NFC: HCI check presence must not fail when driver doesn't support it

When the driver does not support checking the tag is still present, it
must return -EOPNOTSUPP. The NFC Core will then stop asking and not
report a tag lost event to user space.
Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/pn544_hci.c

@@ -986,7 +986,7 @@ static int pn544_hci_check_presence(struct nfc_hci_dev *hdev,
 	} else if (target->supported_protocols & NFC_PROTO_MIFARE_MASK) {
 		if (target->nfcid1_len != 4 && target->nfcid1_len != 7 &&
 		    target->nfcid1_len != 10)
-			return -EPROTO;
+			return -EOPNOTSUPP;
 
 		 return nfc_hci_send_cmd(hdev, NFC_HCI_RF_READER_A_GATE,
 				     PN544_RF_READER_CMD_ACTIVATE_NEXT,

net/nfc/core.c

@@ -697,6 +697,8 @@ static void nfc_check_pres_work(struct work_struct *work)
 
 	if (dev->active_target && timer_pending(&dev->check_pres_timer) == 0) {
 		rc = dev->ops->check_presence(dev, dev->active_target);
+		if (rc == -EOPNOTSUPP)
+			goto exit;
 		if (!rc) {
 			mod_timer(&dev->check_pres_timer, jiffies +
 				  msecs_to_jiffies(NFC_CHECK_PRES_FREQ_MS));
@@ -708,6 +710,7 @@ static void nfc_check_pres_work(struct work_struct *work)
 		}
 	}
 
+exit:
 	device_unlock(&dev->dev);
 }