HID: wacom: Don't report anything prior to the tool entering range

If the tool spends some time in prox before entering range, a series of
events (e.g. ABS_DISTANCE, MSC_SERIAL) can be sent before we or userspace
have any clue about the pen whose data is being reported. We need to hold
off on reporting anything until the pen has entered range. Since we still
want to report events that occur "in prox" after the pen has *left* range
we use 'wacom-tool[0]' as the indicator that the pen did at one point
enter range and provide us/userspace with tool type and serial number
information.

Fixes: a48324de ("HID: wacom: Bluetooth IRQ for Intuos Pro should handle prox/range")
Cc: <stable@vger.kernel.org> # 4.11+
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/wacom_wac.c

@@ -1290,6 +1290,8 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 						 get_unaligned_le16(&frame[11]));
 			}
 		}
+
+		if (wacom->tool[0]) {
 			input_report_abs(pen_input, ABS_PRESSURE, get_unaligned_le16(&frame[5]));
 			if (wacom->features.type == INTUOSP2_BT) {
 				input_report_abs(pen_input, ABS_DISTANCE,
@@ -1307,6 +1309,7 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 			input_event(pen_input, EV_MSC, MSC_SERIAL, wacom->serial[0]);
 			input_report_abs(pen_input, ABS_MISC,
 					 wacom_intuos_id_mangle(wacom->id[0])); /* report tool id */
+		}
 
 		wacom->shared->stylus_in_proximity = prox;