HID: logitech-dj: prevent false errors to be shown

Commit "HID: logitech: perform bounds checking on device_id early
enough" unfortunately leaks some errors to dmesg which are not real
ones:
- if the report is not a DJ one, then there is not point in checking
the device_id
- the receiver (index 0) can also receive some notifications which
can be safely ignored given the current implementation

Move out the test regarding the report_id and also discards
printing errors when the receiver got notified.

Fixes: ad3e14d7c5268c2e24477c6ef54bbdf88add5d36

Cc: [e-mail]
Reported-and-tested-by: Markus Trippelsdorf <[e-mail]>
Signed-off-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-logitech-dj.c

···
 	struct dj_receiver_dev *djrcv_dev = hid_get_drvdata(hdev);
 	struct dj_report *dj_report = (struct dj_report *) data;
 	unsigned long flags;
-	bool report_processed = false;
 
 	dbg_hid("%s, size:%d\n", __func__, size);
 
···
 	 * device (via hid_input_report() ) and return 1 so hid-core does not do
 	 * anything else with it.
 	 */
+
+	/* case 1) */
+	if (data[0] != REPORT_ID_DJ_SHORT)
+		return false;
+
 	if ((dj_report->device_index < DJ_DEVICE_INDEX_MIN) ||
 	    (dj_report->device_index > DJ_DEVICE_INDEX_MAX)) {
-		dev_err(&hdev->dev, "%s: invalid device index:%d\n",
+		/*
+		 * Device index is wrong, bail out.
+		 * This driver can ignore safely the receiver notifications,
+		 * so ignore those reports too.
+		 */
+		if (dj_report->device_index != DJ_RECEIVER_INDEX)
+			dev_err(&hdev->dev, "%s: invalid device index:%d\n",
 				__func__, dj_report->device_index);
 		return false;
 	}
 
 	spin_lock_irqsave(&djrcv_dev->lock, flags);
-	if (dj_report->report_id == REPORT_ID_DJ_SHORT) {
-		switch (dj_report->report_type) {
-		case REPORT_TYPE_NOTIF_DEVICE_PAIRED:
-		case REPORT_TYPE_NOTIF_DEVICE_UNPAIRED:
-			logi_dj_recv_queue_notification(djrcv_dev, dj_report);
-			break;
-		case REPORT_TYPE_NOTIF_CONNECTION_STATUS:
-			if (dj_report->report_params[CONNECTION_STATUS_PARAM_STATUS] ==
-			    STATUS_LINKLOSS) {
-				logi_dj_recv_forward_null_report(djrcv_dev, dj_report);
-			}
-			break;
-		default:
-			logi_dj_recv_forward_report(djrcv_dev, dj_report);
+	switch (dj_report->report_type) {
+	case REPORT_TYPE_NOTIF_DEVICE_PAIRED:
+	case REPORT_TYPE_NOTIF_DEVICE_UNPAIRED:
+		logi_dj_recv_queue_notification(djrcv_dev, dj_report);
+		break;
+	case REPORT_TYPE_NOTIF_CONNECTION_STATUS:
+		if (dj_report->report_params[CONNECTION_STATUS_PARAM_STATUS] ==
+		    STATUS_LINKLOSS) {
+			logi_dj_recv_forward_null_report(djrcv_dev, dj_report);
 		}
-		report_processed = true;
+		break;
+	default:
+		logi_dj_recv_forward_report(djrcv_dev, dj_report);
 	}
 	spin_unlock_irqrestore(&djrcv_dev->lock, flags);
 
-	return report_processed;
+	return true;
 }
 
 static int logi_dj_probe(struct hid_device *hdev,

drivers/hid/hid-logitech-dj.h

···
 
 #define DJ_MAX_PAIRED_DEVICES			6
 #define DJ_MAX_NUMBER_NOTIFICATIONS		8
+#define DJ_RECEIVER_INDEX			0
 #define DJ_DEVICE_INDEX_MIN 			1
 #define DJ_DEVICE_INDEX_MAX 			6