can: usb_8dev: Add support for USB2CAN interface from 8 devices

Add device driver for USB2CAN interface from "8 devices" (http://www.8devices.com).

changes since v10:
* small cleanups

changes since v9:
* fixed syslog messages
* fixed crc error number
* increased MAX_RX_URBS and MAX_TX_URBS

changes since v8:
* remove all sysfs files

changes since v7:
* add sysfs documentation
* fix minor styling issue
* fixed can state for passive mode
* changed handling for crc errors

changes since v6:
* changed some variable types to big endian equivalent
* small cleanups

changes since v5:
* unlock mutex on error

changes since v4:
* removed FSF address
* renamed struct usb_8dev
* removed unused variable free_slots
* replaced some _to_cpu functions with pointer equivalent
* fix return value for usb_8dev_set_mode
* handle can errors with separate function
* fix overrun error handling
* rewrite error handling for usb_8dev_start_xmit
* fix urb submit in usb_8dev_start
* various small fixes

Acked-by: Wolfgang Grandegger <[e-mail]>
Tested-by: Oliver Hartkopp <[e-mail]>
Signed-off-by: Bernd Krumboeck <[e-mail]>
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/usb/Kconfig

···
 	  This driver supports the PCAN-USB and PCAN-USB Pro adapters
 	  from PEAK-System Technik (http://www.peak-system.com).
 
+config CAN_8DEV_USB
+	tristate "8 devices USB2CAN interface"
+	---help---
+	  This driver supports the USB2CAN interface
+	  from 8 devices (http://www.8devices.com).
+
 endmenu

drivers/net/can/usb/Makefile

···
 obj-$(CONFIG_CAN_ESD_USB2) += esd_usb2.o
 obj-$(CONFIG_CAN_KVASER_USB) += kvaser_usb.o
 obj-$(CONFIG_CAN_PEAK_USB) += peak_usb/
+obj-$(CONFIG_CAN_8DEV_USB) += usb_8dev.o
 
 ccflags-$(CONFIG_CAN_DEBUG_DEVICES) := -DDEBUG

drivers/net/can/usb/usb_8dev.c

···
+/*
+ * CAN driver for "8 devices" USB2CAN converter
+ *
+ * Copyright (C) 2012 Bernd Krumboeck ([e-mail])
+ *
+ * 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 of the License.
+ *
+ * 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.
+ *
+ * This driver is inspired by the 3.2.0 version of drivers/net/can/usb/ems_usb.c
+ * and drivers/net/can/usb/esd_usb2.c
+ *
+ * Many thanks to Gerhard Bertelsmann ([e-mail])
+ * for testing and fixing this driver. Also many thanks to "8 devices",
+ * who were very cooperative and answered my questions.
+ */
+
+#include <linux/init.h>
+#include <linux/signal.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/usb.h>
+
+#include <linux/can.h>
+#include <linux/can/dev.h>
+#include <linux/can/error.h>
+
+/* driver constants */
+#define MAX_RX_URBS			20
+#define MAX_TX_URBS			20
+#define RX_BUFFER_SIZE			64
+
+/* vendor and product id */
+#define USB_8DEV_VENDOR_ID		0x0483
+#define USB_8DEV_PRODUCT_ID		0x1234
+
+/* endpoints */
+enum usb_8dev_endpoint {
+	USB_8DEV_ENDP_DATA_RX = 1,
+	USB_8DEV_ENDP_DATA_TX,
+	USB_8DEV_ENDP_CMD_RX,
+	USB_8DEV_ENDP_CMD_TX
+};
+
+/* device CAN clock */
+#define USB_8DEV_ABP_CLOCK		32000000
+
+/* setup flags */
+#define USB_8DEV_SILENT			0x01
+#define USB_8DEV_LOOPBACK		0x02
+#define USB_8DEV_DISABLE_AUTO_RESTRANS	0x04
+#define USB_8DEV_STATUS_FRAME		0x08
+
+/* commands */
+enum usb_8dev_cmd {
+	USB_8DEV_RESET = 1,
+	USB_8DEV_OPEN,
+	USB_8DEV_CLOSE,
+	USB_8DEV_SET_SPEED,
+	USB_8DEV_SET_MASK_FILTER,
+	USB_8DEV_GET_STATUS,
+	USB_8DEV_GET_STATISTICS,
+	USB_8DEV_GET_SERIAL,
+	USB_8DEV_GET_SOFTW_VER,
+	USB_8DEV_GET_HARDW_VER,
+	USB_8DEV_RESET_TIMESTAMP,
+	USB_8DEV_GET_SOFTW_HARDW_VER
+};
+
+/* command options */
+#define USB_8DEV_BAUD_MANUAL		0x09
+#define USB_8DEV_CMD_START		0x11
+#define USB_8DEV_CMD_END		0x22
+
+#define USB_8DEV_CMD_SUCCESS		0
+#define USB_8DEV_CMD_ERROR		255
+
+#define USB_8DEV_CMD_TIMEOUT		1000
+
+/* frames */
+#define USB_8DEV_DATA_START		0x55
+#define USB_8DEV_DATA_END		0xAA
+
+#define USB_8DEV_TYPE_CAN_FRAME		0
+#define USB_8DEV_TYPE_ERROR_FRAME	3
+
+#define USB_8DEV_EXTID			0x01
+#define USB_8DEV_RTR			0x02
+#define USB_8DEV_ERR_FLAG		0x04
+
+/* status */
+#define USB_8DEV_STATUSMSG_OK		0x00  /* Normal condition. */
+#define USB_8DEV_STATUSMSG_OVERRUN	0x01  /* Overrun occured when sending */
+#define USB_8DEV_STATUSMSG_BUSLIGHT	0x02  /* Error counter has reached 96 */
+#define USB_8DEV_STATUSMSG_BUSHEAVY	0x03  /* Error count. has reached 128 */
+#define USB_8DEV_STATUSMSG_BUSOFF	0x04  /* Device is in BUSOFF */
+#define USB_8DEV_STATUSMSG_STUFF	0x20  /* Stuff Error */
+#define USB_8DEV_STATUSMSG_FORM		0x21  /* Form Error */
+#define USB_8DEV_STATUSMSG_ACK		0x23  /* Ack Error */
+#define USB_8DEV_STATUSMSG_BIT0		0x24  /* Bit1 Error */
+#define USB_8DEV_STATUSMSG_BIT1		0x25  /* Bit0 Error */
+#define USB_8DEV_STATUSMSG_CRC		0x27  /* CRC Error */
+
+#define USB_8DEV_RP_MASK		0x7F  /* Mask for Receive Error Bit */
+
+
+/* table of devices that work with this driver */
+static const struct usb_device_id usb_8dev_table[] = {
+	{ USB_DEVICE(USB_8DEV_VENDOR_ID, USB_8DEV_PRODUCT_ID) },
+	{ }					/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, usb_8dev_table);
+
+struct usb_8dev_tx_urb_context {
+	struct usb_8dev_priv *priv;
+
+	u32 echo_index;
+	u8 dlc;
+};
+
+/* Structure to hold all of our device specific stuff */
+struct usb_8dev_priv {
+	struct can_priv can; /* must be the first member */
+
+	struct sk_buff *echo_skb[MAX_TX_URBS];
+
+	struct usb_device *udev;
+	struct net_device *netdev;
+
+	atomic_t active_tx_urbs;
+	struct usb_anchor tx_submitted;
+	struct usb_8dev_tx_urb_context tx_contexts[MAX_TX_URBS];
+
+	struct usb_anchor rx_submitted;
+
+	struct can_berr_counter bec;
+
+	u8 *cmd_msg_buffer;
+
+	struct mutex usb_8dev_cmd_lock;
+
+};
+
+/* tx frame */
+struct __packed usb_8dev_tx_msg {
+	u8 begin;
+	u8 flags;	/* RTR and EXT_ID flag */
+	__be32 id;	/* upper 3 bits not used */
+	u8 dlc;		/* data length code 0-8 bytes */
+	u8 data[8];	/* 64-bit data */
+	u8 end;
+};
+
+/* rx frame */
+struct __packed usb_8dev_rx_msg {
+	u8 begin;
+	u8 type;		/* frame type */
+	u8 flags;		/* RTR and EXT_ID flag */
+	__be32 id;		/* upper 3 bits not used */
+	u8 dlc;			/* data length code 0-8 bytes */
+	u8 data[8];		/* 64-bit data */
+	__be32 timestamp;	/* 32-bit timestamp */
+	u8 end;
+};
+
+/* command frame */
+struct __packed usb_8dev_cmd_msg {
+	u8 begin;
+	u8 channel;	/* unkown - always 0 */
+	u8 command;	/* command to execute */
+	u8 opt1;	/* optional parameter / return value */
+	u8 opt2;	/* optional parameter 2 */
+	u8 data[10];	/* optional parameter and data */
+	u8 end;
+};
+
+static int usb_8dev_send_cmd_msg(struct usb_8dev_priv *priv, u8 *msg, int size)
+{
+	int actual_length;
+
+	return usb_bulk_msg(priv->udev,
+			    usb_sndbulkpipe(priv->udev, USB_8DEV_ENDP_CMD_TX),
+			    msg, size, &actual_length, USB_8DEV_CMD_TIMEOUT);
+}
+
+static int usb_8dev_wait_cmd_msg(struct usb_8dev_priv *priv, u8 *msg, int size,
+				int *actual_length)
+{
+	return usb_bulk_msg(priv->udev,
+			    usb_rcvbulkpipe(priv->udev, USB_8DEV_ENDP_CMD_RX),
+			    msg, size, actual_length, USB_8DEV_CMD_TIMEOUT);
+}
+
+/* Send command to device and receive result.
+ * Command was successful when opt1 = 0.
+ */
+static int usb_8dev_send_cmd(struct usb_8dev_priv *priv,
+			     struct usb_8dev_cmd_msg *out,
+			     struct usb_8dev_cmd_msg *in)
+{
+	int err;
+	int num_bytes_read;
+	struct net_device *netdev;
+
+	netdev = priv->netdev;
+
+	out->begin = USB_8DEV_CMD_START;
+	out->end = USB_8DEV_CMD_END;
+
+	mutex_lock(&priv->usb_8dev_cmd_lock);
+
+	memcpy(priv->cmd_msg_buffer, out,
+		sizeof(struct usb_8dev_cmd_msg));
+
+	err = usb_8dev_send_cmd_msg(priv, priv->cmd_msg_buffer,
+				    sizeof(struct usb_8dev_cmd_msg));
+	if (err < 0) {
+		netdev_err(netdev, "sending command message failed\n");
+		goto failed;
+	}
+
+	err = usb_8dev_wait_cmd_msg(priv, priv->cmd_msg_buffer,
+				    sizeof(struct usb_8dev_cmd_msg),
+				    &num_bytes_read);
+	if (err < 0) {
+		netdev_err(netdev, "no command message answer\n");
+		goto failed;
+	}
+
+	memcpy(in, priv->cmd_msg_buffer, sizeof(struct usb_8dev_cmd_msg));
+
+	if (in->begin != USB_8DEV_CMD_START || in->end != USB_8DEV_CMD_END ||
+			num_bytes_read != 16 || in->opt1 != 0)
+		err = -EPROTO;
+
+failed:
+	mutex_unlock(&priv->usb_8dev_cmd_lock);
+	return err;
+}
+
+/* Send open command to device */
+static int usb_8dev_cmd_open(struct usb_8dev_priv *priv)
+{
+	struct can_bittiming *bt = &priv->can.bittiming;
+	struct usb_8dev_cmd_msg outmsg;
+	struct usb_8dev_cmd_msg inmsg;
+	u32 ctrlmode = priv->can.ctrlmode;
+	u32 flags = USB_8DEV_STATUS_FRAME;
+	__be32 beflags;
+	__be16 bebrp;
+
+	memset(&outmsg, 0, sizeof(outmsg));
+	outmsg.command = USB_8DEV_OPEN;
+	outmsg.opt1 = USB_8DEV_BAUD_MANUAL;
+	outmsg.data[0] = bt->prop_seg + bt->phase_seg1;
+	outmsg.data[1] = bt->phase_seg2;
+	outmsg.data[2] = bt->sjw;
+
+	/* BRP */
+	bebrp = cpu_to_be16((u16)bt->brp);
+	memcpy(&outmsg.data[3], &bebrp, sizeof(bebrp));
+
+	/* flags */
+	if (ctrlmode & CAN_CTRLMODE_LOOPBACK)
+		flags |= USB_8DEV_LOOPBACK;
+	if (ctrlmode & CAN_CTRLMODE_LISTENONLY)
+		flags |= USB_8DEV_SILENT;
+	if (ctrlmode & CAN_CTRLMODE_ONE_SHOT)
+		flags |= USB_8DEV_DISABLE_AUTO_RESTRANS;
+
+	beflags = cpu_to_be32(flags);
+	memcpy(&outmsg.data[5], &beflags, sizeof(beflags));
+
+	return usb_8dev_send_cmd(priv, &outmsg, &inmsg);
+}
+
+/* Send close command to device */
+static int usb_8dev_cmd_close(struct usb_8dev_priv *priv)
+{
+	struct usb_8dev_cmd_msg inmsg;
+	struct usb_8dev_cmd_msg outmsg = {
+		.channel = 0,
+		.command = USB_8DEV_CLOSE,
+		.opt1 = 0,
+		.opt2 = 0
+	};
+
+	return usb_8dev_send_cmd(priv, &outmsg, &inmsg);
+}
+
+/* Get firmware and hardware version */
+static int usb_8dev_cmd_version(struct usb_8dev_priv *priv, u32 *res)
+{
+	struct usb_8dev_cmd_msg	inmsg;
+	struct usb_8dev_cmd_msg	outmsg = {
+		.channel = 0,
+		.command = USB_8DEV_GET_SOFTW_HARDW_VER,
+		.opt1 = 0,
+		.opt2 = 0
+	};
+
+	int err = usb_8dev_send_cmd(priv, &outmsg, &inmsg);
+	if (err)
+		return err;
+
+	*res = be32_to_cpup((__be32 *)inmsg.data);
+
+	return err;
+}
+
+/* Set network device mode
+ *
+ * Maybe we should leave this function empty, because the device
+ * set mode variable with open command.
+ */
+static int usb_8dev_set_mode(struct net_device *netdev, enum can_mode mode)
+{
+	struct usb_8dev_priv *priv = netdev_priv(netdev);
+	int err = 0;
+
+	switch (mode) {
+	case CAN_MODE_START:
+		err = usb_8dev_cmd_open(priv);
+		if (err)
+			netdev_warn(netdev, "couldn't start device");
+		break;
+
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return err;
+}
+
+/* Read error/status frames */
+static void usb_8dev_rx_err_msg(struct usb_8dev_priv *priv,
+				struct usb_8dev_rx_msg *msg)
+{
+	struct can_frame *cf;
+	struct sk_buff *skb;
+	struct net_device_stats *stats = &priv->netdev->stats;
+
+	/* Error message:
+	 * byte 0: Status
+	 * byte 1: bit   7: Receive Passive
+	 * byte 1: bit 0-6: Receive Error Counter
+	 * byte 2: Transmit Error Counter
+	 * byte 3: Always 0 (maybe reserved for future use)
+	 */
+
+	u8 state = msg->data[0];
+	u8 rxerr = msg->data[1] & USB_8DEV_RP_MASK;
+	u8 txerr = msg->data[2];
+	int rx_errors = 0;
+	int tx_errors = 0;
+
+	skb = alloc_can_err_skb(priv->netdev, &cf);
+	if (!skb)
+		return;
+
+	switch (state) {
+	case USB_8DEV_STATUSMSG_OK:
+		priv->can.state = CAN_STATE_ERROR_ACTIVE;
+		cf->can_id |= CAN_ERR_PROT;
+		cf->data[2] = CAN_ERR_PROT_ACTIVE;
+		break;
+	case USB_8DEV_STATUSMSG_BUSOFF:
+		priv->can.state = CAN_STATE_BUS_OFF;
+		cf->can_id |= CAN_ERR_BUSOFF;
+		can_bus_off(priv->netdev);
+		break;
+	case USB_8DEV_STATUSMSG_OVERRUN:
+	case USB_8DEV_STATUSMSG_BUSLIGHT:
+	case USB_8DEV_STATUSMSG_BUSHEAVY:
+		cf->can_id |= CAN_ERR_CRTL;
+		break;
+	default:
+		priv->can.state = CAN_STATE_ERROR_WARNING;
+		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
+		priv->can.can_stats.bus_error++;
+		break;
+	}
+
+	switch (state) {
+	case USB_8DEV_STATUSMSG_OK:
+	case USB_8DEV_STATUSMSG_BUSOFF:
+		break;
+	case USB_8DEV_STATUSMSG_ACK:
+		cf->can_id |= CAN_ERR_ACK;
+		tx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_CRC:
+		cf->data[2] |= CAN_ERR_PROT_UNSPEC;
+		cf->data[3] |= CAN_ERR_PROT_LOC_CRC_SEQ |
+			       CAN_ERR_PROT_LOC_CRC_DEL;
+		rx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_BIT0:
+		cf->data[2] |= CAN_ERR_PROT_BIT0;
+		tx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_BIT1:
+		cf->data[2] |= CAN_ERR_PROT_BIT1;
+		tx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_FORM:
+		cf->data[2] |= CAN_ERR_PROT_FORM;
+		rx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_STUFF:
+		cf->data[2] |= CAN_ERR_PROT_STUFF;
+		rx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_OVERRUN:
+		cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
+		stats->rx_over_errors++;
+		rx_errors = 1;
+		break;
+	case USB_8DEV_STATUSMSG_BUSLIGHT:
+		priv->can.state = CAN_STATE_ERROR_WARNING;
+		cf->data[1] = (txerr > rxerr) ?
+			CAN_ERR_CRTL_TX_WARNING :
+			CAN_ERR_CRTL_RX_WARNING;
+		priv->can.can_stats.error_warning++;
+		break;
+	case USB_8DEV_STATUSMSG_BUSHEAVY:
+		priv->can.state = CAN_STATE_ERROR_PASSIVE;
+		cf->data[1] = (txerr > rxerr) ?
+			CAN_ERR_CRTL_TX_PASSIVE :
+			CAN_ERR_CRTL_RX_PASSIVE;
+		priv->can.can_stats.error_passive++;
+		break;
+	default:
+		netdev_warn(priv->netdev,
+			    "Unknown status/error message (%d)\n", state);
+		break;
+	}
+
+	if (tx_errors) {
+		cf->data[2] |= CAN_ERR_PROT_TX;
+		stats->tx_errors++;
+	}
+
+	if (rx_errors)
+		stats->rx_errors++;
+
+	cf->data[6] = txerr;
+	cf->data[7] = rxerr;
+
+	priv->bec.txerr = txerr;
+	priv->bec.rxerr = rxerr;
+
+	netif_rx(skb);
+
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+}
+
+/* Read data and status frames */
+static void usb_8dev_rx_can_msg(struct usb_8dev_priv *priv,
+				struct usb_8dev_rx_msg *msg)
+{
+	struct can_frame *cf;
+	struct sk_buff *skb;
+	struct net_device_stats *stats = &priv->netdev->stats;
+
+	if (msg->type == USB_8DEV_TYPE_ERROR_FRAME &&
+		   msg->flags == USB_8DEV_ERR_FLAG) {
+		usb_8dev_rx_err_msg(priv, msg);
+	} else if (msg->type == USB_8DEV_TYPE_CAN_FRAME) {
+		skb = alloc_can_skb(priv->netdev, &cf);
+		if (!skb)
+			return;
+
+		cf->can_id = be32_to_cpu(msg->id);
+		cf->can_dlc = get_can_dlc(msg->dlc & 0xF);
+
+		if (msg->flags & USB_8DEV_EXTID)
+			cf->can_id |= CAN_EFF_FLAG;
+
+		if (msg->flags & USB_8DEV_RTR)
+			cf->can_id |= CAN_RTR_FLAG;
+		else
+			memcpy(cf->data, msg->data, cf->can_dlc);
+
+		netif_rx(skb);
+
+		stats->rx_packets++;
+		stats->rx_bytes += cf->can_dlc;
+	} else {
+		netdev_warn(priv->netdev, "frame type %d unknown",
+			 msg->type);
+	}
+
+}
+
+/* Callback for reading data from device
+ *
+ * Check urb status, call read function and resubmit urb read operation.
+ */
+static void usb_8dev_read_bulk_callback(struct urb *urb)
+{
+	struct usb_8dev_priv *priv = urb->context;
+	struct net_device *netdev;
+	int retval;
+	int pos = 0;
+
+	netdev = priv->netdev;
+
+	if (!netif_device_present(netdev))
+		return;
+
+	switch (urb->status) {
+	case 0: /* success */
+		break;
+
+	case -ENOENT:
+	case -ESHUTDOWN:
+		return;
+
+	default:
+		netdev_info(netdev, "Rx URB aborted (%d)\n",
+			 urb->status);
+		goto resubmit_urb;
+	}
+
+	while (pos < urb->actual_length) {
+		struct usb_8dev_rx_msg *msg;
+
+		if (pos + sizeof(struct usb_8dev_rx_msg) > urb->actual_length) {
+			netdev_err(priv->netdev, "format error\n");
+			break;
+		}
+
+		msg = (struct usb_8dev_rx_msg *)(urb->transfer_buffer + pos);
+		usb_8dev_rx_can_msg(priv, msg);
+
+		pos += sizeof(struct usb_8dev_rx_msg);
+	}
+
+resubmit_urb:
+	usb_fill_bulk_urb(urb, priv->udev,
+			  usb_rcvbulkpipe(priv->udev, USB_8DEV_ENDP_DATA_RX),
+			  urb->transfer_buffer, RX_BUFFER_SIZE,
+			  usb_8dev_read_bulk_callback, priv);
+
+	retval = usb_submit_urb(urb, GFP_ATOMIC);
+
+	if (retval == -ENODEV)
+		netif_device_detach(netdev);
+	else if (retval)
+		netdev_err(netdev,
+			"failed resubmitting read bulk urb: %d\n", retval);
+}
+
+/* Callback handler for write operations
+ *
+ * Free allocated buffers, check transmit status and
+ * calculate statistic.
+ */
+static void usb_8dev_write_bulk_callback(struct urb *urb)
+{
+	struct usb_8dev_tx_urb_context *context = urb->context;
+	struct usb_8dev_priv *priv;
+	struct net_device *netdev;
+
+	BUG_ON(!context);
+
+	priv = context->priv;
+	netdev = priv->netdev;
+
+	/* free up our allocated buffer */
+	usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+			  urb->transfer_buffer, urb->transfer_dma);
+
+	atomic_dec(&priv->active_tx_urbs);
+
+	if (!netif_device_present(netdev))
+		return;
+
+	if (urb->status)
+		netdev_info(netdev, "Tx URB aborted (%d)\n",
+			 urb->status);
+
+	netdev->stats.tx_packets++;
+	netdev->stats.tx_bytes += context->dlc;
+
+	can_get_echo_skb(netdev, context->echo_index);
+
+	/* Release context */
+	context->echo_index = MAX_TX_URBS;
+
+	netif_wake_queue(netdev);
+}
+
+/* Send data to device */
+static netdev_tx_t usb_8dev_start_xmit(struct sk_buff *skb,
+				      struct net_device *netdev)
+{
+	struct usb_8dev_priv *priv = netdev_priv(netdev);
+	struct net_device_stats *stats = &netdev->stats;
+	struct can_frame *cf = (struct can_frame *) skb->data;
+	struct usb_8dev_tx_msg *msg;
+	struct urb *urb;
+	struct usb_8dev_tx_urb_context *context = NULL;
+	u8 *buf;
+	int i, err;
+	size_t size = sizeof(struct usb_8dev_tx_msg);
+
+	if (can_dropped_invalid_skb(netdev, skb))
+		return NETDEV_TX_OK;
+
+	/* create a URB, and a buffer for it, and copy the data to the URB */
+	urb = usb_alloc_urb(0, GFP_ATOMIC);
+	if (!urb) {
+		netdev_err(netdev, "No memory left for URBs\n");
+		goto nomem;
+	}
+
+	buf = usb_alloc_coherent(priv->udev, size, GFP_ATOMIC,
+				 &urb->transfer_dma);
+	if (!buf) {
+		netdev_err(netdev, "No memory left for USB buffer\n");
+		goto nomembuf;
+	}
+
+	memset(buf, 0, size);
+
+	msg = (struct usb_8dev_tx_msg *)buf;
+	msg->begin = USB_8DEV_DATA_START;
+	msg->flags = 0x00;
+
+	if (cf->can_id & CAN_RTR_FLAG)
+		msg->flags |= USB_8DEV_RTR;
+
+	if (cf->can_id & CAN_EFF_FLAG)
+		msg->flags |= USB_8DEV_EXTID;
+
+	msg->id = cpu_to_be32(cf->can_id & CAN_ERR_MASK);
+	msg->dlc = cf->can_dlc;
+	memcpy(msg->data, cf->data, cf->can_dlc);
+	msg->end = USB_8DEV_DATA_END;
+
+	for (i = 0; i < MAX_TX_URBS; i++) {
+		if (priv->tx_contexts[i].echo_index == MAX_TX_URBS) {
+			context = &priv->tx_contexts[i];
+			break;
+		}
+	}
+
+	/* May never happen! When this happens we'd more URBs in flight as
+	 * allowed (MAX_TX_URBS).
+	 */
+	if (!context)
+		goto nofreecontext;
+
+	context->priv = priv;
+	context->echo_index = i;
+	context->dlc = cf->can_dlc;
+
+	usb_fill_bulk_urb(urb, priv->udev,
+			  usb_sndbulkpipe(priv->udev, USB_8DEV_ENDP_DATA_TX),
+			  buf, size, usb_8dev_write_bulk_callback, context);
+	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+	usb_anchor_urb(urb, &priv->tx_submitted);
+
+	can_put_echo_skb(skb, netdev, context->echo_index);
+
+	atomic_inc(&priv->active_tx_urbs);
+
+	err = usb_submit_urb(urb, GFP_ATOMIC);
+	if (unlikely(err))
+		goto failed;
+	else if (atomic_read(&priv->active_tx_urbs) >= MAX_TX_URBS)
+		/* Slow down tx path */
+		netif_stop_queue(netdev);
+
+	/* Release our reference to this URB, the USB core will eventually free
+	 * it entirely.
+	 */
+	usb_free_urb(urb);
+
+	return NETDEV_TX_OK;
+
+nofreecontext:
+	usb_unanchor_urb(urb);
+	usb_free_coherent(priv->udev, size, buf, urb->transfer_dma);
+
+	netdev_warn(netdev, "couldn't find free context");
+
+	return NETDEV_TX_BUSY;
+
+failed:
+	can_free_echo_skb(netdev, context->echo_index);
+
+	usb_unanchor_urb(urb);
+	usb_free_coherent(priv->udev, size, buf, urb->transfer_dma);
+
+	atomic_dec(&priv->active_tx_urbs);
+
+	if (err == -ENODEV)
+		netif_device_detach(netdev);
+	else
+		netdev_warn(netdev, "failed tx_urb %d\n", err);
+
+nomembuf:
+	usb_free_urb(urb);
+
+nomem:
+	dev_kfree_skb(skb);
+	stats->tx_dropped++;
+
+	return NETDEV_TX_OK;
+}
+
+static int usb_8dev_get_berr_counter(const struct net_device *netdev,
+				     struct can_berr_counter *bec)
+{
+	struct usb_8dev_priv *priv = netdev_priv(netdev);
+
+	bec->txerr = priv->bec.txerr;
+	bec->rxerr = priv->bec.rxerr;
+
+	return 0;
+}
+
+/* Start USB device */
+static int usb_8dev_start(struct usb_8dev_priv *priv)
+{
+	struct net_device *netdev = priv->netdev;
+	int err, i;
+
+	for (i = 0; i < MAX_RX_URBS; i++) {
+		struct urb *urb = NULL;
+		u8 *buf;
+
+		/* create a URB, and a buffer for it */
+		urb = usb_alloc_urb(0, GFP_KERNEL);
+		if (!urb) {
+			netdev_err(netdev, "No memory left for URBs\n");
+			err = -ENOMEM;
+			break;
+		}
+
+		buf = usb_alloc_coherent(priv->udev, RX_BUFFER_SIZE, GFP_KERNEL,
+					 &urb->transfer_dma);
+		if (!buf) {
+			netdev_err(netdev, "No memory left for USB buffer\n");
+			usb_free_urb(urb);
+			err = -ENOMEM;
+			break;
+		}
+
+		usb_fill_bulk_urb(urb, priv->udev,
+				  usb_rcvbulkpipe(priv->udev,
+						  USB_8DEV_ENDP_DATA_RX),
+				  buf, RX_BUFFER_SIZE,
+				  usb_8dev_read_bulk_callback, priv);
+		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+		usb_anchor_urb(urb, &priv->rx_submitted);
+
+		err = usb_submit_urb(urb, GFP_KERNEL);
+		if (err) {
+			usb_unanchor_urb(urb);
+			usb_free_coherent(priv->udev, RX_BUFFER_SIZE, buf,
+					  urb->transfer_dma);
+			break;
+		}
+
+		/* Drop reference, USB core will take care of freeing it */
+		usb_free_urb(urb);
+	}
+
+	/* Did we submit any URBs */
+	if (i == 0) {
+		netdev_warn(netdev, "couldn't setup read URBs\n");
+		return err;
+	}
+
+	/* Warn if we've couldn't transmit all the URBs */
+	if (i < MAX_RX_URBS)
+		netdev_warn(netdev, "rx performance may be slow\n");
+
+	err = usb_8dev_cmd_open(priv);
+	if (err)
+		goto failed;
+
+	priv->can.state = CAN_STATE_ERROR_ACTIVE;
+
+	return 0;
+
+failed:
+	if (err == -ENODEV)
+		netif_device_detach(priv->netdev);
+
+	netdev_warn(netdev, "couldn't submit control: %d\n", err);
+
+	return err;
+}
+
+/* Open USB device */
+static int usb_8dev_open(struct net_device *netdev)
+{
+	struct usb_8dev_priv *priv = netdev_priv(netdev);
+	int err;
+
+	/* common open */
+	err = open_candev(netdev);
+	if (err)
+		return err;
+
+	/* finally start device */
+	err = usb_8dev_start(priv);
+	if (err) {
+		if (err == -ENODEV)
+			netif_device_detach(priv->netdev);
+
+		netdev_warn(netdev, "couldn't start device: %d\n",
+			 err);
+
+		close_candev(netdev);
+
+		return err;
+	}
+
+	netif_start_queue(netdev);
+
+	return 0;
+}
+
+static void unlink_all_urbs(struct usb_8dev_priv *priv)
+{
+	int i;
+
+	usb_kill_anchored_urbs(&priv->rx_submitted);
+
+	usb_kill_anchored_urbs(&priv->tx_submitted);
+	atomic_set(&priv->active_tx_urbs, 0);
+
+	for (i = 0; i < MAX_TX_URBS; i++)
+		priv->tx_contexts[i].echo_index = MAX_TX_URBS;
+}
+
+/* Close USB device */
+static int usb_8dev_close(struct net_device *netdev)
+{
+	struct usb_8dev_priv *priv = netdev_priv(netdev);
+	int err = 0;
+
+	/* Send CLOSE command to CAN controller */
+	err = usb_8dev_cmd_close(priv);
+	if (err)
+		netdev_warn(netdev, "couldn't stop device");
+
+	priv->can.state = CAN_STATE_STOPPED;
+
+	netif_stop_queue(netdev);
+
+	/* Stop polling */
+	unlink_all_urbs(priv);
+
+	close_candev(netdev);
+
+	return err;
+}
+
+static const struct net_device_ops usb_8dev_netdev_ops = {
+	.ndo_open = usb_8dev_open,
+	.ndo_stop = usb_8dev_close,
+	.ndo_start_xmit = usb_8dev_start_xmit,
+};
+
+static const struct can_bittiming_const usb_8dev_bittiming_const = {
+	.name = "usb_8dev",
+	.tseg1_min = 1,
+	.tseg1_max = 16,
+	.tseg2_min = 1,
+	.tseg2_max = 8,
+	.sjw_max = 4,
+	.brp_min = 1,
+	.brp_max = 1024,
+	.brp_inc = 1,
+};
+
+/* Probe USB device
+ *
+ * Check device and firmware.
+ * Set supported modes and bittiming constants.
+ * Allocate some memory.
+ */
+static int usb_8dev_probe(struct usb_interface *intf,
+			 const struct usb_device_id *id)
+{
+	struct net_device *netdev;
+	struct usb_8dev_priv *priv;
+	int i, err = -ENOMEM;
+	u32 version;
+	char buf[18];
+	struct usb_device *usbdev = interface_to_usbdev(intf);
+
+	/* product id looks strange, better we also check iProduct string */
+	if (usb_string(usbdev, usbdev->descriptor.iProduct, buf,
+		       sizeof(buf)) > 0 && strcmp(buf, "USB2CAN converter")) {
+		dev_info(&usbdev->dev, "ignoring: not an USB2CAN converter\n");
+		return -ENODEV;
+	}
+
+	netdev = alloc_candev(sizeof(struct usb_8dev_priv), MAX_TX_URBS);
+	if (!netdev) {
+		dev_err(&intf->dev, "Couldn't alloc candev\n");
+		return -ENOMEM;
+	}
+
+	priv = netdev_priv(netdev);
+
+	priv->udev = usbdev;
+	priv->netdev = netdev;
+
+	priv->can.state = CAN_STATE_STOPPED;
+	priv->can.clock.freq = USB_8DEV_ABP_CLOCK;
+	priv->can.bittiming_const = &usb_8dev_bittiming_const;
+	priv->can.do_set_mode = usb_8dev_set_mode;
+	priv->can.do_get_berr_counter = usb_8dev_get_berr_counter;
+	priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
+				      CAN_CTRLMODE_LISTENONLY |
+				      CAN_CTRLMODE_ONE_SHOT;
+
+	netdev->netdev_ops = &usb_8dev_netdev_ops;
+
+	netdev->flags |= IFF_ECHO; /* we support local echo */
+
+	init_usb_anchor(&priv->rx_submitted);
+
+	init_usb_anchor(&priv->tx_submitted);
+	atomic_set(&priv->active_tx_urbs, 0);
+
+	for (i = 0; i < MAX_TX_URBS; i++)
+		priv->tx_contexts[i].echo_index = MAX_TX_URBS;
+
+	priv->cmd_msg_buffer = kzalloc(sizeof(struct usb_8dev_cmd_msg),
+				      GFP_KERNEL);
+	if (!priv->cmd_msg_buffer) {
+		netdev_err(netdev, "Couldn't alloc Tx buffer\n");
+		goto cleanup_candev;
+	}
+
+	usb_set_intfdata(intf, priv);
+
+	SET_NETDEV_DEV(netdev, &intf->dev);
+
+	mutex_init(&priv->usb_8dev_cmd_lock);
+
+	err = register_candev(netdev);
+	if (err) {
+		netdev_err(netdev,
+			"couldn't register CAN device: %d\n", err);
+		goto cleanup_cmd_msg_buffer;
+	}
+
+	err = usb_8dev_cmd_version(priv, &version);
+	if (err) {
+		netdev_err(netdev, "can't get firmware version\n");
+		goto cleanup_cmd_msg_buffer;
+	} else {
+		netdev_info(netdev,
+			 "firmware: %d.%d, hardware: %d.%d\n",
+			 (version>>24) & 0xff, (version>>16) & 0xff,
+			 (version>>8) & 0xff, version & 0xff);
+	}
+
+	return 0;
+
+cleanup_cmd_msg_buffer:
+	kfree(priv->cmd_msg_buffer);
+
+cleanup_candev:
+	free_candev(netdev);
+
+	return err;
+
+}
+
+/* Called by the usb core when driver is unloaded or device is removed */
+static void usb_8dev_disconnect(struct usb_interface *intf)
+{
+	struct usb_8dev_priv *priv = usb_get_intfdata(intf);
+
+	usb_set_intfdata(intf, NULL);
+
+	if (priv) {
+		netdev_info(priv->netdev, "device disconnected\n");
+
+		unregister_netdev(priv->netdev);
+		free_candev(priv->netdev);
+
+		unlink_all_urbs(priv);
+	}
+
+}
+
+static struct usb_driver usb_8dev_driver = {
+	.name =		"usb_8dev",
+	.probe =	usb_8dev_probe,
+	.disconnect =	usb_8dev_disconnect,
+	.id_table =	usb_8dev_table,
+};
+
+module_usb_driver(usb_8dev_driver);
+
+MODULE_AUTHOR("Bernd Krumboeck <[e-mail]>");
+MODULE_DESCRIPTION("CAN driver for 8 devices USB2CAN interfaces");
+MODULE_LICENSE("GPL v2");