Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754959AbbBTSKJ (ORCPT ); Fri, 20 Feb 2015 13:10:09 -0500 Received: from mail-qc0-f181.google.com ([209.85.216.181]:45983 "EHLO mail-qc0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754439AbbBTSKH (ORCPT ); Fri, 20 Feb 2015 13:10:07 -0500 Message-ID: <54E77876.9020500@hurleysoftware.com> Date: Fri, 20 Feb 2015 13:09:58 -0500 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Guenter Roeck CC: Pantelis Antoniou , frowand.list@gmail.com, Mark Rutland , "devicetree@vger.kernel.org" , Tony Lindgren , Koen Kooi , Nicolas Ferre , "linux-kernel@vger.kernel.org" , Grant Likely , Ludovic Desroches , "linux-arm-kernel@lists.infradead.org" , Matt Porter Subject: Re: [PATCH 2/4] of: DT quirks infrastructure References: <1424271576-1952-3-git-send-email-pantelis.antoniou@konsulko.com> <20150218154106.GC29429@leverpostej> <20150218173115.GG29429@leverpostej> <76BD1B22-BAED-4205-9B34-186907CE0217@konsulko.com> <54E613E7.2020405@gmail.com> <670D0881-DBF0-45E8-A502-A6DB2B77A750@konsulko.com> <54E61DD2.3060002@gmail.com> <53F2F94C-0C43-4A54-B8CD-EEC454A0AC19@konsulko.com> <54E742F2.80506@hurleysoftware.com> <20150220164753.GC22752@roeck-us.net> In-Reply-To: <20150220164753.GC22752@roeck-us.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3130 Lines: 71 Hi Guenter, On 02/20/2015 11:47 AM, Guenter Roeck wrote: [...] > I am open to hearing your suggestions for our use case, where the CPU card with > the eeprom is manufactured separately from its carier cards. I think your use case may be more compelling than two flavors of Beaglebone (one of which is pretty much a dead stick), but it's also less clear what your design constraints are (not that I really want to know, 'cause I don't). But the logical extension of this is an N-way dtb that supports unrelated SOCs, and I think most would agree that's not an acceptable outcome. My thought was that every design that can afford an EEPROM to probe can afford a bootloader to select the appropriate dtb, and can afford the extra space required for multiple dtbs. I'm not naysaying; I just want to elicit enough information so the community can make informed decisions. > I assume you might suggest that manufacturing should (re-)program the EEPROM > on the CPU card after it was inserted into the carrier. > > Problem is though that the CPU card may be inserted into ts carrier outside > manufacturing, at the final stages of assembly or in product repair. Those > groups would typically not even have the means to (re-)program the eeprom. > Besides, manufacturing would, quite understandably, go ballistic if we demand > that they start programming EEPROMs after insertion into carrier, and no longer > use pre-programmed EEPROMs. I agree; that would be The Wrong Way. > Note that it is not feasible to put the necessary EEPROM onto the carrier > either. Maybe in a later design. Maybe that makes sense, and we will go along > that route at some point. However, forcing a specific hardware solution > due to software limitations, ie lack of ability by core software to handle > the different carries, seems to be not the right decision to make on an > OS level. Agreed; hardware is what it is. > In the PCI world it has long since been accepted that the world is not perfect. > The argument here is pretty much equivalent to demanding that PCI drop its > quirks mechanism, to force the HW manufacturers to finally get it right from > the beginning. I somehow suspect that this won't happen. I was thinking back to the introductions of fast DEVSEL# and AGP :( > Instead of questioning the need for a mechanism such as the one proposed by > Pantelis, I think our time would be better spent arguing if it is the right > mechanism and, if not, how it can be improved. My thoughts exactly. Apologies if something I wrote came across as "You Shall Not Pass" :) One issue seems to be the moving target that is the compelling use case(s). The initial submission implied it was the Beaglebone, which comes with 4GB eMMC/microSD so naturally the argument for space-savings with DTBs doesn't fly. That has since been clarified so no need to rehash that. Regards, Peter Hurley -- 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/