linux_kernel/net/nfc/core.c

/*
 * Copyright (C) 2011 Instituto Nokia de Tecnologia
 *
 * Authors:
 *    Lauro Ramos Venancio <lauro.venancio@openbossa.org>
 *    Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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/>.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": %s: " fmt, __func__

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/rfkill.h>
#include <linux/nfc.h>

#include <net/genetlink.h>

#include "nfc.h"

#define VERSION "0.1"

#define NFC_CHECK_PRES_FREQ_MS	2000

int nfc_devlist_generation;
DEFINE_MUTEX(nfc_devlist_mutex);

/* NFC device ID bitmap */
static DEFINE_IDA(nfc_index_ida);

int nfc_fw_download(struct nfc_dev *dev, const char *firmware_name)
{
	int rc = 0;

	pr_debug("%s do firmware %s\n", dev_name(&dev->dev), firmware_name);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->dev_up) {
		rc = -EBUSY;
		goto error;
	}

	if (!dev->ops->fw_download) {
		rc = -EOPNOTSUPP;
		goto error;
	}

	dev->fw_download_in_progress = true;
	rc = dev->ops->fw_download(dev, firmware_name);
	if (rc)
		dev->fw_download_in_progress = false;

error:
	device_unlock(&dev->dev);
	return rc;
}

/**
 * nfc_fw_download_done - inform that a firmware download was completed
 *
 * @dev: The nfc device to which firmware was downloaded
 * @firmware_name: The firmware filename
 * @result: The positive value of a standard errno value
 */
int nfc_fw_download_done(struct nfc_dev *dev, const char *firmware_name,
			 u32 result)
{
	dev->fw_download_in_progress = false;

	return nfc_genl_fw_download_done(dev, firmware_name, result);
}
EXPORT_SYMBOL(nfc_fw_download_done);

/**
 * nfc_dev_up - turn on the NFC device
 *
 * @dev: The nfc device to be turned on
 *
 * The device remains up until the nfc_dev_down function is called.
 */
int nfc_dev_up(struct nfc_dev *dev)
{
	int rc = 0;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	device_lock(&dev->dev);

	if (dev->rfkill && rfkill_blocked(dev->rfkill)) {
		rc = -ERFKILL;
		goto error;
	}

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->fw_download_in_progress) {
		rc = -EBUSY;
		goto error;
	}

	if (dev->dev_up) {
		rc = -EALREADY;
		goto error;
	}

	if (dev->ops->dev_up)
		rc = dev->ops->dev_up(dev);

	if (!rc)
		dev->dev_up = true;

	/* We have to enable the device before discovering SEs */
	if (dev->ops->discover_se) {
		rc = dev->ops->discover_se(dev);
		if (rc)
			pr_warn("SE discovery failed\n");
	}

error:
	device_unlock(&dev->dev);
	return rc;
}

/**
 * nfc_dev_down - turn off the NFC device
 *
 * @dev: The nfc device to be turned off
 */
int nfc_dev_down(struct nfc_dev *dev)
{
	int rc = 0;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->dev_up) {
		rc = -EALREADY;
		goto error;
	}

	if (dev->polling || dev->active_target) {
		rc = -EBUSY;
		goto error;
	}

	if (dev->ops->dev_down)
		dev->ops->dev_down(dev);

	dev->dev_up = false;

error:
	device_unlock(&dev->dev);
	return rc;
}

static int nfc_rfkill_set_block(void *data, bool blocked)
{
	struct nfc_dev *dev = data;

	pr_debug("%s blocked %d", dev_name(&dev->dev), blocked);

	if (!blocked)
		return 0;

	nfc_dev_down(dev);

	return 0;
}

static const struct rfkill_ops nfc_rfkill_ops = {
	.set_block = nfc_rfkill_set_block,
};

/**
 * nfc_start_poll - start polling for nfc targets
 *
 * @dev: The nfc device that must start polling
 * @protocols: bitset of nfc protocols that must be used for polling
 *
 * The device remains polling for targets until a target is found or
 * the nfc_stop_poll function is called.
 */
int nfc_start_poll(struct nfc_dev *dev, u32 im_protocols, u32 tm_protocols)
{
	int rc;

	pr_debug("dev_name %s initiator protocols 0x%x target protocols 0x%x\n",
		 dev_name(&dev->dev), im_protocols, tm_protocols);

	if (!im_protocols && !tm_protocols)
		return -EINVAL;

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->dev_up) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->polling) {
		rc = -EBUSY;
		goto error;
	}

	rc = dev->ops->start_poll(dev, im_protocols, tm_protocols);
	if (!rc) {
		dev->polling = true;
		dev->rf_mode = NFC_RF_NONE;
	}

error:
	device_unlock(&dev->dev);
	return rc;
}

/**
 * nfc_stop_poll - stop polling for nfc targets
 *
 * @dev: The nfc device that must stop polling
 */
int nfc_stop_poll(struct nfc_dev *dev)
{
	int rc = 0;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->polling) {
		rc = -EINVAL;
		goto error;
	}

	dev->ops->stop_poll(dev);
	dev->polling = false;
	dev->rf_mode = NFC_RF_NONE;

error:
	device_unlock(&dev->dev);
	return rc;
}

static struct nfc_target *nfc_find_target(struct nfc_dev *dev, u32 target_idx)
{
	int i;

	if (dev->n_targets == 0)
		return NULL;

	for (i = 0; i < dev->n_targets; i++) {
		if (dev->targets[i].idx == target_idx)
			return &dev->targets[i];
	}

	return NULL;
}

int nfc_dep_link_up(struct nfc_dev *dev, int target_index, u8 comm_mode)
{
	int rc = 0;
	u8 *gb;
	size_t gb_len;
	struct nfc_target *target;

	pr_debug("dev_name=%s comm %d\n", dev_name(&dev->dev), comm_mode);

	if (!dev->ops->dep_link_up)
		return -EOPNOTSUPP;

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->dep_link_up == true) {
		rc = -EALREADY;
		goto error;
	}

	gb = nfc_llcp_general_bytes(dev, &gb_len);
	if (gb_len > NFC_MAX_GT_LEN) {
		rc = -EINVAL;
		goto error;
	}

	target = nfc_find_target(dev, target_index);
	if (target == NULL) {
		rc = -ENOTCONN;
		goto error;
	}

	rc = dev->ops->dep_link_up(dev, target, comm_mode, gb, gb_len);
	if (!rc) {
		dev->active_target = target;
		dev->rf_mode = NFC_RF_INITIATOR;
	}

error:
	device_unlock(&dev->dev);
	return rc;
}

int nfc_dep_link_down(struct nfc_dev *dev)
{
	int rc = 0;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	if (!dev->ops->dep_link_down)
		return -EOPNOTSUPP;

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->dep_link_up == false) {
		rc = -EALREADY;
		goto error;
	}

	rc = dev->ops->dep_link_down(dev);
	if (!rc) {
		dev->dep_link_up = false;
		dev->active_target = NULL;
		dev->rf_mode = NFC_RF_NONE;
		nfc_llcp_mac_is_down(dev);
		nfc_genl_dep_link_down_event(dev);
	}

error:
	device_unlock(&dev->dev);

	return rc;
}

int nfc_dep_link_is_up(struct nfc_dev *dev, u32 target_idx,
		       u8 comm_mode, u8 rf_mode)
{
	dev->dep_link_up = true;

	if (!dev->active_target) {
		struct nfc_target *target;

		target = nfc_find_target(dev, target_idx);
		if (target == NULL)
			return -ENOTCONN;

		dev->active_target = target;
	}

	dev->polling = false;
	dev->rf_mode = rf_mode;

	nfc_llcp_mac_is_up(dev, target_idx, comm_mode, rf_mode);

	return nfc_genl_dep_link_up_event(dev, target_idx, comm_mode, rf_mode);
}
EXPORT_SYMBOL(nfc_dep_link_is_up);

/**
 * nfc_activate_target - prepare the target for data exchange
 *
 * @dev: The nfc device that found the target
 * @target_idx: index of the target that must be activated
 * @protocol: nfc protocol that will be used for data exchange
 */
int nfc_activate_target(struct nfc_dev *dev, u32 target_idx, u32 protocol)
{
	int rc;
	struct nfc_target *target;

	pr_debug("dev_name=%s target_idx=%u protocol=%u\n",
		 dev_name(&dev->dev), target_idx, protocol);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->active_target) {
		rc = -EBUSY;
		goto error;
	}

	target = nfc_find_target(dev, target_idx);
	if (target == NULL) {
		rc = -ENOTCONN;
		goto error;
	}

	rc = dev->ops->activate_target(dev, target, protocol);
	if (!rc) {
		dev->active_target = target;
		dev->rf_mode = NFC_RF_INITIATOR;

		if (dev->ops->check_presence && !dev->shutting_down)
			mod_timer(&dev->check_pres_timer, jiffies +
				  msecs_to_jiffies(NFC_CHECK_PRES_FREQ_MS));
	}

error:
	device_unlock(&dev->dev);
	return rc;
}

/**
 * nfc_deactivate_target - deactivate a nfc target
 *
 * @dev: The nfc device that found the target
 * @target_idx: index of the target that must be deactivated
 */
int nfc_deactivate_target(struct nfc_dev *dev, u32 target_idx)
{
	int rc = 0;

	pr_debug("dev_name=%s target_idx=%u\n",
		 dev_name(&dev->dev), target_idx);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->active_target == NULL) {
		rc = -ENOTCONN;
		goto error;
	}

	if (dev->active_target->idx != target_idx) {
		rc = -ENOTCONN;
		goto error;
	}

	if (dev->ops->check_presence)
		del_timer_sync(&dev->check_pres_timer);

	dev->ops->deactivate_target(dev, dev->active_target);
	dev->active_target = NULL;

error:
	device_unlock(&dev->dev);
	return rc;
}

/**
 * nfc_data_exchange - transceive data
 *
 * @dev: The nfc device that found the target
 * @target_idx: index of the target
 * @skb: data to be sent
 * @cb: callback called when the response is received
 * @cb_context: parameter for the callback function
 *
 * The user must wait for the callback before calling this function again.
 */
int nfc_data_exchange(struct nfc_dev *dev, u32 target_idx, struct sk_buff *skb,
		      data_exchange_cb_t cb, void *cb_context)
{
	int rc;

	pr_debug("dev_name=%s target_idx=%u skb->len=%u\n",
		 dev_name(&dev->dev), target_idx, skb->len);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		kfree_skb(skb);
		goto error;
	}

	if (dev->rf_mode == NFC_RF_INITIATOR && dev->active_target != NULL) {
		if (dev->active_target->idx != target_idx) {
			rc = -EADDRNOTAVAIL;
			kfree_skb(skb);
			goto error;
		}

		if (dev->ops->check_presence)
			del_timer_sync(&dev->check_pres_timer);

		rc = dev->ops->im_transceive(dev, dev->active_target, skb, cb,
					     cb_context);

		if (!rc && dev->ops->check_presence && !dev->shutting_down)
			mod_timer(&dev->check_pres_timer, jiffies +
				  msecs_to_jiffies(NFC_CHECK_PRES_FREQ_MS));
	} else if (dev->rf_mode == NFC_RF_TARGET && dev->ops->tm_send != NULL) {
		rc = dev->ops->tm_send(dev, skb);
	} else {
		rc = -ENOTCONN;
		kfree_skb(skb);
		goto error;
	}


error:
	device_unlock(&dev->dev);
	return rc;
}

struct nfc_se *nfc_find_se(struct nfc_dev *dev, u32 se_idx)
{
	struct nfc_se *se, *n;

	list_for_each_entry_safe(se, n, &dev->secure_elements, list)
		if (se->idx == se_idx)
			return se;

	return NULL;
}
EXPORT_SYMBOL(nfc_find_se);

int nfc_enable_se(struct nfc_dev *dev, u32 se_idx)
{

	struct nfc_se *se;
	int rc;

	pr_debug("%s se index %d\n", dev_name(&dev->dev), se_idx);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->dev_up) {
		rc = -ENODEV;
		goto error;
	}

	if (dev->polling) {
		rc = -EBUSY;
		goto error;
	}

	if (!dev->ops->enable_se || !dev->ops->disable_se) {
		rc = -EOPNOTSUPP;
		goto error;
	}

	se = nfc_find_se(dev, se_idx);
	if (!se) {
		rc = -EINVAL;
		goto error;
	}

	if (se->state == NFC_SE_ENABLED) {
		rc = -EALREADY;
		goto error;
	}

	rc = dev->ops->enable_se(dev, se_idx);
	if (rc >= 0)
		se->state = NFC_SE_ENABLED;

error:
	device_unlock(&dev->dev);
	return rc;
}

int nfc_disable_se(struct nfc_dev *dev, u32 se_idx)
{

	struct nfc_se *se;
	int rc;

	pr_debug("%s se index %d\n", dev_name(&dev->dev), se_idx);

	device_lock(&dev->dev);

	if (!device_is_registered(&dev->dev)) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->dev_up) {
		rc = -ENODEV;
		goto error;
	}

	if (!dev->ops->enable_se || !dev->ops->disable_se) {
		rc = -EOPNOTSUPP;
		goto error;
	}

	se = nfc_find_se(dev, se_idx);
	if (!se) {
		rc = -EINVAL;
		goto error;
	}

	if (se->state == NFC_SE_DISABLED) {
		rc = -EALREADY;
		goto error;
	}

	rc = dev->ops->disable_se(dev, se_idx);
	if (rc >= 0)
		se->state = NFC_SE_DISABLED;

error:
	device_unlock(&dev->dev);
	return rc;
}

int nfc_set_remote_general_bytes(struct nfc_dev *dev, u8 *gb, u8 gb_len)
{
	pr_debug("dev_name=%s gb_len=%d\n", dev_name(&dev->dev), gb_len);

	if (gb_len > NFC_MAX_GT_LEN)
		return -EINVAL;

	return nfc_llcp_set_remote_gb(dev, gb, gb_len);
}
EXPORT_SYMBOL(nfc_set_remote_general_bytes);

u8 *nfc_get_local_general_bytes(struct nfc_dev *dev, size_t *gb_len)
{
	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	return nfc_llcp_general_bytes(dev, gb_len);
}
EXPORT_SYMBOL(nfc_get_local_general_bytes);

int nfc_tm_data_received(struct nfc_dev *dev, struct sk_buff *skb)
{
	/* Only LLCP target mode for now */
	if (dev->dep_link_up == false) {
		kfree_skb(skb);
		return -ENOLINK;
	}

	return nfc_llcp_data_received(dev, skb);
}
EXPORT_SYMBOL(nfc_tm_data_received);

int nfc_tm_activated(struct nfc_dev *dev, u32 protocol, u8 comm_mode,
		     u8 *gb, size_t gb_len)
{
	int rc;

	device_lock(&dev->dev);

	dev->polling = false;

	if (gb != NULL) {
		rc = nfc_set_remote_general_bytes(dev, gb, gb_len);
		if (rc < 0)
			goto out;
	}

	dev->rf_mode = NFC_RF_TARGET;

	if (protocol == NFC_PROTO_NFC_DEP_MASK)
		nfc_dep_link_is_up(dev, 0, comm_mode, NFC_RF_TARGET);

	rc = nfc_genl_tm_activated(dev, protocol);

out:
	device_unlock(&dev->dev);

	return rc;
}
EXPORT_SYMBOL(nfc_tm_activated);

int nfc_tm_deactivated(struct nfc_dev *dev)
{
	dev->dep_link_up = false;
	dev->rf_mode = NFC_RF_NONE;

	return nfc_genl_tm_deactivated(dev);
}
EXPORT_SYMBOL(nfc_tm_deactivated);

/**
 * nfc_alloc_send_skb - allocate a skb for data exchange responses
 *
 * @size: size to allocate
 * @gfp: gfp flags
 */
struct sk_buff *nfc_alloc_send_skb(struct nfc_dev *dev, struct sock *sk,
				   unsigned int flags, unsigned int size,
				   unsigned int *err)
{
	struct sk_buff *skb;
	unsigned int total_size;

	total_size = size +
		dev->tx_headroom + dev->tx_tailroom + NFC_HEADER_SIZE;

	skb = sock_alloc_send_skb(sk, total_size, flags & MSG_DONTWAIT, err);
	if (skb)
		skb_reserve(skb, dev->tx_headroom + NFC_HEADER_SIZE);

	return skb;
}

/**
 * nfc_alloc_recv_skb - allocate a skb for data exchange responses
 *
 * @size: size to allocate
 * @gfp: gfp flags
 */
struct sk_buff *nfc_alloc_recv_skb(unsigned int size, gfp_t gfp)
{
	struct sk_buff *skb;
	unsigned int total_size;

	total_size = size + 1;
	skb = alloc_skb(total_size, gfp);

	if (skb)
		skb_reserve(skb, 1);

	return skb;
}
EXPORT_SYMBOL(nfc_alloc_recv_skb);

/**
 * nfc_targets_found - inform that targets were found
 *
 * @dev: The nfc device that found the targets
 * @targets: array of nfc targets found
 * @ntargets: targets array size
 *
 * The device driver must call this function when one or many nfc targets
 * are found. After calling this function, the device driver must stop
 * polling for targets.
 * NOTE: This function can be called with targets=NULL and n_targets=0 to
 * notify a driver error, meaning that the polling operation cannot complete.
 * IMPORTANT: this function must not be called from an atomic context.
 * In addition, it must also not be called from a context that would prevent
 * the NFC Core to call other nfc ops entry point concurrently.
 */
int nfc_targets_found(struct nfc_dev *dev,
		      struct nfc_target *targets, int n_targets)
{
	int i;

	pr_debug("dev_name=%s n_targets=%d\n", dev_name(&dev->dev), n_targets);

	for (i = 0; i < n_targets; i++)
		targets[i].idx = dev->target_next_idx++;

	device_lock(&dev->dev);

	if (dev->polling == false) {
		device_unlock(&dev->dev);
		return 0;
	}

	dev->polling = false;

	dev->targets_generation++;

	kfree(dev->targets);
	dev->targets = NULL;

	if (targets) {
		dev->targets = kmemdup(targets,
				       n_targets * sizeof(struct nfc_target),
				       GFP_ATOMIC);

		if (!dev->targets) {
			dev->n_targets = 0;
			device_unlock(&dev->dev);
			return -ENOMEM;
		}
	}

	dev->n_targets = n_targets;
	device_unlock(&dev->dev);

	nfc_genl_targets_found(dev);

	return 0;
}
EXPORT_SYMBOL(nfc_targets_found);

/**
 * nfc_target_lost - inform that an activated target went out of field
 *
 * @dev: The nfc device that had the activated target in field
 * @target_idx: the nfc index of the target
 *
 * The device driver must call this function when the activated target
 * goes out of the field.
 * IMPORTANT: this function must not be called from an atomic context.
 * In addition, it must also not be called from a context that would prevent
 * the NFC Core to call other nfc ops entry point concurrently.
 */
int nfc_target_lost(struct nfc_dev *dev, u32 target_idx)
{
	struct nfc_target *tg;
	int i;

	pr_debug("dev_name %s n_target %d\n", dev_name(&dev->dev), target_idx);

	device_lock(&dev->dev);

	for (i = 0; i < dev->n_targets; i++) {
		tg = &dev->targets[i];
		if (tg->idx == target_idx)
			break;
	}

	if (i == dev->n_targets) {
		device_unlock(&dev->dev);
		return -EINVAL;
	}

	dev->targets_generation++;
	dev->n_targets--;
	dev->active_target = NULL;

	if (dev->n_targets) {
		memcpy(&dev->targets[i], &dev->targets[i + 1],
		       (dev->n_targets - i) * sizeof(struct nfc_target));
	} else {
		kfree(dev->targets);
		dev->targets = NULL;
	}

	device_unlock(&dev->dev);

	nfc_genl_target_lost(dev, target_idx);

	return 0;
}
EXPORT_SYMBOL(nfc_target_lost);

inline void nfc_driver_failure(struct nfc_dev *dev, int err)
{
	nfc_targets_found(dev, NULL, 0);
}
EXPORT_SYMBOL(nfc_driver_failure);

int nfc_add_se(struct nfc_dev *dev, u32 se_idx, u16 type)
{
	struct nfc_se *se;
	int rc;

	pr_debug("%s se index %d\n", dev_name(&dev->dev), se_idx);

	se = nfc_find_se(dev, se_idx);
	if (se)
		return -EALREADY;

	se = kzalloc(sizeof(struct nfc_se), GFP_KERNEL);
	if (!se)
		return -ENOMEM;

	se->idx = se_idx;
	se->type = type;
	se->state = NFC_SE_DISABLED;
	INIT_LIST_HEAD(&se->list);

	list_add(&se->list, &dev->secure_elements);

	rc = nfc_genl_se_added(dev, se_idx, type);
	if (rc < 0) {
		list_del(&se->list);
		kfree(se);

		return rc;
	}

	return 0;
}
EXPORT_SYMBOL(nfc_add_se);

int nfc_remove_se(struct nfc_dev *dev, u32 se_idx)
{
	struct nfc_se *se, *n;
	int rc;

	pr_debug("%s se index %d\n", dev_name(&dev->dev), se_idx);

	list_for_each_entry_safe(se, n, &dev->secure_elements, list)
		if (se->idx == se_idx) {
			rc = nfc_genl_se_removed(dev, se_idx);
			if (rc < 0)
				return rc;

			list_del(&se->list);
			kfree(se);

			return 0;
		}

	return -EINVAL;
}
EXPORT_SYMBOL(nfc_remove_se);

static void nfc_release(struct device *d)
{
	struct nfc_dev *dev = to_nfc_dev(d);
	struct nfc_se *se, *n;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	nfc_genl_data_exit(&dev->genl_data);
	kfree(dev->targets);

	list_for_each_entry_safe(se, n, &dev->secure_elements, list) {
			nfc_genl_se_removed(dev, se->idx);
			list_del(&se->list);
			kfree(se);
	}

	kfree(dev);
}

static void nfc_check_pres_work(struct work_struct *work)
{
	struct nfc_dev *dev = container_of(work, struct nfc_dev,
					   check_pres_work);
	int rc;

	device_lock(&dev->dev);

	if (dev->active_target && timer_pending(&dev->check_pres_timer) == 0) {
		rc = dev->ops->check_presence(dev, dev->active_target);
		if (rc == -EOPNOTSUPP)
			goto exit;
		if (rc) {
			u32 active_target_idx = dev->active_target->idx;
			device_unlock(&dev->dev);
			nfc_target_lost(dev, active_target_idx);
			return;
		}

		if (!dev->shutting_down)
			mod_timer(&dev->check_pres_timer, jiffies +
				  msecs_to_jiffies(NFC_CHECK_PRES_FREQ_MS));
	}

exit:
	device_unlock(&dev->dev);
}

static void nfc_check_pres_timeout(unsigned long data)
{
	struct nfc_dev *dev = (struct nfc_dev *)data;

	schedule_work(&dev->check_pres_work);
}

struct class nfc_class = {
	.name = "nfc",
	.dev_release = nfc_release,
};
EXPORT_SYMBOL(nfc_class);

static int match_idx(struct device *d, const void *data)
{
	struct nfc_dev *dev = to_nfc_dev(d);
	const unsigned int *idx = data;

	return dev->idx == *idx;
}

struct nfc_dev *nfc_get_device(unsigned int idx)
{
	struct device *d;

	d = class_find_device(&nfc_class, NULL, &idx, match_idx);
	if (!d)
		return NULL;

	return to_nfc_dev(d);
}

/**
 * nfc_allocate_device - allocate a new nfc device
 *
 * @ops: device operations
 * @supported_protocols: NFC protocols supported by the device
 */
struct nfc_dev *nfc_allocate_device(struct nfc_ops *ops,
				    u32 supported_protocols,
				    int tx_headroom, int tx_tailroom)
{
	struct nfc_dev *dev;

	if (!ops->start_poll || !ops->stop_poll || !ops->activate_target ||
	    !ops->deactivate_target || !ops->im_transceive)
		return NULL;

	if (!supported_protocols)
		return NULL;

	dev = kzalloc(sizeof(struct nfc_dev), GFP_KERNEL);
	if (!dev)
		return NULL;

	dev->ops = ops;
	dev->supported_protocols = supported_protocols;
	dev->tx_headroom = tx_headroom;
	dev->tx_tailroom = tx_tailroom;
	INIT_LIST_HEAD(&dev->secure_elements);

	nfc_genl_data_init(&dev->genl_data);

	dev->rf_mode = NFC_RF_NONE;

	/* first generation must not be 0 */
	dev->targets_generation = 1;

	if (ops->check_presence) {
		init_timer(&dev->check_pres_timer);
		dev->check_pres_timer.data = (unsigned long)dev;
		dev->check_pres_timer.function = nfc_check_pres_timeout;

		INIT_WORK(&dev->check_pres_work, nfc_check_pres_work);
	}

	return dev;
}
EXPORT_SYMBOL(nfc_allocate_device);

/**
 * nfc_register_device - register a nfc device in the nfc subsystem
 *
 * @dev: The nfc device to register
 */
int nfc_register_device(struct nfc_dev *dev)
{
	int rc;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	dev->idx = ida_simple_get(&nfc_index_ida, 0, 0, GFP_KERNEL);
	if (dev->idx < 0)
		return dev->idx;

	dev->dev.class = &nfc_class;
	dev_set_name(&dev->dev, "nfc%d", dev->idx);
	device_initialize(&dev->dev);

	mutex_lock(&nfc_devlist_mutex);
	nfc_devlist_generation++;
	rc = device_add(&dev->dev);
	mutex_unlock(&nfc_devlist_mutex);

	if (rc < 0)
		return rc;

	rc = nfc_llcp_register_device(dev);
	if (rc)
		pr_err("Could not register llcp device\n");

	rc = nfc_genl_device_added(dev);
	if (rc)
		pr_debug("The userspace won't be notified that the device %s was added\n",
			 dev_name(&dev->dev));

	dev->rfkill = rfkill_alloc(dev_name(&dev->dev), &dev->dev,
				   RFKILL_TYPE_NFC, &nfc_rfkill_ops, dev);
	if (dev->rfkill) {
		if (rfkill_register(dev->rfkill) < 0) {
			rfkill_destroy(dev->rfkill);
			dev->rfkill = NULL;
		}
	}

	return 0;
}
EXPORT_SYMBOL(nfc_register_device);

/**
 * nfc_unregister_device - unregister a nfc device in the nfc subsystem
 *
 * @dev: The nfc device to unregister
 */
void nfc_unregister_device(struct nfc_dev *dev)
{
	int rc, id;

	pr_debug("dev_name=%s\n", dev_name(&dev->dev));

	id = dev->idx;

	if (dev->rfkill) {
		rfkill_unregister(dev->rfkill);
		rfkill_destroy(dev->rfkill);
	}

	if (dev->ops->check_presence) {
		device_lock(&dev->dev);
		dev->shutting_down = true;
		device_unlock(&dev->dev);
		del_timer_sync(&dev->check_pres_timer);
		cancel_work_sync(&dev->check_pres_work);
	}

	rc = nfc_genl_device_removed(dev);
	if (rc)
		pr_debug("The userspace won't be notified that the device %s "
			 "was removed\n", dev_name(&dev->dev));

	nfc_llcp_unregister_device(dev);

	mutex_lock(&nfc_devlist_mutex);
	nfc_devlist_generation++;
	device_del(&dev->dev);
	mutex_unlock(&nfc_devlist_mutex);

	ida_simple_remove(&nfc_index_ida, id);
}
EXPORT_SYMBOL(nfc_unregister_device);

static int __init nfc_init(void)
{
	int rc;

	pr_info("NFC Core ver %s\n", VERSION);

	rc = class_register(&nfc_class);
	if (rc)
		return rc;

	rc = nfc_genl_init();
	if (rc)
		goto err_genl;

	/* the first generation must not be 0 */
	nfc_devlist_generation = 1;

	rc = rawsock_init();
	if (rc)
		goto err_rawsock;

	rc = nfc_llcp_init();
	if (rc)
		goto err_llcp_sock;

	rc = af_nfc_init();
	if (rc)
		goto err_af_nfc;

	return 0;

err_af_nfc:
	nfc_llcp_exit();
err_llcp_sock:
	rawsock_exit();
err_rawsock:
	nfc_genl_exit();
err_genl:
	class_unregister(&nfc_class);
	return rc;
}

static void __exit nfc_exit(void)
{
	af_nfc_exit();
	nfc_llcp_exit();
	rawsock_exit();
	nfc_genl_exit();
	class_unregister(&nfc_class);
}

subsys_initcall(nfc_init);
module_exit(nfc_exit);

MODULE_AUTHOR("Lauro Ramos Venancio <lauro.venancio@openbossa.org>");
MODULE_DESCRIPTION("NFC Core ver " VERSION);
MODULE_VERSION(VERSION);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(PF_NFC);
MODULE_ALIAS_GENL_FAMILY(NFC_GENL_NAME);