Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753008AbbBSSND (ORCPT ); Thu, 19 Feb 2015 13:13:03 -0500 Received: from bh-25.webhostbox.net ([208.91.199.152]:57335 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751527AbbBSSNA (ORCPT ); Thu, 19 Feb 2015 13:13:00 -0500 Date: Thu, 19 Feb 2015 10:12:48 -0800 From: Guenter Roeck To: Rob Herring Cc: Frank Rowand , Pantelis Antoniou , Grant Likely , "devicetree@vger.kernel.org" , Tony Lindgren , Koen Kooi , Nicolas Ferre , "linux-kernel@vger.kernel.org" , Ludovic Desroches , "linux-arm-kernel@lists.infradead.org" , Pantelis Antoniou , Matt Porter Subject: Re: [PATCH 2/4] of: DT quirks infrastructure Message-ID: <20150219181248.GA7713@roeck-us.net> References: <1424271576-1952-1-git-send-email-pantelis.antoniou@konsulko.com> <1424271576-1952-3-git-send-email-pantelis.antoniou@konsulko.com> <54E54586.5070602@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020206.54E627AC.0223,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.001 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 9 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2468 Lines: 47 On Thu, Feb 19, 2015 at 12:01:14PM -0600, Rob Herring wrote: > On Wed, Feb 18, 2015 at 8:08 PM, Frank Rowand wrote: > > On 2/18/2015 6:59 AM, Pantelis Antoniou wrote: > >> Implement a method of applying DT quirks early in the boot sequence. > >> > >> A DT quirk is a subtree of the boot DT that can be applied to > >> a target in the base DT resulting in a modification of the live > >> tree. The format of the quirk nodes is that of a device tree overlay. > > > > The use of the word "quirk" is a different mental model for me than what > > this patch series appears to be addressing. I would suggest totally > > removing the word "quirk" from this proposal to avoid confusing the > > mental models of future generations of kernel folks. > > This comes from me as quirks are a different usecase I had in mind, > but one that could use a similar mechanism. Although, in the case of > quirks, I would expect them to be overlays built into the kernel. It > would be more a way to update old dtbs. > > > What this patch series seems to be proposing is a method to apply DT > > overlays as soon as unflatten_device_tree() completes. In other words, > > making the device tree a dynamic object, that is partially defined by > > the kernel during boot. Well, to be fair, the kernel chooses among > > several possible alternatives encoded in the DT blob. So the device > > tree is no longer a static object that describes the hardware of the > > system. It may not sound like a big deal, but it seems to me to be > > a fundamental shift in what the device tree blob is. Something that > > should be thought about carefully and not just applied as a patch to > > solve a point problem. > > I agree. I would not want to see every board for an SOC become an > overlay for example. I think it has to be limited to truly plugable > h/w (e.g. capes) or minor changes. We just have to define what is > minor. :) > Everything that isn't OIR capable but fixed at boot time. OIR can and should be handled with "real" overlays. OIR implies removal; I would assume that what is discused here is insertion-only, and runtime removal is neither required nor wanted. Or at least that is our use case. Guenter -- 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/