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Message-ID: <1513288412.18523.285.camel@codethink.co.uk> Date: Thu, 14 Dec 2017 21:53:32 +0000 From: Ben Hutchings <ben.hutchings@...ethink.co.uk> To: Deepa Dinamani <deepa.kernel@...il.com> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, "open list:HID CORE LAYER" <linux-input@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, y2038 Mailman List <y2038@...ts.linaro.org>, Peter Hutterer <peter.hutterer@...-t.net>, Arnd Bergmann <arnd@...db.de> Subject: Re: [Y2038] [PATCH v4 1/4] uinput: Use monotonic times for uinput timestamps. On Thu, 2017-12-14 at 13:44 -0800, Deepa Dinamani wrote: > On Thu, Dec 14, 2017 at 1:18 PM, Ben Hutchings > > <ben.hutchings@...ethink.co.uk> 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.
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