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

[Peter Hutterer]

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>
---
 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