ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface

This patch adds support for one channel CAN/USB interace CPC-USB/ARM7 from
EMS Dr. Thomas Wuensche (http://www.ems-wuensche.com).

Signed-off-by: Sebastian Haas <haas@ems-wuensche.com>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 1160 insertions, 0 deletions

diff --git a/drivers/net/can/usb/Makefile b/drivers/net/can/usb/Makefile
new file mode 100644
index 00000000000..c3f75ba701b
--- /dev/null
+++ b/drivers/net/can/usb/Makefile
@@ -0,0 +1,5 @@
+#
+#  Makefile for the Linux Controller Area Network USB drivers.
+#
+
+obj-$(CONFIG_CAN_EMS_USB) += ems_usb.o
diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
new file mode 100644
index 00000000000..9012e0abc62
--- /dev/null
+++ b/drivers/net/can/usb/ems_usb.c
@@ -0,0 +1,1155 @@
+/*
+ * 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/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>
+
+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
+
+/*
+ * 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 {
+        u32 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 __attribute__ ((packed)) ems_cpc_msg {
+        u8 type;        /* type of message */
+        u8 length;      /* length of data within union 'msg' */
+        u8 msgid;       /* confirmation handle */
+        u32 ts_sec;     /* timestamp in seconds */
+        u32 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 CAN_ECHO_SKB_MAX
+
+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 */
+        int open_time;
+
+        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];
+                break;
+
+        case -ECONNRESET: /* unlink */
+        case -ENOENT:
+        case -ESHUTDOWN:
+                return;
+
+        default:
+                dev_info(netdev->dev.parent, "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)
+                dev_err(netdev->dev.parent,
+                        "failed resubmitting intr urb: %d\n", err);
+
+        return;
+}
+
+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 = netdev_alloc_skb(dev->netdev, sizeof(struct can_frame));
+        if (skb == NULL)
+                return;
+
+        skb->protocol = htons(ETH_P_CAN);
+
+        cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
+
+        cf->can_id = msg->msg.can_msg.id;
+        cf->can_dlc = min_t(u8, msg->msg.can_msg.length, 8);
+
+        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];
+        }
+
+        netif_rx(skb);
+
+        stats->rx_packets++;
+        stats->rx_bytes += cf->can_dlc;
+}
+
+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 = netdev_alloc_skb(dev->netdev, sizeof(struct can_frame));
+        if (skb == NULL)
+                return;
+
+        skb->protocol = htons(ETH_P_CAN);
+
+        cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
+        memset(cf, 0, sizeof(struct can_frame));
+
+        cf->can_id = CAN_ERR_FLAG;
+        cf->can_dlc = CAN_ERR_DLC;
+
+        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;
+
+                        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[2] |= CAN_ERR_PROT_UNSPEC;
+                        cf->data[3] = ecc & SJA1000_ECC_SEG;
+                        break;
+                }
+
+                /* Error occured 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->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++;
+        }
+
+        netif_rx(skb);
+
+        stats->rx_packets++;
+        stats->rx_bytes += cf->can_dlc;
+}
+
+/*
+ * 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:
+                dev_info(netdev->dev.parent, "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, again, start;
+
+                msg_count = ibuf[0] & ~0x80;
+                again = 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) {
+                                dev_err(netdev->dev.parent, "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)
+                dev_err(netdev->dev.parent,
+                        "failed resubmitting read bulk urb: %d\n", retval);
+
+        return;
+}
+
+/*
+ * 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_buffer_free(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)
+                dev_info(netdev->dev.parent, "Tx URB aborted (%d)\n",
+                         urb->status);
+
+        netdev->trans_start = jiffies;
+
+        /* 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;
+
+        if (netif_queue_stopped(netdev))
+                netif_wake_queue(netdev);
+}
+
+/*
+ * 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 = 15; /* 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) {
+                        dev_err(netdev->dev.parent,
+                                "No memory left for URBs\n");
+                        return -ENOMEM;
+                }
+
+                buf = usb_buffer_alloc(dev->udev, RX_BUFFER_SIZE, GFP_KERNEL,
+                                       &urb->transfer_dma);
+                if (!buf) {
+                        dev_err(netdev->dev.parent,
+                                "No memory left for USB buffer\n");
+                        usb_free_urb(urb);
+                        return -ENOMEM;
+                }
+
+                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) {
+                        if (err == -ENODEV)
+                                netif_device_detach(dev->netdev);
+
+                        usb_unanchor_urb(urb);
+                        usb_buffer_free(dev->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) {
+                dev_warn(netdev->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(netdev->dev.parent, "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) {
+                if (err == -ENODEV)
+                        netif_device_detach(dev->netdev);
+
+                dev_warn(netdev->dev.parent, "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:
+        if (err == -ENODEV)
+                netif_device_detach(dev->netdev);
+
+        dev_warn(netdev->dev.parent, "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);
+
+                dev_warn(netdev->dev.parent, "couldn't start device: %d\n",
+                         err);
+
+                close_candev(netdev);
+
+                return err;
+        }
+
+        dev->open_time = jiffies;
+
+        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);
+
+        /* create a URB, and a buffer for it, and copy the data to the URB */
+        urb = usb_alloc_urb(0, GFP_ATOMIC);
+        if (!urb) {
+                dev_err(netdev->dev.parent, "No memory left for URBs\n");
+                goto nomem;
+        }
+
+        buf = usb_buffer_alloc(dev->udev, size, GFP_ATOMIC, &urb->transfer_dma);
+        if (!buf) {
+                dev_err(netdev->dev.parent, "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 = 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_unanchor_urb(urb);
+                usb_buffer_free(dev->udev, size, buf, urb->transfer_dma);
+
+                dev_warn(netdev->dev.parent, "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_buffer_free(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 {
+                        dev_warn(netdev->dev.parent, "failed tx_urb %d\n", err);
+
+                        stats->tx_dropped++;
+                }
+        } else {
+                netdev->trans_start = jiffies;
+
+                /* Slow down tx path */
+                if (atomic_read(&dev->active_tx_urbs) >= MAX_TX_URBS ||
+                    dev->free_slots < 5) {
+                        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:
+        if (skb)
+                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))
+                dev_warn(netdev->dev.parent, "couldn't stop device");
+
+        close_candev(netdev);
+
+        dev->open_time = 0;
+
+        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,
+};
+
+static 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);
+
+        if (!dev->open_time)
+                return -EINVAL;
+
+        switch (mode) {
+        case CAN_MODE_START:
+                if (ems_usb_write_mode(dev, SJA1000_MOD_NORMAL))
+                        dev_warn(netdev->dev.parent, "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;
+
+        dev_info(netdev->dev.parent, "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));
+        if (!netdev) {
+                dev_err(netdev->dev.parent, "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;
+
+        netdev->flags |= IFF_ECHO; /* we support local echo */
+
+        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) {
+                dev_err(netdev->dev.parent, "Couldn't alloc intr URB\n");
+                goto cleanup_candev;
+        }
+
+        dev->intr_in_buffer = kzalloc(INTR_IN_BUFFER_SIZE, GFP_KERNEL);
+        if (!dev->intr_in_buffer) {
+                dev_err(netdev->dev.parent, "Couldn't alloc Intr buffer\n");
+                goto cleanup_intr_urb;
+        }
+
+        dev->tx_msg_buffer = kzalloc(CPC_HEADER_SIZE +
+                                     sizeof(struct ems_cpc_msg), GFP_KERNEL);
+        if (!dev->tx_msg_buffer) {
+                dev_err(netdev->dev.parent, "Couldn't alloc Tx buffer\n");
+                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) {
+                dev_err(netdev->dev.parent,
+                        "couldn't initialize controller: %d\n", err);
+                goto cleanup_tx_msg_buffer;
+        }
+
+        err = register_candev(netdev);
+        if (err) {
+                dev_err(netdev->dev.parent,
+                        "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);
+        }
+}
+
+/* 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,
+};
+
+static int __init ems_usb_init(void)
+{
+        int err;
+
+        printk(KERN_INFO "CPC-USB kernel driver loaded\n");
+
+        /* register this driver with the USB subsystem */
+        err = usb_register(&ems_usb_driver);
+
+        if (err) {
+                err("usb_register failed. Error number %d\n", err);
+                return err;
+        }
+
+        return 0;
+}
+
+static void __exit ems_usb_exit(void)
+{
+        /* deregister this driver with the USB subsystem */
+        usb_deregister(&ems_usb_driver);
+}
+
+module_init(ems_usb_init);
+module_exit(ems_usb_exit);