drivers/nfc/nfcsim.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * NFC hardware simulation driver
  * Copyright (c) 2013, Intel Corporation.
  */

 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/nfc.h>
 #include <net/nfc/nfc.h>
 #include <net/nfc/digital.h>

 #define NFCSIM_ERR(d, fmt, args...) nfc_err(&d->nfc_digital_dev->nfc_dev->dev, \
 					    "%s: " fmt, __func__, ## args)

 #define NFCSIM_DBG(d, fmt, args...) dev_dbg(&d->nfc_digital_dev->nfc_dev->dev, \
 					    "%s: " fmt, __func__, ## args)

 #define NFCSIM_VERSION "0.2"

 #define NFCSIM_MODE_NONE	0
 #define NFCSIM_MODE_INITIATOR	1
 #define NFCSIM_MODE_TARGET	2

 #define NFCSIM_CAPABILITIES (NFC_DIGITAL_DRV_CAPS_IN_CRC   | \
 			     NFC_DIGITAL_DRV_CAPS_TG_CRC)

 struct nfcsim {
 	struct nfc_digital_dev *nfc_digital_dev;

 	struct work_struct recv_work;
 	struct delayed_work send_work;

 	struct nfcsim_link *link_in;
 	struct nfcsim_link *link_out;

 	bool up;
 	u8 mode;
 	u8 rf_tech;

 	u16 recv_timeout;

 	nfc_digital_cmd_complete_t cb;
 	void *arg;

 	u8 dropframe;
 };

 struct nfcsim_link {
 	struct mutex lock;

 	u8 rf_tech;
 	u8 mode;

 	u8 shutdown;

 	struct sk_buff *skb;
 	wait_queue_head_t recv_wait;
 	u8 cond;
 };

 static struct nfcsim_link *nfcsim_link_new(void)
 {
 	struct nfcsim_link *link;

 	link = kzalloc(sizeof(struct nfcsim_link), GFP_KERNEL);
 	if (!link)
 		return NULL;

 	mutex_init(&link->lock);
 	init_waitqueue_head(&link->recv_wait);

 	return link;
 }

 static void nfcsim_link_free(struct nfcsim_link *link)
 {
 	dev_kfree_skb(link->skb);
 	kfree(link);
 }

 static void nfcsim_link_recv_wake(struct nfcsim_link *link)
 {
 	link->cond = 1;
 	wake_up_interruptible(&link->recv_wait);
 }

 static void nfcsim_link_set_skb(struct nfcsim_link *link, struct sk_buff *skb,
 				u8 rf_tech, u8 mode)
 {
 	mutex_lock(&link->lock);

 	dev_kfree_skb(link->skb);
 	link->skb = skb;
 	link->rf_tech = rf_tech;
 	link->mode = mode;

 	mutex_unlock(&link->lock);
 }

 static void nfcsim_link_recv_cancel(struct nfcsim_link *link)
 {
 	mutex_lock(&link->lock);

 	link->mode = NFCSIM_MODE_NONE;

 	mutex_unlock(&link->lock);

 	nfcsim_link_recv_wake(link);
 }

 static void nfcsim_link_shutdown(struct nfcsim_link *link)
 {
 	mutex_lock(&link->lock);

 	link->shutdown = 1;
 	link->mode = NFCSIM_MODE_NONE;

 	mutex_unlock(&link->lock);

 	nfcsim_link_recv_wake(link);
 }

 static struct sk_buff *nfcsim_link_recv_skb(struct nfcsim_link *link,
 					    int timeout, u8 rf_tech, u8 mode)
 {
 	int rc;
 	struct sk_buff *skb;

 	rc = wait_event_interruptible_timeout(link->recv_wait,
 					      link->cond,
 					      msecs_to_jiffies(timeout));

 	mutex_lock(&link->lock);

 	skb = link->skb;
 	link->skb = NULL;

 	if (!rc) {
 		rc = -ETIMEDOUT;
 		goto done;
 	}

 	if (!skb || link->rf_tech != rf_tech || link->mode == mode) {
 		rc = -EINVAL;
 		goto done;
 	}

 	if (link->shutdown) {
 		rc = -ENODEV;
 		goto done;
 	}

 done:
 	mutex_unlock(&link->lock);

 	if (rc < 0) {
 		dev_kfree_skb(skb);
 		skb = ERR_PTR(rc);
 	}

 	link->cond = 0;

 	return skb;
 }

 static void nfcsim_send_wq(struct work_struct *work)
 {
 	struct nfcsim *dev = container_of(work, struct nfcsim, send_work.work);

 	/*
 	 * To effectively send data, the device just wake up its link_out which
 	 * is the link_in of the peer device. The exchanged skb has already been
 	 * stored in the dev->link_out through nfcsim_link_set_skb().
 	 */
 	nfcsim_link_recv_wake(dev->link_out);
 }

 static void nfcsim_recv_wq(struct work_struct *work)
 {
 	struct nfcsim *dev = container_of(work, struct nfcsim, recv_work);
 	struct sk_buff *skb;

 	skb = nfcsim_link_recv_skb(dev->link_in, dev->recv_timeout,
 				   dev->rf_tech, dev->mode);

 	if (!dev->up) {
 		NFCSIM_ERR(dev, "Device is down\n");

 		if (!IS_ERR(skb))
 			dev_kfree_skb(skb);
 		return;
 	}

 	dev->cb(dev->nfc_digital_dev, dev->arg, skb);
 }

 static int nfcsim_send(struct nfc_digital_dev *ddev, struct sk_buff *skb,
 		       u16 timeout, nfc_digital_cmd_complete_t cb, void *arg)
 {
 	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);
 	u8 delay;

 	if (!dev->up) {
 		NFCSIM_ERR(dev, "Device is down\n");
 		return -ENODEV;
 	}

 	dev->recv_timeout = timeout;
 	dev->cb = cb;
 	dev->arg = arg;

 	schedule_work(&dev->recv_work);

 	if (dev->dropframe) {
 		NFCSIM_DBG(dev, "dropping frame (out of %d)\n", dev->dropframe);
 		dev_kfree_skb(skb);
 		dev->dropframe--;

 		return 0;
 	}

 	if (skb) {
 		nfcsim_link_set_skb(dev->link_out, skb, dev->rf_tech,
 				    dev->mode);

 		/* Add random delay (between 3 and 10 ms) before sending data */
 		get_random_bytes(&delay, 1);
 		delay = 3 + (delay & 0x07);

 		schedule_delayed_work(&dev->send_work, msecs_to_jiffies(delay));
 	}

 	return 0;
 }

 static void nfcsim_abort_cmd(struct nfc_digital_dev *ddev)
 {
 	const struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

 	nfcsim_link_recv_cancel(dev->link_in);
 }

 static int nfcsim_switch_rf(struct nfc_digital_dev *ddev, bool on)
 {
 	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

 	dev->up = on;

 	return 0;
 }

 static int nfcsim_in_configure_hw(struct nfc_digital_dev *ddev,
 					  int type, int param)
 {
 	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

 	switch (type) {
 	case NFC_DIGITAL_CONFIG_RF_TECH:
 		dev->up = true;
 		dev->mode = NFCSIM_MODE_INITIATOR;
 		dev->rf_tech = param;
 		break;

 	case NFC_DIGITAL_CONFIG_FRAMING:
 		break;

 	default:
 		NFCSIM_ERR(dev, "Invalid configuration type: %d\n", type);
 		return -EINVAL;
 	}

 	return 0;
 }

 static int nfcsim_in_send_cmd(struct nfc_digital_dev *ddev,
 			       struct sk_buff *skb, u16 timeout,
 			       nfc_digital_cmd_complete_t cb, void *arg)
 {
 	return nfcsim_send(ddev, skb, timeout, cb, arg);
 }

 static int nfcsim_tg_configure_hw(struct nfc_digital_dev *ddev,
 					  int type, int param)
 {
 	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

 	switch (type) {
 	case NFC_DIGITAL_CONFIG_RF_TECH:
 		dev->up = true;
 		dev->mode = NFCSIM_MODE_TARGET;
 		dev->rf_tech = param;
 		break;

 	case NFC_DIGITAL_CONFIG_FRAMING:
 		break;

 	default:
 		NFCSIM_ERR(dev, "Invalid configuration type: %d\n", type);
 		return -EINVAL;
 	}

 	return 0;
 }

 static int nfcsim_tg_send_cmd(struct nfc_digital_dev *ddev,
 			       struct sk_buff *skb, u16 timeout,
 			       nfc_digital_cmd_complete_t cb, void *arg)
 {
 	return nfcsim_send(ddev, skb, timeout, cb, arg);
 }

 static int nfcsim_tg_listen(struct nfc_digital_dev *ddev, u16 timeout,
 			    nfc_digital_cmd_complete_t cb, void *arg)
 {
 	return nfcsim_send(ddev, NULL, timeout, cb, arg);
 }

 static const struct nfc_digital_ops nfcsim_digital_ops = {
 	.in_configure_hw = nfcsim_in_configure_hw,
 	.in_send_cmd = nfcsim_in_send_cmd,

 	.tg_listen = nfcsim_tg_listen,
 	.tg_configure_hw = nfcsim_tg_configure_hw,
 	.tg_send_cmd = nfcsim_tg_send_cmd,

 	.abort_cmd = nfcsim_abort_cmd,
 	.switch_rf = nfcsim_switch_rf,
 };

 static struct dentry *nfcsim_debugfs_root;

 static void nfcsim_debugfs_init(void)
 {
 	nfcsim_debugfs_root = debugfs_create_dir("nfcsim", NULL);

 	if (!nfcsim_debugfs_root)
 		pr_err("Could not create debugfs entry\n");

 }

 static void nfcsim_debugfs_remove(void)
 {
 	debugfs_remove_recursive(nfcsim_debugfs_root);
 }

 static void nfcsim_debugfs_init_dev(struct nfcsim *dev)
 {
 	struct dentry *dev_dir;
 	char devname[5]; /* nfcX\0 */
 	u32 idx;
 	int n;

 	if (!nfcsim_debugfs_root) {
 		NFCSIM_ERR(dev, "nfcsim debugfs not initialized\n");
 		return;
 	}

 	idx = dev->nfc_digital_dev->nfc_dev->idx;
 	n = snprintf(devname, sizeof(devname), "nfc%d", idx);
 	if (n >= sizeof(devname)) {
 		NFCSIM_ERR(dev, "Could not compute dev name for dev %d\n", idx);
 		return;
 	}

 	dev_dir = debugfs_create_dir(devname, nfcsim_debugfs_root);

 	debugfs_create_u8("dropframe", 0664, dev_dir, &dev->dropframe);
 }

 static struct nfcsim *nfcsim_device_new(struct nfcsim_link *link_in,
 					struct nfcsim_link *link_out)
 {
 	struct nfcsim *dev;
 	int rc;

 	dev = kzalloc(sizeof(struct nfcsim), GFP_KERNEL);
 	if (!dev)
 		return ERR_PTR(-ENOMEM);

 	INIT_DELAYED_WORK(&dev->send_work, nfcsim_send_wq);
 	INIT_WORK(&dev->recv_work, nfcsim_recv_wq);

 	dev->nfc_digital_dev =
 			nfc_digital_allocate_device(&nfcsim_digital_ops,
 						    NFC_PROTO_NFC_DEP_MASK,
 						    NFCSIM_CAPABILITIES,
 						    0, 0);
 	if (!dev->nfc_digital_dev) {
 		kfree(dev);
 		return ERR_PTR(-ENOMEM);
 	}

 	nfc_digital_set_drvdata(dev->nfc_digital_dev, dev);

 	dev->link_in = link_in;
 	dev->link_out = link_out;

 	rc = nfc_digital_register_device(dev->nfc_digital_dev);
 	if (rc) {
 		pr_err("Could not register digital device (%d)\n", rc);
 		nfc_digital_free_device(dev->nfc_digital_dev);
 		kfree(dev);

 		return ERR_PTR(rc);
 	}

 	nfcsim_debugfs_init_dev(dev);

 	return dev;
 }

 static void nfcsim_device_free(struct nfcsim *dev)
 {
 	nfc_digital_unregister_device(dev->nfc_digital_dev);

 	dev->up = false;

 	nfcsim_link_shutdown(dev->link_in);

 	cancel_delayed_work_sync(&dev->send_work);
 	cancel_work_sync(&dev->recv_work);

 	nfc_digital_free_device(dev->nfc_digital_dev);

 	kfree(dev);
 }

 static struct nfcsim *dev0;
 static struct nfcsim *dev1;

 static int __init nfcsim_init(void)
 {
 	struct nfcsim_link *link0, *link1;
 	int rc;

 	link0 = nfcsim_link_new();
 	link1 = nfcsim_link_new();
 	if (!link0 || !link1) {
 		rc = -ENOMEM;
 		goto exit_err;
 	}

 	nfcsim_debugfs_init();

 	dev0 = nfcsim_device_new(link0, link1);
 	if (IS_ERR(dev0)) {
 		rc = PTR_ERR(dev0);
 		goto exit_err;
 	}

 	dev1 = nfcsim_device_new(link1, link0);
 	if (IS_ERR(dev1)) {
 		nfcsim_device_free(dev0);

 		rc = PTR_ERR(dev1);
 		goto exit_err;
 	}

 	pr_info("nfcsim " NFCSIM_VERSION " initialized\n");

 	return 0;

 exit_err:
 	pr_err("Failed to initialize nfcsim driver (%d)\n", rc);

 	if (link0)
 		nfcsim_link_free(link0);
 	if (link1)
 		nfcsim_link_free(link1);

 	return rc;
 }

 static void __exit nfcsim_exit(void)
 {
 	struct nfcsim_link *link0, *link1;

 	link0 = dev0->link_in;
 	link1 = dev0->link_out;

 	nfcsim_device_free(dev0);
 	nfcsim_device_free(dev1);

 	nfcsim_link_free(link0);
 	nfcsim_link_free(link1);

 	nfcsim_debugfs_remove();
 }

 module_init(nfcsim_init);
 module_exit(nfcsim_exit);

 MODULE_DESCRIPTION("NFCSim driver ver " NFCSIM_VERSION);
 MODULE_VERSION(NFCSIM_VERSION);
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* NFC hardware simulation driver
	* Copyright (c) 2013, Intel Corporation.
	*/

	#include <linux/device.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/ctype.h>
	#include <linux/debugfs.h>
	#include <linux/nfc.h>
	#include <net/nfc/nfc.h>
	#include <net/nfc/digital.h>

	#define NFCSIM_ERR(d, fmt, args...) nfc_err(&d->nfc_digital_dev->nfc_dev->dev, \
	"%s: " fmt, __func__, ## args)

	#define NFCSIM_DBG(d, fmt, args...) dev_dbg(&d->nfc_digital_dev->nfc_dev->dev, \
	"%s: " fmt, __func__, ## args)

	#define NFCSIM_VERSION "0.2"

	#define NFCSIM_MODE_NONE 0
	#define NFCSIM_MODE_INITIATOR 1
	#define NFCSIM_MODE_TARGET 2

	#define NFCSIM_CAPABILITIES (NFC_DIGITAL_DRV_CAPS_IN_CRC \| \
	NFC_DIGITAL_DRV_CAPS_TG_CRC)

	struct nfcsim {
	struct nfc_digital_dev *nfc_digital_dev;

	struct work_struct recv_work;
	struct delayed_work send_work;

	struct nfcsim_link *link_in;
	struct nfcsim_link *link_out;

	bool up;
	u8 mode;
	u8 rf_tech;

	u16 recv_timeout;

	nfc_digital_cmd_complete_t cb;
	void *arg;

	u8 dropframe;
	};

	struct nfcsim_link {
	struct mutex lock;

	u8 rf_tech;
	u8 mode;

	u8 shutdown;

	struct sk_buff *skb;
	wait_queue_head_t recv_wait;
	u8 cond;
	};

	static struct nfcsim_link *nfcsim_link_new(void)
	{
	struct nfcsim_link *link;

	link = kzalloc(sizeof(struct nfcsim_link), GFP_KERNEL);
	if (!link)
	return NULL;

	mutex_init(&link->lock);
	init_waitqueue_head(&link->recv_wait);

	return link;
	}

	static void nfcsim_link_free(struct nfcsim_link *link)
	{
	dev_kfree_skb(link->skb);
	kfree(link);
	}

	static void nfcsim_link_recv_wake(struct nfcsim_link *link)
	{
	link->cond = 1;
	wake_up_interruptible(&link->recv_wait);
	}

	static void nfcsim_link_set_skb(struct nfcsim_link link, struct sk_buff skb,
	u8 rf_tech, u8 mode)
	{
	mutex_lock(&link->lock);

	dev_kfree_skb(link->skb);
	link->skb = skb;
	link->rf_tech = rf_tech;
	link->mode = mode;

	mutex_unlock(&link->lock);
	}

	static void nfcsim_link_recv_cancel(struct nfcsim_link *link)
	{
	mutex_lock(&link->lock);

	link->mode = NFCSIM_MODE_NONE;

	mutex_unlock(&link->lock);

	nfcsim_link_recv_wake(link);
	}

	static void nfcsim_link_shutdown(struct nfcsim_link *link)
	{
	mutex_lock(&link->lock);

	link->shutdown = 1;
	link->mode = NFCSIM_MODE_NONE;

	mutex_unlock(&link->lock);

	nfcsim_link_recv_wake(link);
	}

	static struct sk_buff nfcsim_link_recv_skb(struct nfcsim_link link,
	int timeout, u8 rf_tech, u8 mode)
	{
	int rc;
	struct sk_buff *skb;

	rc = wait_event_interruptible_timeout(link->recv_wait,
	link->cond,
	msecs_to_jiffies(timeout));

	mutex_lock(&link->lock);

	skb = link->skb;
	link->skb = NULL;

	if (!rc) {
	rc = -ETIMEDOUT;
	goto done;
	}

	if (!skb \|\| link->rf_tech != rf_tech \|\| link->mode == mode) {
	rc = -EINVAL;
	goto done;
	}

	if (link->shutdown) {
	rc = -ENODEV;
	goto done;
	}

	done:
	mutex_unlock(&link->lock);

	if (rc < 0) {
	dev_kfree_skb(skb);
	skb = ERR_PTR(rc);
	}

	link->cond = 0;

	return skb;
	}

	static void nfcsim_send_wq(struct work_struct *work)
	{
	struct nfcsim *dev = container_of(work, struct nfcsim, send_work.work);

	/*
	* To effectively send data, the device just wake up its link_out which
	* is the link_in of the peer device. The exchanged skb has already been
	* stored in the dev->link_out through nfcsim_link_set_skb().
	*/
	nfcsim_link_recv_wake(dev->link_out);
	}

	static void nfcsim_recv_wq(struct work_struct *work)
	{
	struct nfcsim *dev = container_of(work, struct nfcsim, recv_work);
	struct sk_buff *skb;

	skb = nfcsim_link_recv_skb(dev->link_in, dev->recv_timeout,
	dev->rf_tech, dev->mode);

	if (!dev->up) {
	NFCSIM_ERR(dev, "Device is down\n");

	if (!IS_ERR(skb))
	dev_kfree_skb(skb);
	return;
	}

	dev->cb(dev->nfc_digital_dev, dev->arg, skb);
	}

	static int nfcsim_send(struct nfc_digital_dev ddev, struct sk_buff skb,
	u16 timeout, nfc_digital_cmd_complete_t cb, void *arg)
	{
	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);
	u8 delay;

	if (!dev->up) {
	NFCSIM_ERR(dev, "Device is down\n");
	return -ENODEV;
	}

	dev->recv_timeout = timeout;
	dev->cb = cb;
	dev->arg = arg;

	schedule_work(&dev->recv_work);

	if (dev->dropframe) {
	NFCSIM_DBG(dev, "dropping frame (out of %d)\n", dev->dropframe);
	dev_kfree_skb(skb);
	dev->dropframe--;

	return 0;
	}

	if (skb) {
	nfcsim_link_set_skb(dev->link_out, skb, dev->rf_tech,
	dev->mode);

	/* Add random delay (between 3 and 10 ms) before sending data */
	get_random_bytes(&delay, 1);
	delay = 3 + (delay & 0x07);

	schedule_delayed_work(&dev->send_work, msecs_to_jiffies(delay));
	}

	return 0;
	}

	static void nfcsim_abort_cmd(struct nfc_digital_dev *ddev)
	{
	const struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

	nfcsim_link_recv_cancel(dev->link_in);
	}

	static int nfcsim_switch_rf(struct nfc_digital_dev *ddev, bool on)
	{
	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

	dev->up = on;

	return 0;
	}

	static int nfcsim_in_configure_hw(struct nfc_digital_dev *ddev,
	int type, int param)
	{
	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

	switch (type) {
	case NFC_DIGITAL_CONFIG_RF_TECH:
	dev->up = true;
	dev->mode = NFCSIM_MODE_INITIATOR;
	dev->rf_tech = param;
	break;

	case NFC_DIGITAL_CONFIG_FRAMING:
	break;

	default:
	NFCSIM_ERR(dev, "Invalid configuration type: %d\n", type);
	return -EINVAL;
	}

	return 0;
	}

	static int nfcsim_in_send_cmd(struct nfc_digital_dev *ddev,
	struct sk_buff *skb, u16 timeout,
	nfc_digital_cmd_complete_t cb, void *arg)
	{
	return nfcsim_send(ddev, skb, timeout, cb, arg);
	}

	static int nfcsim_tg_configure_hw(struct nfc_digital_dev *ddev,
	int type, int param)
	{
	struct nfcsim *dev = nfc_digital_get_drvdata(ddev);

	switch (type) {
	case NFC_DIGITAL_CONFIG_RF_TECH:
	dev->up = true;
	dev->mode = NFCSIM_MODE_TARGET;
	dev->rf_tech = param;
	break;

	case NFC_DIGITAL_CONFIG_FRAMING:
	break;

	default:
	NFCSIM_ERR(dev, "Invalid configuration type: %d\n", type);
	return -EINVAL;
	}

	return 0;
	}

	static int nfcsim_tg_send_cmd(struct nfc_digital_dev *ddev,
	struct sk_buff *skb, u16 timeout,
	nfc_digital_cmd_complete_t cb, void *arg)
	{
	return nfcsim_send(ddev, skb, timeout, cb, arg);
	}

	static int nfcsim_tg_listen(struct nfc_digital_dev *ddev, u16 timeout,
	nfc_digital_cmd_complete_t cb, void *arg)
	{
	return nfcsim_send(ddev, NULL, timeout, cb, arg);
	}

	static const struct nfc_digital_ops nfcsim_digital_ops = {
	.in_configure_hw = nfcsim_in_configure_hw,
	.in_send_cmd = nfcsim_in_send_cmd,

	.tg_listen = nfcsim_tg_listen,
	.tg_configure_hw = nfcsim_tg_configure_hw,
	.tg_send_cmd = nfcsim_tg_send_cmd,

	.abort_cmd = nfcsim_abort_cmd,
	.switch_rf = nfcsim_switch_rf,
	};

	static struct dentry *nfcsim_debugfs_root;

	static void nfcsim_debugfs_init(void)
	{
	nfcsim_debugfs_root = debugfs_create_dir("nfcsim", NULL);

	if (!nfcsim_debugfs_root)
	pr_err("Could not create debugfs entry\n");

	}

	static void nfcsim_debugfs_remove(void)
	{
	debugfs_remove_recursive(nfcsim_debugfs_root);
	}

	static void nfcsim_debugfs_init_dev(struct nfcsim *dev)
	{
	struct dentry *dev_dir;
	char devname[5]; /* nfcX\0 */
	u32 idx;
	int n;

	if (!nfcsim_debugfs_root) {
	NFCSIM_ERR(dev, "nfcsim debugfs not initialized\n");
	return;
	}

	idx = dev->nfc_digital_dev->nfc_dev->idx;
	n = snprintf(devname, sizeof(devname), "nfc%d", idx);
	if (n >= sizeof(devname)) {
	NFCSIM_ERR(dev, "Could not compute dev name for dev %d\n", idx);
	return;
	}

	dev_dir = debugfs_create_dir(devname, nfcsim_debugfs_root);

	debugfs_create_u8("dropframe", 0664, dev_dir, &dev->dropframe);
	}

	static struct nfcsim nfcsim_device_new(struct nfcsim_link link_in,
	struct nfcsim_link *link_out)
	{
	struct nfcsim *dev;
	int rc;

	dev = kzalloc(sizeof(struct nfcsim), GFP_KERNEL);
	if (!dev)
	return ERR_PTR(-ENOMEM);

	INIT_DELAYED_WORK(&dev->send_work, nfcsim_send_wq);
	INIT_WORK(&dev->recv_work, nfcsim_recv_wq);

	dev->nfc_digital_dev =
	nfc_digital_allocate_device(&nfcsim_digital_ops,
	NFC_PROTO_NFC_DEP_MASK,
	NFCSIM_CAPABILITIES,
	0, 0);
	if (!dev->nfc_digital_dev) {
	kfree(dev);
	return ERR_PTR(-ENOMEM);
	}

	nfc_digital_set_drvdata(dev->nfc_digital_dev, dev);

	dev->link_in = link_in;
	dev->link_out = link_out;

	rc = nfc_digital_register_device(dev->nfc_digital_dev);
	if (rc) {
	pr_err("Could not register digital device (%d)\n", rc);
	nfc_digital_free_device(dev->nfc_digital_dev);
	kfree(dev);

	return ERR_PTR(rc);
	}

	nfcsim_debugfs_init_dev(dev);

	return dev;
	}

	static void nfcsim_device_free(struct nfcsim *dev)
	{
	nfc_digital_unregister_device(dev->nfc_digital_dev);

	dev->up = false;

	nfcsim_link_shutdown(dev->link_in);

	cancel_delayed_work_sync(&dev->send_work);
	cancel_work_sync(&dev->recv_work);

	nfc_digital_free_device(dev->nfc_digital_dev);

	kfree(dev);
	}

	static struct nfcsim *dev0;
	static struct nfcsim *dev1;

	static int __init nfcsim_init(void)
	{
	struct nfcsim_link link0, link1;
	int rc;

	link0 = nfcsim_link_new();
	link1 = nfcsim_link_new();
	if (!link0 \|\| !link1) {
	rc = -ENOMEM;
	goto exit_err;
	}

	nfcsim_debugfs_init();

	dev0 = nfcsim_device_new(link0, link1);
	if (IS_ERR(dev0)) {
	rc = PTR_ERR(dev0);
	goto exit_err;
	}

	dev1 = nfcsim_device_new(link1, link0);
	if (IS_ERR(dev1)) {
	nfcsim_device_free(dev0);

	rc = PTR_ERR(dev1);
	goto exit_err;
	}

	pr_info("nfcsim " NFCSIM_VERSION " initialized\n");

	return 0;

	exit_err:
	pr_err("Failed to initialize nfcsim driver (%d)\n", rc);

	if (link0)
	nfcsim_link_free(link0);
	if (link1)
	nfcsim_link_free(link1);

	return rc;
	}

	static void __exit nfcsim_exit(void)
	{
	struct nfcsim_link link0, link1;

	link0 = dev0->link_in;
	link1 = dev0->link_out;

	nfcsim_device_free(dev0);
	nfcsim_device_free(dev1);

	nfcsim_link_free(link0);
	nfcsim_link_free(link1);

	nfcsim_debugfs_remove();
	}

	module_init(nfcsim_init);
	module_exit(nfcsim_exit);

	MODULE_DESCRIPTION("NFCSim driver ver " NFCSIM_VERSION);
	MODULE_VERSION(NFCSIM_VERSION);
	MODULE_LICENSE("GPL");