NFC: Add basic NCI over SPI

The NFC Forum defines a transport interface based on
Serial Peripheral Interface (SPI) for the NFC Controller
Interface (NCI).

This module implements the SPI transport of NCI, calling SPI module
directly to read/write data to NFC controller (NFCC).

NFCC driver should provide functions performing device open and close.
It should also provide functions asserting/de-asserting interruption
to prevent TX/RX race conditions.
NFCC driver can also fix a delay between transactions if needed by
the hardware.

Signed-off-by: Frederic Danis <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

include/net/nfc/nci_core.h

···
  *  NFC Controller (NFCC) and a Device Host (DH).
  *
  *  Copyright (C) 2011 Texas Instruments, Inc.
+ *  Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  *  Written by Ilan Elias <[e-mail]>
  *
···
 
 /* ----- NCI status code ----- */
 int nci_to_errno(__u8 code);
+
+/* ----- NCI over SPI acknowledge modes ----- */
+#define NCI_SPI_CRC_DISABLED	0x00
+#define NCI_SPI_CRC_ENABLED	0x01
+
+/* ----- NCI SPI structures ----- */
+struct nci_spi_dev;
+
+struct nci_spi_ops {
+	int (*open)(struct nci_spi_dev *ndev);
+	int (*close)(struct nci_spi_dev *ndev);
+	void (*assert_int)(struct nci_spi_dev *ndev);
+	void (*deassert_int)(struct nci_spi_dev *ndev);
+};
+
+struct nci_spi_dev {
+	struct nci_dev		*nci_dev;
+	struct spi_device	*spi;
+	struct nci_spi_ops	*ops;
+
+	unsigned int		xfer_udelay;	/* microseconds delay between
+						  transactions */
+	u8			acknowledge_mode;
+
+	void			*driver_data;
+};
+
+/* ----- NCI SPI Devices ----- */
+struct nci_spi_dev *nci_spi_allocate_device(struct spi_device *spi,
+						struct nci_spi_ops *ops,
+						u32 supported_protocols,
+						u32 supported_se,
+						u8 acknowledge_mode,
+						unsigned int delay);
+void nci_spi_free_device(struct nci_spi_dev *ndev);
+int nci_spi_register_device(struct nci_spi_dev *ndev);
+void nci_spi_unregister_device(struct nci_spi_dev *ndev);
+
+static inline void nci_spi_set_drvdata(struct nci_spi_dev *ndev,
+					    void *data)
+{
+	ndev->driver_data = data;
+}
+
+static inline void *nci_spi_get_drvdata(struct nci_spi_dev *ndev)
+{
+	return ndev->driver_data;
+}
 
 #endif /* __NCI_CORE_H */

net/nfc/nci/Kconfig

···
 
 	  Say Y here to compile NCI support into the kernel or say M to
 	  compile it as module (nci).
+
+config NFC_NCI_SPI
+	depends on NFC_NCI && SPI
+	bool "NCI over SPI protocol support"
+	default n
+	help
+	  NCI (NFC Controller Interface) is a communication protocol between
+	  an NFC Controller (NFCC) and a Device Host (DH).
+
+	  Say yes if you use an NCI driver that requires SPI link layer.

net/nfc/nci/Makefile

···
 obj-$(CONFIG_NFC_NCI) += nci.o
 
 nci-objs := core.o data.o lib.o ntf.o rsp.o
+
+nci-$(CONFIG_NFC_NCI_SPI) += spi.o

net/nfc/nci/spi.c

···
+/*
+ * Copyright (C) 2013  Intel Corporation. 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 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
+
+#include <linux/export.h>
+#include <linux/spi/spi.h>
+#include <linux/nfc.h>
+#include <net/nfc/nci_core.h>
+
+#define NCI_SPI_HDR_LEN			4
+#define NCI_SPI_CRC_LEN			2
+
+static int nci_spi_open(struct nci_dev *nci_dev)
+{
+	struct nci_spi_dev *ndev = nci_get_drvdata(nci_dev);
+
+	return ndev->ops->open(ndev);
+}
+
+static int nci_spi_close(struct nci_dev *nci_dev)
+{
+	struct nci_spi_dev *ndev = nci_get_drvdata(nci_dev);
+
+	return ndev->ops->close(ndev);
+}
+
+static int nci_spi_send(struct nci_dev *nci_dev, struct sk_buff *skb)
+{
+	return 0;
+}
+
+static struct nci_ops nci_spi_ops = {
+	.open = nci_spi_open,
+	.close = nci_spi_close,
+	.send = nci_spi_send,
+};
+
+/* ---- Interface to NCI SPI drivers ---- */
+
+/**
+ * nci_spi_allocate_device - allocate a new nci spi device
+ *
+ * @spi: SPI device
+ * @ops: device operations
+ * @supported_protocols: NFC protocols supported by the device
+ * @supported_se: NFC Secure Elements supported by the device
+ * @acknowledge_mode: Acknowledge mode used by the device
+ * @delay: delay between transactions in us
+ */
+struct nci_spi_dev *nci_spi_allocate_device(struct spi_device *spi,
+						struct nci_spi_ops *ops,
+						u32 supported_protocols,
+						u32 supported_se,
+						u8 acknowledge_mode,
+						unsigned int delay)
+{
+	struct nci_spi_dev *ndev;
+	int tailroom = 0;
+
+	if (!ops->open || !ops->close || !ops->assert_int || !ops->deassert_int)
+		return NULL;
+
+	if (!supported_protocols)
+		return NULL;
+
+	ndev = devm_kzalloc(&spi->dev, sizeof(struct nci_dev), GFP_KERNEL);
+	if (!ndev)
+		return NULL;
+
+	ndev->ops = ops;
+	ndev->acknowledge_mode = acknowledge_mode;
+	ndev->xfer_udelay = delay;
+
+	if (acknowledge_mode == NCI_SPI_CRC_ENABLED)
+		tailroom += NCI_SPI_CRC_LEN;
+
+	ndev->nci_dev = nci_allocate_device(&nci_spi_ops, supported_protocols,
+					    supported_se, NCI_SPI_HDR_LEN,
+					    tailroom);
+	if (!ndev->nci_dev)
+		return NULL;
+
+	nci_set_drvdata(ndev->nci_dev, ndev);
+
+	return ndev;
+}
+EXPORT_SYMBOL_GPL(nci_spi_allocate_device);
+
+/**
+ * nci_spi_free_device - deallocate nci spi device
+ *
+ * @ndev: The nci spi device to deallocate
+ */
+void nci_spi_free_device(struct nci_spi_dev *ndev)
+{
+	nci_free_device(ndev->nci_dev);
+}
+EXPORT_SYMBOL_GPL(nci_spi_free_device);
+
+/**
+ * nci_spi_register_device - register a nci spi device in the nfc subsystem
+ *
+ * @pdev: The nci spi device to register
+ */
+int nci_spi_register_device(struct nci_spi_dev *ndev)
+{
+	return nci_register_device(ndev->nci_dev);
+}
+EXPORT_SYMBOL_GPL(nci_spi_register_device);
+
+/**
+ * nci_spi_unregister_device - unregister a nci spi device in the nfc subsystem
+ *
+ * @dev: The nci spi device to unregister
+ */
+void nci_spi_unregister_device(struct nci_spi_dev *ndev)
+{
+	nci_unregister_device(ndev->nci_dev);
+}
+EXPORT_SYMBOL_GPL(nci_spi_unregister_device);