HID: wacom: Initialize MT slots for generic devices at post_parse_hid

If a HID descriptor places HID_DG_CONTACTID before HID_DG_X and HID_DG_Y then
the ABS_X and ABS_Y will not be automatically initialized by the call to
input_mt_init_slots. To ensure that this is not a problem, we relocate that
call to occur after HID parsing has been completed and we've initalized all the
multitouch axes.
Signed-off-by: Jason Gerecke <killertofu@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_sys.c

@@ -13,6 +13,7 @@
 
 #include "wacom_wac.h"
 #include "wacom.h"
+#include <linux/input/mt.h>
 
 #define WAC_MSG_RETRIES		5
 
@@ -236,6 +237,21 @@ static void wacom_usage_mapping(struct hid_device *hdev,
 		wacom_wac_usage_mapping(hdev, field, usage);
 }
 
+static void wacom_post_parse_hid(struct hid_device *hdev,
+				 struct wacom_features *features)
+{
+	struct wacom *wacom = hid_get_drvdata(hdev);
+	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
+
+	if (features->type == HID_GENERIC) {
+		/* Any last-minute generic device setup */
+		if (features->touch_max > 1) {
+			input_mt_init_slots(wacom_wac->input, wacom_wac->features.touch_max,
+				    INPUT_MT_DIRECT);
+		}
+	}
+}
+
 static void wacom_parse_hid(struct hid_device *hdev,
 			   struct wacom_features *features)
 {
@@ -270,6 +286,8 @@ static void wacom_parse_hid(struct hid_device *hdev,
 				wacom_usage_mapping(hdev, hreport->field[i],
 						hreport->field[i]->usage + j);
 	}
+
+	wacom_post_parse_hid(hdev, features);
 }
 
 static int wacom_hid_set_device_mode(struct hid_device *hdev)

drivers/hid/wacom_wac.c

@@ -1381,7 +1381,6 @@ static void wacom_wac_finger_usage_mapping(struct hid_device *hdev,
 {
 	struct wacom *wacom = hid_get_drvdata(hdev);
 	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
-	struct input_dev *input = wacom_wac->input;
 	unsigned touch_max = wacom_wac->features.touch_max;
 
 	switch (usage->hid) {
@@ -1400,8 +1399,6 @@ static void wacom_wac_finger_usage_mapping(struct hid_device *hdev,
 					ABS_MT_POSITION_Y, 4);
 		break;
 	case HID_DG_CONTACTID:
-		input_mt_init_slots(input, wacom_wac->features.touch_max,
-			INPUT_MT_DIRECT);
 		break;
 	case HID_DG_INRANGE:
 		break;