[PATCH libinput] touchpad: disable MT for all semi-mt devices

[Benjamin Tissoires]

On Tue, Jan 19, 2016 at 1:01 AM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> Synaptics, Elantech and Alps semi-mt devices all have issues with reporting
> correct MT data, even the bounding box which semi-mt devices are supposed to
> report is wrong.
>
> Synaptics devices have massive jumps with two fingers down. Elantech devices
> may open slots without coordinate data. Alps devices may send 0/0 coordinates
> as initial slot position.
>
> All these may be addressable with specific quirks, but the actual benefit is
> largely restricted to better palm detection (though even with quirks this is
> unlikely to work) and support for pinch gestures (again, lack of coordinates
> makes supporting those hard anyway).
>
> Elantech: https://bugs.freedesktop.org/show_bug.cgi?id=93583
> Alps: https://bugzilla.redhat.com/show_bug.cgi?id=1295073
>
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---

I am definitively in favor of this. The patch looks good, so I can
give my Reviewed-by. However, I think it would be better if Hans (or
anybody else) could have a look at the side effects, as I am not
familiar enough in the gestures/palm-rejection code anymore.

Cheers,
Benjamin

>  src/evdev-mt-touchpad-gestures.c |  6 ++----
>  src/evdev-mt-touchpad.c          | 21 +++++++++++++--------
>  test/gestures.c                  |  2 +-
>  test/litest.h                    | 10 ----------
>  test/touchpad-tap.c              |  2 +-
>  5 files changed, 17 insertions(+), 24 deletions(-)
>
> diff --git a/src/evdev-mt-touchpad-gestures.c b/src/evdev-mt-touchpad-gestures.c
> index 80aa89f..24f6a6d 100644
> --- a/src/evdev-mt-touchpad-gestures.c
> +++ b/src/evdev-mt-touchpad-gestures.c
> @@ -568,10 +568,8 @@ tp_gesture_handle_state(struct tp_dispatch *tp, uint64_t time)
>  int
>  tp_init_gesture(struct tp_dispatch *tp)
>  {
> -       if (tp->device->model_flags & EVDEV_MODEL_JUMPING_SEMI_MT)
> -               tp->gesture.enabled = false;
> -       else
> -               tp->gesture.enabled = true;
> +       /* semi-mt devices are too unreliable to do pinch gestures */
> +       tp->gesture.enabled = !tp->semi_mt;
>
>         tp->gesture.twofinger_state = GESTURE_2FG_STATE_NONE;
>
> diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
> index 62087fb..7f5bbf5 100644
> --- a/src/evdev-mt-touchpad.c
> +++ b/src/evdev-mt-touchpad.c
> @@ -1490,17 +1490,22 @@ tp_init_slots(struct tp_dispatch *tp,
>
>         tp->semi_mt = libevdev_has_property(device->evdev, INPUT_PROP_SEMI_MT);
>
> -       /* This device has a terrible resolution when two fingers are down,
> +       /* Semi-mt devices are not reliable for true multitouch data, so we
> +        * simply pretend they're single touch touchpads with BTN_TOOL bits.
> +        * Synaptics:
> +        * Terrible resolution when two fingers are down,
>          * causing scroll jumps. The single-touch emulation ABS_X/Y is
>          * accurate but the ABS_MT_POSITION touchpoints report the bounding
> -        * box and that causes jumps.  So we simply pretend it's a single
> -        * touch touchpad with the BTN_TOOL bits.
> -        * See https://bugzilla.redhat.com/show_bug.cgi?id=1235175 for an
> -        * explanation.
> +        * box and that causes jumps. See https://bugzilla.redhat.com/1235175
> +        * Elantech:
> +        * On three-finger taps/clicks, one slot doesn't get a coordinate
> +        * assigned. See https://bugs.freedesktop.org/show_bug.cgi?id=93583
> +        * Alps:
> +        * If three fingers are set down in the same frame, one slot has the
> +        * coordinates 0/0 and may not get updated for several frames.
> +        * See https://bugzilla.redhat.com/show_bug.cgi?id=1295073
>          */
> -       if (tp->semi_mt &&
> -           (device->model_flags &
> -            (EVDEV_MODEL_JUMPING_SEMI_MT|EVDEV_MODEL_ELANTECH_TOUCHPAD))) {
> +       if (tp->semi_mt) {
>                 tp->num_slots = 1;
>                 tp->slot = 0;
>                 tp->has_mt = false;
> diff --git a/test/gestures.c b/test/gestures.c
> index 9fc73b9..0fc3964 100644
> --- a/test/gestures.c
> +++ b/test/gestures.c
> @@ -34,7 +34,7 @@ START_TEST(gestures_cap)
>         struct litest_device *dev = litest_current_device();
>         struct libinput_device *device = dev->libinput_device;
>
> -       if (litest_is_synaptics_semi_mt(dev))
> +       if (libevdev_has_property(dev->evdev, INPUT_PROP_SEMI_MT))
>                 ck_assert(!libinput_device_has_capability(device,
>                                           LIBINPUT_DEVICE_CAP_GESTURE));
>         else
> diff --git a/test/litest.h b/test/litest.h
> index e74e923..61b1b01 100644
> --- a/test/litest.h
> +++ b/test/litest.h
> @@ -552,16 +552,6 @@ litest_enable_buttonareas(struct litest_device *dev)
>         litest_assert_int_eq(status, expected);
>  }
>
> -static inline int
> -litest_is_synaptics_semi_mt(struct litest_device *dev)
> -{
> -       struct libevdev *evdev = dev->evdev;
> -
> -       return libevdev_has_property(evdev, INPUT_PROP_SEMI_MT) &&
> -               libevdev_get_id_vendor(evdev) == 0x2 &&
> -               libevdev_get_id_product(evdev) == 0x7;
> -}
> -
>  static inline void
>  litest_enable_drag_lock(struct libinput_device *device)
>  {
> diff --git a/test/touchpad-tap.c b/test/touchpad-tap.c
> index 4450ec3..7a7e64c 100644
> --- a/test/touchpad-tap.c
> +++ b/test/touchpad-tap.c
> @@ -241,7 +241,7 @@ START_TEST(touchpad_1fg_multitap_n_drag_2fg)
>         int range = _i,
>             ntaps;
>
> -       if (litest_is_synaptics_semi_mt(dev))
> +       if (libevdev_has_property(dev->evdev, INPUT_PROP_SEMI_MT))
>                 return;
>
>         litest_enable_tap(dev->libinput_device);
> --
> 2.5.0
>