linux-kernel - Re: [PATCH 8/8] HID: logitech: Enable high-resolution scrolling on Logitech mice

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Message-ID: <CAHk-=wh9pB3k6kuKHUfxeMaCLqm35CJs3W1kQteEHR5r8G4RUQ@mail.gmail.com>
Date:   Thu, 22 Nov 2018 09:05:47 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Hutterer <peter.hutterer@...-t.net>
Cc:     linux-input@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Harry Cutts <hcutts@...omium.org>, nlopezcasad@...itech.com,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: Re: [PATCH 8/8] HID: logitech: Enable high-resolution scrolling on
 Logitech mice

On Wed, Nov 21, 2018 at 10:35 PM Peter Hutterer
<peter.hutterer@...-t.net> wrote:
>
> This patch is a combinations of the now-reverted commits 1ff2e1a44e0,
> d56ca9855bf9, 5fe2ccbef9d, 044ee89028 together with some extra bits for the
> directional and timeout-based reset.

Instead of using an actual timer (which is quite expensive), how about
just saving the "last time" data along with the remainder?

We have a fairly low-overhead 'sched_clock()' function that gives a
clock approximation in nanoseconds (64 bits). Note that it doesn't
actually give nanosecond precision - it might fall back to jiffies for
hardware that doesn't have anything better, but for timeouts on the
order of a second, it's fine.

                      Linus