Re: PROBLEM: Missing events on thinkpad trackpoint buttons

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Wed, Aug 19, 2015 at 09:52:00AM -0400, Benjamin Tissoires wrote:
> On Tue, Aug 18, 2015 at 3:06 PM, Benjamin Tissoires
> <benjamin.tissoires@gmail.com> wrote:
> > Hi Nick,
> >
> > thanks for the report.
> >
> > On Mon, Aug 17, 2015 at 10:31 PM, Nick Bowler <nbowler@draconx.ca> wrote:
> >> Hi,
> >>
> >> I'm not sure if this is actually a Linux issue but figured I'd at least
> >> report it here to start...
> >>
> >> I have a Lenovo Thinkpad X250, with the newfangled trackpoint buttons.
> >> I have a problem with missing button press or release events: sometimes
> >> pressing a button has no effect, and sometimes releasing a button has no
> >> effect (the latter is especially annoying, as the button remains depressed
> >> as far as any applications are concerned).
> >>
> >> After some testing, the problem apparently depends on the position of my
> >> hands over the touchpad.  I can reliably reproduce it as follows: place
> >> two fingers on the touchpad, then press the button repeatedly.  Watching
> >> with evtest, several events (could be either press or release) will
> >> simply be missin, although the kernel never does anything weird like
> >> send two release events in a row.  There are no problems if there are
> >> 0 or 1 fingers on the touchpad.
> >>
> >> My current kernel version is 4.1.6, although the problem occurs in all
> >> versions that I tried.
> >>
> >> Here is the evtest result from placing two fingers on the touchpad, then
> >> pressing the left trackpoint button 10 times, counting 1 second between
> >> each press.  As you can see, only 3 presses and 3 release events total
> >> were sent by the kernel, sometimes with many physical button presses
> >> between the press and its corresponding release:
> >
> > OK, so this is definitively weird. My first idea would be a firmware
> > problem. I have asked Chandler to reproduce it on his t450 and see if
> > we observe it on our laptops too.
> 
> Update on this one : Chandler reproduced it on the t450, so it's
> likely that all of these sensors are affected. It is still unclear if
> it is a firmware bug or a driver problem, but the chances are huge
> that this is a firmware bug. Anyway, that's one more reason to push
> towards RMI4 over SMBus for these sensors: the bug is not present with
> this protocol :)

By the way, how are we going to handle Trackpoint (PS/2 device) with
touchpads in RMI4 mode? I do not recall anything in RMI4 spec, but I
looked at it quite some time ago.

Thanks.

-- 
Dmitry