/*
 * atusb.c - Driver for the ATUSB IEEE 802.15.4 dongle
 *
 * Written 2013 by Werner Almesberger <werner@almesberger.net>
 *
 * 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, version 2
 *
 * Based on at86rf230.c and spi_atusb.c.
 * at86rf230.c is
 * Copyright (C) 2009 Siemens AG
 * Written by: Dmitry Eremin-Solenikov <dmitry.baryshkov@siemens.com>
 *
 * spi_atusb.c is
 * Copyright (c) 2011 Richard Sharpe <realrichardsharpe@gmail.com>
 * Copyright (c) 2011 Stefan Schmidt <stefan@datenfreihafen.org>
 * Copyright (c) 2011 Werner Almesberger <werner@almesberger.net>
 *
 * USB initialization is
 * Copyright (c) 2013 Alexander Aring <alex.aring@gmail.com>
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/jiffies.h>
#include <linux/usb.h>
#include <linux/skbuff.h>

#include <net/cfg802154.h>
#include <net/mac802154.h>

#include "at86rf230.h"
#include "atusb.h"

#define ATUSB_JEDEC_ATMEL	0x1f	/* JEDEC manufacturer ID */

#define ATUSB_NUM_RX_URBS	4	/* allow for a bit of local latency */
#define ATUSB_ALLOC_DELAY_MS	100	/* delay after failed allocation */
#define ATUSB_TX_TIMEOUT_MS	200	/* on the air timeout */

struct atusb {
	struct ieee802154_hw *hw;
	struct usb_device *usb_dev;
	int shutdown;			/* non-zero if shutting down */
	int err;			/* set by first error */

	/* RX variables */
	struct delayed_work work;	/* memory allocations */
	struct usb_anchor idle_urbs;	/* URBs waiting to be submitted */
	struct usb_anchor rx_urbs;	/* URBs waiting for reception */

	/* TX variables */
	struct usb_ctrlrequest tx_dr;
	struct urb *tx_urb;
	struct sk_buff *tx_skb;
	uint8_t tx_ack_seq;		/* current TX ACK sequence number */
};

/* ----- USB commands without data ----------------------------------------- */

/* To reduce the number of error checks in the code, we record the first error
 * in atusb->err and reject all subsequent requests until the error is cleared.
 */

static int atusb_control_msg(struct atusb *atusb, unsigned int pipe,
			     __u8 request, __u8 requesttype,
			     __u16 value, __u16 index,
			     void *data, __u16 size, int timeout)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	int ret;

	if (atusb->err)
		return atusb->err;

	ret = usb_control_msg(usb_dev, pipe, request, requesttype,
			      value, index, data, size, timeout);
	if (ret < 0) {
		atusb->err = ret;
		dev_err(&usb_dev->dev,
			"atusb_control_msg: req 0x%02x val 0x%x idx 0x%x, error %d\n",
			request, value, index, ret);
	}
	return ret;
}

static int atusb_command(struct atusb *atusb, uint8_t cmd, uint8_t arg)
{
	struct usb_device *usb_dev = atusb->usb_dev;

	dev_dbg(&usb_dev->dev, "atusb_command: cmd = 0x%x\n", cmd);
	return atusb_control_msg(atusb, usb_sndctrlpipe(usb_dev, 0),
				 cmd, ATUSB_REQ_TO_DEV, arg, 0, NULL, 0, 1000);
}

static int atusb_write_reg(struct atusb *atusb, uint8_t reg, uint8_t value)
{
	struct usb_device *usb_dev = atusb->usb_dev;

	dev_dbg(&usb_dev->dev, "atusb_write_reg: 0x%02x <- 0x%02x\n",
		reg, value);
	return atusb_control_msg(atusb, usb_sndctrlpipe(usb_dev, 0),
				 ATUSB_REG_WRITE, ATUSB_REQ_TO_DEV,
				 value, reg, NULL, 0, 1000);
}

static int atusb_read_reg(struct atusb *atusb, uint8_t reg)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	int ret;
	uint8_t *buffer;
	uint8_t value;

	buffer = kmalloc(1, GFP_KERNEL);
	if (!buffer)
		return -ENOMEM;

	dev_dbg(&usb_dev->dev, "atusb: reg = 0x%x\n", reg);
	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
				ATUSB_REG_READ, ATUSB_REQ_FROM_DEV,
				0, reg, buffer, 1, 1000);

	if (ret >= 0) {
		value = buffer[0];
		kfree(buffer);
		return value;
	} else {
		kfree(buffer);
		return ret;
	}
}

static int atusb_write_subreg(struct atusb *atusb, uint8_t reg, uint8_t mask,
			      uint8_t shift, uint8_t value)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	uint8_t orig, tmp;
	int ret = 0;

	dev_dbg(&usb_dev->dev, "atusb_write_subreg: 0x%02x <- 0x%02x\n",
		reg, value);

	orig = atusb_read_reg(atusb, reg);

	/* Write the value only into that part of the register which is allowed
	 * by the mask. All other bits stay as before.
	 */
	tmp = orig & ~mask;
	tmp |= (value << shift) & mask;

	if (tmp != orig)
		ret = atusb_write_reg(atusb, reg, tmp);

	return ret;
}

static int atusb_get_and_clear_error(struct atusb *atusb)
{
	int err = atusb->err;

	atusb->err = 0;
	return err;
}

/* ----- skb allocation ---------------------------------------------------- */

#define MAX_PSDU	127
#define MAX_RX_XFER	(1 + MAX_PSDU + 2 + 1)	/* PHR+PSDU+CRC+LQI */

#define SKB_ATUSB(skb)	(*(struct atusb **)(skb)->cb)

static void atusb_in(struct urb *urb);

static int atusb_submit_rx_urb(struct atusb *atusb, struct urb *urb)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	struct sk_buff *skb = urb->context;
	int ret;

	if (!skb) {
		skb = alloc_skb(MAX_RX_XFER, GFP_KERNEL);
		if (!skb) {
			dev_warn_ratelimited(&usb_dev->dev,
					     "atusb_in: can't allocate skb\n");
			return -ENOMEM;
		}
		skb_put(skb, MAX_RX_XFER);
		SKB_ATUSB(skb) = atusb;
	}

	usb_fill_bulk_urb(urb, usb_dev, usb_rcvbulkpipe(usb_dev, 1),
			  skb->data, MAX_RX_XFER, atusb_in, skb);
	usb_anchor_urb(urb, &atusb->rx_urbs);

	ret = usb_submit_urb(urb, GFP_KERNEL);
	if (ret) {
		usb_unanchor_urb(urb);
		kfree_skb(skb);
		urb->context = NULL;
	}
	return ret;
}

static void atusb_work_urbs(struct work_struct *work)
{
	struct atusb *atusb =
	    container_of(to_delayed_work(work), struct atusb, work);
	struct usb_device *usb_dev = atusb->usb_dev;
	struct urb *urb;
	int ret;

	if (atusb->shutdown)
		return;

	do {
		urb = usb_get_from_anchor(&atusb->idle_urbs);
		if (!urb)
			return;
		ret = atusb_submit_rx_urb(atusb, urb);
	} while (!ret);

	usb_anchor_urb(urb, &atusb->idle_urbs);
	dev_warn_ratelimited(&usb_dev->dev,
			     "atusb_in: can't allocate/submit URB (%d)\n", ret);
	schedule_delayed_work(&atusb->work,
			      msecs_to_jiffies(ATUSB_ALLOC_DELAY_MS) + 1);
}

/* ----- Asynchronous USB -------------------------------------------------- */

static void atusb_tx_done(struct atusb *atusb, uint8_t seq)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	uint8_t expect = atusb->tx_ack_seq;

	dev_dbg(&usb_dev->dev, "atusb_tx_done (0x%02x/0x%02x)\n", seq, expect);
	if (seq == expect) {
		/* TODO check for ifs handling in firmware */
		ieee802154_xmit_complete(atusb->hw, atusb->tx_skb, false);
	} else {
		/* TODO I experience this case when atusb has a tx complete
		 * irq before probing, we should fix the firmware it's an
		 * unlikely case now that seq == expect is then true, but can
		 * happen and fail with a tx_skb = NULL;
		 */
		ieee802154_wake_queue(atusb->hw);
		if (atusb->tx_skb)
			dev_kfree_skb_irq(atusb->tx_skb);
	}
}

static void atusb_in_good(struct urb *urb)
{
	struct usb_device *usb_dev = urb->dev;
	struct sk_buff *skb = urb->context;
	struct atusb *atusb = SKB_ATUSB(skb);
	uint8_t len, lqi;

	if (!urb->actual_length) {
		dev_dbg(&usb_dev->dev, "atusb_in: zero-sized URB ?\n");
		return;
	}

	len = *skb->data;

	if (urb->actual_length == 1) {
		atusb_tx_done(atusb, len);
		return;
	}

	if (len + 1 > urb->actual_length - 1) {
		dev_dbg(&usb_dev->dev, "atusb_in: frame len %d+1 > URB %u-1\n",
			len, urb->actual_length);
		return;
	}

	if (!ieee802154_is_valid_psdu_len(len)) {
		dev_dbg(&usb_dev->dev, "atusb_in: frame corrupted\n");
		return;
	}

	lqi = skb->data[len + 1];
	dev_dbg(&usb_dev->dev, "atusb_in: rx len %d lqi 0x%02x\n", len, lqi);
	skb_pull(skb, 1);	/* remove PHR */
	skb_trim(skb, len);	/* get payload only */
	ieee802154_rx_irqsafe(atusb->hw, skb, lqi);
	urb->context = NULL;	/* skb is gone */
}

static void atusb_in(struct urb *urb)
{
	struct usb_device *usb_dev = urb->dev;
	struct sk_buff *skb = urb->context;
	struct atusb *atusb = SKB_ATUSB(skb);

	dev_dbg(&usb_dev->dev, "atusb_in: status %d len %d\n",
		urb->status, urb->actual_length);
	if (urb->status) {
		if (urb->status == -ENOENT) { /* being killed */
			kfree_skb(skb);
			urb->context = NULL;
			return;
		}
		dev_dbg(&usb_dev->dev, "atusb_in: URB error %d\n", urb->status);
	} else {
		atusb_in_good(urb);
	}

	usb_anchor_urb(urb, &atusb->idle_urbs);
	if (!atusb->shutdown)
		schedule_delayed_work(&atusb->work, 0);
}

/* ----- URB allocation/deallocation --------------------------------------- */

static void atusb_free_urbs(struct atusb *atusb)
{
	struct urb *urb;

	while (1) {
		urb = usb_get_from_anchor(&atusb->idle_urbs);
		if (!urb)
			break;
		if (urb->context)
			kfree_skb(urb->context);
		usb_free_urb(urb);
	}
}

static int atusb_alloc_urbs(struct atusb *atusb, int n)
{
	struct urb *urb;

	while (n) {
		urb = usb_alloc_urb(0, GFP_KERNEL);
		if (!urb) {
			atusb_free_urbs(atusb);
			return -ENOMEM;
		}
		usb_anchor_urb(urb, &atusb->idle_urbs);
		n--;
	}
	return 0;
}

/* ----- IEEE 802.15.4 interface operations -------------------------------- */

static void atusb_xmit_complete(struct urb *urb)
{
	dev_dbg(&urb->dev->dev, "atusb_xmit urb completed");
}

static int atusb_xmit(struct ieee802154_hw *hw, struct sk_buff *skb)
{
	struct atusb *atusb = hw->priv;
	struct usb_device *usb_dev = atusb->usb_dev;
	int ret;

	dev_dbg(&usb_dev->dev, "atusb_xmit (%d)\n", skb->len);
	atusb->tx_skb = skb;
	atusb->tx_ack_seq++;
	atusb->tx_dr.wIndex = cpu_to_le16(atusb->tx_ack_seq);
	atusb->tx_dr.wLength = cpu_to_le16(skb->len);

	usb_fill_control_urb(atusb->tx_urb, usb_dev,
			     usb_sndctrlpipe(usb_dev, 0),
			     (unsigned char *)&atusb->tx_dr, skb->data,
			     skb->len, atusb_xmit_complete, NULL);
	ret = usb_submit_urb(atusb->tx_urb, GFP_ATOMIC);
	dev_dbg(&usb_dev->dev, "atusb_xmit done (%d)\n", ret);
	return ret;
}

static int atusb_channel(struct ieee802154_hw *hw, u8 page, u8 channel)
{
	struct atusb *atusb = hw->priv;
	int ret;

	/* This implicitly sets the CCA (Clear Channel Assessment) mode to 0,
	 * "Mode 3a, Carrier sense OR energy above threshold".
	 * We should probably make this configurable. @@@
	 */
	ret = atusb_write_reg(atusb, RG_PHY_CC_CCA, channel);
	if (ret < 0)
		return ret;
	msleep(1);	/* @@@ ugly synchronization */
	return 0;
}

static int atusb_ed(struct ieee802154_hw *hw, u8 *level)
{
	BUG_ON(!level);
	*level = 0xbe;
	return 0;
}

static int atusb_set_hw_addr_filt(struct ieee802154_hw *hw,
				  struct ieee802154_hw_addr_filt *filt,
				  unsigned long changed)
{
	struct atusb *atusb = hw->priv;
	struct device *dev = &atusb->usb_dev->dev;

	if (changed & IEEE802154_AFILT_SADDR_CHANGED) {
		u16 addr = le16_to_cpu(filt->short_addr);

		dev_vdbg(dev, "atusb_set_hw_addr_filt called for saddr\n");
		atusb_write_reg(atusb, RG_SHORT_ADDR_0, addr);
		atusb_write_reg(atusb, RG_SHORT_ADDR_1, addr >> 8);
	}

	if (changed & IEEE802154_AFILT_PANID_CHANGED) {
		u16 pan = le16_to_cpu(filt->pan_id);

		dev_vdbg(dev, "atusb_set_hw_addr_filt called for pan id\n");
		atusb_write_reg(atusb, RG_PAN_ID_0, pan);
		atusb_write_reg(atusb, RG_PAN_ID_1, pan >> 8);
	}

	if (changed & IEEE802154_AFILT_IEEEADDR_CHANGED) {
		u8 i, addr[IEEE802154_EXTENDED_ADDR_LEN];

		memcpy(addr, &filt->ieee_addr, IEEE802154_EXTENDED_ADDR_LEN);
		dev_vdbg(dev, "atusb_set_hw_addr_filt called for IEEE addr\n");
		for (i = 0; i < 8; i++)
			atusb_write_reg(atusb, RG_IEEE_ADDR_0 + i, addr[i]);
	}

	if (changed & IEEE802154_AFILT_PANC_CHANGED) {
		dev_vdbg(dev,
			 "atusb_set_hw_addr_filt called for panc change\n");
		if (filt->pan_coord)
			atusb_write_subreg(atusb, SR_AACK_I_AM_COORD, 1);
		else
			atusb_write_subreg(atusb, SR_AACK_I_AM_COORD, 0);
	}

	return atusb_get_and_clear_error(atusb);
}

static int atusb_start(struct ieee802154_hw *hw)
{
	struct atusb *atusb = hw->priv;
	struct usb_device *usb_dev = atusb->usb_dev;
	int ret;

	dev_dbg(&usb_dev->dev, "atusb_start\n");
	schedule_delayed_work(&atusb->work, 0);
	atusb_command(atusb, ATUSB_RX_MODE, 1);
	ret = atusb_get_and_clear_error(atusb);
	if (ret < 0)
		usb_kill_anchored_urbs(&atusb->idle_urbs);
	return ret;
}

static void atusb_stop(struct ieee802154_hw *hw)
{
	struct atusb *atusb = hw->priv;
	struct usb_device *usb_dev = atusb->usb_dev;

	dev_dbg(&usb_dev->dev, "atusb_stop\n");
	usb_kill_anchored_urbs(&atusb->idle_urbs);
	atusb_command(atusb, ATUSB_RX_MODE, 0);
	atusb_get_and_clear_error(atusb);
}

#define ATUSB_MAX_TX_POWERS 0xF
static const s32 atusb_powers[ATUSB_MAX_TX_POWERS + 1] = {
	300, 280, 230, 180, 130, 70, 0, -100, -200, -300, -400, -500, -700,
	-900, -1200, -1700,
};

static int
atusb_set_txpower(struct ieee802154_hw *hw, s32 mbm)
{
	struct atusb *atusb = hw->priv;
	u32 i;

	for (i = 0; i < hw->phy->supported.tx_powers_size; i++) {
		if (hw->phy->supported.tx_powers[i] == mbm)
			return atusb_write_subreg(atusb, SR_TX_PWR_23X, i);
	}

	return -EINVAL;
}

static int
atusb_set_promiscuous_mode(struct ieee802154_hw *hw, const bool on)
{
	struct atusb *atusb = hw->priv;
	int ret;

	if (on) {
		ret = atusb_write_subreg(atusb, SR_AACK_DIS_ACK, 1);
		if (ret < 0)
			return ret;

		ret = atusb_write_subreg(atusb, SR_AACK_PROM_MODE, 1);
		if (ret < 0)
			return ret;
	} else {
		ret = atusb_write_subreg(atusb, SR_AACK_PROM_MODE, 0);
		if (ret < 0)
			return ret;

		ret = atusb_write_subreg(atusb, SR_AACK_DIS_ACK, 0);
		if (ret < 0)
			return ret;
	}

	return 0;
}

static struct ieee802154_ops atusb_ops = {
	.owner			= THIS_MODULE,
	.xmit_async		= atusb_xmit,
	.ed			= atusb_ed,
	.set_channel		= atusb_channel,
	.start			= atusb_start,
	.stop			= atusb_stop,
	.set_hw_addr_filt	= atusb_set_hw_addr_filt,
	.set_txpower		= atusb_set_txpower,
	.set_promiscuous_mode	= atusb_set_promiscuous_mode,
};

/* ----- Firmware and chip version information ----------------------------- */

static int atusb_get_and_show_revision(struct atusb *atusb)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	unsigned char *buffer;
	int ret;

	buffer = kmalloc(3, GFP_KERNEL);
	if (!buffer)
		return -ENOMEM;

	/* Get a couple of the ATMega Firmware values */
	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
				ATUSB_ID, ATUSB_REQ_FROM_DEV, 0, 0,
				buffer, 3, 1000);
	if (ret >= 0)
		dev_info(&usb_dev->dev,
			 "Firmware: major: %u, minor: %u, hardware type: %u\n",
			 buffer[0], buffer[1], buffer[2]);
	if (buffer[0] == 0 && buffer[1] < 2) {
		dev_info(&usb_dev->dev,
			 "Firmware version (%u.%u) is predates our first public release.",
			 buffer[0], buffer[1]);
		dev_info(&usb_dev->dev, "Please update to version 0.2 or newer");
	}

	kfree(buffer);
	return ret;
}

static int atusb_get_and_show_build(struct atusb *atusb)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	char *build;
	int ret;

	build = kmalloc(ATUSB_BUILD_SIZE + 1, GFP_KERNEL);
	if (!build)
		return -ENOMEM;

	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
				ATUSB_BUILD, ATUSB_REQ_FROM_DEV, 0, 0,
				build, ATUSB_BUILD_SIZE, 1000);
	if (ret >= 0) {
		build[ret] = 0;
		dev_info(&usb_dev->dev, "Firmware: build %s\n", build);
	}

	kfree(build);
	return ret;
}

static int atusb_get_and_show_chip(struct atusb *atusb)
{
	struct usb_device *usb_dev = atusb->usb_dev;
	uint8_t man_id_0, man_id_1, part_num, version_num;
	const char *chip;

	man_id_0 = atusb_read_reg(atusb, RG_MAN_ID_0);
	man_id_1 = atusb_read_reg(atusb, RG_MAN_ID_1);
	part_num = atusb_read_reg(atusb, RG_PART_NUM);
	version_num = atusb_read_reg(atusb, RG_VERSION_NUM);

	if (atusb->err)
		return atusb->err;

	if ((man_id_1 << 8 | man_id_0) != ATUSB_JEDEC_ATMEL) {
		dev_err(&usb_dev->dev,
			"non-Atmel transceiver xxxx%02x%02x\n",
			man_id_1, man_id_0);
		goto fail;
	}

	switch (part_num) {
	case 2:
		chip = "AT86RF230";
		break;
	case 3:
		chip = "AT86RF231";
		break;
	default:
		dev_err(&usb_dev->dev,
			"unexpected transceiver, part 0x%02x version 0x%02x\n",
			part_num, version_num);
		goto fail;
	}

	dev_info(&usb_dev->dev, "ATUSB: %s version %d\n", chip, version_num);

	return 0;

fail:
	atusb->err = -ENODEV;
	return -ENODEV;
}

/* ----- Setup ------------------------------------------------------------- */

static int atusb_probe(struct usb_interface *interface,
		       const struct usb_device_id *id)
{
	struct usb_device *usb_dev = interface_to_usbdev(interface);
	struct ieee802154_hw *hw;
	struct atusb *atusb = NULL;
	int ret = -ENOMEM;

	hw = ieee802154_alloc_hw(sizeof(struct atusb), &atusb_ops);
	if (!hw)
		return -ENOMEM;

	atusb = hw->priv;
	atusb->hw = hw;
	atusb->usb_dev = usb_get_dev(usb_dev);
	usb_set_intfdata(interface, atusb);

	atusb->shutdown = 0;
	atusb->err = 0;
	INIT_DELAYED_WORK(&atusb->work, atusb_work_urbs);
	init_usb_anchor(&atusb->idle_urbs);
	init_usb_anchor(&atusb->rx_urbs);

	if (atusb_alloc_urbs(atusb, ATUSB_NUM_RX_URBS))
		goto fail;

	atusb->tx_dr.bRequestType = ATUSB_REQ_TO_DEV;
	atusb->tx_dr.bRequest = ATUSB_TX;
	atusb->tx_dr.wValue = cpu_to_le16(0);

	atusb->tx_urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!atusb->tx_urb)
		goto fail;

	hw->parent = &usb_dev->dev;
	hw->flags = IEEE802154_HW_TX_OMIT_CKSUM | IEEE802154_HW_AFILT |
		    IEEE802154_HW_PROMISCUOUS;

	hw->phy->flags = WPAN_PHY_FLAG_TXPOWER;

	hw->phy->current_page = 0;
	hw->phy->current_channel = 11;	/* reset default */
	hw->phy->supported.channels[0] = 0x7FFF800;
	hw->phy->supported.tx_powers = atusb_powers;
	hw->phy->supported.tx_powers_size = ARRAY_SIZE(atusb_powers);
	hw->phy->transmit_power = hw->phy->supported.tx_powers[0];
	ieee802154_random_extended_addr(&hw->phy->perm_extended_addr);

	atusb_command(atusb, ATUSB_RF_RESET, 0);
	atusb_get_and_show_chip(atusb);
	atusb_get_and_show_revision(atusb);
	atusb_get_and_show_build(atusb);
	ret = atusb_get_and_clear_error(atusb);
	if (ret) {
		dev_err(&atusb->usb_dev->dev,
			"%s: initialization failed, error = %d\n",
			__func__, ret);
		goto fail;
	}

	ret = ieee802154_register_hw(hw);
	if (ret)
		goto fail;

	/* If we just powered on, we're now in P_ON and need to enter TRX_OFF
	 * explicitly. Any resets after that will send us straight to TRX_OFF,
	 * making the command below redundant.
	 */
	atusb_write_reg(atusb, RG_TRX_STATE, STATE_FORCE_TRX_OFF);
	msleep(1);	/* reset => TRX_OFF, tTR13 = 37 us */

#if 0
	/* Calculating the maximum time available to empty the frame buffer
	 * on reception:
	 *
	 * According to [1], the inter-frame gap is
	 * R * 20 * 16 us + 128 us
	 * where R is a random number from 0 to 7. Furthermore, we have 20 bit
	 * times (80 us at 250 kbps) of SHR of the next frame before the
	 * transceiver begins storing data in the frame buffer.
	 *
	 * This yields a minimum time of 208 us between the last data of a
	 * frame and the first data of the next frame. This time is further
	 * reduced by interrupt latency in the atusb firmware.
	 *
	 * atusb currently needs about 500 us to retrieve a maximum-sized
	 * frame. We therefore have to allow reception of a new frame to begin
	 * while we retrieve the previous frame.
	 *
	 * [1] "JN-AN-1035 Calculating data rates in an IEEE 802.15.4-based
	 *      network", Jennic 2006.
	 *     http://www.jennic.com/download_file.php?supportFile=JN-AN-1035%20Calculating%20802-15-4%20Data%20Rates-1v0.pdf
	 */

	atusb_write_subreg(atusb, SR_RX_SAFE_MODE, 1);
#endif
	atusb_write_reg(atusb, RG_IRQ_MASK, 0xff);

	ret = atusb_get_and_clear_error(atusb);
	if (!ret)
		return 0;

	dev_err(&atusb->usb_dev->dev,
		"%s: setup failed, error = %d\n",
		__func__, ret);

	ieee802154_unregister_hw(hw);
fail:
	atusb_free_urbs(atusb);
	usb_kill_urb(atusb->tx_urb);
	usb_free_urb(atusb->tx_urb);
	usb_put_dev(usb_dev);
	ieee802154_free_hw(hw);
	return ret;
}

static void atusb_disconnect(struct usb_interface *interface)
{
	struct atusb *atusb = usb_get_intfdata(interface);

	dev_dbg(&atusb->usb_dev->dev, "atusb_disconnect\n");

	atusb->shutdown = 1;
	cancel_delayed_work_sync(&atusb->work);

	usb_kill_anchored_urbs(&atusb->rx_urbs);
	atusb_free_urbs(atusb);
	usb_kill_urb(atusb->tx_urb);
	usb_free_urb(atusb->tx_urb);

	ieee802154_unregister_hw(atusb->hw);

	ieee802154_free_hw(atusb->hw);

	usb_set_intfdata(interface, NULL);
	usb_put_dev(atusb->usb_dev);

	pr_debug("atusb_disconnect done\n");
}

/* The devices we work with */
static const struct usb_device_id atusb_device_table[] = {
	{
		.match_flags		= USB_DEVICE_ID_MATCH_DEVICE |
					  USB_DEVICE_ID_MATCH_INT_INFO,
		.idVendor		= ATUSB_VENDOR_ID,
		.idProduct		= ATUSB_PRODUCT_ID,
		.bInterfaceClass	= USB_CLASS_VENDOR_SPEC
	},
	/* end with null element */
	{}
};
MODULE_DEVICE_TABLE(usb, atusb_device_table);

static struct usb_driver atusb_driver = {
	.name		= "atusb",
	.probe		= atusb_probe,
	.disconnect	= atusb_disconnect,
	.id_table	= atusb_device_table,
};
module_usb_driver(atusb_driver);

MODULE_AUTHOR("Alexander Aring <alex.aring@gmail.com>");
MODULE_AUTHOR("Richard Sharpe <realrichardsharpe@gmail.com>");
MODULE_AUTHOR("Stefan Schmidt <stefan@datenfreihafen.org>");
MODULE_AUTHOR("Werner Almesberger <werner@almesberger.net>");
MODULE_DESCRIPTION("ATUSB IEEE 802.15.4 Driver");
MODULE_LICENSE("GPL");