NFC: Add STMicroelectronics ST95HF driver

This driver supports STMicroelectronics NFC Transceiver
"ST95HF", in in initiator role to read/write ISO14443 Type 4A,
ISO14443 Type 4B and ISO15693 Type5 tags.

The ST95HF datasheet is available here:
http://www.st.com/web/en/resource/technical/document/datasheet/DM00102056.pdf

Signed-off-by: Shikha Singh <shikha.singh@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/st95hf/spi.h

@@ -0,0 +1,64 @@
+/*
+ * ---------------------------------------------------------------------------
+ * drivers/nfc/st95hf/spi.h functions declarations for SPI communication
+ * ---------------------------------------------------------------------------
+ * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __LINUX_ST95HF_SPI_H
+#define __LINUX_ST95HF_SPI_H
+
+#include <linux/spi/spi.h>
+
+/* Basic ST95HF SPI CMDs */
+#define ST95HF_COMMAND_SEND	0x0
+#define ST95HF_COMMAND_RESET	0x1
+#define ST95HF_COMMAND_RECEIVE	0x2
+
+#define ST95HF_RESET_CMD_LEN	0x1
+
+/*
+ * structure to contain st95hf spi communication specific information.
+ * @req_issync: true for synchronous calls.
+ * @spidev: st95hf spi device object.
+ * @done: completion structure to wait for st95hf response
+ *	for synchronous calls.
+ * @spi_lock: mutex to allow only one spi transfer at a time.
+ */
+struct st95hf_spi_context {
+	bool req_issync;
+	struct spi_device *spidev;
+	struct completion done;
+	struct mutex spi_lock;
+};
+
+/* flag to differentiate synchronous & asynchronous spi request */
+enum req_type {
+	SYNC,
+	ASYNC,
+};
+
+int st95hf_spi_send(struct st95hf_spi_context *spicontext,
+		    unsigned char *buffertx,
+		    int datalen,
+		    enum req_type reqtype);
+
+int st95hf_spi_recv_response(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff);
+
+int st95hf_spi_recv_echo_res(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff);
+
+#endif