Input: ALPS - fix TrackStick support for SS5 hardware

The current Alps SS5 (SS4 v2) code generates bogus TouchPad events when
TrackStick packets are processed.

This causes the xorg synaptics driver to print
"unable to find touch point 0" and
"BUG: triggered 'if (priv->num_active_touches > priv->num_slots)'"
messages.  It also causes unexpected TouchPad button release and re-click
event sequences if the TrackStick is moved while holding a TouchPad
button.

This commit corrects the problem by adjusting alps_process_packet_ss4_v2()
so that it only sends TrackStick reports when processing TrackStick
packets.

Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Paul Donohue <linux-kernel@PaulSD.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/alps.c

@@ -1346,6 +1346,18 @@ static void alps_process_packet_ss4_v2(struct psmouse *psmouse)
 
 	priv->multi_packet = 0;
 
+	/* Report trackstick */
+	if (alps_get_pkt_id_ss4_v2(packet) == SS4_PACKET_ID_STICK) {
+		if (priv->flags & ALPS_DUALPOINT) {
+			input_report_key(dev2, BTN_LEFT, f->ts_left);
+			input_report_key(dev2, BTN_RIGHT, f->ts_right);
+			input_report_key(dev2, BTN_MIDDLE, f->ts_middle);
+			input_sync(dev2);
+		}
+		return;
+	}
+
+	/* Report touchpad */
 	alps_report_mt_data(psmouse, (f->fingers <= 4) ? f->fingers : 4);
 
 	input_mt_report_finger_count(dev, f->fingers);
@@ -1356,13 +1368,6 @@ static void alps_process_packet_ss4_v2(struct psmouse *psmouse)
 
 	input_report_abs(dev, ABS_PRESSURE, f->pressure);
 	input_sync(dev);
-
-	if (priv->flags & ALPS_DUALPOINT) {
-		input_report_key(dev2, BTN_LEFT, f->ts_left);
-		input_report_key(dev2, BTN_RIGHT, f->ts_right);
-		input_report_key(dev2, BTN_MIDDLE, f->ts_middle);
-		input_sync(dev2);
-	}
 }
 
 static bool alps_is_valid_package_ss4_v2(struct psmouse *psmouse)