While a button is held SS5 hardware will give us single-finger packets
with x, y, and pressure equal to zero. This causes annoying jumps in
pointer position if a touch is released while the button is held. Handle
this by claiming zero contacts to ensure that no position events are
provided to the user.
Reviewed-by: Pali Rohár <redacted>
---
drivers/input/mouse/alps.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index b8454af..7874f4f 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -1197,7 +1197,12 @@ static int alps_decode_ss4_v2(struct alps_fields *f,
f->mt[0].x = SS4_1F_X_V2(p);
f->mt[0].y = SS4_1F_Y_V2(p);
f->pressure = ((SS4_1F_Z_V2(p)) * 2) & 0x7f;
- f->fingers = 1;
+ /*
+ * When a button is held the device will give us events with x, y, and
+ * pressure of 0. This causes annoying jumps if a touch is released while
+ * the button is held. Handle this by claiming zero contacts.
+ */
+ f->fingers = f->pressure > 0 ? 1 : 0;
f->first_mp = 0;
f->is_mp = 0;
break;
--
2.8.1
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