Input: synaptics - fuzz position for touchpad with reduced filtering

Synaptics touchpads indicate via a capability bit when they perform reduced
filtering on position data. In such a case, use a non-zero fuzz value.
Fuzz = 8 was chosen empirically by observing the raw position data
reported by a clickpad indicating it had reduced filtering.
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Acked-by: Chase Douglas <chase.douglas@canonical.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/synaptics.c

@@ -684,23 +684,25 @@ static psmouse_ret_t synaptics_process_byte(struct psmouse *psmouse)
 static void set_input_params(struct input_dev *dev, struct synaptics_data *priv)
 {
 	int i;
+	int fuzz = SYN_CAP_REDUCED_FILTERING(priv->ext_cap_0c) ?
+			SYN_REDUCED_FILTER_FUZZ : 0;
 
 	__set_bit(INPUT_PROP_POINTER, dev->propbit);
 
 	__set_bit(EV_ABS, dev->evbit);
-	input_set_abs_params(dev, ABS_X,
-			     XMIN_NOMINAL, priv->x_max ?: XMAX_NOMINAL, 0, 0);
-	input_set_abs_params(dev, ABS_Y,
-			     YMIN_NOMINAL, priv->y_max ?: YMAX_NOMINAL, 0, 0);
+	input_set_abs_params(dev, ABS_X, XMIN_NOMINAL,
+			     priv->x_max ?: XMAX_NOMINAL, fuzz, 0);
+	input_set_abs_params(dev, ABS_Y, YMIN_NOMINAL,
+			     priv->y_max ?: YMAX_NOMINAL, fuzz, 0);
 	input_set_abs_params(dev, ABS_PRESSURE, 0, 255, 0, 0);
 
 	if (SYN_CAP_ADV_GESTURE(priv->ext_cap_0c)) {
 		__set_bit(INPUT_PROP_SEMI_MT, dev->propbit);
 		input_mt_init_slots(dev, 2);
 		input_set_abs_params(dev, ABS_MT_POSITION_X, XMIN_NOMINAL,
-				     priv->x_max ?: XMAX_NOMINAL, 0, 0);
+				     priv->x_max ?: XMAX_NOMINAL, fuzz, 0);
 		input_set_abs_params(dev, ABS_MT_POSITION_Y, YMIN_NOMINAL,
-				     priv->y_max ?: YMAX_NOMINAL, 0, 0);
+				     priv->y_max ?: YMAX_NOMINAL, fuzz, 0);
 
 		input_abs_set_res(dev, ABS_MT_POSITION_X, priv->x_res);
 		input_abs_set_res(dev, ABS_MT_POSITION_Y, priv->y_res);
@@ -974,4 +976,3 @@ bool synaptics_supported(void)
 }
 
 #endif /* CONFIG_MOUSE_PS2_SYNAPTICS */
-

drivers/input/mouse/synaptics.h

@@ -66,9 +66,9 @@
  * 1	0x60	multifinger mode	identifies firmware finger counting
  *					(not reporting!) algorithm.
  *					Not particularly meaningful
- * 1	0x80    covered pad		W clipped to 14, 15 == pad mostly covered
- * 2	0x01    clickpad bit 1		2-button ClickPad
- * 2	0x02    deluxe LED controls	touchpad support LED commands
+ * 1	0x80	covered pad		W clipped to 14, 15 == pad mostly covered
+ * 2	0x01	clickpad bit 1		2-button ClickPad
+ * 2	0x02	deluxe LED controls	touchpad support LED commands
  *					ala multimedia control bar
  * 2	0x04	reduced filtering	firmware does less filtering on
  *					position data, driver should watch
@@ -78,6 +78,7 @@
 #define SYN_CAP_CLICKPAD2BTN(ex0c)	((ex0c) & 0x000100) /* 2-button ClickPad */
 #define SYN_CAP_MAX_DIMENSIONS(ex0c)	((ex0c) & 0x020000)
 #define SYN_CAP_ADV_GESTURE(ex0c)	((ex0c) & 0x080000)
+#define SYN_CAP_REDUCED_FILTERING(ex0c)	((ex0c) & 0x000400)
 
 /* synaptics modes query bits */
 #define SYN_MODE_ABSOLUTE(m)		((m) & (1 << 7))
@@ -104,6 +105,9 @@
 #define SYN_NEWABS_RELAXED		2
 #define SYN_OLDABS			3
 
+/* amount to fuzz position data when touchpad reports reduced filtering */
+#define SYN_REDUCED_FILTER_FUZZ		8
+
 /*
  * A structure to describe the state of the touchpad hardware (buttons and pad)
  */