text: /*
   * CAN driver for EMS Dr. Thomas Wuensche CPC-USB/ARM7
   *
   * Copyright (C) 2004-2009 EMS Dr. Thomas Wuensche
   *
   * 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("Sebastian Haas <haas@ems-wuensche.com>");
  MODULE_DESCRIPTION("CAN driver for EMS Dr. Thomas Wuensche CAN/USB interfaces");
  MODULE_LICENSE("GPL v2");
  
  /* Control-Values for CPC_Control() Command Subject Selection */
  #define CONTR_CAN_MESSAGE 0x04
  #define CONTR_CAN_STATE   0x0C
  #define CONTR_BUS_ERROR   0x1C
  
  /* Control Command Actions */
  #define CONTR_CONT_OFF 0
  #define CONTR_CONT_ON  1
  #define CONTR_ONCE     2
  
  /* Messages from CPC to PC */
  #define CPC_MSG_TYPE_CAN_FRAME       1  /* CAN data frame */
  #define CPC_MSG_TYPE_RTR_FRAME       8  /* CAN remote frame */
  #define CPC_MSG_TYPE_CAN_PARAMS      12 /* Actual CAN parameters */
  #define CPC_MSG_TYPE_CAN_STATE       14 /* CAN state message */
  #define CPC_MSG_TYPE_EXT_CAN_FRAME   16 /* Extended CAN data frame */
  #define CPC_MSG_TYPE_EXT_RTR_FRAME   17 /* Extended remote frame */
  #define CPC_MSG_TYPE_CONTROL         19 /* change interface behavior */
  #define CPC_MSG_TYPE_CONFIRM         20 /* command processed confirmation */
  #define CPC_MSG_TYPE_OVERRUN         21 /* overrun events */
  #define CPC_MSG_TYPE_CAN_FRAME_ERROR 23 /* detected bus errors */
  #define CPC_MSG_TYPE_ERR_COUNTER     25 /* RX/TX error counter */
  
  /* Messages from the PC to the CPC interface  */
  #define CPC_CMD_TYPE_CAN_FRAME     1   /* CAN data frame */
  #define CPC_CMD_TYPE_CONTROL       3   /* control of interface behavior */
  #define CPC_CMD_TYPE_CAN_PARAMS    6   /* set CAN parameters */
  #define CPC_CMD_TYPE_RTR_FRAME     13  /* CAN remote frame */
  #define CPC_CMD_TYPE_CAN_STATE     14  /* CAN state message */
  #define CPC_CMD_TYPE_EXT_CAN_FRAME 15  /* Extended CAN data frame */
  #define CPC_CMD_TYPE_EXT_RTR_FRAME 16  /* Extended CAN remote frame */
  #define CPC_CMD_TYPE_CAN_EXIT      200 /* exit the CAN */
  
  #define CPC_CMD_TYPE_INQ_ERR_COUNTER 25 /* request the CAN error counters */
  #define CPC_CMD_TYPE_CLEAR_MSG_QUEUE 8  /* clear CPC_MSG queue */
  #define CPC_CMD_TYPE_CLEAR_CMD_QUEUE 28 /* clear CPC_CMD queue */
  
  #define CPC_CC_TYPE_SJA1000 2 /* Philips basic CAN controller */
  
  #define CPC_CAN_ECODE_ERRFRAME 0x01 /* Ecode type */
  
  /* Overrun types */
  #define CPC_OVR_EVENT_CAN       0x01
  #define CPC_OVR_EVENT_CANSTATE  0x02
  #define CPC_OVR_EVENT_BUSERROR  0x04
  
  /*
   * If the CAN controller lost a message we indicate it with the highest bit
   * set in the count field.
   */
  #define CPC_OVR_HW 0x80
  
  /* Size of the "struct ems_cpc_msg" without the union */
  #define CPC_MSG_HEADER_LEN   11
  #define CPC_CAN_MSG_MIN_SIZE 5
  
  /* Define these values to match your devices */
  #define USB_CPCUSB_VENDOR_ID 0x12D6
  
  #define USB_CPCUSB_ARM7_PRODUCT_ID 0x0444
  
  /* Mode register NXP LPC2119/SJA1000 CAN Controller */
  #define SJA1000_MOD_NORMAL 0x00
  #define SJA1000_MOD_RM     0x01
  
  /* ECC register NXP LPC2119/SJA1000 CAN Controller */
  #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
  
  /* Status register content */
  #define SJA1000_SR_BS 0x80
  #define SJA1000_SR_ES 0x40
  
  #define SJA1000_DEFAULT_OUTPUT_CONTROL 0xDA
  
  /*
   * The device actually uses a 16MHz clock to generate the CAN clock
   * but it expects SJA1000 bit settings based on 8MHz (is internally
   * converted).
   */
  #define EMS_USB_ARM7_CLOCK 8000000
  
  #define CPC_TX_QUEUE_TRIGGER_LOW	25
  #define CPC_TX_QUEUE_TRIGGER_HIGH	35
  
  /*
   * CAN-Message representation in a CPC_MSG. Message object type is
   * CPC_MSG_TYPE_CAN_FRAME or CPC_MSG_TYPE_RTR_FRAME or
   * CPC_MSG_TYPE_EXT_CAN_FRAME or CPC_MSG_TYPE_EXT_RTR_FRAME.
   */
  struct cpc_can_msg {
  	__le32 id;
  	u8 length;
  	u8 msg[8];
  };
  
  /* Representation of the CAN parameters for the SJA1000 controller */
  struct cpc_sja1000_params {
  	u8 mode;
  	u8 acc_code0;
  	u8 acc_code1;
  	u8 acc_code2;
  	u8 acc_code3;
  	u8 acc_mask0;
  	u8 acc_mask1;
  	u8 acc_mask2;
  	u8 acc_mask3;
  	u8 btr0;
  	u8 btr1;
  	u8 outp_contr;
  };
  
  /* CAN params message representation */
  struct cpc_can_params {
  	u8 cc_type;
  
  	/* Will support M16C CAN controller in the future */
  	union {
  		struct cpc_sja1000_params sja1000;
  	} cc_params;
  };
  
  /* Structure for confirmed message handling */
  struct cpc_confirm {
  	u8 error; /* error code */
  };
  
  /* Structure for overrun conditions */
  struct cpc_overrun {
  	u8 event;
  	u8 count;
  };
  
  /* SJA1000 CAN errors (compatible to NXP LPC2119) */
  struct cpc_sja1000_can_error {
  	u8 ecc;
  	u8 rxerr;
  	u8 txerr;
  };
  
  /* structure for CAN error conditions */
  struct cpc_can_error {
  	u8 ecode;
  
  	struct {
  		u8 cc_type;
  
  		/* Other controllers may also provide error code capture regs */
  		union {
  			struct cpc_sja1000_can_error sja1000;
  		} regs;
  	} cc;
  };
  
  /*
   * Structure containing RX/TX error counter. This structure is used to request
   * the values of the CAN controllers TX and RX error counter.
   */
  struct cpc_can_err_counter {
  	u8 rx;
  	u8 tx;
  };
  
  /* Main message type used between library and application */
  struct __packed ems_cpc_msg {
  	u8 type;	/* type of message */
  	u8 length;	/* length of data within union 'msg' */
  	u8 msgid;	/* confirmation handle */
  	__le32 ts_sec;	/* timestamp in seconds */
  	__le32 ts_nsec;	/* timestamp in nano seconds */
  
  	union {
  		u8 generic[64];
  		struct cpc_can_msg can_msg;
  		struct cpc_can_params can_params;
  		struct cpc_confirm confirmation;
  		struct cpc_overrun overrun;
  		struct cpc_can_error error;
  		struct cpc_can_err_counter err_counter;
  		u8 can_state;
  	} msg;
  };
  
  /*
   * Table of devices that work with this driver
   * NOTE: This driver supports only CPC-USB/ARM7 (LPC2119) yet.
   */
  static struct usb_device_id ems_usb_table[] = {
  	{USB_DEVICE(USB_CPCUSB_VENDOR_ID, USB_CPCUSB_ARM7_PRODUCT_ID)},
  	{} /* Terminating entry */
  };
  
  MODULE_DEVICE_TABLE(usb, ems_usb_table);
  
  #define RX_BUFFER_SIZE      64
  #define CPC_HEADER_SIZE     4
  #define INTR_IN_BUFFER_SIZE 4
  
  #define MAX_RX_URBS 10
  #define MAX_TX_URBS 10
  
  struct ems_usb;
  
  struct ems_tx_urb_context {
  	struct ems_usb *dev;
  
  	u32 echo_index;
  	u8 dlc;
  };
  
  struct ems_usb {
  	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 ems_tx_urb_context tx_contexts[MAX_TX_URBS];
  
  	struct usb_anchor rx_submitted;
  
  	struct urb *intr_urb;
  
  	u8 *tx_msg_buffer;
  
  	u8 *intr_in_buffer;
  	unsigned int free_slots; /* remember number of available slots */
  
  	struct ems_cpc_msg active_params; /* active controller parameters */
  };
  
  static void ems_usb_read_interrupt_callback(struct urb *urb)
  {
  	struct ems_usb *dev = urb->context;
  	struct net_device *netdev = dev->netdev;
  	int err;
  
  	if (!netif_device_present(netdev))
  		return;
  
  	switch (urb->status) {
  	case 0:
  		dev->free_slots = dev->intr_in_buffer[1];
  		if (dev->free_slots > CPC_TX_QUEUE_TRIGGER_HIGH &&
  		    netif_queue_stopped(netdev))
  			netif_wake_queue(netdev);
  		break;
  
  	case -ECONNRESET: /* unlink */
  	case -ENOENT:
  	case -EPIPE:
  	case -EPROTO:
  	case -ESHUTDOWN:
  		return;
  
  	default:
  		netdev_info(netdev, "Rx interrupt aborted %d\n", urb->status);
  		break;
  	}
  
  	err = usb_submit_urb(urb, GFP_ATOMIC);
  
  	if (err == -ENODEV)
  		netif_device_detach(netdev);
  	else if (err)
  		netdev_err(netdev, "failed resubmitting intr urb: %d\n", err);
  }
  
  static void ems_usb_rx_can_msg(struct ems_usb *dev, struct ems_cpc_msg *msg)
  {
  	struct can_frame *cf;
  	struct sk_buff *skb;
  	int i;
  	struct net_device_stats *stats = &dev->netdev->stats;
  
  	skb = alloc_can_skb(dev->netdev, &cf);
  	if (skb == NULL)
  		return;
  
  	cf->can_id = le32_to_cpu(msg->msg.can_msg.id);
  	cf->can_dlc = get_can_dlc(msg->msg.can_msg.length & 0xF);
  
  	if (msg->type == CPC_MSG_TYPE_EXT_CAN_FRAME ||
  	    msg->type == CPC_MSG_TYPE_EXT_RTR_FRAME)
  		cf->can_id |= CAN_EFF_FLAG;
  
  	if (msg->type == CPC_MSG_TYPE_RTR_FRAME ||
  	    msg->type == CPC_MSG_TYPE_EXT_RTR_FRAME) {
  		cf->can_id |= CAN_RTR_FLAG;
  	} else {
  		for (i = 0; i < cf->can_dlc; i++)
  			cf->data[i] = msg->msg.can_msg.msg[i];
  	}
  
  	stats->rx_packets++;
  	stats->rx_bytes += cf->can_dlc;
  	netif_rx(skb);
  }
  
  static void ems_usb_rx_err(struct ems_usb *dev, struct ems_cpc_msg *msg)
  {
  	struct can_frame *cf;
  	struct sk_buff *skb;
  	struct net_device_stats *stats = &dev->netdev->stats;
  
  	skb = alloc_can_err_skb(dev->netdev, &cf);
  	if (skb == NULL)
  		return;
  
  	if (msg->type == CPC_MSG_TYPE_CAN_STATE) {
  		u8 state = msg->msg.can_state;
  
  		if (state & SJA1000_SR_BS) {
  			dev->can.state = CAN_STATE_BUS_OFF;
  			cf->can_id |= CAN_ERR_BUSOFF;
  
  			dev->can.can_stats.bus_off++;
  			can_bus_off(dev->netdev);
  		} else if (state & SJA1000_SR_ES) {
  			dev->can.state = CAN_STATE_ERROR_WARNING;
  			dev->can.can_stats.error_warning++;
  		} else {
  			dev->can.state = CAN_STATE_ERROR_ACTIVE;
  			dev->can.can_stats.error_passive++;
  		}
  	} else if (msg->type == CPC_MSG_TYPE_CAN_FRAME_ERROR) {
  		u8 ecc = msg->msg.error.cc.regs.sja1000.ecc;
  		u8 txerr = msg->msg.error.cc.regs.sja1000.txerr;
  		u8 rxerr = msg->msg.error.cc.regs.sja1000.rxerr;
  
  		/* bus error interrupt */
  		dev->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[3] = ecc & SJA1000_ECC_SEG;
  			break;
  		}
  
  		/* Error occurred during transmission? */
  		if ((ecc & SJA1000_ECC_DIR) == 0)
  			cf->data[2] |= CAN_ERR_PROT_TX;
  
  		if (dev->can.state == CAN_STATE_ERROR_WARNING ||
  		    dev->can.state == CAN_STATE_ERROR_PASSIVE) {
  			cf->can_id |= CAN_ERR_CRTL;
  			cf->data[1] = (txerr > rxerr) ?
  			    CAN_ERR_CRTL_TX_PASSIVE : CAN_ERR_CRTL_RX_PASSIVE;
  		}
  	} else if (msg->type == CPC_MSG_TYPE_OVERRUN) {
  		cf->can_id |= CAN_ERR_CRTL;
  		cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
  
  		stats->rx_over_errors++;
  		stats->rx_errors++;
  	}
  
  	stats->rx_packets++;
  	stats->rx_bytes += cf->can_dlc;
  	netif_rx(skb);
  }
  
  /*
   * callback for bulk IN urb
   */
  static void ems_usb_read_bulk_callback(struct urb *urb)
  {
  	struct ems_usb *dev = urb->context;
  	struct net_device *netdev;
  	int retval;
  
  	netdev = dev->netdev;
  
  	if (!netif_device_present(netdev))
  		return;
  
  	switch (urb->status) {
  	case 0: /* success */
  		break;
  
  	case -ENOENT:
  		return;
  
  	default:
  		netdev_info(netdev, "Rx URB aborted (%d)\n", urb->status);
  		goto resubmit_urb;
  	}
  
  	if (urb->actual_length > CPC_HEADER_SIZE) {
  		struct ems_cpc_msg *msg;
  		u8 *ibuf = urb->transfer_buffer;
  		u8 msg_count, start;
  
  		msg_count = ibuf[0] & ~0x80;
  
  		start = CPC_HEADER_SIZE;
  
  		while (msg_count) {
  			msg = (struct ems_cpc_msg *)&ibuf[start];
  
  			switch (msg->type) {
  			case CPC_MSG_TYPE_CAN_STATE:
  				/* Process CAN state changes */
  				ems_usb_rx_err(dev, msg);
  				break;
  
  			case CPC_MSG_TYPE_CAN_FRAME:
  			case CPC_MSG_TYPE_EXT_CAN_FRAME:
  			case CPC_MSG_TYPE_RTR_FRAME:
  			case CPC_MSG_TYPE_EXT_RTR_FRAME:
  				ems_usb_rx_can_msg(dev, msg);
  				break;
  
  			case CPC_MSG_TYPE_CAN_FRAME_ERROR:
  				/* Process errorframe */
  				ems_usb_rx_err(dev, msg);
  				break;
  
  			case CPC_MSG_TYPE_OVERRUN:
  				/* Message lost while receiving */
  				ems_usb_rx_err(dev, msg);
  				break;
  			}
  
  			start += CPC_MSG_HEADER_LEN + msg->length;
  			msg_count--;
  
  			if (start > urb->transfer_buffer_length) {
  				netdev_err(netdev, "format error\n");
  				break;
  			}
  		}
  	}
  
  resubmit_urb:
  	usb_fill_bulk_urb(urb, dev->udev, usb_rcvbulkpipe(dev->udev, 2),
  			  urb->transfer_buffer, RX_BUFFER_SIZE,
  			  ems_usb_read_bulk_callback, dev);
  
  	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 for bulk IN urb
   */
  static void ems_usb_write_bulk_callback(struct urb *urb)
  {
  	struct ems_tx_urb_context *context = urb->context;
  	struct ems_usb *dev;
  	struct net_device *netdev;
  
  	BUG_ON(!context);
  
  	dev = context->dev;
  	netdev = dev->netdev;
  
  	/* free up our allocated buffer */
  	usb_free_coherent(urb->dev, urb->transfer_buffer_length,
  			  urb->transfer_buffer, urb->transfer_dma);
  
  	atomic_dec(&dev->active_tx_urbs);
  
  	if (!netif_device_present(netdev))
  		return;
  
  	if (urb->status)
  		netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);
  
  	netif_trans_update(netdev);
  
  	/* transmission complete interrupt */
  	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;
  
  }
  
  /*
   * Send the given CPC command synchronously
   */
  static int ems_usb_command_msg(struct ems_usb *dev, struct ems_cpc_msg *msg)
  {
  	int actual_length;
  
  	/* Copy payload */
  	memcpy(&dev->tx_msg_buffer[CPC_HEADER_SIZE], msg,
  	       msg->length + CPC_MSG_HEADER_LEN);
  
  	/* Clear header */
  	memset(&dev->tx_msg_buffer[0], 0, CPC_HEADER_SIZE);
  
  	return usb_bulk_msg(dev->udev, usb_sndbulkpipe(dev->udev, 2),
  			    &dev->tx_msg_buffer[0],
  			    msg->length + CPC_MSG_HEADER_LEN + CPC_HEADER_SIZE,
  			    &actual_length, 1000);
  }
  
  /*
   * Change CAN controllers' mode register
   */
  static int ems_usb_write_mode(struct ems_usb *dev, u8 mode)
  {
  	dev->active_params.msg.can_params.cc_params.sja1000.mode = mode;
  
  	return ems_usb_command_msg(dev, &dev->active_params);
  }
  
  /*
   * Send a CPC_Control command to change behaviour when interface receives a CAN
   * message, bus error or CAN state changed notifications.
   */
  static int ems_usb_control_cmd(struct ems_usb *dev, u8 val)
  {
  	struct ems_cpc_msg cmd;
  
  	cmd.type = CPC_CMD_TYPE_CONTROL;
  	cmd.length = CPC_MSG_HEADER_LEN + 1;
  
  	cmd.msgid = 0;
  
  	cmd.msg.generic[0] = val;
  
  	return ems_usb_command_msg(dev, &cmd);
  }
  
  /*
   * Start interface
   */
  static int ems_usb_start(struct ems_usb *dev)
  {
  	struct net_device *netdev = dev->netdev;
  	int err, i;
  
  	dev->intr_in_buffer[0] = 0;
  	dev->free_slots = 50; /* initial size */
  
  	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) {
  			err = -ENOMEM;
  			break;
  		}
  
  		buf = usb_alloc_coherent(dev->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, dev->udev, usb_rcvbulkpipe(dev->udev, 2),
  				  buf, RX_BUFFER_SIZE,
  				  ems_usb_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);
  			usb_free_urb(urb);
  			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");
  
  	/* Setup and start interrupt URB */
  	usb_fill_int_urb(dev->intr_urb, dev->udev,
  			 usb_rcvintpipe(dev->udev, 1),
  			 dev->intr_in_buffer,
  			 INTR_IN_BUFFER_SIZE,
  			 ems_usb_read_interrupt_callback, dev, 1);
  
  	err = usb_submit_urb(dev->intr_urb, GFP_KERNEL);
  	if (err) {
  		netdev_warn(netdev, "intr URB submit failed: %d\n", err);
  
  		return err;
  	}
  
  	/* CPC-USB will transfer received message to host */
  	err = ems_usb_control_cmd(dev, CONTR_CAN_MESSAGE | CONTR_CONT_ON);
  	if (err)
  		goto failed;
  
  	/* CPC-USB will transfer CAN state changes to host */
  	err = ems_usb_control_cmd(dev, CONTR_CAN_STATE | CONTR_CONT_ON);
  	if (err)
  		goto failed;
  
  	/* CPC-USB will transfer bus errors to host */
  	err = ems_usb_control_cmd(dev, CONTR_BUS_ERROR | CONTR_CONT_ON);
  	if (err)
  		goto failed;
  
  	err = ems_usb_write_mode(dev, SJA1000_MOD_NORMAL);
  	if (err)
  		goto failed;
  
  	dev->can.state = CAN_STATE_ERROR_ACTIVE;
  
  	return 0;
  
  failed:
  	netdev_warn(netdev, "couldn't submit control: %d\n", err);
  
  	return err;
  }
  
  static void unlink_all_urbs(struct ems_usb *dev)
  {
  	int i;
  
  	usb_unlink_urb(dev->intr_urb);
  
  	usb_kill_anchored_urbs(&dev->rx_submitted);
  
  	usb_kill_anchored_urbs(&dev->tx_submitted);
  	atomic_set(&dev->active_tx_urbs, 0);
  
  	for (i = 0; i < MAX_TX_URBS; i++)
  		dev->tx_contexts[i].echo_index = MAX_TX_URBS;
  }
  
  static int ems_usb_open(struct net_device *netdev)
  {
  	struct ems_usb *dev = netdev_priv(netdev);
  	int err;
  
  	err = ems_usb_write_mode(dev, SJA1000_MOD_RM);
  	if (err)
  		return err;
  
  	/* common open */
  	err = open_candev(netdev);
  	if (err)
  		return err;
  
  	/* finally start device */
  	err = ems_usb_start(dev);
  	if (err) {
  		if (err == -ENODEV)
  			netif_device_detach(dev->netdev);
  
  		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 ems_usb_start_xmit(struct sk_buff *skb, struct net_device *netdev)
  {
  	struct ems_usb *dev = netdev_priv(netdev);
  	struct ems_tx_urb_context *context = NULL;
  	struct net_device_stats *stats = &netdev->stats;
  	struct can_frame *cf = (struct can_frame *)skb->data;
  	struct ems_cpc_msg *msg;
  	struct urb *urb;
  	u8 *buf;
  	int i, err;
  	size_t size = CPC_HEADER_SIZE + CPC_MSG_HEADER_LEN
  			+ sizeof(struct cpc_can_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(dev->udev, size, GFP_ATOMIC, &urb->transfer_dma);
  	if (!buf) {
  		netdev_err(netdev, "No memory left for USB buffer\n");
  		usb_free_urb(urb);
  		goto nomem;
  	}
  
  	msg = (struct ems_cpc_msg *)&buf[CPC_HEADER_SIZE];
  
  	msg->msg.can_msg.id = cpu_to_le32(cf->can_id & CAN_ERR_MASK);
  	msg->msg.can_msg.length = cf->can_dlc;
  
  	if (cf->can_id & CAN_RTR_FLAG) {
  		msg->type = cf->can_id & CAN_EFF_FLAG ?
  			CPC_CMD_TYPE_EXT_RTR_FRAME : CPC_CMD_TYPE_RTR_FRAME;
  
  		msg->length = CPC_CAN_MSG_MIN_SIZE;
  	} else {
  		msg->type = cf->can_id & CAN_EFF_FLAG ?
  			CPC_CMD_TYPE_EXT_CAN_FRAME : CPC_CMD_TYPE_CAN_FRAME;
  
  		for (i = 0; i < cf->can_dlc; i++)
  			msg->msg.can_msg.msg[i] = cf->data[i];
  
  		msg->length = CPC_CAN_MSG_MIN_SIZE + cf->can_dlc;
  	}
  
  	for (i = 0; i < MAX_TX_URBS; i++) {
  		if (dev->tx_contexts[i].echo_index == MAX_TX_URBS) {
  			context = &dev->tx_contexts[i];
  			break;
  		}
  	}
  
  	/*
  	 * May never happen! When this happens we'd more URBs in flight as
  	 * allowed (MAX_TX_URBS).
  	 */
  	if (!context) {
  		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
  		usb_free_urb(urb);
  
  		netdev_warn(netdev, "couldn't find free context\n");
  
  		return NETDEV_TX_BUSY;
  	}
  
  	context->dev = dev;
  	context->echo_index = i;
  	context->dlc = cf->can_dlc;
  
  	usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 2), buf,
  			  size, ems_usb_write_bulk_callback, context);
  	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
  	usb_anchor_urb(urb, &dev->tx_submitted);
  
  	can_put_echo_skb(skb, netdev, context->echo_index);
  
  	atomic_inc(&dev->active_tx_urbs);
  
  	err = usb_submit_urb(urb, GFP_ATOMIC);
  	if (unlikely(err)) {
  		can_free_echo_skb(netdev, context->echo_index);
  
  		usb_unanchor_urb(urb);
  		usb_free_coherent(dev->udev, size, buf, urb->transfer_dma);
  		dev_kfree_skb(skb);
  
  		atomic_dec(&dev->active_tx_urbs);
  
  		if (err == -ENODEV) {
  			netif_device_detach(netdev);
  		} else {
  			netdev_warn(netdev, "failed tx_urb %d\n", err);
  
  			stats->tx_dropped++;
  		}
  	} else {
  		netif_trans_update(netdev);
  
  		/* Slow down tx path */
  		if (atomic_read(&dev->active_tx_urbs) >= MAX_TX_URBS ||
  		    dev->free_slots < CPC_TX_QUEUE_TRIGGER_LOW) {
  			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;
  
  nomem:
  	dev_kfree_skb(skb);
  	stats->tx_dropped++;
  
  	return NETDEV_TX_OK;
  }
  
  static int ems_usb_close(struct net_device *netdev)
  {
  	struct ems_usb *dev = netdev_priv(netdev);
  
  	/* Stop polling */
  	unlink_all_urbs(dev);
  
  	netif_stop_queue(netdev);
  
  	/* Set CAN controller to reset mode */
  	if (ems_usb_write_mode(dev, SJA1000_MOD_RM))
  		netdev_warn(netdev, "couldn't stop device");
  
  	close_candev(netdev);
  
  	return 0;
  }
  
  static const struct net_device_ops ems_usb_netdev_ops = {
  	.ndo_open = ems_usb_open,
  	.ndo_stop = ems_usb_close,
  	.ndo_start_xmit = ems_usb_start_xmit,
  	.ndo_change_mtu = can_change_mtu,
  };
  
  static const struct can_bittiming_const ems_usb_bittiming_const = {
  	.name = "ems_usb",
  	.tseg1_min = 1,
  	.tseg1_max = 16,
  	.tseg2_min = 1,
  	.tseg2_max = 8,
  	.sjw_max = 4,
  	.brp_min = 1,
  	.brp_max = 64,
  	.brp_inc = 1,
  };
  
  static int ems_usb_set_mode(struct net_device *netdev, enum can_mode mode)
  {
  	struct ems_usb *dev = netdev_priv(netdev);
  
  	switch (mode) {
  	case CAN_MODE_START:
  		if (ems_usb_write_mode(dev, SJA1000_MOD_NORMAL))
  			netdev_warn(netdev, "couldn't start device");
  
  		if (netif_queue_stopped(netdev))
  			netif_wake_queue(netdev);
  		break;
  
  	default:
  		return -EOPNOTSUPP;
  	}
  
  	return 0;
  }
  
  static int ems_usb_set_bittiming(struct net_device *netdev)
  {
  	struct ems_usb *dev = netdev_priv(netdev);
  	struct can_bittiming *bt = &dev->can.bittiming;
  	u8 btr0, btr1;
  
  	btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
  	btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
  		(((bt->phase_seg2 - 1) & 0x7) << 4);
  	if (dev->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
  		btr1 |= 0x80;
  
  	netdev_info(netdev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);
  
  	dev->active_params.msg.can_params.cc_params.sja1000.btr0 = btr0;
  	dev->active_params.msg.can_params.cc_params.sja1000.btr1 = btr1;
  
  	return ems_usb_command_msg(dev, &dev->active_params);
  }
  
  static void init_params_sja1000(struct ems_cpc_msg *msg)
  {
  	struct cpc_sja1000_params *sja1000 =
  		&msg->msg.can_params.cc_params.sja1000;
  
  	msg->type = CPC_CMD_TYPE_CAN_PARAMS;
  	msg->length = sizeof(struct cpc_can_params);
  	msg->msgid = 0;
  
  	msg->msg.can_params.cc_type = CPC_CC_TYPE_SJA1000;
  
  	/* Acceptance filter open */
  	sja1000->acc_code0 = 0x00;
  	sja1000->acc_code1 = 0x00;
  	sja1000->acc_code2 = 0x00;
  	sja1000->acc_code3 = 0x00;
  
  	/* Acceptance filter open */
  	sja1000->acc_mask0 = 0xFF;
  	sja1000->acc_mask1 = 0xFF;
  	sja1000->acc_mask2 = 0xFF;
  	sja1000->acc_mask3 = 0xFF;
  
  	sja1000->btr0 = 0;
  	sja1000->btr1 = 0;
  
  	sja1000->outp_contr = SJA1000_DEFAULT_OUTPUT_CONTROL;
  	sja1000->mode = SJA1000_MOD_RM;
  }
  
  /*
   * probe function for new CPC-USB devices
   */
  static int ems_usb_probe(struct usb_interface *intf,
  			 const struct usb_device_id *id)
  {
  	struct net_device *netdev;
  	struct ems_usb *dev;
  	int i, err = -ENOMEM;
  
  	netdev = alloc_candev(sizeof(struct ems_usb), MAX_TX_URBS);
  	if (!netdev) {
  		dev_err(&intf->dev, "ems_usb: Couldn't alloc candev\n");
  		return -ENOMEM;
  	}
  
  	dev = netdev_priv(netdev);
  
  	dev->udev = interface_to_usbdev(intf);
  	dev->netdev = netdev;
  
  	dev->can.state = CAN_STATE_STOPPED;
  	dev->can.clock.freq = EMS_USB_ARM7_CLOCK;
  	dev->can.bittiming_const = &ems_usb_bittiming_const;
  	dev->can.do_set_bittiming = ems_usb_set_bittiming;
  	dev->can.do_set_mode = ems_usb_set_mode;
  	dev->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;
  
  	netdev->netdev_ops = &ems_usb_netdev_ops;
  
  	netdev->flags |= IFF_ECHO; /* we support local echo */
  
  	init_usb_anchor(&dev->rx_submitted);
  
  	init_usb_anchor(&dev->tx_submitted);
  	atomic_set(&dev->active_tx_urbs, 0);
  
  	for (i = 0; i < MAX_TX_URBS; i++)
  		dev->tx_contexts[i].echo_index = MAX_TX_URBS;
  
  	dev->intr_urb = usb_alloc_urb(0, GFP_KERNEL);
  	if (!dev->intr_urb)
  		goto cleanup_candev;
  
  	dev->intr_in_buffer = kzalloc(INTR_IN_BUFFER_SIZE, GFP_KERNEL);
  	if (!dev->intr_in_buffer)
  		goto cleanup_intr_urb;
  
  	dev->tx_msg_buffer = kzalloc(CPC_HEADER_SIZE +
  				     sizeof(struct ems_cpc_msg), GFP_KERNEL);
  	if (!dev->tx_msg_buffer)
  		goto cleanup_intr_in_buffer;
  
  	usb_set_intfdata(intf, dev);
  
  	SET_NETDEV_DEV(netdev, &intf->dev);
  
  	init_params_sja1000(&dev->active_params);
  
  	err = ems_usb_command_msg(dev, &dev->active_params);
  	if (err) {
  		netdev_err(netdev, "couldn't initialize controller: %d\n", err);
  		goto cleanup_tx_msg_buffer;
  	}
  
  	err = register_candev(netdev);
  	if (err) {
  		netdev_err(netdev, "couldn't register CAN device: %d\n", err);
  		goto cleanup_tx_msg_buffer;
  	}
  
  	return 0;
  
  cleanup_tx_msg_buffer:
  	kfree(dev->tx_msg_buffer);
  
  cleanup_intr_in_buffer:
  	kfree(dev->intr_in_buffer);
  
  cleanup_intr_urb:
  	usb_free_urb(dev->intr_urb);
  
  cleanup_candev:
  	free_candev(netdev);
  
  	return err;
  }
  
  /*
   * called by the usb core when the device is removed from the system
   */
  static void ems_usb_disconnect(struct usb_interface *intf)
  {
  	struct ems_usb *dev = usb_get_intfdata(intf);
  
  	usb_set_intfdata(intf, NULL);
  
  	if (dev) {
  		unregister_netdev(dev->netdev);
  		free_candev(dev->netdev);
  
  		unlink_all_urbs(dev);
  
  		usb_free_urb(dev->intr_urb);
  
  		kfree(dev->intr_in_buffer);
  		kfree(dev->tx_msg_buffer);
  	}
  }
  
  /* usb specific object needed to register this driver with the usb subsystem */
  static struct usb_driver ems_usb_driver = {
  	.name = "ems_usb",
  	.probe = ems_usb_probe,
  	.disconnect = ems_usb_disconnect,
  	.id_table = ems_usb_table,
  };
  
  module_usb_driver(ems_usb_driver);
  