[PATCH V4 5/6] net: maclorawan: Implement maclorawan class module

[Jian-Hong Pan]

LoRaWAN defined by LoRa Alliance(TM) is the MAC layer over LoRa devices.

This patch implements part of Class A end-devices SoftMAC defined in
LoRaWAN(TM) Specification Ver. 1.0.2:
1. End-device receive slot timing
2. Only single channel and single data rate for now
3. Unconfirmed data up/down message types

On the other side, it defines the basic interface and operation
functions for compatible LoRa device drivers.

Signed-off-by: Jian-Hong Pan <starnight@xxxxxxxxxxxx>
---
V2:
- Split the LoRaWAN class module patch in V1 into LoRaWAN socket and
  LoRaWAN Soft MAC modules
- Modify for Big/Little-Endian
- Use SPDX license identifiers

V3:
- Remove the decoration word - inline of the functions
- Order local variables from longest to shortest line in the functions
- Change the calling mac_cb function to lrw_get_mac_cb macro

V4:
- Fix the delay period between RX window#1 and window#2
- Fix by coding style report from scripts/checkpatch.pl

 net/maclorawan/Kconfig  |  14 +
 net/maclorawan/Makefile |   2 +
 net/maclorawan/mac.c    | 518 ++++++++++++++++++++++++++++++++++
 net/maclorawan/main.c   | 605 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 1139 insertions(+)
 create mode 100644 net/maclorawan/Kconfig
 create mode 100644 net/maclorawan/Makefile
 create mode 100644 net/maclorawan/mac.c
 create mode 100644 net/maclorawan/main.c

diff --git a/net/maclorawan/Kconfig b/net/maclorawan/Kconfig
new file mode 100644
index 000000000000..d700314edf26
--- /dev/null
+++ b/net/maclorawan/Kconfig
@@ -0,0 +1,14 @@
+config MACLORAWAN
+	tristate "Generic LoRaWAN Soft Networking Stack (maclorawan)"
+	depends on LORAWAN
+	select CRYPTO
+	select CRYPTO_CMAC
+	select CRYPTO_CBC
+	select CRYPTO_AES
+	help
+	  This option enables the hardware independent LoRaWAN
+	  networking stack for SoftMAC devices (the ones implementing
+	  only PHY level of LoRa standard).
+
+	  If you plan to use HardMAC LoRaWAN devices, you can say N
+	  here.  Alternatively you can say M to compile it as a module.
diff --git a/net/maclorawan/Makefile b/net/maclorawan/Makefile
new file mode 100644
index 000000000000..562831e66c82
--- /dev/null
+++ b/net/maclorawan/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_MACLORAWAN)	+= maclorawan.o
+maclorawan-objs			:= main.o mac.o crypto.o
diff --git a/net/maclorawan/mac.c b/net/maclorawan/mac.c
new file mode 100644
index 000000000000..70e6923bf63e
--- /dev/null
+++ b/net/maclorawan/mac.c
@@ -0,0 +1,518 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause
+/*-
+ * LoRaWAN soft MAC
+ *
+ * Copyright (c) 2018 Jian-Hong, Pan <starnight@xxxxxxxxxxxx>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/poll.h>
+#include <linux/uaccess.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/interrupt.h>
+#include <linux/netdevice.h>
+#include <linux/lora/lorawan.h>
+#include <linux/lora/lorawan_netdev.h>
+
+#include "maclorawan.h"
+#include "crypto.h"
+
+static void rx_timeout_work(struct work_struct *work);
+
+struct lrw_session *
+lrw_alloc_ss(struct lrw_struct *lrw_st)
+{
+	struct lrw_session *ss;
+
+	ss = kzalloc(sizeof(*ss), GFP_KERNEL);
+	if (!ss)
+		goto lrw_alloc_ss_end;
+
+	ss->lrw_st = lrw_st;
+	ss->devaddr = lrw_st->devaddr;
+	INIT_LIST_HEAD(&ss->entry);
+
+	ss->tx_should_ack = false;
+	ss->retry = 3;
+	spin_lock_init(&ss->state_lock);
+	INIT_WORK(&ss->timeout_work, rx_timeout_work);
+
+lrw_alloc_ss_end:
+	return ss;
+}
+
+void
+lrw_free_ss(struct lrw_session *ss)
+{
+	netdev_dbg(ss->lrw_st->ndev, "%s\n", __func__);
+	if (ss->tx_skb)
+		consume_skb(ss->tx_skb);
+	netdev_dbg(ss->lrw_st->ndev, "%s: free rx skb\n", __func__);
+	if (ss->rx_skb)
+		consume_skb(ss->rx_skb);
+
+	netdev_dbg(ss->lrw_st->ndev, "%s: free ss\n", __func__);
+	kfree(ss);
+}
+
+void
+lrw_del_ss(struct lrw_session *ss)
+{
+	netdev_dbg(ss->lrw_st->ndev, "%s\n", __func__);
+	list_del(&ss->entry);
+	lrw_free_ss(ss);
+}
+
+void
+lrw_del_all_ss(struct lrw_struct *lrw_st)
+{
+	struct lrw_session *ss, *tmp;
+
+	mutex_lock(&lrw_st->ss_list_lock);
+	lrw_st->_cur_ss = NULL;
+	list_for_each_entry_safe(ss, tmp, &lrw_st->ss_list, entry) {
+		del_timer(&ss->timer);
+		lrw_del_ss(ss);
+	}
+	mutex_unlock(&lrw_st->ss_list_lock);
+}
+
+void
+lrw_ready_hw(struct lrw_struct *lrw_st)
+{
+	lrw_st->state = LRW_STATE_IDLE;
+}
+
+int
+lrw_start_hw(struct lrw_struct *lrw_st)
+{
+	int ret = 0;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+	lrw_st->nwks_shash_tfm = lrw_mic_key_setup(lrw_st->nwkskey,
+						   LRW_KEY_LEN);
+	lrw_st->nwks_skc_tfm = lrw_encrypt_key_setup(lrw_st->nwkskey,
+						     LRW_KEY_LEN);
+	lrw_st->apps_skc_tfm = lrw_encrypt_key_setup(lrw_st->appskey,
+						     LRW_KEY_LEN);
+	lrw_st->state = LRW_START;
+	ret = lrw_st->ops->start(&lrw_st->hw);
+	if (!ret)
+		lrw_ready_hw(lrw_st);
+
+	return ret;
+}
+
+void
+lrw_stop_hw(struct lrw_struct *lrw_st)
+{
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+	lrw_st->state = LRW_STOP;
+	netdev_dbg(lrw_st->ndev, "%s: going to stop hardware\n", __func__);
+	lrw_st->ops->stop(&lrw_st->hw);
+
+	netdev_dbg(lrw_st->ndev, "%s: going to kill tasks & flush works",
+		   __func__);
+	tasklet_kill(&lrw_st->xmit_task);
+	flush_work(&lrw_st->rx_work);
+
+	netdev_dbg(lrw_st->ndev, "%s: going to delete all session\n", __func__);
+	lrw_del_all_ss(lrw_st);
+
+	netdev_dbg(lrw_st->ndev, "%s: going to free mic tfm\n", __func__);
+	lrw_mic_key_free(lrw_st->nwks_shash_tfm);
+	netdev_dbg(lrw_st->ndev, "%s: going to free nwks tfm\n", __func__);
+	lrw_encrypt_key_free(lrw_st->nwks_skc_tfm);
+	netdev_dbg(lrw_st->ndev, "%s: going to free apps tfm\n", __func__);
+	lrw_encrypt_key_free(lrw_st->apps_skc_tfm);
+}
+
+void
+lrw_prepare_tx_frame(struct lrw_session *ss)
+{
+	struct lrw_struct *lrw_st = ss->lrw_st;
+	struct sk_buff *skb = ss->tx_skb;
+	u8 mhdr, fctrl, fport, mic[4];
+	__le32 le_devaddr;
+	__le16 le_fcnt_up;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	/* Encrypt the plain buffer content */
+	lrw_encrypt_buf(lrw_st->apps_skc_tfm, LRW_UPLINK,
+			ss->devaddr, ss->fcnt_up, skb->data, skb->len);
+
+	/* Push FPort */
+	if (skb->len) {
+		fport = ss->fport;
+		memcpy(skb_push(skb, LRW_FPORT_LEN), &fport, LRW_FPORT_LEN);
+	}
+
+	/* Push FCnt_Up */
+	le_fcnt_up = cpu_to_le16(ss->fcnt_up);
+	memcpy(skb_push(skb, 2), &le_fcnt_up, 2);
+
+	/* Push FCtrl */
+	fctrl = 0;
+	if (lrw_st->rx_should_ack) {
+		fctrl |= 0x20;
+		lrw_st->rx_should_ack = false;
+	}
+	memcpy(skb_push(skb, 1), &fctrl, 1);
+
+	/* Push DevAddr */
+	le_devaddr = cpu_to_le32(ss->devaddr);
+	memcpy(skb_push(skb, LRW_DEVADDR_LEN), &le_devaddr, LRW_DEVADDR_LEN);
+
+	/* Push MHDR */
+	mhdr = LRW_UNCONFIRMED_DATA_UP << 5;
+	if ((mhdr & (0x6 << 5)) == (0x4 << 5))
+		ss->tx_should_ack = true;
+	memcpy(skb_push(skb, LRW_MHDR_LEN), &mhdr, LRW_MHDR_LEN);
+
+	/* Put MIC */
+	lrw_calc_mic(lrw_st->nwks_shash_tfm, LRW_UPLINK,
+		     ss->devaddr, ss->fcnt_up, skb->data, skb->len, mic);
+	memcpy(skb_put(skb, LRW_MIC_LEN), mic, LRW_MIC_LEN);
+}
+
+void
+lrw_xmit(unsigned long data)
+{
+	struct lrw_struct *lrw_st = (struct lrw_struct *)data;
+	struct lrw_session *ss = lrw_st->_cur_ss;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+	ss->state = LRW_XMITTING_SS;
+	lrw_st->ops->xmit_async(&lrw_st->hw, ss->tx_skb);
+}
+
+void
+lrw_parse_frame(struct lrw_session *ss, struct sk_buff *skb)
+{
+	struct lrw_fhdr *fhdr = &ss->rx_fhdr;
+	__le16 *p_fcnt;
+
+	pr_debug("%s: %s\n", LORAWAN_MODULE_NAME, __func__);
+
+	/* Get message type */
+	fhdr->mtype = skb->data[0];
+	skb_pull(skb, LRW_MHDR_LEN);
+
+	/* Trim Device Address */
+	skb_pull(skb, 4);
+
+	/* Get frame control */
+	fhdr->fctrl = skb->data[0];
+	skb_pull(skb, 1);
+
+	/* Ack the original TX frame if it should be acked */
+	if (ss->tx_should_ack && (fhdr->fctrl & 0x20))
+		ss->tx_should_ack = false;
+
+	/* Get frame count */
+	p_fcnt = (__le16 *)skb->data;
+	fhdr->fcnt = le16_to_cpu(*p_fcnt);
+	skb_pull(skb, 2);
+
+	/* Get frame options */
+	fhdr->fopts_len = fhdr->fctrl & 0xF;
+	if (fhdr->fopts_len > 0) {
+		memcpy(fhdr->fopts, skb->data, fhdr->fopts_len);
+		skb_pull(skb, fhdr->fopts_len);
+	}
+
+	/* TODO: Parse frame options */
+
+	/* Remove message integrity code */
+	skb_trim(skb, skb->len - LRW_MIC_LEN);
+}
+
+struct lrw_session *
+lrw_rx_skb_2_session(struct lrw_struct *lrw_st, struct sk_buff *rx_skb)
+{
+	struct lrw_session *ss;
+	__le16 *p_fcnt;
+	u16 fcnt;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	p_fcnt = (__le16 *)(rx_skb->data + 6);
+	fcnt = le16_to_cpu(*p_fcnt);
+
+	/* Find the corresponding session */
+	ss = lrw_st->_cur_ss;
+
+	/* Frame count downlink check */
+	if (fcnt >= (ss->fcnt_down & 0xFFFF))
+		ss->rx_skb = rx_skb;
+	else
+		ss = NULL;
+
+	return ss;
+}
+
+void
+lrw_rx_work(struct work_struct *work)
+{
+	struct lrw_struct *lrw_st;
+	struct lrw_session *ss;
+	struct sk_buff *skb;
+
+	lrw_st = container_of(work, struct lrw_struct, rx_work);
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	skb = lrw_st->rx_skb_list.next;
+	skb_dequeue(&lrw_st->rx_skb_list);
+
+	/* Check and parse the RX frame */
+	ss = lrw_rx_skb_2_session(lrw_st, skb);
+	if (!ss)
+		goto lrw_rx_work_not_new_frame;
+
+	lrw_parse_frame(ss, skb);
+
+	/* Check the TX frame is acked or not */
+	if (ss->tx_should_ack) {
+		ss->rx_skb = NULL;
+		goto lrw_rx_work_not_new_frame;
+	}
+
+	/* The TX frame is acked or no need to be acked */
+	del_timer(&ss->timer);
+	lrw_st->rx_should_ack = (ss->rx_fhdr.mtype & 0xC0) == 0x40;
+
+	lrw_st->ndev->stats.rx_packets++;
+	lrw_st->ndev->stats.rx_bytes += ss->rx_skb->len;
+
+	if (ss->rx_skb->len > 0) {
+		spin_lock_bh(&ss->state_lock);
+		ss->state = LRW_RXRECEIVED_SS;
+		spin_unlock_bh(&ss->state_lock);
+
+		lrw_get_mac_cb(skb)->devaddr = lrw_st->devaddr;
+		netif_receive_skb(skb);
+
+		ss->rx_skb = NULL;
+	}
+
+	mutex_lock(&lrw_st->ss_list_lock);
+	lrw_st->fcnt_down = ss->rx_fhdr.fcnt;
+	lrw_st->_cur_ss = NULL;
+	lrw_del_ss(ss);
+	lrw_st->state = LRW_STATE_IDLE;
+	mutex_unlock(&lrw_st->ss_list_lock);
+
+	return;
+
+lrw_rx_work_not_new_frame:
+	/* Drop the RX frame if checked failed */
+	kfree_skb(skb);
+}
+
+int
+lrw_check_mic(struct crypto_shash *tfm, struct sk_buff *skb)
+{
+	u32 devaddr;
+	size_t len;
+	u8 cks[4];
+	u16 fcnt;
+	u8 *buf;
+	u8 *mic;
+
+	buf = skb->data;
+	devaddr = le32_to_cpu(*((__le32 *)(buf + LRW_MHDR_LEN)));
+	fcnt = le16_to_cpu(*(__le16 *)(buf + 6));
+	len = skb->len - 4;
+	mic = skb->data + len;
+
+	lrw_calc_mic(tfm, LRW_DOWNLINK, devaddr, fcnt, buf, len, cks);
+
+	return (!memcmp(cks, mic, 4));
+}
+
+/**
+ * lrw_rx_irqsave - Tell LoRaWAN module that there is new received frame
+ * @hw:		the LoRa device
+ * @skb:	the new received frame
+ */
+void
+lrw_rx_irqsave(struct lrw_hw *hw, struct sk_buff *skb)
+{
+	struct lrw_struct *lrw_st = container_of(hw, struct lrw_struct, hw);
+	u32 devaddr;
+	u8 mtype;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	mtype = skb->data[0] >> 5;
+	devaddr = le32_to_cpu(*(__le32 *)(skb->data + LRW_MHDR_LEN));
+
+	/* Check the frame is the downlink frame */
+	if ((mtype == LRW_UNCONFIRMED_DATA_DOWN ||
+	     mtype == LRW_CONFIRMED_DATA_DOWN) &&
+	     devaddr == lrw_st->devaddr &&
+	     lrw_check_mic(lrw_st->nwks_shash_tfm, skb)) {
+		skb_queue_tail(&lrw_st->rx_skb_list, skb);
+		schedule_work(&lrw_st->rx_work);
+	} else {
+		kfree_skb(skb);
+	}
+}
+EXPORT_SYMBOL(lrw_rx_irqsave);
+
+static void
+lrw_rexmit(struct timer_list *timer)
+{
+	struct lrw_session *ss = container_of(timer, struct lrw_session, timer);
+	struct lrw_struct *lrw_st = ss->lrw_st;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	lrw_st->state = LRW_STATE_TX;
+	lrw_xmit((unsigned long)lrw_st);
+}
+
+static void
+rx_timeout_work(struct work_struct *work)
+{
+	struct lrw_struct *lrw_st;
+	struct lrw_session *ss;
+
+	ss = container_of(work, struct lrw_session, timeout_work);
+	lrw_st = ss->lrw_st;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+	mutex_lock(&lrw_st->ss_list_lock);
+	lrw_st->_cur_ss = NULL;
+	lrw_st->state = LRW_STATE_IDLE;
+	lrw_del_ss(ss);
+	mutex_unlock(&lrw_st->ss_list_lock);
+}
+
+static void
+rx2_timeout_isr(struct timer_list *timer)
+{
+	struct lrw_session *ss = container_of(timer, struct lrw_session, timer);
+	struct lrw_struct *lrw_st = ss->lrw_st;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	/* Check TX is acked or not */
+	if (!ss->tx_should_ack) {
+		spin_lock_bh(&ss->state_lock);
+		if (ss->state != LRW_RXRECEIVED_SS)
+			ss->state = LRW_RXTIMEOUT_SS;
+		spin_unlock_bh(&ss->state_lock);
+
+		if (ss->state == LRW_RXTIMEOUT_SS) {
+			netdev_dbg(lrw_st->ndev, "%s: rx time out\n", __func__);
+			goto rx2_timeout_isr_no_retry_rx_frame;
+		} else {
+			return;
+		}
+	}
+
+	/* Check the session need to be retransmitted or not */
+	if (ss->retry > 0) {
+		ss->state = LRW_RETRANSMIT_SS;
+		ss->retry--;
+
+		/* Start timer for ack timeout and retransmit */
+		ss->timer.function = lrw_rexmit;
+		ss->timer.expires = jiffies_64 + ss->ack_timeout * HZ;
+		add_timer(&ss->timer);
+	} else {
+		/* Retry failed */
+rx2_timeout_isr_no_retry_rx_frame:
+		schedule_work(&ss->timeout_work);
+	}
+}
+
+static void
+rx2_delay_isr(struct timer_list *timer)
+{
+	struct lrw_session *ss = container_of(timer, struct lrw_session, timer);
+	struct lrw_struct *lrw_st = ss->lrw_st;
+	unsigned long delay;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	/* Start timer for RX2 window */
+	ss->timer.function = rx2_timeout_isr;
+	delay = jiffies_64 + (ss->rx2_window + 20) * HZ / 1000 + HZ;
+	ss->timer.expires = delay;
+	add_timer(&ss->timer);
+
+	/* Start LoRa hardware to RX2 window */
+	ss->state = LRW_RX2_SS;
+	lrw_st->ops->start_rx_window(&lrw_st->hw, ss->rx2_window + 20);
+}
+
+static void
+rx1_delay_isr(struct timer_list *timer)
+{
+	struct lrw_session *ss = container_of(timer, struct lrw_session, timer);
+	struct lrw_struct *lrw_st = ss->lrw_st;
+	unsigned long delay;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	/* Start timer for RX_Delay2 - RX_Delay2 */
+	ss->timer.function = rx2_delay_isr;
+	delay = jiffies_64 + (ss->rx_delay2 - ss->rx_delay1) * HZ;
+	ss->timer.expires = delay;
+	add_timer(&ss->timer);
+
+	/* Start LoRa hardware to RX1 window */
+	ss->state = LRW_RX1_SS;
+	lrw_st->ops->start_rx_window(&lrw_st->hw, ss->rx1_window + 20);
+}
+
+void
+lrw_sent_tx_work(struct lrw_struct *lrw_st, struct sk_buff *skb)
+{
+	struct lrw_session *ss = lrw_st->_cur_ss;
+	struct net_device *ndev;
+	unsigned long delay;
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	ss->state = LRW_XMITTED;
+
+	/* Start session timer for RX_Delay1 */
+	timer_setup(&ss->timer, rx1_delay_isr, 0);
+	delay = jiffies_64 + ss->rx_delay1 * HZ - 20 * HZ / 1000;
+	ss->timer.expires = delay;
+	add_timer(&ss->timer);
+
+	ndev = skb->dev;
+	ndev->stats.tx_packets++;
+	ndev->stats.tx_bytes += skb->len;
+	dev_consume_skb_any(skb);
+	ss->tx_skb = NULL;
+}
+
+/**
+ * lrw_xmit_complete - Tell LoRaWAN module that the frame is xmitted completely
+ * @hw:		the LoRa device
+ * @skb:	the xmitted frame
+ */
+void
+lrw_xmit_complete(struct lrw_hw *hw, struct sk_buff *skb)
+{
+	struct lrw_struct *lrw_st = container_of(hw, struct lrw_struct, hw);
+
+	netdev_dbg(lrw_st->ndev, "%s\n", __func__);
+
+	lrw_sent_tx_work(lrw_st, skb);
+	lrw_st->state = LRW_STATE_RX;
+}
+EXPORT_SYMBOL(lrw_xmit_complete);
diff --git a/net/maclorawan/main.c b/net/maclorawan/main.c
new file mode 100644
index 000000000000..49beed5111b8
--- /dev/null
+++ b/net/maclorawan/main.c
@@ -0,0 +1,605 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause
+/*-
+ * LoRaWAN soft MAC
+ *
+ * Copyright (c) 2018 Jian-Hong, Pan <starnight@xxxxxxxxxxxx>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+
+#include <linux/lora/lorawan.h>
+#include <linux/lora/lorawan_netdev.h>
+#include "maclorawan.h"
+
+#define	PHY_NAME		"lora"
+
+/* Need to find a way to define or assign */
+#define	LORAWAN_MTU		20
+
+static struct class *lrw_sys_class;
+
+static void
+lrw_if_setup(struct net_device *ndev)
+{
+	ndev->addr_len = LRW_DEVADDR_LEN;
+	memset(ndev->broadcast, 0xFF, ndev->addr_len);
+	ndev->type = ARPHRD_LORAWAN;
+
+	ndev->hard_header_len = LRW_MHDR_LEN + LRW_FHDR_MAX_LEN + LRW_FPORT_LEN;
+	ndev->needed_tailroom = LRW_MIC_LEN;
+
+	/**
+	 * TODO: M should be a dynamic value defined by Regional Parameters,
+	 *	 Being fixed for now.  Going to be changed.
+	 */
+	ndev->mtu = LORAWAN_MTU;
+}
+
+/**
+ * lrw_alloc_hw - Allocate a memory space for the LoRa device
+ * @priv_data_len:	the private data size
+ * @lrw_operations:	the implemented operations of the LoRa device
+ *
+ * Return:		address of the LoRa device or NULL for failed
+ */
+struct lrw_hw *
+lrw_alloc_hw(size_t priv_data_len, struct lrw_operations *ops)
+{
+	struct lrw_struct *lrw_st;
+	struct net_device *ndev;
+	int ret;
+
+	if (WARN_ON(!ops || !ops->start || !ops->stop || !ops->xmit_async ||
+		    !ops->set_txpower || !ops->set_dr ||
+		    !ops->start_rx_window || !ops->set_state))
+		return NULL;
+
+	/* In memory it'll be like this:
+	 *
+	 * +-----------------------+
+	 * | struct net_device     |
+	 * +-----------------------+
+	 * | struct lrw_struct     |
+	 * +-----------------------+
+	 * | driver's private data |
+	 * +-----------------------+
+	 */
+	ndev = alloc_netdev(sizeof(struct lrw_struct) + priv_data_len,
+			    PHY_NAME "%d", NET_NAME_ENUM, lrw_if_setup);
+	if (!ndev)
+		return ERR_PTR(-ENOMEM);
+	ret = dev_alloc_name(ndev, ndev->name);
+	if (ret < 0)
+		goto lrw_alloc_hw_err;
+
+	lrw_st = (struct lrw_struct *)netdev_priv(ndev);
+	lrw_st->ndev = ndev;
+
+	lrw_st->state = LRW_STOP;
+	lrw_st->ops = ops;
+	lrw_st->hw.priv = (u8 *)lrw_st + sizeof(struct lrw_struct);
+
+	ndev->flags |= IFF_NOARP;
+	ndev->features |= NETIF_F_HW_CSUM;
+
+	return &lrw_st->hw;
+
+lrw_alloc_hw_err:
+	free_netdev(ndev);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(lrw_alloc_hw);
+
+/**
+ * lrw_free_hw - Free the LoRa device's memory resource
+ * @hw:		the LoRa device going to be freed
+ */
+void
+lrw_free_hw(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	free_netdev(lrw_st->ndev);
+}
+EXPORT_SYMBOL(lrw_free_hw);
+
+/**
+ * lrw_set_deveui - Set the LoRa device's DevEUI
+ * @hw:		the LoRa device going to be set
+ * @eui:	the global end-device ID in IEEE EUI64 address space
+ */
+void
+lrw_set_deveui(struct lrw_hw *hw, u64 eui)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	lrw_st->dev_eui = eui;
+}
+EXPORT_SYMBOL(lrw_set_deveui);
+
+/**
+ * lrw_get_deveui - Get the LoRa device's DevEUI
+ * @hw:		the LoRa device going to be got from
+ *
+ * Return:	the device's DevEUI in IEEE EUI64 address space
+ */
+u64
+lrw_get_deveui(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	return lrw_st->dev_eui;
+}
+EXPORT_SYMBOL(lrw_get_deveui);
+
+/**
+ * lrw_set_appeui - Set the LoRa device's AppEUI
+ * @hw:		the LoRa device going to be set
+ * @eui:	the global end-device ID in IEEE EUI64 address space
+ */
+void
+lrw_set_appeui(struct lrw_hw *hw, u64 eui)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	lrw_st->app_eui = eui;
+}
+EXPORT_SYMBOL(lrw_set_appeui);
+
+/**
+ * lrw_get_appeui - Get the LoRa device's AppEUI
+ * @hw:		the LoRa device going to be got from
+ *
+ * Return:	the device's AppEUI in IEEE EUI64 address space
+ */
+u64
+lrw_get_appeui(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	return lrw_st->app_eui;
+}
+EXPORT_SYMBOL(lrw_get_appeui);
+
+/**
+ * lrw_set_devaddr - Set the LoRa device's address
+ * @hw:		the LoRa device going to be set
+ * @devaddr:	the device address
+ */
+void
+lrw_set_devaddr(struct lrw_hw *hw, u32 devaddr)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	lrw_st->devaddr = devaddr;
+}
+EXPORT_SYMBOL(lrw_set_devaddr);
+
+/**
+ * lrw_get_devaddr - Get the LoRa device's address
+ * @hw:		the LoRa device going to be got from
+ *
+ * Return:	the device address
+ */
+u32
+lrw_get_devaddr(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+	return lrw_st->devaddr;
+}
+EXPORT_SYMBOL(lrw_get_devaddr);
+
+/**
+ * lrw_add_hw - Add a LoRaWAN hardware as a network device
+ * @lrw_st:	the LoRa device going to be added
+ *
+ * Return:	0 / other number for success / failed
+ */
+static int
+lrw_add_hw(struct lrw_struct *lrw_st)
+{
+	struct net_device *ndev = lrw_st->ndev;
+	__be32 be_addr;
+	int ret;
+
+	lrw_st->fcnt_up = 0;
+	lrw_st->fcnt_down = 0;
+	lrw_st->_cur_ss = NULL;
+
+	mutex_init(&lrw_st->ss_list_lock);
+	INIT_LIST_HEAD(&lrw_st->ss_list);
+
+	tasklet_init(&lrw_st->xmit_task, lrw_xmit, (unsigned long)lrw_st);
+	INIT_WORK(&lrw_st->rx_work, lrw_rx_work);
+
+	be_addr = cpu_to_be32(lrw_st->devaddr);
+	memcpy(ndev->perm_addr, &be_addr, ndev->addr_len);
+	memcpy(ndev->dev_addr, ndev->perm_addr, ndev->addr_len);
+
+	write_pnet(&lrw_st->_net, &init_net);
+	ret = register_netdev(ndev);
+
+	return ret;
+}
+
+/**
+ * lrw_remove_hw - Remove a LoRaWAN hardware from a network device
+ * @lrw_st:	the LoRa device going to be removed
+ */
+static void
+lrw_remove_hw(struct lrw_struct *lrw_st)
+{
+	unregister_netdev(lrw_st->ndev);
+	tasklet_kill(&lrw_st->xmit_task);
+}
+
+bool
+ready2write(struct lrw_struct *lrw_st)
+{
+	bool status = false;
+
+	if (!lrw_st->_cur_ss && lrw_st->state == LRW_STATE_IDLE)
+		status = true;
+
+	return status;
+}
+
+bool
+ready2read(struct lrw_struct *lrw_st)
+{
+	struct lrw_session *ss;
+	bool status = false;
+
+	if (!list_empty(&lrw_st->ss_list) && lrw_st->state != LRW_STOP) {
+		ss = list_first_entry(&lrw_st->ss_list,
+				      struct lrw_session,
+				      entry);
+		if (ss->state == LRW_RXRECEIVED_SS)
+			status = true;
+	}
+
+	return status;
+}
+
+static int
+lrw_if_up(struct net_device *ndev)
+{
+	struct lrw_struct *lrw_st = NETDEV_2_LRW(ndev);
+	int ret = -EBUSY;
+
+	if (lrw_st->state == LRW_STOP) {
+		ret = lrw_start_hw(lrw_st);
+		netif_start_queue(ndev);
+	}
+
+	return ret;
+}
+
+static int
+lrw_if_down(struct net_device *ndev)
+{
+	struct lrw_struct *lrw_st = NETDEV_2_LRW(ndev);
+
+	if (lrw_st->state != LRW_STOP) {
+		netif_stop_queue(ndev);
+		lrw_stop_hw(lrw_st);
+	}
+
+	return 0;
+}
+
+static netdev_tx_t
+lrw_if_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+{
+	struct lrw_struct *lrw_st = NETDEV_2_LRW(ndev);
+	struct lrw_session *ss;
+	netdev_tx_t ret;
+
+	ret = NETDEV_TX_OK;
+
+	ss = lrw_alloc_ss(lrw_st);
+	if (!ss)
+		return NETDEV_TX_BUSY;
+
+	mutex_lock(&lrw_st->ss_list_lock);
+	if (ready2write(lrw_st)) {
+		list_add_tail(&ss->entry, &lrw_st->ss_list);
+		lrw_st->state = LRW_STATE_TX;
+		lrw_st->_cur_ss = ss;
+		ss->fcnt_up = lrw_st->fcnt_up;
+		ss->fcnt_down = lrw_st->fcnt_down;
+		/* TODO: RX delay #1/#2 should be set by regional parameters */
+		ss->rx_delay1 = 1;
+		ss->rx_delay2 = 2;
+		ss->rx1_window = 500;
+		ss->rx2_window = 500;
+	} else {
+		ret = NETDEV_TX_BUSY;
+	}
+	mutex_unlock(&lrw_st->ss_list_lock);
+
+	if (ret == NETDEV_TX_OK) {
+		ss->state = LRW_INIT_SS;
+		ss->tx_skb = skb;
+		lrw_prepare_tx_frame(ss);
+		tasklet_schedule(&lrw_st->xmit_task);
+	} else {
+		lrw_free_ss(ss);
+	}
+
+	return ret;
+}
+
+static int
+lrw_if_get_addr(struct lrw_struct *lrw_st, struct sockaddr_lorawan *addr)
+{
+	int ret = 0;
+
+	switch (addr->addr_in.addr_type) {
+	case LRW_ADDR_DEVADDR:
+		addr->addr_in.devaddr = lrw_st->devaddr;
+		break;
+	case LRW_ADDR_DEVEUI:
+		addr->addr_in.dev_eui = lrw_st->dev_eui;
+		break;
+	case LRW_ADDR_APPEUI:
+		addr->addr_in.app_eui = lrw_st->app_eui;
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+
+static int
+lrw_if_set_addr(struct lrw_struct *lrw_st, struct sockaddr_lorawan *addr)
+{
+	struct lrw_hw *hw = &lrw_st->hw;
+	int ret = 0;
+
+	if (netif_running(lrw_st->ndev))
+		return -EBUSY;
+
+	switch (addr->addr_in.addr_type) {
+	case LRW_ADDR_DEVADDR:
+		lrw_set_devaddr(hw, addr->addr_in.devaddr);
+		break;
+	case LRW_ADDR_DEVEUI:
+		lrw_set_deveui(hw, addr->addr_in.dev_eui);
+		break;
+	case LRW_ADDR_APPEUI:
+		lrw_set_appeui(hw, addr->addr_in.app_eui);
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+
+static void
+swap_bytes(u8 *dst, u8 *src, size_t l)
+{
+	/* Human reading is big-endian, but LoRaWAN is little-endian */
+	unsigned int i;
+
+	for (i = 0; i < l; i++)
+		dst[i] = src[l - i - 1];
+}
+
+int
+lrw_set_key(struct lrw_hw *hw, u8 type, u8 *key, size_t key_len)
+{
+	struct lrw_struct *lrw_st;
+	int ret = 0;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+
+	netdev_dbg(lrw_st->ndev, "%s: type=%d\n", __func__, type);
+	if (lrw_st->state != LRW_STOP)
+		return -EINVAL;
+
+	print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,
+		       16, 1, key, key_len, true);
+	switch (type) {
+	case LRW_APPKEY:
+		swap_bytes(lrw_st->appkey, key, key_len);
+		break;
+	case LRW_NWKSKEY:
+		swap_bytes(lrw_st->nwkskey, key, key_len);
+		break;
+	case LRW_APPSKEY:
+		swap_bytes(lrw_st->appskey, key, key_len);
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(lrw_set_key);
+
+int
+lrw_get_key(struct lrw_hw *hw, u8 type, u8 *key, size_t key_len)
+{
+	struct lrw_struct *lrw_st;
+	int ret = 0;
+
+	lrw_st = container_of(hw, struct lrw_struct, hw);
+
+	netdev_dbg(lrw_st->ndev, "%s: type=%d\n", __func__, type);
+	switch (type) {
+	case LRW_APPKEY:
+		swap_bytes(key, lrw_st->appkey, key_len);
+		break;
+	case LRW_NWKSKEY:
+		swap_bytes(key, lrw_st->nwkskey, key_len);
+		break;
+	case LRW_APPSKEY:
+		swap_bytes(key, lrw_st->appskey, key_len);
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+
+static int
+lrw_if_ioctl(struct net_device *ndev, struct ifreq *ifr, int cmd)
+{
+	struct lrw_struct *lrw_st = NETDEV_2_LRW(ndev);
+	struct sockaddr_lorawan *addr;
+	int ret = 0;
+
+	netdev_dbg(ndev, "%s: ioctl file (cmd=0x%X)\n", __func__, cmd);
+
+	/* I/O control by each command */
+	switch (cmd) {
+	/* Set & get the DevAddr, DevEUI and AppEUI */
+	case SIOCSIFADDR:
+		addr = (struct sockaddr_lorawan *)&ifr->ifr_addr;
+		ret = lrw_if_set_addr(lrw_st, addr);
+		break;
+	case SIOCGIFADDR:
+		addr = (struct sockaddr_lorawan *)&ifr->ifr_addr;
+		ret = lrw_if_get_addr(lrw_st, addr);
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+
+	return ret;
+}
+
+static int
+lrw_if_set_mac(struct net_device *ndev, void *p)
+{
+	struct lrw_struct *lrw_st = NETDEV_2_LRW(ndev);
+	struct sockaddr *addr = p;
+	__be32 *be_addr;
+
+	be_addr = (__be32 *)addr->sa_data;
+
+	netdev_dbg(ndev, "%s: AF_TYPE:%d set mac address %X\n",
+		   __func__, addr->sa_family, be32_to_cpu(*be_addr));
+
+	if (netif_running(ndev))
+		return -EBUSY;
+
+	lrw_set_devaddr(&lrw_st->hw, be32_to_cpu(*be_addr));
+	memcpy(ndev->dev_addr, be_addr, ndev->addr_len);
+
+	return 0;
+}
+
+static const struct net_device_ops lrw_if_ops = {
+	.ndo_open = lrw_if_up,
+	.ndo_stop = lrw_if_down,
+	.ndo_start_xmit = lrw_if_start_xmit,
+	.ndo_do_ioctl = lrw_if_ioctl,
+	.ndo_set_mac_address = lrw_if_set_mac,
+};
+
+/**
+ * lrw_register_hw - Register as a LoRaWAN compatible device
+ * @hw:		LoRa device going to be registered
+ *
+ * Return:	0 / negative number for success / error number
+ */
+int
+lrw_register_hw(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st = container_of(hw, struct lrw_struct, hw);
+	int ret;
+
+	device_initialize(&lrw_st->dev);
+	dev_set_name(&lrw_st->dev, netdev_name(lrw_st->ndev));
+	lrw_st->dev.class = lrw_sys_class;
+	lrw_st->dev.platform_data = lrw_st;
+
+	ret = device_add(&lrw_st->dev);
+	if (ret)
+		goto lrw_register_hw_end;
+
+	/* Add a LoRa device node as a network device */
+	lrw_st->ndev->netdev_ops = &lrw_if_ops;
+	ret = lrw_add_hw(lrw_st);
+	if (!ret)
+		netdev_info(lrw_st->ndev, "register\n");
+
+lrw_register_hw_end:
+	return ret;
+}
+EXPORT_SYMBOL(lrw_register_hw);
+
+/**
+ * lrw_unregister_hw - Unregister the LoRaWAN compatible device
+ * @hw:		LoRa device going to be unregistered
+ */
+void
+lrw_unregister_hw(struct lrw_hw *hw)
+{
+	struct lrw_struct *lrw_st = container_of(hw, struct lrw_struct, hw);
+
+	netdev_info(lrw_st->ndev, "unregister\n");
+
+	/* Stop and remove the LoRaWAM hardware from system */
+	if (lrw_st->state != LRW_STOP)
+		lrw_stop_hw(lrw_st);
+	device_del(&lrw_st->dev);
+	lrw_remove_hw(lrw_st);
+}
+EXPORT_SYMBOL(lrw_unregister_hw);
+
+static int __init
+lrw_init(void)
+{
+	int err = 0;
+
+	pr_info("%s: module inserted\n", LORAWAN_MODULE_NAME);
+
+	/* Create device class */
+	lrw_sys_class = class_create(THIS_MODULE, LORAWAN_MODULE_NAME);
+	if (IS_ERR(lrw_sys_class)) {
+		pr_err("%s: Failed to create a class of LoRaWAN\n",
+		       LORAWAN_MODULE_NAME);
+		err = PTR_ERR(lrw_sys_class);
+		goto lrw_init_end;
+	}
+
+	pr_debug("%s: class created\n", LORAWAN_MODULE_NAME);
+
+lrw_init_end:
+	return err;
+}
+
+static void __exit
+lrw_exit(void)
+{
+	/* Delete device class */
+	class_destroy(lrw_sys_class);
+	pr_info("%s: module removed\n", LORAWAN_MODULE_NAME);
+}
+
+module_init(lrw_init);
+module_exit(lrw_exit);
+
+MODULE_AUTHOR("Jian-Hong Pan, <starnight@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("LoRaWAN soft MAC kernel module");
+MODULE_LICENSE("Dual BSD/GPL");
-- 
2.19.2