Input: psmouse - ensure that focaltech reports consistent coordinates

We don't know whether x_max or y_max really hold the maximum possible
coordinates, and we don't know for sure whether we correctly interpret the
coordinates sent by the touchpad, so we clamp the reported values to
prevent confusion in userspace code.
Signed-off-by: Mathias Gottschlag <mgottschlag@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/focaltech.c

@@ -126,9 +126,17 @@ static void focaltech_report_state(struct psmouse *psmouse)
 		input_mt_slot(dev, i);
 		input_mt_report_slot_state(dev, MT_TOOL_FINGER, active);
 		if (active) {
-			input_report_abs(dev, ABS_MT_POSITION_X, finger->x);
+			unsigned int clamped_x, clamped_y;
+			/*
+			 * The touchpad might report invalid data, so we clamp
+			 * the resulting values so that we do not confuse
+			 * userspace.
+			 */
+			clamped_x = clamp(finger->x, 0U, priv->x_max);
+			clamped_y = clamp(finger->y, 0U, priv->y_max);
+			input_report_abs(dev, ABS_MT_POSITION_X, clamped_x);
 			input_report_abs(dev, ABS_MT_POSITION_Y,
-					 priv->y_max - finger->y);
+					 priv->y_max - clamped_y);
 		}
 	}
 	input_mt_report_pointer_emulation(dev, true);