text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * CAN driver for "8 devices" USB2CAN converter
   *
   * Copyright (C) 2012 Bernd Krumboeck (krumboeck@universalnet.at)
   *
   * 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 (info@gerhard-bertelsmann.de)
   * for testing and fixing this driver. Also many thanks to "8 devices",
   * who were very cooperative and answered my questions.
   */
  
  #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>
  #include <linux/can/led.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 occurred 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;
  	void *rxbuf[MAX_RX_URBS];
  	dma_addr_t rxbuf_dma[MAX_RX_URBS];
  };
  
  /* 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;	/* unknown - 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;
  		priv->can.can_stats.bus_off++;
  		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[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
  		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;
  
  	stats->rx_packets++;
  	stats->rx_bytes += cf->len;
  	netif_rx(skb);
  }
  
  /* 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);
  		can_frame_set_cc_len(cf, msg->dlc & 0xF, priv->can.ctrlmode);
  
  		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->len);
  
  		stats->rx_packets++;
  		stats->rx_bytes += cf->len;
  		netif_rx(skb);
  
  		can_led_event(priv->netdev, CAN_LED_EVENT_RX);
  	} 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 -EPIPE:
  	case -EPROTO:
  	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, NULL);
  
  	can_led_event(netdev, CAN_LED_EVENT_TX);
  
  	/* 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)
  		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 = can_get_cc_dlc(cf, priv->can.ctrlmode);
  	memcpy(msg->data, cf->data, cf->len);
  	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->len;
  
  	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, 0);
  
  	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_free_coherent(priv->udev, size, buf, urb->transfer_dma);
  	usb_free_urb(urb);
  
  	netdev_warn(netdev, "couldn't find free context");
  
  	return NETDEV_TX_BUSY;
  
  failed:
  	can_free_echo_skb(netdev, context->echo_index, NULL);
  
  	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;
  		dma_addr_t buf_dma;
  
  		/* create a URB, and a buffer for it */
  		urb = usb_alloc_urb(0, GFP_KERNEL);
  		if (!urb) {
  			err = -ENOMEM;
  			break;
  		}
  
  		buf = usb_alloc_coherent(priv->udev, RX_BUFFER_SIZE, GFP_KERNEL,
  					 &buf_dma);
  		if (!buf) {
  			netdev_err(netdev, "No memory left for USB buffer\n");
  			usb_free_urb(urb);
  			err = -ENOMEM;
  			break;
  		}
  
  		urb->transfer_dma = buf_dma;
  
  		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);
  			usb_free_urb(urb);
  			break;
  		}
  
  		priv->rxbuf[i] = buf;
  		priv->rxbuf_dma[i] = buf_dma;
  
  		/* 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;
  
  	can_led_event(netdev, CAN_LED_EVENT_OPEN);
  
  	/* 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);
  
  	for (i = 0; i < MAX_RX_URBS; ++i)
  		usb_free_coherent(priv->udev, RX_BUFFER_SIZE,
  				  priv->rxbuf[i], priv->rxbuf_dma[i]);
  
  	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);
  
  	can_led_event(netdev, CAN_LED_EVENT_STOP);
  
  	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,
  	.ndo_change_mtu = can_change_mtu,
  };
  
  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 |
  				      CAN_CTRLMODE_CC_LEN8_DLC;
  
  	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 = devm_kzalloc(&intf->dev, sizeof(struct usb_8dev_cmd_msg),
  					    GFP_KERNEL);
  	if (!priv->cmd_msg_buffer)
  		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_candev;
  	}
  
  	err = usb_8dev_cmd_version(priv, &version);
  	if (err) {
  		netdev_err(netdev, "can't get firmware version\n");
  		goto cleanup_unregister_candev;
  	} else {
  		netdev_info(netdev,
  			 "firmware: %d.%d, hardware: %d.%d\n",
  			 (version>>24) & 0xff, (version>>16) & 0xff,
  			 (version>>8) & 0xff, version & 0xff);
  	}
  
  	devm_can_led_init(netdev);
  
  	return 0;
  
  cleanup_unregister_candev:
  	unregister_netdev(priv->netdev);
  
  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);
  		unlink_all_urbs(priv);
  		free_candev(priv->netdev);
  	}
  
  }
  
  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 <krumboeck@universalnet.at>");
  MODULE_DESCRIPTION("CAN driver for 8 devices USB2CAN interfaces");
  MODULE_LICENSE("GPL v2");
  