ieee802154: add support for atusb transceiver

This patch adds support for the atusb transceiver.

The current driver supports basic functionality only. Possible further
tasks would be to sync functionality with the at86rf230 driver, because
the atusb use internally an at86rf231 transceiver. Some of these
features need a firmware update like AACK and ARET handling.

I did small changes to this driver to work with xmit_async callback and
setting of a random extended perm address.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Werner Almesberger <werner@almesberger.net>
Cc: Stefan Schmidt <s.schmidt@samsung.com>
Cc: Richard Sharpe <realrichardsharpe@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 692 insertions, 0 deletions

diff --git a/drivers/net/ieee802154/atusb.c b/drivers/net/ieee802154/atusb.c
new file mode 100644
index 000000000000..ea1259ef8508
--- /dev/null
+++ b/drivers/net/ieee802154/atusb.c
@@ -0,0 +1,692 @@
+/*
+ * 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 */
+};
+
+/* at86rf230.h defines values as <reg, mask, shift> tuples. We use the more
+ * traditional style of having registers and or-able values. SR_REG extracts
+ * the register number. SR_VALUE uses the shift to prepare a value accordingly.
+ */
+
+#define __SR_REG(reg, mask, shift)	(reg)
+#define SR_REG(sr)			__SR_REG(sr)
+
+#define __SR_VALUE(reg, mask, shift, val)	((val) << (shift))
+#define SR_VALUE(sr, val)			__SR_VALUE(sr, (val))
+
+/* ----- 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 value;
+
+	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, &value, 1, 1000);
+	return ret >= 0 ? value : 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)
+{
+	/* @@@ not used by the stack yet */
+	*level = 0;
+	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;
+	uint8_t reg;
+
+	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");
+		reg = atusb_read_reg(atusb, SR_REG(SR_AACK_I_AM_COORD));
+		if (filt->pan_coord)
+			reg |= SR_VALUE(SR_AACK_I_AM_COORD, 1);
+		else
+			reg &= ~SR_VALUE(SR_AACK_I_AM_COORD, 1);
+		atusb_write_reg(atusb, SR_REG(SR_AACK_I_AM_COORD), reg);
+	}
+
+	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);
+}
+
+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,
+};
+
+/* ----- 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[3];
+	int ret;
+
+	/* 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]);
+
+	return ret;
+}
+
+static int atusb_get_and_show_build(struct atusb *atusb)
+{
+	struct usb_device *usb_dev = atusb->usb_dev;
+	char build[ATUSB_BUILD_SIZE + 1];
+	int ret;
+
+	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);
+	}
+
+	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;
+
+	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;
+	}
+	if (part_num != 3) {
+		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: AT86RF231 version %d\n", 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;
+
+	hw->phy->current_page = 0;
+	hw->phy->current_channel = 11;	/* reset default */
+	hw->phy->supported.channels[0] = 0x7FFF800;
+	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_reg(atusb,
+			SR_REG(SR_RX_SAFE_MODE), SR_VALUE(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");