NFC: nfc_targets_found() should accept zero target found

The semantics for a zero target found event is that the polling operation
could not complete.
Signed-off-by: NEric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

net/nfc/core.c

@@ -560,6 +560,8 @@ EXPORT_SYMBOL(nfc_alloc_recv_skb);
  * The device driver must call this function when one or many nfc targets
  * are found. After calling this function, the device driver must stop
  * polling for targets.
+ * NOTE: This function can be called with targets=NULL and n_targets=0 to
+ * notify a driver error, meaning that the polling operation cannot complete.
  * IMPORTANT: this function must not be called from an atomic context.
  * In addition, it must also not be called from a context that would prevent
  * the NFC Core to call other nfc ops entry point concurrently.
@@ -586,7 +588,11 @@ int nfc_targets_found(struct nfc_dev *dev,
 	dev->targets_generation++;
 
 	kfree(dev->targets);
-	dev->targets = kmemdup(targets, n_targets * sizeof(struct nfc_target),
+	dev->targets = NULL;
+
+	if (targets) {
+		dev->targets = kmemdup(targets,
+				       n_targets * sizeof(struct nfc_target),
 				       GFP_ATOMIC);
 
 		if (!dev->targets) {
@@ -594,6 +600,7 @@ int nfc_targets_found(struct nfc_dev *dev,
 			device_unlock(&dev->dev);
 			return -ENOMEM;
 		}
+	}
 
 	dev->n_targets = n_targets;
 	device_unlock(&dev->dev);