HID: wacom: generic: read HID_DG_CONTACTMAX from any feature report

In the generic code path, HID_DG_CONTACTMAX was previously
only read from the second byte of report 0x23.

Another report (0x82) has the HID_DG_CONTACTMAX in the
higher nibble of the third byte. We should support reading the
value of HID_DG_CONTACTMAX no matter what report we are reading
or which position that value is in.

To do this we submit the feature report as a event report
using hid_report_raw_event(). Our modified finger event path
records the value of HID_DG_CONTACTMAX when it sees that usage.

Fixes: 8ffffd52 ("HID: wacom: fix timeout on probe for some wacoms")
Signed-off-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_sys.c

@@ -314,14 +314,16 @@ static void wacom_feature_mapping(struct hid_device *hdev,
 		/* leave touch_max as is if predefined */
 		if (!features->touch_max) {
 			/* read manually */
-			data = kzalloc(2, GFP_KERNEL);
+			n = hid_report_len(field->report);
+			data = hid_alloc_report_buf(field->report, GFP_KERNEL);
 			if (!data)
 				break;
 			data[0] = field->report->id;
 			ret = wacom_get_report(hdev, HID_FEATURE_REPORT,
-						data, 2, WAC_CMD_RETRIES);
-			if (ret == 2) {
-				features->touch_max = data[1];
+					       data, n, WAC_CMD_RETRIES);
+			if (ret == n) {
+				ret = hid_report_raw_event(hdev,
+					HID_FEATURE_REPORT, data, n, 0);
 			} else {
 				features->touch_max = 16;
 				hid_warn(hdev, "wacom_feature_mapping: "

drivers/hid/wacom_wac.c

@@ -2492,6 +2492,7 @@ static void wacom_wac_finger_event(struct hid_device *hdev,
 	struct wacom *wacom = hid_get_drvdata(hdev);
 	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
 	unsigned equivalent_usage = wacom_equivalent_usage(usage->hid);
+	struct wacom_features *features = &wacom->wacom_wac.features;
 
 	switch (equivalent_usage) {
 	case HID_GD_X:
@@ -2512,6 +2513,9 @@ static void wacom_wac_finger_event(struct hid_device *hdev,
 	case HID_DG_TIPSWITCH:
 		wacom_wac->hid_data.tipswitch = value;
 		break;
+	case HID_DG_CONTACTMAX:
+		features->touch_max = value;
+		return;
 	}