HID: wacom: generic: read the number of expected touches on a per collection basis

Bluetooth connections may contain more than one set of touches,
or a partial set of touches, in one report.

Set the number of expected touches when reading a collection
instead of once per report (in the pre-report function).

Accordingly, reset the number of touches expected after each sync.
Signed-off-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_wac.c

@@ -2563,25 +2563,9 @@ static void wacom_wac_finger_pre_report(struct hid_device *hdev,
 			case HID_DG_TIPSWITCH:
 				hid_data->last_slot_field = equivalent_usage;
 				break;
-			case HID_DG_CONTACTCOUNT:
-				hid_data->cc_report = report->id;
-				hid_data->cc_index = i;
-				hid_data->cc_value_index = j;
-				break;
 			}
 		}
 	}
-
-	if (hid_data->cc_report != 0 &&
-	    hid_data->cc_index >= 0) {
-		struct hid_field *field = report->field[hid_data->cc_index];
-		int value = field->value[hid_data->cc_value_index];
-		if (value)
-			hid_data->num_expected = value;
-	}
-	else {
-		hid_data->num_expected = wacom_wac->features.touch_max;
-	}
 }
 
 static void wacom_wac_finger_report(struct hid_device *hdev,
@@ -2591,6 +2575,7 @@ static void wacom_wac_finger_report(struct hid_device *hdev,
 	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
 	struct input_dev *input = wacom_wac->touch_input;
 	unsigned touch_max = wacom_wac->features.touch_max;
+	struct hid_data *hid_data = &wacom_wac->hid_data;
 
 	/* If more packets of data are expected, give us a chance to
 	 * process them rather than immediately syncing a partial
@@ -2604,6 +2589,7 @@ static void wacom_wac_finger_report(struct hid_device *hdev,
 
 	input_sync(input);
 	wacom_wac->hid_data.num_received = 0;
+	hid_data->num_expected = 0;
 
 	/* keep touch state for pen event */
 	wacom_wac->shared->touch_down = wacom_wac_finger_count_touches(wacom_wac);
@@ -2678,12 +2664,73 @@ static void wacom_report_events(struct hid_device *hdev,
 	}
 }
 
+static void wacom_set_num_expected(struct hid_device *hdev,
+				   struct hid_report *report,
+				   int collection_index,
+				   struct hid_field *field,
+				   int field_index)
+{
+	struct wacom *wacom = hid_get_drvdata(hdev);
+	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
+	struct hid_data *hid_data = &wacom_wac->hid_data;
+	unsigned int original_collection_level =
+		hdev->collection[collection_index].level;
+	bool end_collection = false;
+	int i;
+
+	if (hid_data->num_expected)
+		return;
+
+	// find the contact count value for this segment
+	for (i = field_index; i < report->maxfield && !end_collection; i++) {
+		struct hid_field *field = report->field[i];
+		unsigned int field_level =
+			hdev->collection[field->usage[0].collection_index].level;
+		unsigned int j;
+
+		if (field_level != original_collection_level)
+			continue;
+
+		for (j = 0; j < field->maxusage; j++) {
+			struct hid_usage *usage = &field->usage[j];
+
+			if (usage->collection_index != collection_index) {
+				end_collection = true;
+				break;
+			}
+			if (wacom_equivalent_usage(usage->hid) == HID_DG_CONTACTCOUNT) {
+				hid_data->cc_report = report->id;
+				hid_data->cc_index = i;
+				hid_data->cc_value_index = j;
+
+				if (hid_data->cc_report != 0 &&
+				    hid_data->cc_index >= 0) {
+
+					struct hid_field *field =
+						report->field[hid_data->cc_index];
+					int value =
+						field->value[hid_data->cc_value_index];
+
+					if (value)
+						hid_data->num_expected = value;
+				}
+			}
+		}
+	}
+
+	if (hid_data->cc_report == 0 || hid_data->cc_index < 0)
+		hid_data->num_expected = wacom_wac->features.touch_max;
+}
+
 static int wacom_wac_collection(struct hid_device *hdev, struct hid_report *report,
 			 int collection_index, struct hid_field *field,
 			 int field_index)
 {
 	struct wacom *wacom = hid_get_drvdata(hdev);
 
+	if (WACOM_FINGER_FIELD(field))
+		wacom_set_num_expected(hdev, report, collection_index, field,
+				       field_index);
 	wacom_report_events(hdev, report, collection_index, field_index);
 
 	/*