linux-kernel - Re: [Y2038] [PATCH v4 1/4] uinput: Use monotonic times for uinput timestamps.

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Message-ID: <CABeXuvpGRtp2fR3yW-eDyCOYpWfLReNytpew7kXD0xOxTEnZZw@mail.gmail.com>
Date:   Thu, 14 Dec 2017 13:44:35 -0800
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
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, 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.

-Deepa