/* CAN driver for Geschwister Schneider USB/CAN devices.
 *
 * Copyright (C) 2013 Geschwister Schneider Technologie-,
 * Entwicklungs- und Vertriebs UG (Haftungsbeschränkt).
 *
 * Many thanks to all socketcan devs!
 *
 * 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.
 */

#include <linux/init.h>
#include <linux/signal.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>

/* Device specific constants */
#define USB_GSUSB_1_VENDOR_ID      0x1d50
#define USB_GSUSB_1_PRODUCT_ID     0x606f

#define GSUSB_ENDPOINT_IN          1
#define GSUSB_ENDPOINT_OUT         2

/* Device specific constants */
enum gs_usb_breq {
        GS_USB_BREQ_HOST_FORMAT = 0,
        GS_USB_BREQ_BITTIMING,
        GS_USB_BREQ_MODE,
        GS_USB_BREQ_BERR,
        GS_USB_BREQ_BT_CONST,
        GS_USB_BREQ_DEVICE_CONFIG
};

enum gs_can_mode {
        /* reset a channel. turns it off */
        GS_CAN_MODE_RESET = 0,
        /* starts a channel */
        GS_CAN_MODE_START
};

enum gs_can_state {
        GS_CAN_STATE_ERROR_ACTIVE = 0,
        GS_CAN_STATE_ERROR_WARNING,
        GS_CAN_STATE_ERROR_PASSIVE,
        GS_CAN_STATE_BUS_OFF,
        GS_CAN_STATE_STOPPED,
        GS_CAN_STATE_SLEEPING
};

/* data types passed between host and device */
struct gs_host_config {
        u32 byte_order;
} __packed;
/* All data exchanged between host and device is exchanged in host byte order,
 * thanks to the struct gs_host_config byte_order member, which is sent first
 * to indicate the desired byte order.
 */

struct gs_device_config {
        u8 reserved1;
        u8 reserved2;
        u8 reserved3;
        u8 icount;
        u32 sw_version;
        u32 hw_version;
} __packed;

#define GS_CAN_MODE_NORMAL               0
#define GS_CAN_MODE_LISTEN_ONLY          (1<<0)
#define GS_CAN_MODE_LOOP_BACK            (1<<1)
#define GS_CAN_MODE_TRIPLE_SAMPLE        (1<<2)
#define GS_CAN_MODE_ONE_SHOT             (1<<3)

struct gs_device_mode {
        u32 mode;
        u32 flags;
} __packed;

struct gs_device_state {
        u32 state;
        u32 rxerr;
        u32 txerr;
} __packed;

struct gs_device_bittiming {
        u32 prop_seg;
        u32 phase_seg1;
        u32 phase_seg2;
        u32 sjw;
        u32 brp;
} __packed;

#define GS_CAN_FEATURE_LISTEN_ONLY      (1<<0)
#define GS_CAN_FEATURE_LOOP_BACK        (1<<1)
#define GS_CAN_FEATURE_TRIPLE_SAMPLE    (1<<2)
#define GS_CAN_FEATURE_ONE_SHOT         (1<<3)

struct gs_device_bt_const {
        u32 feature;
        u32 fclk_can;
        u32 tseg1_min;
        u32 tseg1_max;
        u32 tseg2_min;
        u32 tseg2_max;
        u32 sjw_max;
        u32 brp_min;
        u32 brp_max;
        u32 brp_inc;
} __packed;

#define GS_CAN_FLAG_OVERFLOW 1

struct gs_host_frame {
        u32 echo_id;
        u32 can_id;

        u8 can_dlc;
        u8 channel;
        u8 flags;
        u8 reserved;

        u8 data[8];
} __packed;
/* The GS USB devices make use of the same flags and masks as in
 * linux/can.h and linux/can/error.h, and no additional mapping is necessary.
 */

/* Only send a max of GS_MAX_TX_URBS frames per channel at a time. */
#define GS_MAX_TX_URBS 10
/* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
#define GS_MAX_RX_URBS 30
/* Maximum number of interfaces the driver supports per device.
 * Current hardware only supports 2 interfaces. The future may vary.
 */
#define GS_MAX_INTF 2

struct gs_tx_context {
        struct gs_can *dev;
        unsigned int echo_id;
};

struct gs_can {
        struct can_priv can; /* must be the first member */

        struct gs_usb *parent;

        struct net_device *netdev;
        struct usb_device *udev;
        struct usb_interface *iface;

        struct can_bittiming_const bt_const;
        unsigned int channel;   /* channel number */

        /* This lock prevents a race condition between xmit and recieve. */
        spinlock_t tx_ctx_lock;
        struct gs_tx_context tx_context[GS_MAX_TX_URBS];

        struct usb_anchor tx_submitted;
        atomic_t active_tx_urbs;
};

/* usb interface struct */
struct gs_usb {
        struct gs_can *canch[GS_MAX_INTF];
        struct usb_anchor rx_submitted;
        atomic_t active_channels;
        struct usb_device *udev;
};

/* 'allocate' a tx context.
 * returns a valid tx context or NULL if there is no space.
 */
static struct gs_tx_context *gs_alloc_tx_context(struct gs_can *dev)
{
        int i = 0;
        unsigned long flags;

        spin_lock_irqsave(&dev->tx_ctx_lock, flags);

        for (; i < GS_MAX_TX_URBS; i++) {
                if (dev->tx_context[i].echo_id == GS_MAX_TX_URBS) {
                        dev->tx_context[i].echo_id = i;
                        spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
                        return &dev->tx_context[i];
                }
        }

        spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
        return NULL;
}

/* releases a tx context
 */
static void gs_free_tx_context(struct gs_tx_context *txc)
{
        txc->echo_id = GS_MAX_TX_URBS;
}

/* Get a tx context by id.
 */
static struct gs_tx_context *gs_get_tx_context(struct gs_can *dev, unsigned int id)
{
        unsigned long flags;

        if (id < GS_MAX_TX_URBS) {
                spin_lock_irqsave(&dev->tx_ctx_lock, flags);
                if (dev->tx_context[id].echo_id == id) {
                        spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
                        return &dev->tx_context[id];
                }
                spin_unlock_irqrestore(&dev->tx_ctx_lock, flags);
        }
        return NULL;
}

static int gs_cmd_reset(struct gs_usb *gsusb, struct gs_can *gsdev)
{
        struct gs_device_mode *dm;
        struct usb_interface *intf = gsdev->iface;
        int rc;

        dm = kzalloc(sizeof(*dm), GFP_KERNEL);
        if (!dm)
                return -ENOMEM;

        dm->mode = GS_CAN_MODE_RESET;

        rc = usb_control_msg(interface_to_usbdev(intf),
                             usb_sndctrlpipe(interface_to_usbdev(intf), 0),
                             GS_USB_BREQ_MODE,
                             USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             gsdev->channel,
                             0,
                             dm,
                             sizeof(*dm),
                             1000);

        return rc;
}

static void gs_update_state(struct gs_can *dev, struct can_frame *cf)
{
        struct can_device_stats *can_stats = &dev->can.can_stats;

        if (cf->can_id & CAN_ERR_RESTARTED) {
                dev->can.state = CAN_STATE_ERROR_ACTIVE;
                can_stats->restarts++;
        } else if (cf->can_id & CAN_ERR_BUSOFF) {
                dev->can.state = CAN_STATE_BUS_OFF;
                can_stats->bus_off++;
        } else if (cf->can_id & CAN_ERR_CRTL) {
                if ((cf->data[1] & CAN_ERR_CRTL_TX_WARNING) ||
                    (cf->data[1] & CAN_ERR_CRTL_RX_WARNING)) {
                        dev->can.state = CAN_STATE_ERROR_WARNING;
                        can_stats->error_warning++;
                } else if ((cf->data[1] & CAN_ERR_CRTL_TX_PASSIVE) ||
                           (cf->data[1] & CAN_ERR_CRTL_RX_PASSIVE)) {
                        dev->can.state = CAN_STATE_ERROR_PASSIVE;
                        can_stats->error_passive++;
                } else {
                        dev->can.state = CAN_STATE_ERROR_ACTIVE;
                }
        }
}

static void gs_usb_recieve_bulk_callback(struct urb *urb)
{
        struct gs_usb *usbcan = urb->context;
        struct gs_can *dev;
        struct net_device *netdev;
        int rc;
        struct net_device_stats *stats;
        struct gs_host_frame *hf = urb->transfer_buffer;
        struct gs_tx_context *txc;
        struct can_frame *cf;
        struct sk_buff *skb;

        BUG_ON(!usbcan);

        switch (urb->status) {
        case 0: /* success */
                break;
        case -ENOENT:
        case -ESHUTDOWN:
                return;
        default:
                /* do not resubmit aborted urbs. eg: when device goes down */
                return;
        }

        /* device reports out of range channel id */
        if (hf->channel >= GS_MAX_INTF)
                goto resubmit_urb;

        dev = usbcan->canch[hf->channel];

        netdev = dev->netdev;
        stats = &netdev->stats;

        if (!netif_device_present(netdev))
                return;

        if (hf->echo_id == -1) { /* normal rx */
                skb = alloc_can_skb(dev->netdev, &cf);
                if (!skb)
                        return;

                cf->can_id = hf->can_id;

                cf->can_dlc = get_can_dlc(hf->can_dlc);
                memcpy(cf->data, hf->data, 8);

                /* ERROR frames tell us information about the controller */
                if (hf->can_id & CAN_ERR_FLAG)
                        gs_update_state(dev, cf);

                netdev->stats.rx_packets++;
                netdev->stats.rx_bytes += hf->can_dlc;

                netif_rx(skb);
        } else { /* echo_id == hf->echo_id */
                if (hf->echo_id >= GS_MAX_TX_URBS) {
                        netdev_err(netdev,
                                   "Unexpected out of range echo id %d\n",
                                   hf->echo_id);
                        goto resubmit_urb;
                }

                netdev->stats.tx_packets++;
                netdev->stats.tx_bytes += hf->can_dlc;

                txc = gs_get_tx_context(dev, hf->echo_id);

                /* bad devices send bad echo_ids. */
                if (!txc) {
                        netdev_err(netdev,
                                   "Unexpected unused echo id %d\n",
                                   hf->echo_id);
                        goto resubmit_urb;
                }

                can_get_echo_skb(netdev, hf->echo_id);

                gs_free_tx_context(txc);

                netif_wake_queue(netdev);
        }

        if (hf->flags & GS_CAN_FLAG_OVERFLOW) {
                skb = alloc_can_err_skb(netdev, &cf);
                if (!skb)
                        goto resubmit_urb;

                cf->can_id |= CAN_ERR_CRTL;
                cf->can_dlc = CAN_ERR_DLC;
                cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                stats->rx_over_errors++;
                stats->rx_errors++;
                netif_rx(skb);
        }

 resubmit_urb:
        usb_fill_bulk_urb(urb,
                          usbcan->udev,
                          usb_rcvbulkpipe(usbcan->udev, GSUSB_ENDPOINT_IN),
                          hf,
                          sizeof(struct gs_host_frame),
                          gs_usb_recieve_bulk_callback,
                          usbcan
                          );

        rc = usb_submit_urb(urb, GFP_ATOMIC);

        /* USB failure take down all interfaces */
        if (rc == -ENODEV) {
                for (rc = 0; rc < GS_MAX_INTF; rc++) {
                        if (usbcan->canch[rc])
                                netif_device_detach(usbcan->canch[rc]->netdev);
                }
        }
}

static int gs_usb_set_bittiming(struct net_device *netdev)
{
        struct gs_can *dev = netdev_priv(netdev);
        struct can_bittiming *bt = &dev->can.bittiming;
        struct usb_interface *intf = dev->iface;
        int rc;
        struct gs_device_bittiming *dbt;

        dbt = kmalloc(sizeof(*dbt), GFP_KERNEL);
        if (!dbt)
                return -ENOMEM;

        dbt->prop_seg = bt->prop_seg;
        dbt->phase_seg1 = bt->phase_seg1;
        dbt->phase_seg2 = bt->phase_seg2;
        dbt->sjw = bt->sjw;
        dbt->brp = bt->brp;

        /* request bit timings */
        rc = usb_control_msg(interface_to_usbdev(intf),
                             usb_sndctrlpipe(interface_to_usbdev(intf), 0),
                             GS_USB_BREQ_BITTIMING,
                             USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             dev->channel,
                             0,
                             dbt,
                             sizeof(*dbt),
                             1000);

        kfree(dbt);

        if (rc < 0)
                dev_err(netdev->dev.parent, "Couldn't set bittimings (err=%d)",
                        rc);

        return rc;
}

static void gs_usb_xmit_callback(struct urb *urb)
{
        struct gs_tx_context *txc = urb->context;
        struct gs_can *dev = txc->dev;
        struct net_device *netdev = dev->netdev;

        if (urb->status)
                netdev_info(netdev, "usb xmit fail %d\n", txc->echo_id);

        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 (netif_queue_stopped(netdev))
                netif_wake_queue(netdev);
}

static netdev_tx_t gs_can_start_xmit(struct sk_buff *skb, struct net_device *netdev)
{
        struct gs_can *dev = netdev_priv(netdev);
        struct net_device_stats *stats = &dev->netdev->stats;
        struct urb *urb;
        struct gs_host_frame *hf;
        struct can_frame *cf;
        int rc;
        unsigned int idx;
        struct gs_tx_context *txc;

        if (can_dropped_invalid_skb(netdev, skb))
                return NETDEV_TX_OK;

        /* find an empty context to keep track of transmission */
        txc = gs_alloc_tx_context(dev);
        if (!txc)
                return NETDEV_TX_BUSY;

        /* create a URB, and a buffer for it */
        urb = usb_alloc_urb(0, GFP_ATOMIC);
        if (!urb) {
                netdev_err(netdev, "No memory left for URB\n");
                goto nomem_urb;
        }

        hf = usb_alloc_coherent(dev->udev, sizeof(*hf), GFP_ATOMIC,
                                &urb->transfer_dma);
        if (!hf) {
                netdev_err(netdev, "No memory left for USB buffer\n");
                goto nomem_hf;
        }

        idx = txc->echo_id;

        if (idx >= GS_MAX_TX_URBS) {
                netdev_err(netdev, "Invalid tx context %d\n", idx);
                goto badidx;
        }

        hf->echo_id = idx;
        hf->channel = dev->channel;

        cf = (struct can_frame *)skb->data;

        hf->can_id = cf->can_id;
        hf->can_dlc = cf->can_dlc;
        memcpy(hf->data, cf->data, cf->can_dlc);

        usb_fill_bulk_urb(urb, dev->udev,
                          usb_sndbulkpipe(dev->udev, GSUSB_ENDPOINT_OUT),
                          hf,
                          sizeof(*hf),
                          gs_usb_xmit_callback,
                          txc);

        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
        usb_anchor_urb(urb, &dev->tx_submitted);

        can_put_echo_skb(skb, netdev, idx);

        atomic_inc(&dev->active_tx_urbs);

        rc = usb_submit_urb(urb, GFP_ATOMIC);
        if (unlikely(rc)) {                     /* usb send failed */
                atomic_dec(&dev->active_tx_urbs);

                can_free_echo_skb(netdev, idx);
                gs_free_tx_context(txc);

                usb_unanchor_urb(urb);
                usb_free_coherent(dev->udev,
                                  sizeof(*hf),
                                  hf,
                                  urb->transfer_dma);


                if (rc == -ENODEV) {
                        netif_device_detach(netdev);
                } else {
                        netdev_err(netdev, "usb_submit failed (err=%d)\n", rc);
                        stats->tx_dropped++;
                }
        } else {
                /* Slow down tx path */
                if (atomic_read(&dev->active_tx_urbs) >= GS_MAX_TX_URBS)
                        netif_stop_queue(netdev);
        }

        /* let usb core take care of this urb */
        usb_free_urb(urb);

        return NETDEV_TX_OK;

 badidx:
        usb_free_coherent(dev->udev,
                          sizeof(*hf),
                          hf,
                          urb->transfer_dma);
 nomem_hf:
        usb_free_urb(urb);

 nomem_urb:
        gs_free_tx_context(txc);
        dev_kfree_skb(skb);
        stats->tx_dropped++;
        return NETDEV_TX_OK;
}

static int gs_can_open(struct net_device *netdev)
{
        struct gs_can *dev = netdev_priv(netdev);
        struct gs_usb *parent = dev->parent;
        int rc, i;
        struct gs_device_mode *dm;
        u32 ctrlmode;

        rc = open_candev(netdev);
        if (rc)
                return rc;

        if (atomic_add_return(1, &parent->active_channels) == 1) {
                for (i = 0; i < GS_MAX_RX_URBS; i++) {
                        struct urb *urb;
                        u8 *buf;

                        /* alloc rx urb */
                        urb = usb_alloc_urb(0, GFP_KERNEL);
                        if (!urb) {
                                netdev_err(netdev,
                                           "No memory left for URB\n");
                                return -ENOMEM;
                        }

                        /* alloc rx buffer */
                        buf = usb_alloc_coherent(dev->udev,
                                                 sizeof(struct gs_host_frame),
                                                 GFP_KERNEL,
                                                 &urb->transfer_dma);
                        if (!buf) {
                                netdev_err(netdev,
                                           "No memory left for USB buffer\n");
                                usb_free_urb(urb);
                                return -ENOMEM;
                        }

                        /* fill, anchor, and submit rx urb */
                        usb_fill_bulk_urb(urb,
                                          dev->udev,
                                          usb_rcvbulkpipe(dev->udev,
                                                          GSUSB_ENDPOINT_IN),
                                          buf,
                                          sizeof(struct gs_host_frame),
                                          gs_usb_recieve_bulk_callback,
                                          parent);
                        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

                        usb_anchor_urb(urb, &parent->rx_submitted);

                        rc = usb_submit_urb(urb, GFP_KERNEL);
                        if (rc) {
                                if (rc == -ENODEV)
                                        netif_device_detach(dev->netdev);

                                netdev_err(netdev,
                                           "usb_submit failed (err=%d)\n",
                                           rc);

                                usb_unanchor_urb(urb);
                                break;
                        }

                        /* Drop reference,
                         * USB core will take care of freeing it
                         */
                        usb_free_urb(urb);
                }
        }

        dm = kmalloc(sizeof(*dm), GFP_KERNEL);
        if (!dm)
                return -ENOMEM;

        /* flags */
        ctrlmode = dev->can.ctrlmode;
        dm->flags = 0;

        if (ctrlmode & CAN_CTRLMODE_LOOPBACK)
                dm->flags |= GS_CAN_MODE_LOOP_BACK;
        else if (ctrlmode & CAN_CTRLMODE_LISTENONLY)
                dm->flags |= GS_CAN_MODE_LISTEN_ONLY;

        /* Controller is not allowed to retry TX
         * this mode is unavailable on atmels uc3c hardware
         */
        if (ctrlmode & CAN_CTRLMODE_ONE_SHOT)
                dm->flags |= GS_CAN_MODE_ONE_SHOT;

        if (ctrlmode & CAN_CTRLMODE_3_SAMPLES)
                dm->flags |= GS_CAN_MODE_TRIPLE_SAMPLE;

        /* finally start device */
        dm->mode = GS_CAN_MODE_START;
        rc = usb_control_msg(interface_to_usbdev(dev->iface),
                             usb_sndctrlpipe(interface_to_usbdev(dev->iface), 0),
                             GS_USB_BREQ_MODE,
                             USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             dev->channel,
                             0,
                             dm,
                             sizeof(*dm),
                             1000);

        if (rc < 0) {
                netdev_err(netdev, "Couldn't start device (err=%d)\n", rc);
                kfree(dm);
                return rc;
        }

        kfree(dm);

        dev->can.state = CAN_STATE_ERROR_ACTIVE;

        if (!(dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
                netif_start_queue(netdev);

        return 0;
}

static int gs_can_close(struct net_device *netdev)
{
        int rc;
        struct gs_can *dev = netdev_priv(netdev);
        struct gs_usb *parent = dev->parent;

        netif_stop_queue(netdev);

        /* Stop polling */
        if (atomic_dec_and_test(&parent->active_channels))
                usb_kill_anchored_urbs(&parent->rx_submitted);

        /* Stop sending URBs */
        usb_kill_anchored_urbs(&dev->tx_submitted);
        atomic_set(&dev->active_tx_urbs, 0);

        /* reset the device */
        rc = gs_cmd_reset(parent, dev);
        if (rc < 0)
                netdev_warn(netdev, "Couldn't shutdown device (err=%d)", rc);

        /* reset tx contexts */
        for (rc = 0; rc < GS_MAX_TX_URBS; rc++) {
                dev->tx_context[rc].dev = dev;
                dev->tx_context[rc].echo_id = GS_MAX_TX_URBS;
        }

        /* close the netdev */
        close_candev(netdev);

        return 0;
}

static const struct net_device_ops gs_usb_netdev_ops = {
        .ndo_open = gs_can_open,
        .ndo_stop = gs_can_close,
        .ndo_start_xmit = gs_can_start_xmit,
};

static struct gs_can *gs_make_candev(unsigned int channel, struct usb_interface *intf)
{
        struct gs_can *dev;
        struct net_device *netdev;
        int rc;
        struct gs_device_bt_const *bt_const;

        bt_const = kmalloc(sizeof(*bt_const), GFP_KERNEL);
        if (!bt_const)
                return ERR_PTR(-ENOMEM);

        /* fetch bit timing constants */
        rc = usb_control_msg(interface_to_usbdev(intf),
                             usb_rcvctrlpipe(interface_to_usbdev(intf), 0),
                             GS_USB_BREQ_BT_CONST,
                             USB_DIR_IN|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             channel,
                             0,
                             bt_const,
                             sizeof(*bt_const),
                             1000);

        if (rc < 0) {
                dev_err(&intf->dev,
                        "Couldn't get bit timing const for channel (err=%d)\n",
                        rc);
                kfree(bt_const);
                return ERR_PTR(rc);
        }

        /* create netdev */
        netdev = alloc_candev(sizeof(struct gs_can), GS_MAX_TX_URBS);
        if (!netdev) {
                dev_err(&intf->dev, "Couldn't allocate candev\n");
                kfree(bt_const);
                return ERR_PTR(-ENOMEM);
        }

        dev = netdev_priv(netdev);

        netdev->netdev_ops = &gs_usb_netdev_ops;

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

        /* dev settup */
        strcpy(dev->bt_const.name, "gs_usb");
        dev->bt_const.tseg1_min = bt_const->tseg1_min;
        dev->bt_const.tseg1_max = bt_const->tseg1_max;
        dev->bt_const.tseg2_min = bt_const->tseg2_min;
        dev->bt_const.tseg2_max = bt_const->tseg2_max;
        dev->bt_const.sjw_max = bt_const->sjw_max;
        dev->bt_const.brp_min = bt_const->brp_min;
        dev->bt_const.brp_max = bt_const->brp_max;
        dev->bt_const.brp_inc = bt_const->brp_inc;

        dev->udev = interface_to_usbdev(intf);
        dev->iface = intf;
        dev->netdev = netdev;
        dev->channel = channel;

        init_usb_anchor(&dev->tx_submitted);
        atomic_set(&dev->active_tx_urbs, 0);
        spin_lock_init(&dev->tx_ctx_lock);
        for (rc = 0; rc < GS_MAX_TX_URBS; rc++) {
                dev->tx_context[rc].dev = dev;
                dev->tx_context[rc].echo_id = GS_MAX_TX_URBS;
        }

        /* can settup */
        dev->can.state = CAN_STATE_STOPPED;
        dev->can.clock.freq = bt_const->fclk_can;
        dev->can.bittiming_const = &dev->bt_const;
        dev->can.do_set_bittiming = gs_usb_set_bittiming;

        dev->can.ctrlmode_supported = 0;

        if (bt_const->feature & GS_CAN_FEATURE_LISTEN_ONLY)
                dev->can.ctrlmode_supported |= CAN_CTRLMODE_LISTENONLY;

        if (bt_const->feature & GS_CAN_FEATURE_LOOP_BACK)
                dev->can.ctrlmode_supported |= CAN_CTRLMODE_LOOPBACK;

        if (bt_const->feature & GS_CAN_FEATURE_TRIPLE_SAMPLE)
                dev->can.ctrlmode_supported |= CAN_CTRLMODE_3_SAMPLES;

        if (bt_const->feature & GS_CAN_FEATURE_ONE_SHOT)
                dev->can.ctrlmode_supported |= CAN_CTRLMODE_ONE_SHOT;

        kfree(bt_const);

        SET_NETDEV_DEV(netdev, &intf->dev);

        rc = register_candev(dev->netdev);
        if (rc) {
                free_candev(dev->netdev);
                dev_err(&intf->dev, "Couldn't register candev (err=%d)\n", rc);
                return ERR_PTR(rc);
        }

        return dev;
}

static void gs_destroy_candev(struct gs_can *dev)
{
        unregister_candev(dev->netdev);
        free_candev(dev->netdev);
        usb_kill_anchored_urbs(&dev->tx_submitted);
        kfree(dev);
}

static int gs_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
        struct gs_usb *dev;
        int rc = -ENOMEM;
        unsigned int icount, i;
        struct gs_host_config *hconf;
        struct gs_device_config *dconf;

        hconf = kmalloc(sizeof(*hconf), GFP_KERNEL);
        if (!hconf)
                return -ENOMEM;

        hconf->byte_order = 0x0000beef;

        /* send host config */
        rc = usb_control_msg(interface_to_usbdev(intf),
                             usb_sndctrlpipe(interface_to_usbdev(intf), 0),
                             GS_USB_BREQ_HOST_FORMAT,
                             USB_DIR_OUT|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             1,
                             intf->altsetting[0].desc.bInterfaceNumber,
                             hconf,
                             sizeof(*hconf),
                             1000);

        kfree(hconf);

        if (rc < 0) {
                dev_err(&intf->dev, "Couldn't send data format (err=%d)\n",
                        rc);
                return rc;
        }

        dconf = kmalloc(sizeof(*dconf), GFP_KERNEL);
        if (!dconf)
                return -ENOMEM;

        /* read device config */
        rc = usb_control_msg(interface_to_usbdev(intf),
                             usb_rcvctrlpipe(interface_to_usbdev(intf), 0),
                             GS_USB_BREQ_DEVICE_CONFIG,
                             USB_DIR_IN|USB_TYPE_VENDOR|USB_RECIP_INTERFACE,
                             1,
                             intf->altsetting[0].desc.bInterfaceNumber,
                             dconf,
                             sizeof(*dconf),
                             1000);
        if (rc < 0) {
                dev_err(&intf->dev, "Couldn't get device config: (err=%d)\n",
                        rc);

                kfree(dconf);

                return rc;
        }

        icount = dconf->icount+1;

        kfree(dconf);

        dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);

        if (icount > GS_MAX_INTF) {
                dev_err(&intf->dev,
                        "Driver cannot handle more that %d CAN interfaces\n",
                        GS_MAX_INTF);
                return -EINVAL;
        }

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        init_usb_anchor(&dev->rx_submitted);

        atomic_set(&dev->active_channels, 0);

        usb_set_intfdata(intf, dev);
        dev->udev = interface_to_usbdev(intf);

        for (i = 0; i < icount; i++) {
                dev->canch[i] = gs_make_candev(i, intf);
                if (IS_ERR_OR_NULL(dev->canch[i])) {
                        /* on failure destroy previously created candevs */
                        icount = i;
                        for (i = 0; i < icount; i++) {
                                gs_destroy_candev(dev->canch[i]);
                                dev->canch[i] = NULL;
                        }
                        kfree(dev);
                        return rc;
                }
                dev->canch[i]->parent = dev;
        }

        return 0;
}

static void gs_usb_disconnect(struct usb_interface *intf)
{
        unsigned i;
        struct gs_usb *dev = usb_get_intfdata(intf);
        usb_set_intfdata(intf, NULL);

        if (!dev) {
                dev_err(&intf->dev, "Disconnect (nodata)\n");
                return;
        }

        for (i = 0; i < GS_MAX_INTF; i++) {
                struct gs_can *can = dev->canch[i];

                if (!can)
                        continue;

                gs_destroy_candev(can);
        }

        usb_kill_anchored_urbs(&dev->rx_submitted);
}

static const struct usb_device_id gs_usb_table[] = {
        {USB_DEVICE(USB_GSUSB_1_VENDOR_ID, USB_GSUSB_1_PRODUCT_ID)},
        {} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, gs_usb_table);

static struct usb_driver gs_usb_driver = {
        .name       = "gs_usb",
        .probe      = gs_usb_probe,
        .disconnect = gs_usb_disconnect,
        .id_table   = gs_usb_table,
};

module_usb_driver(gs_usb_driver);

MODULE_AUTHOR("Maximilian Schneider <mws@schneidersoft.net>");
MODULE_DESCRIPTION(
"Socket CAN device driver for Geschwister Schneider Technologie-, "
"Entwicklungs- und Vertriebs UG. USB2.0 to CAN interfaces.");
MODULE_LICENSE("GPL v2");