Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751662AbdHCIOi (ORCPT ); Thu, 3 Aug 2017 04:14:38 -0400 Received: from mail-io0-f170.google.com ([209.85.223.170]:37939 "EHLO mail-io0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751236AbdHCIOe (ORCPT ); Thu, 3 Aug 2017 04:14:34 -0400 MIME-Version: 1.0 In-Reply-To: <596F73BC.1000305@nvidia.com> References: <1491485752-28030-1-git-send-email-ldewangan@nvidia.com> <20170719131640.GA2533@localhost> <596F73BC.1000305@nvidia.com> From: Linus Walleij Date: Thu, 3 Aug 2017 10:14:32 +0200 Message-ID: Subject: Re: [PATCH 1/1] gpio: core: Decouple open drain/source flag with active low/high To: Laxman Dewangan Cc: Johan Hovold , Alexandre Courbot , Rob Herring , Mark Rutland , Frank Rowand , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 46 On Wed, Jul 19, 2017 at 4:59 PM, Laxman Dewangan wrote: > On Wednesday 19 July 2017 06:55 PM, Johan Hovold wrote: >> I guess the latter is fine, even if it is likely to amount to a fair bit >> of debugging world wide. >> >> Perhaps all this can still be avoided by adding further flags and >> deprecating others before people start migrating to 4.12 (after all, >> GPIO_OPEN_DRAIN has been around since 4.4 even if there are no in-kernel >> users). >> >> Or we accept the binary interface breakage -- it probably is pretty rare >> that people update the kernel without updating the dtb. I can just >> update the dts on the system that broke for me, and hopefully anyone >> debugging this issue while updating to 4.12 will find this mail quickly. > > Yes, it breaks the older DTS with new kernel. However, this point was > discussed before sending patch. As there was no user in the mainline DTs for > these macros, we made change. My operating assumption is usually "rough consensus and running code". If the code doesn't run, i.e. if there are regressions then we need to fix them. I am not aware of any systems having picked up the flags as they were set before this patch, but if they exist we need to patch it of course. On the other hand we don't patch theoretical compatibility issues either, only those that occure in practice. It falls back on when a DT binding is really standardized. When it is starting to get discussed? When the final binding is merged to the kernel tree? When the devicetree.org people publish it? When a big enough vendor ships more than 100 devices using it no matter what happened discussion-wise? All these are a bit fluid concepts, so as a result, the handling of bindings is a bit fluid. If we really want DT bindings to have a point when they are "set in stone" then we need to talk to devicetree.org about that. But in reality I think all standards ever are a bit fuzzy around the edges. Yours, Linus Walleij