text: /*
   * CAN driver for esd CAN-USB/2 and CAN-USB/Micro
   *
   * Copyright (C) 2010-2012 Matthias Fuchs <matthias.fuchs@esd.eu>, esd gmbh
   *
   * 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; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
   */
  #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>
  
  MODULE_AUTHOR("Matthias Fuchs <matthias.fuchs@esd.eu>");
  MODULE_DESCRIPTION("CAN driver for esd CAN-USB/2 and CAN-USB/Micro interfaces");
  MODULE_LICENSE("GPL v2");
  
  /* Define these values to match your devices */
  #define USB_ESDGMBH_VENDOR_ID	0x0ab4
  #define USB_CANUSB2_PRODUCT_ID	0x0010
  #define USB_CANUSBM_PRODUCT_ID	0x0011
  
  #define ESD_USB2_CAN_CLOCK	60000000
  #define ESD_USBM_CAN_CLOCK	36000000
  #define ESD_USB2_MAX_NETS	2
  
  /* USB2 commands */
  #define CMD_VERSION		1 /* also used for VERSION_REPLY */
  #define CMD_CAN_RX		2 /* device to host only */
  #define CMD_CAN_TX		3 /* also used for TX_DONE */
  #define CMD_SETBAUD		4 /* also used for SETBAUD_REPLY */
  #define CMD_TS			5 /* also used for TS_REPLY */
  #define CMD_IDADD		6 /* also used for IDADD_REPLY */
  
  /* esd CAN message flags - dlc field */
  #define ESD_RTR			0x10
  
  /* esd CAN message flags - id field */
  #define ESD_EXTID		0x20000000
  #define ESD_EVENT		0x40000000
  #define ESD_IDMASK		0x1fffffff
  
  /* esd CAN event ids used by this driver */
  #define ESD_EV_CAN_ERROR_EXT	2
  
  /* baudrate message flags */
  #define ESD_USB2_UBR		0x80000000
  #define ESD_USB2_LOM		0x40000000
  #define ESD_USB2_NO_BAUDRATE	0x7fffffff
  #define ESD_USB2_TSEG1_MIN	1
  #define ESD_USB2_TSEG1_MAX	16
  #define ESD_USB2_TSEG1_SHIFT	16
  #define ESD_USB2_TSEG2_MIN	1
  #define ESD_USB2_TSEG2_MAX	8
  #define ESD_USB2_TSEG2_SHIFT	20
  #define ESD_USB2_SJW_MAX	4
  #define ESD_USB2_SJW_SHIFT	14
  #define ESD_USBM_SJW_SHIFT	24
  #define ESD_USB2_BRP_MIN	1
  #define ESD_USB2_BRP_MAX	1024
  #define ESD_USB2_BRP_INC	1
  #define ESD_USB2_3_SAMPLES	0x00800000
  
  /* esd IDADD message */
  #define ESD_ID_ENABLE		0x80
  #define ESD_MAX_ID_SEGMENT	64
  
  /* SJA1000 ECC register (emulated by usb2 firmware) */
  #define SJA1000_ECC_SEG		0x1F
  #define SJA1000_ECC_DIR		0x20
  #define SJA1000_ECC_ERR		0x06
  #define SJA1000_ECC_BIT		0x00
  #define SJA1000_ECC_FORM	0x40
  #define SJA1000_ECC_STUFF	0x80
  #define SJA1000_ECC_MASK	0xc0
  
  /* esd bus state event codes */
  #define ESD_BUSSTATE_MASK	0xc0
  #define ESD_BUSSTATE_WARN	0x40
  #define ESD_BUSSTATE_ERRPASSIVE	0x80
  #define ESD_BUSSTATE_BUSOFF	0xc0
  
  #define RX_BUFFER_SIZE		1024
  #define MAX_RX_URBS		4
  #define MAX_TX_URBS		16 /* must be power of 2 */
  
  struct header_msg {
  	u8 len; /* len is always the total message length in 32bit words */
  	u8 cmd;
  	u8 rsvd[2];
  };
  
  struct version_msg {
  	u8 len;
  	u8 cmd;
  	u8 rsvd;
  	u8 flags;
  	__le32 drv_version;
  };
  
  struct version_reply_msg {
  	u8 len;
  	u8 cmd;
  	u8 nets;
  	u8 features;
  	__le32 version;
  	u8 name[16];
  	__le32 rsvd;
  	__le32 ts;
  };
  
  struct rx_msg {
  	u8 len;
  	u8 cmd;
  	u8 net;
  	u8 dlc;
  	__le32 ts;
  	__le32 id; /* upper 3 bits contain flags */
  	u8 data[8];
  };
  
  struct tx_msg {
  	u8 len;
  	u8 cmd;
  	u8 net;
  	u8 dlc;
  	__le32 hnd;
  	__le32 id; /* upper 3 bits contain flags */
  	u8 data[8];
  };
  
  struct tx_done_msg {
  	u8 len;
  	u8 cmd;
  	u8 net;
  	u8 status;
  	__le32 hnd;
  	__le32 ts;
  };
  
  struct id_filter_msg {
  	u8 len;
  	u8 cmd;
  	u8 net;
  	u8 option;
  	__le32 mask[ESD_MAX_ID_SEGMENT + 1];
  };
  
  struct set_baudrate_msg {
  	u8 len;
  	u8 cmd;
  	u8 net;
  	u8 rsvd;
  	__le32 baud;
  };
  
  /* Main message type used between library and application */
  struct __attribute__ ((packed)) esd_usb2_msg {
  	union {
  		struct header_msg hdr;
  		struct version_msg version;
  		struct version_reply_msg version_reply;
  		struct rx_msg rx;
  		struct tx_msg tx;
  		struct tx_done_msg txdone;
  		struct set_baudrate_msg setbaud;
  		struct id_filter_msg filter;
  	} msg;
  };
  
  static struct usb_device_id esd_usb2_table[] = {
  	{USB_DEVICE(USB_ESDGMBH_VENDOR_ID, USB_CANUSB2_PRODUCT_ID)},
  	{USB_DEVICE(USB_ESDGMBH_VENDOR_ID, USB_CANUSBM_PRODUCT_ID)},
  	{}
  };
  MODULE_DEVICE_TABLE(usb, esd_usb2_table);
  
  struct esd_usb2_net_priv;
  
  struct esd_tx_urb_context {
  	struct esd_usb2_net_priv *priv;
  	u32 echo_index;
  	int dlc;
  };
  
  struct esd_usb2 {
  	struct usb_device *udev;
  	struct esd_usb2_net_priv *nets[ESD_USB2_MAX_NETS];
  
  	struct usb_anchor rx_submitted;
  
  	int net_count;
  	u32 version;
  	int rxinitdone;
  };
  
  struct esd_usb2_net_priv {
  	struct can_priv can; /* must be the first member */
  
  	atomic_t active_tx_jobs;
  	struct usb_anchor tx_submitted;
  	struct esd_tx_urb_context tx_contexts[MAX_TX_URBS];
  
  	struct esd_usb2 *usb2;
  	struct net_device *netdev;
  	int index;
  	u8 old_state;
  	struct can_berr_counter bec;
  };
  
  static void esd_usb2_rx_event(struct esd_usb2_net_priv *priv,
  			      struct esd_usb2_msg *msg)
  {
  	struct net_device_stats *stats = &priv->netdev->stats;
  	struct can_frame *cf;
  	struct sk_buff *skb;
  	u32 id = le32_to_cpu(msg->msg.rx.id) & ESD_IDMASK;
  
  	if (id == ESD_EV_CAN_ERROR_EXT) {
  		u8 state = msg->msg.rx.data[0];
  		u8 ecc = msg->msg.rx.data[1];
  		u8 txerr = msg->msg.rx.data[2];
  		u8 rxerr = msg->msg.rx.data[3];
  
  		skb = alloc_can_err_skb(priv->netdev, &cf);
  		if (skb == NULL) {
  			stats->rx_dropped++;
  			return;
  		}
  
  		if (state != priv->old_state) {
  			priv->old_state = state;
  
  			switch (state & ESD_BUSSTATE_MASK) {
  			case ESD_BUSSTATE_BUSOFF:
  				priv->can.state = CAN_STATE_BUS_OFF;
  				cf->can_id |= CAN_ERR_BUSOFF;
  				can_bus_off(priv->netdev);
  				break;
  			case ESD_BUSSTATE_WARN:
  				priv->can.state = CAN_STATE_ERROR_WARNING;
  				priv->can.can_stats.error_warning++;
  				break;
  			case ESD_BUSSTATE_ERRPASSIVE:
  				priv->can.state = CAN_STATE_ERROR_PASSIVE;
  				priv->can.can_stats.error_passive++;
  				break;
  			default:
  				priv->can.state = CAN_STATE_ERROR_ACTIVE;
  				break;
  			}
  		} else {
  			priv->can.can_stats.bus_error++;
  			stats->rx_errors++;
  
  			cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
  
  			switch (ecc & SJA1000_ECC_MASK) {
  			case SJA1000_ECC_BIT:
  				cf->data[2] |= CAN_ERR_PROT_BIT;
  				break;
  			case SJA1000_ECC_FORM:
  				cf->data[2] |= CAN_ERR_PROT_FORM;
  				break;
  			case SJA1000_ECC_STUFF:
  				cf->data[2] |= CAN_ERR_PROT_STUFF;
  				break;
  			default:
  				cf->data[2] |= CAN_ERR_PROT_UNSPEC;
  				cf->data[3] = ecc & SJA1000_ECC_SEG;
  				break;
  			}
  
  			/* Error occurred during transmission? */
  			if (!(ecc & SJA1000_ECC_DIR))
  				cf->data[2] |= CAN_ERR_PROT_TX;
  
  			if (priv->can.state == CAN_STATE_ERROR_WARNING ||
  			    priv->can.state == CAN_STATE_ERROR_PASSIVE) {
  				cf->data[1] = (txerr > rxerr) ?
  					CAN_ERR_CRTL_TX_PASSIVE :
  					CAN_ERR_CRTL_RX_PASSIVE;
  			}
  			cf->data[6] = txerr;
  			cf->data[7] = rxerr;
  		}
  
  		netif_rx(skb);
  
  		priv->bec.txerr = txerr;
  		priv->bec.rxerr = rxerr;
  
  		stats->rx_packets++;
  		stats->rx_bytes += cf->can_dlc;
  	}
  }
  
  static void esd_usb2_rx_can_msg(struct esd_usb2_net_priv *priv,
  				struct esd_usb2_msg *msg)
  {
  	struct net_device_stats *stats = &priv->netdev->stats;
  	struct can_frame *cf;
  	struct sk_buff *skb;
  	int i;
  	u32 id;
  
  	if (!netif_device_present(priv->netdev))
  		return;
  
  	id = le32_to_cpu(msg->msg.rx.id);
  
  	if (id & ESD_EVENT) {
  		esd_usb2_rx_event(priv, msg);
  	} else {
  		skb = alloc_can_skb(priv->netdev, &cf);
  		if (skb == NULL) {
  			stats->rx_dropped++;
  			return;
  		}
  
  		cf->can_id = id & ESD_IDMASK;
  		cf->can_dlc = get_can_dlc(msg->msg.rx.dlc);
  
  		if (id & ESD_EXTID)
  			cf->can_id |= CAN_EFF_FLAG;
  
  		if (msg->msg.rx.dlc & ESD_RTR) {
  			cf->can_id |= CAN_RTR_FLAG;
  		} else {
  			for (i = 0; i < cf->can_dlc; i++)
  				cf->data[i] = msg->msg.rx.data[i];
  		}
  
  		netif_rx(skb);
  
  		stats->rx_packets++;
  		stats->rx_bytes += cf->can_dlc;
  	}
  
  	return;
  }
  
  static void esd_usb2_tx_done_msg(struct esd_usb2_net_priv *priv,
  				 struct esd_usb2_msg *msg)
  {
  	struct net_device_stats *stats = &priv->netdev->stats;
  	struct net_device *netdev = priv->netdev;
  	struct esd_tx_urb_context *context;
  
  	if (!netif_device_present(netdev))
  		return;
  
  	context = &priv->tx_contexts[msg->msg.txdone.hnd & (MAX_TX_URBS - 1)];
  
  	if (!msg->msg.txdone.status) {
  		stats->tx_packets++;
  		stats->tx_bytes += context->dlc;
  		can_get_echo_skb(netdev, context->echo_index);
  	} else {
  		stats->tx_errors++;
  		can_free_echo_skb(netdev, context->echo_index);
  	}
  
  	/* Release context */
  	context->echo_index = MAX_TX_URBS;
  	atomic_dec(&priv->active_tx_jobs);
  
  	netif_wake_queue(netdev);
  }
  
  static void esd_usb2_read_bulk_callback(struct urb *urb)
  {
  	struct esd_usb2 *dev = urb->context;
  	int retval;
  	int pos = 0;
  	int i;
  
  	switch (urb->status) {
  	case 0: /* success */
  		break;
  
  	case -ENOENT:
  	case -ESHUTDOWN:
  		return;
  
  	default:
  		dev_info(dev->udev->dev.parent,
  			 "Rx URB aborted (%d)\n", urb->status);
  		goto resubmit_urb;
  	}
  
  	while (pos < urb->actual_length) {
  		struct esd_usb2_msg *msg;
  
  		msg = (struct esd_usb2_msg *)(urb->transfer_buffer + pos);
  
  		switch (msg->msg.hdr.cmd) {
  		case CMD_CAN_RX:
  			if (msg->msg.rx.net >= dev->net_count) {
  				dev_err(dev->udev->dev.parent, "format error\n");
  				break;
  			}
  
  			esd_usb2_rx_can_msg(dev->nets[msg->msg.rx.net], msg);
  			break;
  
  		case CMD_CAN_TX:
  			if (msg->msg.txdone.net >= dev->net_count) {
  				dev_err(dev->udev->dev.parent, "format error\n");
  				break;
  			}
  
  			esd_usb2_tx_done_msg(dev->nets[msg->msg.txdone.net],
  					     msg);
  			break;
  		}
  
  		pos += msg->msg.hdr.len << 2;
  
  		if (pos > urb->actual_length) {
  			dev_err(dev->udev->dev.parent, "format error\n");
  			break;
  		}
  	}
  
  resubmit_urb:
  	usb_fill_bulk_urb(urb, dev->udev, usb_rcvbulkpipe(dev->udev, 1),
  			  urb->transfer_buffer, RX_BUFFER_SIZE,
  			  esd_usb2_read_bulk_callback, dev);
  
  	retval = usb_submit_urb(urb, GFP_ATOMIC);
  	if (retval == -ENODEV) {
  		for (i = 0; i < dev->net_count; i++) {
  			if (dev->nets[i])
  				netif_device_detach(dev->nets[i]->netdev);
  		}
  	} else if (retval) {
  		dev_err(dev->udev->dev.parent,
  			"failed resubmitting read bulk urb: %d\n", retval);
  	}
  
  	return;
  }
  
  /*
   * callback for bulk IN urb
   */
  static void esd_usb2_write_bulk_callback(struct urb *urb)
  {
  	struct esd_tx_urb_context *context = urb->context;
  	struct esd_usb2_net_priv *priv;
  	struct esd_usb2 *dev;
  	struct net_device *netdev;
  	size_t size = sizeof(struct esd_usb2_msg);
  
  	WARN_ON(!context);
  
  	priv = context->priv;
  	netdev = priv->netdev;
  	dev = priv->usb2;
  
  	/* free up our allocated buffer */
  	usb_free_coherent(urb->dev, size,
  			  urb->transfer_buffer, urb->transfer_dma);
  
  	if (!netif_device_present(netdev))
  		return;
  
  	if (urb->status)
  		netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);
  
  	netdev->trans_start = jiffies;
  }
  
  static ssize_t show_firmware(struct device *d,
  			     struct device_attribute *attr, char *buf)
  {
  	struct usb_interface *intf = to_usb_interface(d);
  	struct esd_usb2 *dev = usb_get_intfdata(intf);
  
  	return sprintf(buf, "%d.%d.%d\n",
  		       (dev->version >> 12) & 0xf,
  		       (dev->version >> 8) & 0xf,
  		       dev->version & 0xff);
  }
  static DEVICE_ATTR(firmware, S_IRUGO, show_firmware, NULL);
  
  static ssize_t show_hardware(struct device *d,
  			     struct device_attribute *attr, char *buf)
  {
  	struct usb_interface *intf = to_usb_interface(d);
  	struct esd_usb2 *dev = usb_get_intfdata(intf);
  
  	return sprintf(buf, "%d.%d.%d\n",
  		       (dev->version >> 28) & 0xf,
  		       (dev->version >> 24) & 0xf,
  		       (dev->version >> 16) & 0xff);
  }
  static DEVICE_ATTR(hardware, S_IRUGO, show_hardware, NULL);
  
  static ssize_t show_nets(struct device *d,
  			 struct device_attribute *attr, char *buf)
  {
  	struct usb_interface *intf = to_usb_interface(d);
  	struct esd_usb2 *dev = usb_get_intfdata(intf);
  
  	return sprintf(buf, "%d", dev->net_count);
  }
  static DEVICE_ATTR(nets, S_IRUGO, show_nets, NULL);
  
  static int esd_usb2_send_msg(struct esd_usb2 *dev, struct esd_usb2_msg *msg)
  {
  	int actual_length;
  
  	return usb_bulk_msg(dev->udev,
  			    usb_sndbulkpipe(dev->udev, 2),
  			    msg,
  			    msg->msg.hdr.len << 2,
  			    &actual_length,
  			    1000);
  }
  
  static int esd_usb2_wait_msg(struct esd_usb2 *dev,
  			     struct esd_usb2_msg *msg)
  {
  	int actual_length;
  
  	return usb_bulk_msg(dev->udev,
  			    usb_rcvbulkpipe(dev->udev, 1),
  			    msg,
  			    sizeof(*msg),
  			    &actual_length,
  			    1000);
  }
  
  static int esd_usb2_setup_rx_urbs(struct esd_usb2 *dev)
  {
  	int i, err = 0;
  
  	if (dev->rxinitdone)
  		return 0;
  
  	for (i = 0; i < MAX_RX_URBS; i++) {
  		struct urb *urb = NULL;
  		u8 *buf = NULL;
  
  		/* create a URB, and a buffer for it */
  		urb = usb_alloc_urb(0, GFP_KERNEL);
  		if (!urb) {
  			dev_warn(dev->udev->dev.parent,
  				 "No memory left for URBs\n");
  			err = -ENOMEM;
  			break;
  		}
  
  		buf = usb_alloc_coherent(dev->udev, RX_BUFFER_SIZE, GFP_KERNEL,
  					 &urb->transfer_dma);
  		if (!buf) {
  			dev_warn(dev->udev->dev.parent,
  				 "No memory left for USB buffer\n");
  			err = -ENOMEM;
  			goto freeurb;
  		}
  
  		usb_fill_bulk_urb(urb, dev->udev,
  				  usb_rcvbulkpipe(dev->udev, 1),
  				  buf, RX_BUFFER_SIZE,
  				  esd_usb2_read_bulk_callback, dev);
  		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
  		usb_anchor_urb(urb, &dev->rx_submitted);
  
  		err = usb_submit_urb(urb, GFP_KERNEL);
  		if (err) {
  			usb_unanchor_urb(urb);
  			usb_free_coherent(dev->udev, RX_BUFFER_SIZE, buf,
  					  urb->transfer_dma);
  		}
  
  freeurb:
  		/* Drop reference, USB core will take care of freeing it */
  		usb_free_urb(urb);
  		if (err)
  			break;
  	}
  
  	/* Did we submit any URBs */
  	if (i == 0) {
  		dev_err(dev->udev->dev.parent, "couldn't setup read URBs\n");
  		return err;
  	}
  
  	/* Warn if we've couldn't transmit all the URBs */
  	if (i < MAX_RX_URBS) {
  		dev_warn(dev->udev->dev.parent,
  			 "rx performance may be slow\n");
  	}
  
  	dev->rxinitdone = 1;
  	return 0;
  }
  
  /*
   * Start interface
   */
  static int esd_usb2_start(struct esd_usb2_net_priv *priv)
  {
  	struct esd_usb2 *dev = priv->usb2;
  	struct net_device *netdev = priv->netdev;
  	struct esd_usb2_msg *msg;
  	int err, i;
  
  	msg = kmalloc(sizeof(*msg), GFP_KERNEL);
  	if (!msg) {
  		err = -ENOMEM;
  		goto out;
  	}
  
  	/*
  	 * Enable all IDs
  	 * The IDADD message takes up to 64 32 bit bitmasks (2048 bits).
  	 * Each bit represents one 11 bit CAN identifier. A set bit
  	 * enables reception of the corresponding CAN identifier. A cleared
  	 * bit disabled this identifier. An additional bitmask value
  	 * following the CAN 2.0A bits is used to enable reception of
  	 * extended CAN frames. Only the LSB of this final mask is checked
  	 * for the complete 29 bit ID range. The IDADD message also allows
  	 * filter configuration for an ID subset. In this case you can add
  	 * the number of the starting bitmask (0..64) to the filter.option
  	 * field followed by only some bitmasks.
  	 */
  	msg->msg.hdr.cmd = CMD_IDADD;
  	msg->msg.hdr.len = 2 + ESD_MAX_ID_SEGMENT;
  	msg->msg.filter.net = priv->index;
  	msg->msg.filter.option = ESD_ID_ENABLE; /* start with segment 0 */
  	for (i = 0; i < ESD_MAX_ID_SEGMENT; i++)
  		msg->msg.filter.mask[i] = cpu_to_le32(0xffffffff);
  	/* enable 29bit extended IDs */
  	msg->msg.filter.mask[ESD_MAX_ID_SEGMENT] = cpu_to_le32(0x00000001);
  
  	err = esd_usb2_send_msg(dev, msg);
  	if (err)
  		goto out;
  
  	err = esd_usb2_setup_rx_urbs(dev);
  	if (err)
  		goto out;
  
  	priv->can.state = CAN_STATE_ERROR_ACTIVE;
  
  out:
  	if (err == -ENODEV)
  		netif_device_detach(netdev);
  	if (err)
  		netdev_err(netdev, "couldn't start device: %d\n", err);
  
  	kfree(msg);
  	return err;
  }
  
  static void unlink_all_urbs(struct esd_usb2 *dev)
  {
  	struct esd_usb2_net_priv *priv;
  	int i, j;
  
  	usb_kill_anchored_urbs(&dev->rx_submitted);
  	for (i = 0; i < dev->net_count; i++) {
  		priv = dev->nets[i];
  		if (priv) {
  			usb_kill_anchored_urbs(&priv->tx_submitted);
  			atomic_set(&priv->active_tx_jobs, 0);
  
  			for (j = 0; j < MAX_TX_URBS; j++)
  				priv->tx_contexts[j].echo_index = MAX_TX_URBS;
  		}
  	}
  }
  
  static int esd_usb2_open(struct net_device *netdev)
  {
  	struct esd_usb2_net_priv *priv = netdev_priv(netdev);
  	int err;
  
  	/* common open */
  	err = open_candev(netdev);
  	if (err)
  		return err;
  
  	/* finally start device */
  	err = esd_usb2_start(priv);
  	if (err) {
  		netdev_warn(netdev, "couldn't start device: %d\n", err);
  		close_candev(netdev);
  		return err;
  	}
  
  	netif_start_queue(netdev);
  
  	return 0;
  }
  
  static netdev_tx_t esd_usb2_start_xmit(struct sk_buff *skb,
  				      struct net_device *netdev)
  {
  	struct esd_usb2_net_priv *priv = netdev_priv(netdev);
  	struct esd_usb2 *dev = priv->usb2;
  	struct esd_tx_urb_context *context = NULL;
  	struct net_device_stats *stats = &netdev->stats;
  	struct can_frame *cf = (struct can_frame *)skb->data;
  	struct esd_usb2_msg *msg;
  	struct urb *urb;
  	u8 *buf;
  	int i, err;
  	int ret = NETDEV_TX_OK;
  	size_t size = sizeof(struct esd_usb2_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");
  		stats->tx_dropped++;
  		dev_kfree_skb(skb);
  		goto nourbmem;
  	}
  
  	buf = usb_alloc_coherent(dev->udev, size, GFP_ATOMIC,
  				 &urb->transfer_dma);
  	if (!buf) {
  		netdev_err(netdev, "No memory left for USB buffer\n");
  		stats->tx_dropped++;
  		dev_kfree_skb(skb);
  		goto nobufmem;
  	}
  
  	msg = (struct esd_usb2_msg *)buf;
  
  	msg->msg.hdr.len = 3; /* minimal length */
  	msg->msg.hdr.cmd = CMD_CAN_TX;
  	msg->msg.tx.net = priv->index;
  	msg->msg.tx.dlc = cf->can_dlc;
  	msg->msg.tx.id = cpu_to_le32(cf->can_id & CAN_ERR_MASK);
  
  	if (cf->can_id & CAN_RTR_FLAG)
  		msg->msg.tx.dlc |= ESD_RTR;
  
  	if (cf->can_id & CAN_EFF_FLAG)
  		msg->msg.tx.id |= cpu_to_le32(ESD_EXTID);
  
  	for (i = 0; i < cf->can_dlc; i++)
  		msg->msg.tx.data[i] = cf->data[i];
  
  	msg->msg.hdr.len += (cf->can_dlc + 3) >> 2;
  
  	for (i = 0; i < MAX_TX_URBS; i++) {
  		if (priv->tx_contexts[i].echo_index == MAX_TX_URBS) {
  			context = &priv->tx_contexts[i];
  			break;
  		}
  	}
  
  	/*
  	 * This may never happen.
  	 */
  	if (!context) {
  		netdev_warn(netdev, "couldn't find free context\n");
  		ret = NETDEV_TX_BUSY;
  		goto releasebuf;
  	}
  
  	context->priv = priv;
  	context->echo_index = i;
  	context->dlc = cf->can_dlc;
  
  	/* hnd must not be 0 - MSB is stripped in txdone handling */
  	msg->msg.tx.hnd = 0x80000000 | i; /* returned in TX done message */
  
  	usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 2), buf,
  			  msg->msg.hdr.len << 2,
  			  esd_usb2_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_jobs);
  
  	/* Slow down tx path */
  	if (atomic_read(&priv->active_tx_jobs) >= MAX_TX_URBS)
  		netif_stop_queue(netdev);
  
  	err = usb_submit_urb(urb, GFP_ATOMIC);
  	if (err) {
  		can_free_echo_skb(netdev, context->echo_index);
  
  		atomic_dec(&priv->active_tx_jobs);
  		usb_unanchor_urb(urb);
  
  		stats->tx_dropped++;
  
  		if (err == -ENODEV)
  			netif_device_detach(netdev);
  		else
  			netdev_warn(netdev, "failed tx_urb %d\n", err);
  
  		goto releasebuf;
  	}
  
  	netdev->trans_start = jiffies;
  
  	/*
  	 * Release our reference to this URB, the USB core will eventually free
  	 * it entirely.
  	 */
  	usb_free_urb(urb);
  
  	return NETDEV_TX_OK;
  
  releasebuf:
  	usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
  
  nobufmem:
  	usb_free_urb(urb);
  
  nourbmem:
  	return ret;
  }
  
  static int esd_usb2_close(struct net_device *netdev)
  {
  	struct esd_usb2_net_priv *priv = netdev_priv(netdev);
  	struct esd_usb2_msg *msg;
  	int i;
  
  	msg = kmalloc(sizeof(*msg), GFP_KERNEL);
  	if (!msg)
  		return -ENOMEM;
  
  	/* Disable all IDs (see esd_usb2_start()) */
  	msg->msg.hdr.cmd = CMD_IDADD;
  	msg->msg.hdr.len = 2 + ESD_MAX_ID_SEGMENT;
  	msg->msg.filter.net = priv->index;
  	msg->msg.filter.option = ESD_ID_ENABLE; /* start with segment 0 */
  	for (i = 0; i <= ESD_MAX_ID_SEGMENT; i++)
  		msg->msg.filter.mask[i] = 0;
  	if (esd_usb2_send_msg(priv->usb2, msg) < 0)
  		netdev_err(netdev, "sending idadd message failed\n");
  
  	/* set CAN controller to reset mode */
  	msg->msg.hdr.len = 2;
  	msg->msg.hdr.cmd = CMD_SETBAUD;
  	msg->msg.setbaud.net = priv->index;
  	msg->msg.setbaud.rsvd = 0;
  	msg->msg.setbaud.baud = cpu_to_le32(ESD_USB2_NO_BAUDRATE);
  	if (esd_usb2_send_msg(priv->usb2, msg) < 0)
  		netdev_err(netdev, "sending setbaud message failed\n");
  
  	priv->can.state = CAN_STATE_STOPPED;
  
  	netif_stop_queue(netdev);
  
  	close_candev(netdev);
  
  	kfree(msg);
  
  	return 0;
  }
  
  static const struct net_device_ops esd_usb2_netdev_ops = {
  	.ndo_open = esd_usb2_open,
  	.ndo_stop = esd_usb2_close,
  	.ndo_start_xmit = esd_usb2_start_xmit,
  	.ndo_change_mtu = can_change_mtu,
  };
  
  static const struct can_bittiming_const esd_usb2_bittiming_const = {
  	.name = "esd_usb2",
  	.tseg1_min = ESD_USB2_TSEG1_MIN,
  	.tseg1_max = ESD_USB2_TSEG1_MAX,
  	.tseg2_min = ESD_USB2_TSEG2_MIN,
  	.tseg2_max = ESD_USB2_TSEG2_MAX,
  	.sjw_max = ESD_USB2_SJW_MAX,
  	.brp_min = ESD_USB2_BRP_MIN,
  	.brp_max = ESD_USB2_BRP_MAX,
  	.brp_inc = ESD_USB2_BRP_INC,
  };
  
  static int esd_usb2_set_bittiming(struct net_device *netdev)
  {
  	struct esd_usb2_net_priv *priv = netdev_priv(netdev);
  	struct can_bittiming *bt = &priv->can.bittiming;
  	struct esd_usb2_msg *msg;
  	int err;
  	u32 canbtr;
  	int sjw_shift;
  
  	canbtr = ESD_USB2_UBR;
  	if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
  		canbtr |= ESD_USB2_LOM;
  
  	canbtr |= (bt->brp - 1) & (ESD_USB2_BRP_MAX - 1);
  
  	if (le16_to_cpu(priv->usb2->udev->descriptor.idProduct) ==
  	    USB_CANUSBM_PRODUCT_ID)
  		sjw_shift = ESD_USBM_SJW_SHIFT;
  	else
  		sjw_shift = ESD_USB2_SJW_SHIFT;
  
  	canbtr |= ((bt->sjw - 1) & (ESD_USB2_SJW_MAX - 1))
  		<< sjw_shift;
  	canbtr |= ((bt->prop_seg + bt->phase_seg1 - 1)
  		   & (ESD_USB2_TSEG1_MAX - 1))
  		<< ESD_USB2_TSEG1_SHIFT;
  	canbtr |= ((bt->phase_seg2 - 1) & (ESD_USB2_TSEG2_MAX - 1))
  		<< ESD_USB2_TSEG2_SHIFT;
  	if (priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
  		canbtr |= ESD_USB2_3_SAMPLES;
  
  	msg = kmalloc(sizeof(*msg), GFP_KERNEL);
  	if (!msg)
  		return -ENOMEM;
  
  	msg->msg.hdr.len = 2;
  	msg->msg.hdr.cmd = CMD_SETBAUD;
  	msg->msg.setbaud.net = priv->index;
  	msg->msg.setbaud.rsvd = 0;
  	msg->msg.setbaud.baud = cpu_to_le32(canbtr);
  
  	netdev_info(netdev, "setting BTR=%#x\n", canbtr);
  
  	err = esd_usb2_send_msg(priv->usb2, msg);
  
  	kfree(msg);
  	return err;
  }
  
  static int esd_usb2_get_berr_counter(const struct net_device *netdev,
  				     struct can_berr_counter *bec)
  {
  	struct esd_usb2_net_priv *priv = netdev_priv(netdev);
  
  	bec->txerr = priv->bec.txerr;
  	bec->rxerr = priv->bec.rxerr;
  
  	return 0;
  }
  
  static int esd_usb2_set_mode(struct net_device *netdev, enum can_mode mode)
  {
  	switch (mode) {
  	case CAN_MODE_START:
  		netif_wake_queue(netdev);
  		break;
  
  	default:
  		return -EOPNOTSUPP;
  	}
  
  	return 0;
  }
  
  static int esd_usb2_probe_one_net(struct usb_interface *intf, int index)
  {
  	struct esd_usb2 *dev = usb_get_intfdata(intf);
  	struct net_device *netdev;
  	struct esd_usb2_net_priv *priv;
  	int err = 0;
  	int i;
  
  	netdev = alloc_candev(sizeof(*priv), MAX_TX_URBS);
  	if (!netdev) {
  		dev_err(&intf->dev, "couldn't alloc candev\n");
  		err = -ENOMEM;
  		goto done;
  	}
  
  	priv = netdev_priv(netdev);
  
  	init_usb_anchor(&priv->tx_submitted);
  	atomic_set(&priv->active_tx_jobs, 0);
  
  	for (i = 0; i < MAX_TX_URBS; i++)
  		priv->tx_contexts[i].echo_index = MAX_TX_URBS;
  
  	priv->usb2 = dev;
  	priv->netdev = netdev;
  	priv->index = index;
  
  	priv->can.state = CAN_STATE_STOPPED;
  	priv->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
  
  	if (le16_to_cpu(dev->udev->descriptor.idProduct) ==
  	    USB_CANUSBM_PRODUCT_ID)
  		priv->can.clock.freq = ESD_USBM_CAN_CLOCK;
  	else {
  		priv->can.clock.freq = ESD_USB2_CAN_CLOCK;
  		priv->can.ctrlmode_supported |= CAN_CTRLMODE_3_SAMPLES;
  	}
  
  	priv->can.bittiming_const = &esd_usb2_bittiming_const;
  	priv->can.do_set_bittiming = esd_usb2_set_bittiming;
  	priv->can.do_set_mode = esd_usb2_set_mode;
  	priv->can.do_get_berr_counter = esd_usb2_get_berr_counter;
  
  	netdev->flags |= IFF_ECHO; /* we support local echo */
  
  	netdev->netdev_ops = &esd_usb2_netdev_ops;
  
  	SET_NETDEV_DEV(netdev, &intf->dev);
  	netdev->dev_id = index;
  
  	err = register_candev(netdev);
  	if (err) {
  		dev_err(&intf->dev, "couldn't register CAN device: %d\n", err);
  		free_candev(netdev);
  		err = -ENOMEM;
  		goto done;
  	}
  
  	dev->nets[index] = priv;
  	netdev_info(netdev, "device %s registered\n", netdev->name);
  
  done:
  	return err;
  }
  
  /*
   * probe function for new USB2 devices
   *
   * check version information and number of available
   * CAN interfaces
   */
  static int esd_usb2_probe(struct usb_interface *intf,
  			 const struct usb_device_id *id)
  {
  	struct esd_usb2 *dev;
  	struct esd_usb2_msg *msg;
  	int i, err;
  
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (!dev) {
  		err = -ENOMEM;
  		goto done;
  	}
  
  	dev->udev = interface_to_usbdev(intf);
  
  	init_usb_anchor(&dev->rx_submitted);
  
  	usb_set_intfdata(intf, dev);
  
  	msg = kmalloc(sizeof(*msg), GFP_KERNEL);
  	if (!msg) {
  		err = -ENOMEM;
  		goto free_msg;
  	}
  
  	/* query number of CAN interfaces (nets) */
  	msg->msg.hdr.cmd = CMD_VERSION;
  	msg->msg.hdr.len = 2;
  	msg->msg.version.rsvd = 0;
  	msg->msg.version.flags = 0;
  	msg->msg.version.drv_version = 0;
  
  	err = esd_usb2_send_msg(dev, msg);
  	if (err < 0) {
  		dev_err(&intf->dev, "sending version message failed\n");
  		goto free_msg;
  	}
  
  	err = esd_usb2_wait_msg(dev, msg);
  	if (err < 0) {
  		dev_err(&intf->dev, "no version message answer\n");
  		goto free_msg;
  	}
  
  	dev->net_count = (int)msg->msg.version_reply.nets;
  	dev->version = le32_to_cpu(msg->msg.version_reply.version);
  
  	if (device_create_file(&intf->dev, &dev_attr_firmware))
  		dev_err(&intf->dev,
  			"Couldn't create device file for firmware\n");
  
  	if (device_create_file(&intf->dev, &dev_attr_hardware))
  		dev_err(&intf->dev,
  			"Couldn't create device file for hardware\n");
  
  	if (device_create_file(&intf->dev, &dev_attr_nets))
  		dev_err(&intf->dev,
  			"Couldn't create device file for nets\n");
  
  	/* do per device probing */
  	for (i = 0; i < dev->net_count; i++)
  		esd_usb2_probe_one_net(intf, i);
  
  free_msg:
  	kfree(msg);
  	if (err)
  		kfree(dev);
  done:
  	return err;
  }
  
  /*
   * called by the usb core when the device is removed from the system
   */
  static void esd_usb2_disconnect(struct usb_interface *intf)
  {
  	struct esd_usb2 *dev = usb_get_intfdata(intf);
  	struct net_device *netdev;
  	int i;
  
  	device_remove_file(&intf->dev, &dev_attr_firmware);
  	device_remove_file(&intf->dev, &dev_attr_hardware);
  	device_remove_file(&intf->dev, &dev_attr_nets);
  
  	usb_set_intfdata(intf, NULL);
  
  	if (dev) {
  		for (i = 0; i < dev->net_count; i++) {
  			if (dev->nets[i]) {
  				netdev = dev->nets[i]->netdev;
  				unregister_netdev(netdev);
  				free_candev(netdev);
  			}
  		}
  		unlink_all_urbs(dev);
  	}
  }
  
  /* usb specific object needed to register this driver with the usb subsystem */
  static struct usb_driver esd_usb2_driver = {
  	.name = "esd_usb2",
  	.probe = esd_usb2_probe,
  	.disconnect = esd_usb2_disconnect,
  	.id_table = esd_usb2_table,
  };
  
  module_usb_driver(esd_usb2_driver);
  