esd_usb2.c

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/*
 * CAN driver for esd CAN-USB/2
 *
 * Copyright (C) 2010 Matthias Fuchs <[email protected]>, 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/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("Matthias Fuchs <[email protected]>");
MODULE_DESCRIPTION("CAN driver for esd CAN-USB/2 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 ESD_USB2_CAN_CLOCK  60000000
#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_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)},
    {}
};
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];

    int open_time;
    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:
            esd_usb2_rx_can_msg(dev->nets[msg->msg.rx.net], msg);
            break;

        case CMD_CAN_TX:
            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;

    /*
     * 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 failed;

    err = esd_usb2_setup_rx_urbs(dev);
    if (err)
        goto failed;

    priv->can.state = CAN_STATE_ERROR_ACTIVE;

    return 0;

failed:
    if (err == -ENODEV)
        netif_device_detach(netdev);

    netdev_err(netdev, "couldn't start device: %d\n", err);

    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;
    }

    priv->open_time = jiffies;

    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;

    /* 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);

    priv->open_time = 0;

    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,
};

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;
    u32 canbtr;

    canbtr = ESD_USB2_UBR;
    canbtr |= (bt->brp - 1) & (ESD_USB2_BRP_MAX - 1);
    canbtr |= ((bt->sjw - 1) & (ESD_USB2_SJW_MAX - 1))
        << ESD_USB2_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.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);

    return esd_usb2_send_msg(priv->usb2, &msg);
}

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)
{
    struct esd_usb2_net_priv *priv = netdev_priv(netdev);

    if (!priv->open_time)
        return -EINVAL;

    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.clock.freq = ESD_USB2_CAN_CLOCK;
    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;
    priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;

    netdev->flags |= IFF_ECHO; /* we support local echo */

    netdev->netdev_ops = &esd_usb2_netdev_ops;

    SET_NETDEV_DEV(netdev, &intf->dev);

    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);

    /* 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_dev;
    }

    err = esd_usb2_wait_msg(dev, &msg);
    if (err < 0) {
        dev_err(&intf->dev, "no version message answer\n");
        goto free_dev;
    }

    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);

    return 0;

free_dev:
    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);