[PATCH] Input: smooth out mouse jitter

From: Dmitry Torokhov <dtor_core@ameritech.net>

When calculating deltas for touchpads that generate absolute events use
average over the last 3 packets to remove jitter

drivers/input/mouse/synaptics.c

@@ -553,16 +553,19 @@ static void synaptics_process_packet(struct psmouse *psmouse)
 		finger_width = 0;
 	}
 
-	/* Post events */
+	/* Post events
+	 * BTN_TOUCH has to be first as mousedev relies on it when doing
+	 * absolute -> relative conversion
+	 */
+	if (hw.z > 30) input_report_key(dev, BTN_TOUCH, 1);
+	if (hw.z < 25) input_report_key(dev, BTN_TOUCH, 0);
+
 	if (hw.z > 0) {
 		input_report_abs(dev, ABS_X, hw.x);
 		input_report_abs(dev, ABS_Y, YMAX_NOMINAL + YMIN_NOMINAL - hw.y);
 	}
 	input_report_abs(dev, ABS_PRESSURE, hw.z);
 
-	if (hw.z > 30) input_report_key(dev, BTN_TOUCH, 1);
-	if (hw.z < 25) input_report_key(dev, BTN_TOUCH, 0);
-
 	input_report_abs(dev, ABS_TOOL_WIDTH, finger_width);
 	input_report_key(dev, BTN_TOOL_FINGER, num_fingers == 1);
 	input_report_key(dev, BTN_TOOL_DOUBLETAP, num_fingers == 2);

drivers/input/mousedev.c

@@ -53,12 +53,14 @@ struct mousedev_list {
 	struct fasync_struct *fasync;
 	struct mousedev *mousedev;
 	struct list_head node;
-	int dx, dy, dz, oldx, oldy;
-	signed char ps2[6];
+	int dx, dy, dz;
+	int old_x[4], old_y[4];
 	unsigned long buttons;
+	signed char ps2[6];
 	unsigned char ready, buffer, bufsiz;
 	unsigned char mode, imexseq, impsseq;
-	int finger;
+	unsigned int pkt_count;
+	unsigned char touch;
 };
 
 #define MOUSEDEV_SEQ_LEN	6
@@ -74,49 +76,49 @@ static struct mousedev mousedev_mix;
 static int xres = CONFIG_INPUT_MOUSEDEV_SCREEN_X;
 static int yres = CONFIG_INPUT_MOUSEDEV_SCREEN_Y;
 
+#define fx(i)  (list->old_x[(list->pkt_count - (i)) & 03])
+#define fy(i)  (list->old_y[(list->pkt_count - (i)) & 03])
+
 static void mousedev_abs_event(struct input_handle *handle, struct mousedev_list *list, unsigned int code, int value)
 {
 	int size;
+	int touchpad;
 
 	/* Ignore joysticks */
 	if (test_bit(BTN_TRIGGER, handle->dev->keybit))
 		return;
 
-	/* Handle touchpad data */
-	if (test_bit(BTN_TOOL_FINGER, handle->dev->keybit)) {
-
-		if (list->finger && list->finger < 3)
-			list->finger++;
+	touchpad = test_bit(BTN_TOOL_FINGER, handle->dev->keybit);
 
 	switch (code) {
 		case ABS_X:
-				if (list->finger == 3)
-					list->dx += (value - list->oldx) / 8;
-				list->oldx = value;
-				return;
-			case ABS_Y:
-				if (list->finger == 3)
-					list->dy -= (value - list->oldy) / 8;
-				list->oldy = value;
-				return;
-		}
-		return;
+			if (touchpad) {
+				if (list->touch) {
+					fx(0) = value;
+					if (list->pkt_count >= 2)
+						list->dx = ((fx(0) - fx(1)) / 2 + (fx(1) - fx(2)) / 2) / 8;
 				}
-
-	/* Handle tablet data */
-	switch (code) {
-		case ABS_X:
+			} else {
 				size = handle->dev->absmax[ABS_X] - handle->dev->absmin[ABS_X];
 				if (size == 0) size = xres;
-			list->dx += (value * xres - list->oldx) / size;
-			list->oldx += list->dx * size;
-			return;
+				list->dx += (value * xres - list->old_x[0]) / size;
+				list->old_x[0] += list->dx * size;
+			}
+			break;
 		case ABS_Y:
+			if (touchpad) {
+				if (list->touch) {
+					fy(0) = value;
+					if (list->pkt_count >= 2)
+						list->dy = -((fy(0) - fy(1)) / 2 + (fy(1) - fy(2)) / 2) / 8;
+				}
+			} else {
 				size = handle->dev->absmax[ABS_Y] - handle->dev->absmin[ABS_Y];
 				if (size == 0) size = yres;
-			list->dy -= (value * yres - list->oldy) / size;
-			list->oldy -= list->dy * size;
-			return;
+				list->dy -= (value * yres - list->old_y[0]) / size;
+				list->old_y[0] -= list->dy * size;
+			}
+			break;
 	}
 }
 
@@ -149,7 +151,9 @@ static void mousedev_event(struct input_handle *handle, unsigned int type, unsig
 					switch (code) {
 						case BTN_TOUCH: /* Handle touchpad data */
 							if (test_bit(BTN_TOOL_FINGER, handle->dev->keybit)) {
-								list->finger = value;
+								list->touch = value;
+								if (!list->touch)
+									list->pkt_count = 0;
 								return;
 							}
 						case BTN_0:
@@ -178,6 +182,16 @@ static void mousedev_event(struct input_handle *handle, unsigned int type, unsig
 				case EV_SYN:
 					switch (code) {
 						case SYN_REPORT:
+							if (list->touch) {
+								list->pkt_count++;
+								/* Input system eats duplicate events,
+								 * but we need all of them to do correct
+								 * averaging so apply present one forward
+								 */
+								fx(0) = fx(1);
+								fy(0) = fy(1);
+							}
+
 							list->ready = 1;
 							kill_fasync(&list->fasync, SIGIO, POLL_IN);
 							wake = 1;