nfc: Add a virtual nci device driver

NCI virtual device simulates a NCI device to the user. It can be used to
validate the NCI module and applications. This driver supports
communication between the virtual NCI device and NCI module.
Signed-off-by: Bongsu Jeon <bongsu.jeon@samsung.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/nfc/Kconfig

@@ -49,6 +49,17 @@ config NFC_PORT100
 
 	  If unsure, say N.
 
+config NFC_VIRTUAL_NCI
+	tristate "NCI device simulator driver"
+	depends on NFC_NCI
+	help
+	  NCI virtual device simulates a NCI device to the user.
+	  It can be used to validate the NCI module and applications.
+	  This driver supports communication between the virtual NCI device and
+	  module.
+
+	  If unsure, say N.
+
 source "drivers/nfc/fdp/Kconfig"
 source "drivers/nfc/pn544/Kconfig"
 source "drivers/nfc/pn533/Kconfig"

drivers/nfc/Makefile

@@ -17,3 +17,4 @@ obj-$(CONFIG_NFC_ST_NCI)	+= st-nci/
 obj-$(CONFIG_NFC_NXP_NCI)	+= nxp-nci/
 obj-$(CONFIG_NFC_S3FWRN5)	+= s3fwrn5/
 obj-$(CONFIG_NFC_ST95HF)	+= st95hf/
+obj-$(CONFIG_NFC_VIRTUAL_NCI)	+= virtual_ncidev.o

drivers/nfc/virtual_ncidev.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtual NCI device simulation driver
+ *
+ * Copyright (C) 2020 Samsung Electrnoics
+ * Bongsu Jeon <bongsu.jeon@samsung.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <net/nfc/nci_core.h>
+
+enum virtual_ncidev_mode {
+	virtual_ncidev_enabled,
+	virtual_ncidev_disabled,
+	virtual_ncidev_disabling,
+};
+
+#define IOCTL_GET_NCIDEV_IDX    0
+#define VIRTUAL_NFC_PROTOCOLS	(NFC_PROTO_JEWEL_MASK | \
+				 NFC_PROTO_MIFARE_MASK | \
+				 NFC_PROTO_FELICA_MASK | \
+				 NFC_PROTO_ISO14443_MASK | \
+				 NFC_PROTO_ISO14443_B_MASK | \
+				 NFC_PROTO_ISO15693_MASK)
+
+static enum virtual_ncidev_mode state;
+static struct miscdevice miscdev;
+static struct sk_buff *send_buff;
+static struct nci_dev *ndev;
+static DEFINE_MUTEX(nci_mutex);
+
+static int virtual_nci_open(struct nci_dev *ndev)
+{
+	return 0;
+}
+
+static int virtual_nci_close(struct nci_dev *ndev)
+{
+	mutex_lock(&nci_mutex);
+	kfree_skb(send_buff);
+	send_buff = NULL;
+	mutex_unlock(&nci_mutex);
+
+	return 0;
+}
+
+static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
+{
+	mutex_lock(&nci_mutex);
+	if (state != virtual_ncidev_enabled) {
+		mutex_unlock(&nci_mutex);
+		return 0;
+	}
+
+	if (send_buff) {
+		mutex_unlock(&nci_mutex);
+		return -1;
+	}
+	send_buff = skb_copy(skb, GFP_KERNEL);
+	mutex_unlock(&nci_mutex);
+
+	return 0;
+}
+
+static struct nci_ops virtual_nci_ops = {
+	.open = virtual_nci_open,
+	.close = virtual_nci_close,
+	.send = virtual_nci_send
+};
+
+static ssize_t virtual_ncidev_read(struct file *file, char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	size_t actual_len;
+
+	mutex_lock(&nci_mutex);
+	if (!send_buff) {
+		mutex_unlock(&nci_mutex);
+		return 0;
+	}
+
+	actual_len = min_t(size_t, count, send_buff->len);
+
+	if (copy_to_user(buf, send_buff->data, actual_len)) {
+		mutex_unlock(&nci_mutex);
+		return -EFAULT;
+	}
+
+	skb_pull(send_buff, actual_len);
+	if (send_buff->len == 0) {
+		consume_skb(send_buff);
+		send_buff = NULL;
+	}
+	mutex_unlock(&nci_mutex);
+
+	return actual_len;
+}
+
+static ssize_t virtual_ncidev_write(struct file *file,
+				    const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct sk_buff *skb;
+
+	skb = alloc_skb(count, GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	if (copy_from_user(skb_put(skb, count), buf, count)) {
+		kfree_skb(skb);
+		return -EFAULT;
+	}
+
+	nci_recv_frame(ndev, skb);
+	return count;
+}
+
+static int virtual_ncidev_open(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+
+	mutex_lock(&nci_mutex);
+	if (state != virtual_ncidev_disabled) {
+		mutex_unlock(&nci_mutex);
+		return -EBUSY;
+	}
+
+	ndev = nci_allocate_device(&virtual_nci_ops, VIRTUAL_NFC_PROTOCOLS,
+				   0, 0);
+	if (!ndev) {
+		mutex_unlock(&nci_mutex);
+		return -ENOMEM;
+	}
+
+	ret = nci_register_device(ndev);
+	if (ret < 0) {
+		nci_free_device(ndev);
+		mutex_unlock(&nci_mutex);
+		return ret;
+	}
+	state = virtual_ncidev_enabled;
+	mutex_unlock(&nci_mutex);
+
+	return 0;
+}
+
+static int virtual_ncidev_close(struct inode *inode, struct file *file)
+{
+	mutex_lock(&nci_mutex);
+
+	if (state == virtual_ncidev_enabled) {
+		state = virtual_ncidev_disabling;
+		mutex_unlock(&nci_mutex);
+
+		nci_unregister_device(ndev);
+		nci_free_device(ndev);
+
+		mutex_lock(&nci_mutex);
+	}
+
+	state = virtual_ncidev_disabled;
+	mutex_unlock(&nci_mutex);
+
+	return 0;
+}
+
+static long virtual_ncidev_ioctl(struct file *flip, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct nfc_dev *nfc_dev = ndev->nfc_dev;
+	void __user *p = (void __user *)arg;
+
+	if (cmd != IOCTL_GET_NCIDEV_IDX)
+		return -ENOTTY;
+
+	if (copy_to_user(p, &nfc_dev->idx, sizeof(nfc_dev->idx)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static const struct file_operations virtual_ncidev_fops = {
+	.owner = THIS_MODULE,
+	.read = virtual_ncidev_read,
+	.write = virtual_ncidev_write,
+	.open = virtual_ncidev_open,
+	.release = virtual_ncidev_close,
+	.unlocked_ioctl = virtual_ncidev_ioctl
+};
+
+static int __init virtual_ncidev_init(void)
+{
+	state = virtual_ncidev_disabled;
+	miscdev.minor = MISC_DYNAMIC_MINOR;
+	miscdev.name = "virtual_nci";
+	miscdev.fops = &virtual_ncidev_fops;
+	miscdev.mode = S_IALLUGO;
+
+	return misc_register(&miscdev);
+}
+
+static void __exit virtual_ncidev_exit(void)
+{
+	misc_deregister(&miscdev);
+}
+
+module_init(virtual_ncidev_init);
+module_exit(virtual_ncidev_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtual NCI device simulation driver");
+MODULE_AUTHOR("Bongsu Jeon <bongsu.jeon@samsung.com>");