[PATCH 7/9 v2] Input: synaptics - improved 2->3 finger transition handling

djkurtz
2011-07-20T13:39:58Z

From: Daniel Kurtz <djkurtz@chromium.org>

As long as we know which slots are currently contained in SGM and AGM
packets, it is possible to track the slot 0 finger when transitioning from
2->3 fingers. This is the case when fingers are being added one at a
time, 1->2->3.

However, when fingers are removed, we sometimes lose track of which slots
are contained in SGM and AGM. In particular, when transitioning from 3->2
and sometimes 3->1. In both of these cases, we can no longer track slot 0
during 2->3 transitions.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
---
drivers/input/mouse/synaptics.c | 33 +++++++++++++++++++++++++++------
drivers/input/mouse/synaptics.h | 1 +
2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index b626b98..893e567 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c
@@ -659,6 +659,7 @@ static void synaptics_image_sensor_0f(struct synaptics_data *priv,
struct synaptics_mt_state *mt_state)
{
synaptics_mt_state_set(mt_state, 0, -1, -1);
+ priv->mt_state_lost = false;
}

/* Handle case where mt_state->count = 1 */
@@ -726,6 +727,7 @@ static void synaptics_image_sensor_1f(struct synaptics_data *priv,
* So, empty all slots. We will guess slot 0 on subsequent 1->1
*/
synaptics_mt_state_set(mt_state, 0, -1, -1);
+ priv->mt_state_lost = true;
break;
}
}
@@ -771,6 +773,7 @@ static void synaptics_image_sensor_2f(struct synaptics_data *priv,
* subsequent 2->2
*/
synaptics_mt_state_set(mt_state, 0, -1, -1);
+ priv->mt_state_lost = true;
break;
}
}
@@ -800,14 +803,32 @@ static void synaptics_image_sensor_3f(struct synaptics_data *priv,
break;
case 2:
/*
- * On 2->3 transitions, we are given no indication which finger
- * was added.
- * We don't even know what finger the current AGM packet
- * contained.
+ * After some 3->1 and all 3->2 transitions, we lose track
+ * of which slot is reported by sgm and agm.
*
- * So, empty all slots. They get filled on a subsequent 3->3
+ * For 2->3 in this state, empty all slots, and we will guess
+ * (0,1) on a subsequent 0->3.
+ *
+ * To userspace, the resulting transition will look like:
+ * 2:[0,1] -> 0:[-1,-1] -> 3:[0,2]
*/
- synaptics_mt_state_set(mt_state, 0, -1, -1);
+ if (priv->mt_state_lost) {
+ synaptics_mt_state_set(mt_state, 0, -1, -1);
+ break;
+ }
+
+ /*
+ * If the (SGM,AGM) really previously contained slots (0, 1),
+ * then we cannot know what slot was just reported by the AGM,
+ * because the 2->3 transition can occur either before or after
+ * the AGM packet. Thus, this most recent AGM could contain
+ * either the same old slot 1 or the new slot 2.
+ * Subsequent AGMs will be reporting slot 2.
+ *
+ * To userspace, the resulting transition will look like:
+ * 2:[0,1] -> 1:[0,-1] -> 3:[0,2]
+ */
+ synaptics_mt_state_set(mt_state, 1, 0, -1);
break;
case 3:
/*
diff --git a/drivers/input/mouse/synaptics.h b/drivers/input/mouse/synaptics.h
index 87be1fe..e3edfea 100644
--- a/drivers/input/mouse/synaptics.h
+++ b/drivers/input/mouse/synaptics.h
@@ -162,6 +162,7 @@ struct synaptics_data {
struct serio *pt_port; /* Pass-through serio port */

struct synaptics_mt_state mt_state; /* Current mt finger state */
+ bool mt_state_lost; /* mt_state may be incorrect */

/*
* Last received Advanced Gesture Mode (AGM) packet. An AGM packet
--
1.7.3.1