expect the kernel to say that the MCM node is missing. -- Timur Tabi Linux kernel developer at Freescale