NFC: Add Core support to generate tag lost event

Some HW/drivers get notifications when a tag moves out of the radio field.
This notification is now forwarded to user space through netlink.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/net/nfc/nfc.h b/include/net/nfc/nfc.h
index 7273ff1..313d00f 100644
--- a/include/net/nfc/nfc.h
+++ b/include/net/nfc/nfc.h
@@ -62,6 +62,7 @@
 	int (*data_exchange)(struct nfc_dev *dev, u32 target_idx,
 			     struct sk_buff *skb, data_exchange_cb_t cb,
 			     void *cb_context);
+	int (*check_presence)(struct nfc_dev *dev, u32 target_idx);
 };
 
 #define NFC_TARGET_IDX_ANY -1
@@ -107,6 +108,10 @@
 	int tx_headroom;
 	int tx_tailroom;
 
+	struct timer_list check_pres_timer;
+	struct workqueue_struct *check_pres_wq;
+	struct work_struct check_pres_work;
+
 	struct nfc_ops *ops;
 };
 #define to_nfc_dev(_dev) container_of(_dev, struct nfc_dev, dev)