NFC: Check if NCI data flow control is used

Check if NCI data flow control is used in nci_tx_work.
Signed-off-by: NIlan Elias <ilane@ti.com>
Acked-by: NLauro Ramos Venancio <lauro.venancio@openbossa.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

include/net/nfc/nci.h

@@ -108,6 +108,9 @@
 /* NCI Static RF connection ID */
 #define NCI_STATIC_RF_CONN_ID					0x00
 
+/* NCI Data Flow Control */
+#define NCI_DATA_FLOW_CONTROL_NOT_USED				0xff
+
 /* NCI RF_DISCOVER_MAP_CMD modes */
 #define NCI_DISC_MAP_MODE_POLL					0x01
 #define NCI_DISC_MAP_MODE_LISTEN				0x02

net/nfc/nci/core.c

@@ -722,7 +722,10 @@ static void nci_tx_work(struct work_struct *work)
 		if (!skb)
 			return;
 
-		atomic_dec(&ndev->credits_cnt);
+		/* Check if data flow control is used */
+		if (atomic_read(&ndev->credits_cnt) !=
+				NCI_DATA_FLOW_CONTROL_NOT_USED)
+			atomic_dec(&ndev->credits_cnt);
 
 		nfc_dbg("NCI TX: MT=data, PBF=%d, conn_id=%d, plen=%d",
 				nci_pbf(skb->data),