[PATCH v2 libinput] touchpad: serial synaptics need to fake new touches on TRIPLETAP

[Peter Hutterer]

On the 4.1 kernels synaptics pretends to have 3 slots (the serial fw only does
2). This was added to avoid cursor jumps but has since been reverted for 4.2
(kernel commit dbf3c37086, 4.1.3 is still buggy). In some cases a TRIPLETAP
may be triggered without slot 2 ever activating.

While there are still those kernels out there, work around this bug by opening
a new touch point where none exists if the fake finger count exceeds the slot
count.

Reported-by: Jan Alexander Steffens <jan.steffens at gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
Tested-by: Jan Alexander Steffens <jan.steffens at gmail.com>
---
Changes to v1: 
- add kernel shas to the commit message for reference
- fix state handling in case of TOUCH_END

Hans:
This patch is queued for stable but not in 4.1.y yet, I'll wait a bit longer
but if it isn't in there in say 2 weeks time I think we should ship this
one anyway as a stopgap measure.

 src/evdev-mt-touchpad.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 6718b61..602c670 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -367,14 +367,24 @@ tp_restore_synaptics_touches(struct tp_dispatch *tp,
 	 */
 	for (i = 0; i < tp->num_slots; i++) {
 		struct tp_touch *t = tp_get_touch(tp, i);
+		enum touch_state state = t->state;
 
-		if (t->state != TOUCH_END)
+		switch(state) {
+		case TOUCH_HOVERING:
+		case TOUCH_BEGIN:
+		case TOUCH_UPDATE:
 			continue;
+		/* new touch, move it through to begin immediately */
+		case TOUCH_NONE:
+		case TOUCH_END:
+			tp_new_touch(tp, t, time);
+			tp_begin_touch(tp, t, time);
+			break;
+		}
 
-		/* new touch, move it through begin to update immediately */
-		tp_new_touch(tp, t, time);
-		tp_begin_touch(tp, t, time);
-		t->state = TOUCH_UPDATE;
+		/* touch just ended ,we need need to restore it to update */
+		if (state == TOUCH_END)
+			t->state = TOUCH_UPDATE;
 	}
 }
 
-- 
2.4.3