Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753835AbdLNVxg (ORCPT ); Thu, 14 Dec 2017 16:53:36 -0500 Received: from imap1.codethink.co.uk ([176.9.8.82]:34657 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753657AbdLNVxf (ORCPT ); Thu, 14 Dec 2017 16:53:35 -0500 Message-ID: <1513288412.18523.285.camel@codethink.co.uk> Subject: Re: [Y2038] [PATCH v4 1/4] uinput: Use monotonic times for uinput timestamps. From: Ben Hutchings To: Deepa Dinamani Cc: Dmitry Torokhov , "open list:HID CORE LAYER" , Linux Kernel Mailing List , y2038 Mailman List , Peter Hutterer , Arnd Bergmann Date: Thu, 14 Dec 2017 21:53:32 +0000 In-Reply-To: References: <20171207181306.5623-1-deepa.kernel@gmail.com> <20171207181306.5623-2-deepa.kernel@gmail.com> <1513286249.18523.280.camel@codethink.co.uk> <1513286332.18523.281.camel@codethink.co.uk> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1755 Lines: 41 On Thu, 2017-12-14 at 13:44 -0800, Deepa Dinamani wrote: > On Thu, Dec 14, 2017 at 1:18 PM, Ben Hutchings > > wrote: > > On Thu, 2017-12-14 at 21:17 +0000, Ben Hutchings wrote: > > > On Thu, 2017-12-07 at 10:13 -0800, Deepa Dinamani wrote: > > > > struct timeval which is part of struct input_event to > > > > maintain the event times is not y2038 safe. > > > > > > > > Real time timestamps are also not ideal for input_event > > > > as this time can go backwards as noted in the patch > > > > a80b83b7b8 by John Stultz. > > > > > > > > The patch switches the timestamps to use monotonic time > > > > from realtime time. This is assuming no one is using > > > > absolute times from these timestamps. > > > > > > Why is this change not opt-in, as for evdev?  I assume there were > > > compatibility reasons for not changing evdev's clock by default, so I > > > would expect them to apply to uinput as well.  (But I'm also prepared > > > to believe that user-space is now generally compatible with and would > > > prefer monotonic time from all input devices.) > > > > Never mind, I've gone back and seen Arnd's comments about compatibility > > on v3.  It might be worth copying those into the commit message though. > > Commit message already talks about this assumption?: > > The patch switches the timestamps to use monotonic time > from realtime time. This is assuming no one is using > absolute times from these timestamps. Yes, but Arnd did a bit of code research to check that assumption. A commit message that says "we checked and it appears that no user- space depends on this" looks better than "I assume that no user-space depends on this". Ben. -- Ben Hutchings Software Developer, Codethink Ltd.