[PATCH v4] Input: synaptics - use firmware data for Cr-48

[Chung-yih Wang <cywang@chromium.org>]

The profile sensor clickpad in a Cr-48 Chromebook does a reasonable job of
tracking individual fingers. This tracking isn't perfect, but, experiments
show that it works better than just passing "semi-mt" data to userspace,
and making userspace try to deduce where the fingers are given a bounding box.

This patch tries to report two-finger positions directly from firmware's sgm
and agm packets instead of the {(min_x, min_y), (max_x, max_y)} for profile
sensor clickpads on Cr-48 chromebooks. Note that this device's firmware always
reports the higher (smaller y) finger in the "sgm" packet, and the lower
(larger y) finger in the "agm" packet for the state transition from one finger
to two finger. Then the firmware keeps tracking of fingers with the same agm
or sgm packets individually. Thus, when a new finger arrives on the pad, the
kernel driver uses a simple Euclidean distance measure to deduce which of the
two new fingers should keep the tracking ID of the previous single finger.
Similarly, when one finger is removed, the same measure is used to determine
which finger remained on the pad.

Signed-off-by: Chung-yih Wang <cywang@chromium.org>
---
 drivers/input/mouse/synaptics.c | 95 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index 2f78538..ee39842 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c
@@ -67,6 +67,8 @@
 #define X_MAX_POSITIVE 8176
 #define Y_MAX_POSITIVE 8176
 
+static bool cr48_profile_sensor;
+
 /*****************************************************************************
  *	Stuff we need even when we do not want native Synaptics support
  ****************************************************************************/
@@ -1064,6 +1066,77 @@ static void synaptics_image_sensor_process(struct psmouse *psmouse,
 	priv->agm_pending = false;
 }
 
+static int synaptics_distsq(const struct input_mt_slot *slot,
+			    const struct synaptics_hw_state *hw)
+{
+	int slot_x = input_mt_get_value(slot, ABS_MT_POSITION_X);
+	int slot_y = input_mt_get_value(slot, ABS_MT_POSITION_Y);
+	int dx = hw->x - slot_x;
+	int dy = synaptics_invert_y(hw->y) - slot_y;
+	return dx * dx + dy * dy;
+}
+
+static bool synaptics_is_sgm_slot(const struct input_mt_slot *slot,
+				  const struct synaptics_hw_state *sgm,
+				  const struct synaptics_hw_state *agm)
+{
+	return (synaptics_distsq(slot, sgm) < synaptics_distsq(slot, agm));
+}
+
+static int synaptics_get_sgm_slot(const struct input_mt_slot *slots,
+				  const struct synaptics_hw_state *sgm)
+{
+	int distsq_slot0 = synaptics_distsq(&slots[0], sgm);
+	int distsq_slot1 = synaptics_distsq(&slots[1], sgm);
+	return (distsq_slot0 < distsq_slot1 ? 0 : 1);
+}
+
+static void synaptics_profile_sensor_process(struct psmouse *psmouse,
+					     struct synaptics_hw_state *sgm,
+					     int num_fingers)
+{
+	struct input_dev *dev = psmouse->dev;
+	struct synaptics_data *priv = psmouse->private;
+	struct synaptics_hw_state *agm = &priv->agm;
+	struct synaptics_mt_state mt_state;
+
+	/* Initialize using current mt_state (as updated by last agm) */
+	mt_state = agm->mt_state;
+
+	if (num_fingers >= 2) {
+		/* Get previous sgm slot if exists */
+		int sgm_slot = (mt_state.count != 0) ? mt_state.sgm : 0;
+		if (mt_state.count == 1) {
+			const struct input_mt_slot *mt = &dev->mt[sgm_slot];
+			if (!synaptics_is_sgm_slot(mt, sgm, agm))
+				sgm_slot = 1 - sgm_slot;
+		}
+		synaptics_report_slot(dev, sgm_slot, sgm);
+		synaptics_report_slot(dev, 1 - sgm_slot, agm);
+		synaptics_mt_state_set(&mt_state, num_fingers,
+				       sgm_slot, 1 - sgm_slot);
+	} else if (num_fingers == 1) {
+		int sgm_slot = (mt_state.count != 0) ? mt_state.sgm : 0;
+		if (mt_state.count >= 2)
+			sgm_slot = synaptics_get_sgm_slot(dev->mt, sgm);
+		synaptics_report_slot(dev, sgm_slot, sgm);
+		synaptics_report_slot(dev, 1 - sgm_slot, NULL);
+		synaptics_mt_state_set(&mt_state, 1, sgm_slot, -1);
+	} else {
+		synaptics_report_slot(dev, 0, NULL);
+		synaptics_report_slot(dev, 1, NULL);
+		synaptics_mt_state_set(&mt_state, 0, -1, -1);
+	}
+	/* Store updated mt_state */
+	priv->mt_state = agm->mt_state = mt_state;
+
+	input_mt_report_pointer_emulation(dev, false);
+	/* Send the number of fingers reported by touchpad itself. */
+	input_mt_report_finger_count(dev, mt_state.count);
+	synaptics_report_buttons(psmouse, sgm);
+	input_sync(dev);
+}
+
 /*
  *  called for each full received packet from the touchpad
  */
@@ -1127,6 +1200,11 @@ static void synaptics_process_packet(struct psmouse *psmouse)
 		finger_width = 0;
 	}
 
+	if (cr48_profile_sensor) {
+		synaptics_profile_sensor_process(psmouse, &hw, num_fingers);
+		return;
+	}
+
 	if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c))
 		synaptics_report_semi_mt_data(dev, &hw, &priv->agm,
 					      num_fingers);
@@ -1288,6 +1366,9 @@ static void set_input_params(struct input_dev *dev, struct synaptics_data *priv)
 					ABS_MT_POSITION_Y);
 	}
 
+	if (cr48_profile_sensor)
+		input_set_abs_params(dev, ABS_MT_PRESSURE, 0, 255, 0, 0);
+
 	if (SYN_CAP_PALMDETECT(priv->capabilities))
 		input_set_abs_params(dev, ABS_TOOL_WIDTH, 0, 15, 0, 0);
 
@@ -1483,10 +1564,24 @@ static const struct dmi_system_id __initconst olpc_dmi_table[] = {
 	{ }
 };
 
+static const struct dmi_system_id __initconst cr48_dmi_table[] = {
+#if defined(CONFIG_DMI) && defined(CONFIG_X86)
+	{
+		/* Cr-48 Chromebook (Codename Mario) */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "IEC"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Mario"),
+		},
+	},
+#endif
+	{ }
+};
+
 void __init synaptics_module_init(void)
 {
 	impaired_toshiba_kbc = dmi_check_system(toshiba_dmi_table);
 	broken_olpc_ec = dmi_check_system(olpc_dmi_table);
+	cr48_profile_sensor = dmi_check_system(cr48_dmi_table);
 }
 
 static int __synaptics_init(struct psmouse *psmouse, bool absolute_mode)
-- 
1.8.1.3