// SPDX-License-Identifier: GPL-2.0

/* Driver for Theobroma Systems UCAN devices, Protocol Version 3
 *
 * Copyright (C) 2018 Theobroma Systems Design und Consulting GmbH
 *
 *
 * General Description:
 *
 * The USB Device uses three Endpoints:
 *
 *   CONTROL Endpoint: Is used the setup the device (start, stop,
 *   info, configure).
 *
 *   IN Endpoint: The device sends CAN Frame Messages and Device
 *   Information using the IN endpoint.
 *
 *   OUT Endpoint: The driver sends configuration requests, and CAN
 *   Frames on the out endpoint.
 *
 * Error Handling:
 *
 *   If error reporting is turned on the device encodes error into CAN
 *   error frames (see uapi/linux/can/error.h) and sends it using the
 *   IN Endpoint. The driver updates statistics and forward it.
 */

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/signal.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/usb.h>

#define UCAN_DRIVER_NAME "ucan"
#define UCAN_MAX_RX_URBS 8
/* the CAN controller needs a while to enable/disable the bus */
#define UCAN_USB_CTL_PIPE_TIMEOUT 1000
/* this driver currently supports protocol version 3 only */
#define UCAN_PROTOCOL_VERSION_MIN 3
#define UCAN_PROTOCOL_VERSION_MAX 3

/* UCAN Message Definitions
 * ------------------------
 *
 *  ucan_message_out_t and ucan_message_in_t define the messages
 *  transmitted on the OUT and IN endpoint.
 *
 *  Multibyte fields are transmitted with little endianness
 *
 *  INTR Endpoint: a single uint32_t storing the current space in the fifo
 *
 *  OUT Endpoint: single message of type ucan_message_out_t is
 *    transmitted on the out endpoint
 *
 *  IN Endpoint: multiple messages ucan_message_in_t concateted in
 *    the following way:
 *
 *      m[n].len <=> the length if message n(including the header in bytes)
 *      m[n] is is aligned to a 4 byte boundary, hence
 *        offset(m[0])   := 0;
 *        offset(m[n+1]) := offset(m[n]) + (m[n].len + 3) & 3
 *
 *      this implies that
 *        offset(m[n]) % 4 <=> 0
 */

/* Device Global Commands */
enum {
        UCAN_DEVICE_GET_FW_STRING = 0,
};

/* UCAN Commands */
enum {
        /* start the can transceiver - val defines the operation mode */
        UCAN_COMMAND_START = 0,
        /* cancel pending transmissions and stop the can transceiver */
        UCAN_COMMAND_STOP = 1,
        /* send can transceiver into low-power sleep mode */
        UCAN_COMMAND_SLEEP = 2,
        /* wake up can transceiver from low-power sleep mode */
        UCAN_COMMAND_WAKEUP = 3,
        /* reset the can transceiver */
        UCAN_COMMAND_RESET = 4,
        /* get piece of info from the can transceiver - subcmd defines what
         * piece
         */
        UCAN_COMMAND_GET = 5,
        /* clear or disable hardware filter - subcmd defines which of the two */
        UCAN_COMMAND_FILTER = 6,
        /* Setup bittiming */
        UCAN_COMMAND_SET_BITTIMING = 7,
        /* recover from bus-off state */
        UCAN_COMMAND_RESTART = 8,
};

/* UCAN_COMMAND_START and UCAN_COMMAND_GET_INFO operation modes (bitmap).
 * Undefined bits must be set to 0.
 */
enum {
        UCAN_MODE_LOOPBACK = BIT(0),
        UCAN_MODE_SILENT = BIT(1),
        UCAN_MODE_3_SAMPLES = BIT(2),
        UCAN_MODE_ONE_SHOT = BIT(3),
        UCAN_MODE_BERR_REPORT = BIT(4),
};

/* UCAN_COMMAND_GET subcommands */
enum {
        UCAN_COMMAND_GET_INFO = 0,
        UCAN_COMMAND_GET_PROTOCOL_VERSION = 1,
};

/* UCAN_COMMAND_FILTER subcommands */
enum {
        UCAN_FILTER_CLEAR = 0,
        UCAN_FILTER_DISABLE = 1,
        UCAN_FILTER_ENABLE = 2,
};

/* OUT endpoint message types */
enum {
        UCAN_OUT_TX = 2,     /* transmit a CAN frame */
};

/* IN endpoint message types */
enum {
        UCAN_IN_TX_COMPLETE = 1,  /* CAN frame transmission completed */
        UCAN_IN_RX = 2,           /* CAN frame received */
};

struct ucan_ctl_cmd_start {
        __le16 mode;         /* OR-ing any of UCAN_MODE_* */
} __packed;

struct ucan_ctl_cmd_set_bittiming {
        __le32 tq;           /* Time quanta (TQ) in nanoseconds */
        __le16 brp;          /* TQ Prescaler */
        __le16 sample_point; /* Samplepoint on tenth percent */
        u8 prop_seg;         /* Propagation segment in TQs */
        u8 phase_seg1;       /* Phase buffer segment 1 in TQs */
        u8 phase_seg2;       /* Phase buffer segment 2 in TQs */
        u8 sjw;              /* Synchronisation jump width in TQs */
} __packed;

struct ucan_ctl_cmd_device_info {
        __le32 freq;         /* Clock Frequency for tq generation */
        u8 tx_fifo;          /* Size of the transmission fifo */
        u8 sjw_max;          /* can_bittiming fields... */
        u8 tseg1_min;
        u8 tseg1_max;
        u8 tseg2_min;
        u8 tseg2_max;
        __le16 brp_inc;
        __le32 brp_min;
        __le32 brp_max;      /* ...can_bittiming fields */
        __le16 ctrlmodes;    /* supported control modes */
        __le16 hwfilter;     /* Number of HW filter banks */
        __le16 rxmboxes;     /* Number of receive Mailboxes */
} __packed;

struct ucan_ctl_cmd_get_protocol_version {
        __le32 version;
} __packed;

union ucan_ctl_payload {
        /* Setup Bittiming
         * bmRequest == UCAN_COMMAND_START
         */
        struct ucan_ctl_cmd_start cmd_start;
        /* Setup Bittiming
         * bmRequest == UCAN_COMMAND_SET_BITTIMING
         */
        struct ucan_ctl_cmd_set_bittiming cmd_set_bittiming;
        /* Get Device Information
         * bmRequest == UCAN_COMMAND_GET; wValue = UCAN_COMMAND_GET_INFO
         */
        struct ucan_ctl_cmd_device_info cmd_get_device_info;
        /* Get Protocol Version
         * bmRequest == UCAN_COMMAND_GET;
         * wValue = UCAN_COMMAND_GET_PROTOCOL_VERSION
         */
        struct ucan_ctl_cmd_get_protocol_version cmd_get_protocol_version;

        u8 raw[128];
} __packed;

enum {
        UCAN_TX_COMPLETE_SUCCESS = BIT(0),
};

/* Transmission Complete within ucan_message_in */
struct ucan_tx_complete_entry_t {
        u8 echo_index;
        u8 flags;
} __packed __aligned(0x2);

/* CAN Data message format within ucan_message_in/out */
struct ucan_can_msg {
        /* note DLC is computed by
         *    msg.len - sizeof (msg.len)
         *            - sizeof (msg.type)
         *            - sizeof (msg.can_msg.id)
         */
        __le32 id;

        union {
                u8 data[CAN_MAX_DLEN];  /* Data of CAN frames */
                u8 dlc;                 /* RTR dlc */
        };
} __packed;

/* OUT Endpoint, outbound messages */
struct ucan_message_out {
        __le16 len; /* Length of the content include header */
        u8 type;    /* UCAN_OUT_TX and friends */
        u8 subtype; /* command sub type */

        union {
                /* Transmit CAN frame
                 * (type == UCAN_TX) && ((msg.can_msg.id & CAN_RTR_FLAG) == 0)
                 * subtype stores the echo id
                 */
                struct ucan_can_msg can_msg;
        } msg;
} __packed __aligned(0x4);

/* IN Endpoint, inbound messages */
struct ucan_message_in {
        __le16 len; /* Length of the content include header */
        u8 type;    /* UCAN_IN_RX and friends */
        u8 subtype; /* command sub type */

        union {
                /* CAN Frame received
                 * (type == UCAN_IN_RX)
                 * && ((msg.can_msg.id & CAN_RTR_FLAG) == 0)
                 */
                struct ucan_can_msg can_msg;

                /* CAN transmission complete
                 * (type == UCAN_IN_TX_COMPLETE)
                 */
                struct ucan_tx_complete_entry_t can_tx_complete_msg[0];
        } __aligned(0x4) msg;
} __packed __aligned(0x4);

/* Macros to calculate message lengths */
#define UCAN_OUT_HDR_SIZE offsetof(struct ucan_message_out, msg)

#define UCAN_IN_HDR_SIZE offsetof(struct ucan_message_in, msg)
#define UCAN_IN_LEN(member) (UCAN_OUT_HDR_SIZE + sizeof(member))

struct ucan_priv;

/* Context Information for transmission URBs */
struct ucan_urb_context {
        struct ucan_priv *up;
        bool allocated;
};

/* Information reported by the USB device */
struct ucan_device_info {
        struct can_bittiming_const bittiming_const;
        u8 tx_fifo;
};

/* Driver private data */
struct ucan_priv {
        /* must be the first member */
        struct can_priv can;

        /* linux USB device structures */
        struct usb_device *udev;
        struct usb_interface *intf;
        struct net_device *netdev;

        /* lock for can->echo_skb (used around
         * can_put/get/free_echo_skb
         */
        spinlock_t echo_skb_lock;

        /* usb device information information */
        u8 intf_index;
        u8 in_ep_addr;
        u8 out_ep_addr;
        u16 in_ep_size;

        /* transmission and reception buffers */
        struct usb_anchor rx_urbs;
        struct usb_anchor tx_urbs;

        union ucan_ctl_payload *ctl_msg_buffer;
        struct ucan_device_info device_info;

        /* transmission control information and locks */
        spinlock_t context_lock;
        unsigned int available_tx_urbs;
        struct ucan_urb_context *context_array;
};

static u8 ucan_can_cc_dlc2len(struct ucan_can_msg *msg, u16 len)
{
        if (le32_to_cpu(msg->id) & CAN_RTR_FLAG)
                return can_cc_dlc2len(msg->dlc);
        else
                return can_cc_dlc2len(len - (UCAN_IN_HDR_SIZE + sizeof(msg->id)));
}

static void ucan_release_context_array(struct ucan_priv *up)
{
        if (!up->context_array)
                return;

        /* lock is not needed because, driver is currently opening or closing */
        up->available_tx_urbs = 0;

        kfree(up->context_array);
        up->context_array = NULL;
}

static int ucan_alloc_context_array(struct ucan_priv *up)
{
        int i;

        /* release contexts if any */
        ucan_release_context_array(up);

        up->context_array = kcalloc(up->device_info.tx_fifo,
                                    sizeof(*up->context_array),
                                    GFP_KERNEL);
        if (!up->context_array) {
                netdev_err(up->netdev,
                           "Not enough memory to allocate tx contexts\n");
                return -ENOMEM;
        }

        for (i = 0; i < up->device_info.tx_fifo; i++) {
                up->context_array[i].allocated = false;
                up->context_array[i].up = up;
        }

        /* lock is not needed because, driver is currently opening */
        up->available_tx_urbs = up->device_info.tx_fifo;

        return 0;
}

static struct ucan_urb_context *ucan_alloc_context(struct ucan_priv *up)
{
        int i;
        unsigned long flags;
        struct ucan_urb_context *ret = NULL;

        if (WARN_ON_ONCE(!up->context_array))
                return NULL;

        /* execute context operation atomically */
        spin_lock_irqsave(&up->context_lock, flags);

        for (i = 0; i < up->device_info.tx_fifo; i++) {
                if (!up->context_array[i].allocated) {
                        /* update context */
                        ret = &up->context_array[i];
                        up->context_array[i].allocated = true;

                        /* stop queue if necessary */
                        up->available_tx_urbs--;
                        if (!up->available_tx_urbs)
                                netif_stop_queue(up->netdev);

                        break;
                }
        }

        spin_unlock_irqrestore(&up->context_lock, flags);
        return ret;
}

static bool ucan_release_context(struct ucan_priv *up,
                                 struct ucan_urb_context *ctx)
{
        unsigned long flags;
        bool ret = false;

        if (WARN_ON_ONCE(!up->context_array))
                return false;

        /* execute context operation atomically */
        spin_lock_irqsave(&up->context_lock, flags);

        /* context was not allocated, maybe the device sent garbage */
        if (ctx->allocated) {
                ctx->allocated = false;

                /* check if the queue needs to be woken */
                if (!up->available_tx_urbs)
                        netif_wake_queue(up->netdev);
                up->available_tx_urbs++;

                ret = true;
        }

        spin_unlock_irqrestore(&up->context_lock, flags);
        return ret;
}

static int ucan_ctrl_command_out(struct ucan_priv *up,
                                 u8 cmd, u16 subcmd, u16 datalen)
{
        return usb_control_msg(up->udev,
                               usb_sndctrlpipe(up->udev, 0),
                               cmd,
                               USB_DIR_OUT | USB_TYPE_VENDOR |
                                                USB_RECIP_INTERFACE,
                               subcmd,
                               up->intf_index,
                               up->ctl_msg_buffer,
                               datalen,
                               UCAN_USB_CTL_PIPE_TIMEOUT);
}

static int ucan_device_request_in(struct ucan_priv *up,
                                  u8 cmd, u16 subcmd, u16 datalen)
{
        return usb_control_msg(up->udev,
                               usb_rcvctrlpipe(up->udev, 0),
                               cmd,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               subcmd,
                               0,
                               up->ctl_msg_buffer,
                               datalen,
                               UCAN_USB_CTL_PIPE_TIMEOUT);
}

/* Parse the device information structure reported by the device and
 * setup private variables accordingly
 */
static void ucan_parse_device_info(struct ucan_priv *up,
                                   struct ucan_ctl_cmd_device_info *device_info)
{
        struct can_bittiming_const *bittiming =
                &up->device_info.bittiming_const;
        u16 ctrlmodes;

        /* store the data */
        up->can.clock.freq = le32_to_cpu(device_info->freq);
        up->device_info.tx_fifo = device_info->tx_fifo;
        strcpy(bittiming->name, "ucan");
        bittiming->tseg1_min = device_info->tseg1_min;
        bittiming->tseg1_max = device_info->tseg1_max;
        bittiming->tseg2_min = device_info->tseg2_min;
        bittiming->tseg2_max = device_info->tseg2_max;
        bittiming->sjw_max = device_info->sjw_max;
        bittiming->brp_min = le32_to_cpu(device_info->brp_min);
        bittiming->brp_max = le32_to_cpu(device_info->brp_max);
        bittiming->brp_inc = le16_to_cpu(device_info->brp_inc);

        ctrlmodes = le16_to_cpu(device_info->ctrlmodes);

        up->can.ctrlmode_supported = 0;

        if (ctrlmodes & UCAN_MODE_LOOPBACK)
                up->can.ctrlmode_supported |= CAN_CTRLMODE_LOOPBACK;
        if (ctrlmodes & UCAN_MODE_SILENT)
                up->can.ctrlmode_supported |= CAN_CTRLMODE_LISTENONLY;
        if (ctrlmodes & UCAN_MODE_3_SAMPLES)
                up->can.ctrlmode_supported |= CAN_CTRLMODE_3_SAMPLES;
        if (ctrlmodes & UCAN_MODE_ONE_SHOT)
                up->can.ctrlmode_supported |= CAN_CTRLMODE_ONE_SHOT;
        if (ctrlmodes & UCAN_MODE_BERR_REPORT)
                up->can.ctrlmode_supported |= CAN_CTRLMODE_BERR_REPORTING;
}

/* Handle a CAN error frame that we have received from the device.
 * Returns true if the can state has changed.
 */
static bool ucan_handle_error_frame(struct ucan_priv *up,
                                    struct ucan_message_in *m,
                                    canid_t canid)
{
        enum can_state new_state = up->can.state;
        struct net_device_stats *net_stats = &up->netdev->stats;
        struct can_device_stats *can_stats = &up->can.can_stats;

        if (canid & CAN_ERR_LOSTARB)
                can_stats->arbitration_lost++;

        if (canid & CAN_ERR_BUSERROR)
                can_stats->bus_error++;

        if (canid & CAN_ERR_ACK)
                net_stats->tx_errors++;

        if (canid & CAN_ERR_BUSOFF)
                new_state = CAN_STATE_BUS_OFF;

        /* controller problems, details in data[1] */
        if (canid & CAN_ERR_CRTL) {
                u8 d1 = m->msg.can_msg.data[1];

                if (d1 & CAN_ERR_CRTL_RX_OVERFLOW)
                        net_stats->rx_over_errors++;

                /* controller state bits: if multiple are set the worst wins */
                if (d1 & CAN_ERR_CRTL_ACTIVE)
                        new_state = CAN_STATE_ERROR_ACTIVE;

                if (d1 & (CAN_ERR_CRTL_RX_WARNING | CAN_ERR_CRTL_TX_WARNING))
                        new_state = CAN_STATE_ERROR_WARNING;

                if (d1 & (CAN_ERR_CRTL_RX_PASSIVE | CAN_ERR_CRTL_TX_PASSIVE))
                        new_state = CAN_STATE_ERROR_PASSIVE;
        }

        /* protocol error, details in data[2] */
        if (canid & CAN_ERR_PROT) {
                u8 d2 = m->msg.can_msg.data[2];

                if (d2 & CAN_ERR_PROT_TX)
                        net_stats->tx_errors++;
                else
                        net_stats->rx_errors++;
        }

        /* no state change - we are done */
        if (up->can.state == new_state)
                return false;

        /* we switched into a better state */
        if (up->can.state > new_state) {
                up->can.state = new_state;
                return true;
        }

        /* we switched into a worse state */
        up->can.state = new_state;
        switch (new_state) {
        case CAN_STATE_BUS_OFF:
                can_stats->bus_off++;
                can_bus_off(up->netdev);
                break;
        case CAN_STATE_ERROR_PASSIVE:
                can_stats->error_passive++;
                break;
        case CAN_STATE_ERROR_WARNING:
                can_stats->error_warning++;
                break;
        default:
                break;
        }
        return true;
}

/* Callback on reception of a can frame via the IN endpoint
 *
 * This function allocates an skb and transferres it to the Linux
 * network stack
 */
static void ucan_rx_can_msg(struct ucan_priv *up, struct ucan_message_in *m)
{
        int len;
        canid_t canid;
        struct can_frame *cf;
        struct sk_buff *skb;
        struct net_device_stats *stats = &up->netdev->stats;

        /* get the contents of the length field */
        len = le16_to_cpu(m->len);

        /* check sanity */
        if (len < UCAN_IN_HDR_SIZE + sizeof(m->msg.can_msg.id)) {
                netdev_warn(up->netdev, "invalid input message len: %d\n", len);
                return;
        }

        /* handle error frames */
        canid = le32_to_cpu(m->msg.can_msg.id);
        if (canid & CAN_ERR_FLAG) {
                bool busstate_changed = ucan_handle_error_frame(up, m, canid);

                /* if berr-reporting is off only state changes get through */
                if (!(up->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
                    !busstate_changed)
                        return;
        } else {
                canid_t canid_mask;
                /* compute the mask for canid */
                canid_mask = CAN_RTR_FLAG;
                if (canid & CAN_EFF_FLAG)
                        canid_mask |= CAN_EFF_MASK | CAN_EFF_FLAG;
                else
                        canid_mask |= CAN_SFF_MASK;

                if (canid & ~canid_mask)
                        netdev_warn(up->netdev,
                                    "unexpected bits set (canid %x, mask %x)",
                                    canid, canid_mask);

                canid &= canid_mask;
        }

        /* allocate skb */
        skb = alloc_can_skb(up->netdev, &cf);
        if (!skb)
                return;

        /* fill the can frame */
        cf->can_id = canid;

        /* compute DLC taking RTR_FLAG into account */
        cf->len = ucan_can_cc_dlc2len(&m->msg.can_msg, len);

        /* copy the payload of non RTR frames */
        if (!(cf->can_id & CAN_RTR_FLAG) || (cf->can_id & CAN_ERR_FLAG))
                memcpy(cf->data, m->msg.can_msg.data, cf->len);

        /* don't count error frames as real packets */
        if (!(cf->can_id & CAN_ERR_FLAG)) {
                stats->rx_packets++;
                if (!(cf->can_id & CAN_RTR_FLAG))
                        stats->rx_bytes += cf->len;
        }

        /* pass it to Linux */
        netif_rx(skb);
}

/* callback indicating completed transmission */
static void ucan_tx_complete_msg(struct ucan_priv *up,
                                 struct ucan_message_in *m)
{
        unsigned long flags;
        u16 count, i;
        u8 echo_index;
        u16 len = le16_to_cpu(m->len);

        struct ucan_urb_context *context;

        if (len < UCAN_IN_HDR_SIZE || (len % 2 != 0)) {
                netdev_err(up->netdev, "invalid tx complete length\n");
                return;
        }

        count = (len - UCAN_IN_HDR_SIZE) / 2;
        for (i = 0; i < count; i++) {
                /* we did not submit such echo ids */
                echo_index = m->msg.can_tx_complete_msg[i].echo_index;
                if (echo_index >= up->device_info.tx_fifo) {
                        up->netdev->stats.tx_errors++;
                        netdev_err(up->netdev,
                                   "invalid echo_index %d received\n",
                                   echo_index);
                        continue;
                }

                /* gather information from the context */
                context = &up->context_array[echo_index];

                /* Release context and restart queue if necessary.
                 * Also check if the context was allocated
                 */
                if (!ucan_release_context(up, context))
                        continue;

                spin_lock_irqsave(&up->echo_skb_lock, flags);
                if (m->msg.can_tx_complete_msg[i].flags &
                    UCAN_TX_COMPLETE_SUCCESS) {
                        /* update statistics */
                        up->netdev->stats.tx_packets++;
                        up->netdev->stats.tx_bytes +=
                                can_get_echo_skb(up->netdev, echo_index, NULL);
                } else {
                        up->netdev->stats.tx_dropped++;
                        can_free_echo_skb(up->netdev, echo_index, NULL);
                }
                spin_unlock_irqrestore(&up->echo_skb_lock, flags);
        }
}

/* callback on reception of a USB message */
static void ucan_read_bulk_callback(struct urb *urb)
{
        int ret;
        int pos;
        struct ucan_priv *up = urb->context;
        struct net_device *netdev = up->netdev;
        struct ucan_message_in *m;

        /* the device is not up and the driver should not receive any
         * data on the bulk in pipe
         */
        if (WARN_ON(!up->context_array)) {
                usb_free_coherent(up->udev,
                                  up->in_ep_size,
                                  urb->transfer_buffer,
                                  urb->transfer_dma);
                return;
        }

        /* check URB status */
        switch (urb->status) {
        case 0:
                break;
        case -ENOENT:
        case -EPIPE:
        case -EPROTO:
        case -ESHUTDOWN:
        case -ETIME:
                /* urb is not resubmitted -> free dma data */
                usb_free_coherent(up->udev,
                                  up->in_ep_size,
                                  urb->transfer_buffer,
                                  urb->transfer_dma);
                netdev_dbg(up->netdev, "not resubmitting urb; status: %d\n",
                           urb->status);
                return;
        default:
                goto resubmit;
        }

        /* sanity check */
        if (!netif_device_present(netdev))
                return;

        /* iterate over input */
        pos = 0;
        while (pos < urb->actual_length) {
                int len;

                /* check sanity (length of header) */
                if ((urb->actual_length - pos) < UCAN_IN_HDR_SIZE) {
                        netdev_warn(up->netdev,
                                    "invalid message (short; no hdr; l:%d)\n",
                                    urb->actual_length);
                        goto resubmit;
                }

                /* setup the message address */
                m = (struct ucan_message_in *)
                        ((u8 *)urb->transfer_buffer + pos);
                len = le16_to_cpu(m->len);

                /* check sanity (length of content) */
                if (urb->actual_length - pos < len) {
                        netdev_warn(up->netdev,
                                    "invalid message (short; no data; l:%d)\n",
                                    urb->actual_length);
                        print_hex_dump(KERN_WARNING,
                                       "raw data: ",
                                       DUMP_PREFIX_ADDRESS,
                                       16,
                                       1,
                                       urb->transfer_buffer,
                                       urb->actual_length,
                                       true);

                        goto resubmit;
                }

                switch (m->type) {
                case UCAN_IN_RX:
                        ucan_rx_can_msg(up, m);
                        break;
                case UCAN_IN_TX_COMPLETE:
                        ucan_tx_complete_msg(up, m);
                        break;
                default:
                        netdev_warn(up->netdev,
                                    "invalid message (type; t:%d)\n",
                                    m->type);
                        break;
                }

                /* proceed to next message */
                pos += len;
                /* align to 4 byte boundary */
                pos = round_up(pos, 4);
        }

resubmit:
        /* resubmit urb when done */
        usb_fill_bulk_urb(urb, up->udev,
                          usb_rcvbulkpipe(up->udev,
                                          up->in_ep_addr),
                          urb->transfer_buffer,
                          up->in_ep_size,
                          ucan_read_bulk_callback,
                          up);

        usb_anchor_urb(urb, &up->rx_urbs);
        ret = usb_submit_urb(urb, GFP_ATOMIC);

        if (ret < 0) {
                netdev_err(up->netdev,
                           "failed resubmitting read bulk urb: %d\n",
                           ret);

                usb_unanchor_urb(urb);
                usb_free_coherent(up->udev,
                                  up->in_ep_size,
                                  urb->transfer_buffer,
                                  urb->transfer_dma);

                if (ret == -ENODEV)
                        netif_device_detach(netdev);
        }
}

/* callback after transmission of a USB message */
static void ucan_write_bulk_callback(struct urb *urb)
{
        unsigned long flags;
        struct ucan_priv *up;
        struct ucan_urb_context *context = urb->context;

        /* get the urb context */
        if (WARN_ON_ONCE(!context))
                return;

        /* free up our allocated buffer */
        usb_free_coherent(urb->dev,
                          sizeof(struct ucan_message_out),
                          urb->transfer_buffer,
                          urb->transfer_dma);

        up = context->up;
        if (WARN_ON_ONCE(!up))
                return;

        /* sanity check */
        if (!netif_device_present(up->netdev))
                return;

        /* transmission failed (USB - the device will not send a TX complete) */
        if (urb->status) {
                netdev_warn(up->netdev,
                            "failed to transmit USB message to device: %d\n",
                             urb->status);

                /* update counters an cleanup */
                spin_lock_irqsave(&up->echo_skb_lock, flags);
                can_free_echo_skb(up->netdev, context - up->context_array, NULL);
                spin_unlock_irqrestore(&up->echo_skb_lock, flags);

                up->netdev->stats.tx_dropped++;

                /* release context and restart the queue if necessary */
                if (!ucan_release_context(up, context))
                        netdev_err(up->netdev,
                                   "urb failed, failed to release context\n");
        }
}

static void ucan_cleanup_rx_urbs(struct ucan_priv *up, struct urb **urbs)
{
        int i;

        for (i = 0; i < UCAN_MAX_RX_URBS; i++) {
                if (urbs[i]) {
                        usb_unanchor_urb(urbs[i]);
                        usb_free_coherent(up->udev,
                                          up->in_ep_size,
                                          urbs[i]->transfer_buffer,
                                          urbs[i]->transfer_dma);
                        usb_free_urb(urbs[i]);
                }
        }

        memset(urbs, 0, sizeof(*urbs) * UCAN_MAX_RX_URBS);
}

static int ucan_prepare_and_anchor_rx_urbs(struct ucan_priv *up,
                                           struct urb **urbs)
{
        int i;

        memset(urbs, 0, sizeof(*urbs) * UCAN_MAX_RX_URBS);

        for (i = 0; i < UCAN_MAX_RX_URBS; i++) {
                void *buf;

                urbs[i] = usb_alloc_urb(0, GFP_KERNEL);
                if (!urbs[i])
                        goto err;

                buf = usb_alloc_coherent(up->udev,
                                         up->in_ep_size,
                                         GFP_KERNEL, &urbs[i]->transfer_dma);
                if (!buf) {
                        /* cleanup this urb */
                        usb_free_urb(urbs[i]);
                        urbs[i] = NULL;
                        goto err;
                }

                usb_fill_bulk_urb(urbs[i], up->udev,
                                  usb_rcvbulkpipe(up->udev,
                                                  up->in_ep_addr),
                                  buf,
                                  up->in_ep_size,
                                  ucan_read_bulk_callback,
                                  up);

                urbs[i]->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

                usb_anchor_urb(urbs[i], &up->rx_urbs);
        }
        return 0;

err:
        /* cleanup other unsubmitted urbs */
        ucan_cleanup_rx_urbs(up, urbs);
        return -ENOMEM;
}

/* Submits rx urbs with the semantic: Either submit all, or cleanup
 * everything. I case of errors submitted urbs are killed and all urbs in
 * the array are freed. I case of no errors every entry in the urb
 * array is set to NULL.
 */
static int ucan_submit_rx_urbs(struct ucan_priv *up, struct urb **urbs)
{
        int i, ret;

        /* Iterate over all urbs to submit. On success remove the urb
         * from the list.
         */
        for (i = 0; i < UCAN_MAX_RX_URBS; i++) {
                ret = usb_submit_urb(urbs[i], GFP_KERNEL);
                if (ret) {
                        netdev_err(up->netdev,
                                   "could not submit urb; code: %d\n",
                                   ret);
                        goto err;
                }

                /* Anchor URB and drop reference, USB core will take
                 * care of freeing it
                 */
                usb_free_urb(urbs[i]);
                urbs[i] = NULL;
        }
        return 0;

err:
        /* Cleanup unsubmitted urbs */
        ucan_cleanup_rx_urbs(up, urbs);

        /* Kill urbs that are already submitted */
        usb_kill_anchored_urbs(&up->rx_urbs);

        return ret;
}

/* Open the network device */
static int ucan_open(struct net_device *netdev)
{
        int ret, ret_cleanup;
        u16 ctrlmode;
        struct urb *urbs[UCAN_MAX_RX_URBS];
        struct ucan_priv *up = netdev_priv(netdev);

        ret = ucan_alloc_context_array(up);
        if (ret)
                return ret;

        /* Allocate and prepare IN URBS - allocated and anchored
         * urbs are stored in urbs[] for clean
         */
        ret = ucan_prepare_and_anchor_rx_urbs(up, urbs);
        if (ret)
                goto err_contexts;

        /* Check the control mode */
        ctrlmode = 0;
        if (up->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
                ctrlmode |= UCAN_MODE_LOOPBACK;
        if (up->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
                ctrlmode |= UCAN_MODE_SILENT;
        if (up->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
                ctrlmode |= UCAN_MODE_3_SAMPLES;
        if (up->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT)
                ctrlmode |= UCAN_MODE_ONE_SHOT;

        /* Enable this in any case - filtering is down within the
         * receive path
         */
        ctrlmode |= UCAN_MODE_BERR_REPORT;
        up->ctl_msg_buffer->cmd_start.mode = cpu_to_le16(ctrlmode);

        /* Driver is ready to receive data - start the USB device */
        ret = ucan_ctrl_command_out(up, UCAN_COMMAND_START, 0, 2);
        if (ret < 0) {
                netdev_err(up->netdev,
                           "could not start device, code: %d\n",

                           ret);
                goto err_reset;
        }

        /* Call CAN layer open */
        ret = open_candev(netdev);
        if (ret)
                goto err_stop;

        /* Driver is ready to receive data. Submit RX URBS */
        ret = ucan_submit_rx_urbs(up, urbs);
        if (ret)
                goto err_stop;

        up->can.state = CAN_STATE_ERROR_ACTIVE;

        /* Start the network queue */
        netif_start_queue(netdev);

        return 0;

err_stop:
        /* The device have started already stop it */
        ret_cleanup = ucan_ctrl_command_out(up, UCAN_COMMAND_STOP, 0, 0);
        if (ret_cleanup < 0)
                netdev_err(up->netdev,
                           "could not stop device, code: %d\n",
                           ret_cleanup);

err_reset:
        /* The device might have received data, reset it for
         * consistent state
         */
        ret_cleanup = ucan_ctrl_command_out(up, UCAN_COMMAND_RESET, 0, 0);
        if (ret_cleanup < 0)
                netdev_err(up->netdev,
                           "could not reset device, code: %d\n",
                           ret_cleanup);

        /* clean up unsubmitted urbs */
        ucan_cleanup_rx_urbs(up, urbs);

err_contexts:
        ucan_release_context_array(up);
        return ret;
}

static struct urb *ucan_prepare_tx_urb(struct ucan_priv *up,
                                       struct ucan_urb_context *context,
                                       struct can_frame *cf,
                                       u8 echo_index)
{
        int mlen;
        struct urb *urb;
        struct ucan_message_out *m;

        /* 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(up->netdev, "no memory left for URBs\n");
                return NULL;
        }

        m = usb_alloc_coherent(up->udev,
                               sizeof(struct ucan_message_out),
                               GFP_ATOMIC,
                               &urb->transfer_dma);
        if (!m) {
                netdev_err(up->netdev, "no memory left for USB buffer\n");
                usb_free_urb(urb);
                return NULL;
        }

        /* build the USB message */
        m->type = UCAN_OUT_TX;
        m->msg.can_msg.id = cpu_to_le32(cf->can_id);

        if (cf->can_id & CAN_RTR_FLAG) {
                mlen = UCAN_OUT_HDR_SIZE +
                        offsetof(struct ucan_can_msg, dlc) +
                        sizeof(m->msg.can_msg.dlc);
                m->msg.can_msg.dlc = cf->len;
        } else {
                mlen = UCAN_OUT_HDR_SIZE +
                        sizeof(m->msg.can_msg.id) + cf->len;
                memcpy(m->msg.can_msg.data, cf->data, cf->len);
        }
        m->len = cpu_to_le16(mlen);

        m->subtype = echo_index;

        /* build the urb */
        usb_fill_bulk_urb(urb, up->udev,
                          usb_sndbulkpipe(up->udev,
                                          up->out_ep_addr),
                          m, mlen, ucan_write_bulk_callback, context);
        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

        return urb;
}

static void ucan_clean_up_tx_urb(struct ucan_priv *up, struct urb *urb)
{
        usb_free_coherent(up->udev, sizeof(struct ucan_message_out),
                          urb->transfer_buffer, urb->transfer_dma);
        usb_free_urb(urb);
}

/* callback when Linux needs to send a can frame */
static netdev_tx_t ucan_start_xmit(struct sk_buff *skb,
                                   struct net_device *netdev)
{
        unsigned long flags;
        int ret;
        u8 echo_index;
        struct urb *urb;
        struct ucan_urb_context *context;
        struct ucan_priv *up = netdev_priv(netdev);
        struct can_frame *cf = (struct can_frame *)skb->data;

        /* check skb */
        if (can_dropped_invalid_skb(netdev, skb))
                return NETDEV_TX_OK;

        /* allocate a context and slow down tx path, if fifo state is low */
        context = ucan_alloc_context(up);
        echo_index = context - up->context_array;

        if (WARN_ON_ONCE(!context))
                return NETDEV_TX_BUSY;

        /* prepare urb for transmission */
        urb = ucan_prepare_tx_urb(up, context, cf, echo_index);
        if (!urb)
                goto drop;

        /* put the skb on can loopback stack */
        spin_lock_irqsave(&up->echo_skb_lock, flags);
        can_put_echo_skb(skb, up->netdev, echo_index, 0);
        spin_unlock_irqrestore(&up->echo_skb_lock, flags);

        /* transmit it */
        usb_anchor_urb(urb, &up->tx_urbs);
        ret = usb_submit_urb(urb, GFP_ATOMIC);

        /* cleanup urb */
        if (ret) {
                /* on error, clean up */
                usb_unanchor_urb(urb);
                ucan_clean_up_tx_urb(up, urb);
                if (!ucan_release_context(up, context))
                        netdev_err(up->netdev,
                                   "xmit err: failed to release context\n");

                /* remove the skb from the echo stack - this also
                 * frees the skb
                 */
                spin_lock_irqsave(&up->echo_skb_lock, flags);
                can_free_echo_skb(up->netdev, echo_index, NULL);
                spin_unlock_irqrestore(&up->echo_skb_lock, flags);

                if (ret == -ENODEV) {
                        netif_device_detach(up->netdev);
                } else {
                        netdev_warn(up->netdev,
                                    "xmit err: failed to submit urb %d\n",
                                    ret);
                        up->netdev->stats.tx_dropped++;
                }
                return NETDEV_TX_OK;
        }

        netif_trans_update(netdev);

        /* release ref, as we do not need the urb anymore */
        usb_free_urb(urb);

        return NETDEV_TX_OK;

drop:
        if (!ucan_release_context(up, context))
                netdev_err(up->netdev,
                           "xmit drop: failed to release context\n");
        dev_kfree_skb(skb);
        up->netdev->stats.tx_dropped++;

        return NETDEV_TX_OK;
}

/* Device goes down
 *
 * Clean up used resources
 */
static int ucan_close(struct net_device *netdev)
{
        int ret;
        struct ucan_priv *up = netdev_priv(netdev);

        up->can.state = CAN_STATE_STOPPED;

        /* stop sending data */
        usb_kill_anchored_urbs(&up->tx_urbs);

        /* stop receiving data */
        usb_kill_anchored_urbs(&up->rx_urbs);

        /* stop and reset can device */
        ret = ucan_ctrl_command_out(up, UCAN_COMMAND_STOP, 0, 0);
        if (ret < 0)
                netdev_err(up->netdev,
                           "could not stop device, code: %d\n",
                           ret);

        ret = ucan_ctrl_command_out(up, UCAN_COMMAND_RESET, 0, 0);
        if (ret < 0)
                netdev_err(up->netdev,
                           "could not reset device, code: %d\n",
                           ret);

        netif_stop_queue(netdev);

        ucan_release_context_array(up);

        close_candev(up->netdev);
        return 0;
}

/* CAN driver callbacks */
static const struct net_device_ops ucan_netdev_ops = {
        .ndo_open = ucan_open,
        .ndo_stop = ucan_close,
        .ndo_start_xmit = ucan_start_xmit,
        .ndo_change_mtu = can_change_mtu,
};

/* Request to set bittiming
 *
 * This function generates an USB set bittiming message and transmits
 * it to the device
 */
static int ucan_set_bittiming(struct net_device *netdev)
{
        int ret;
        struct ucan_priv *up = netdev_priv(netdev);
        struct ucan_ctl_cmd_set_bittiming *cmd_set_bittiming;

        cmd_set_bittiming = &up->ctl_msg_buffer->cmd_set_bittiming;
        cmd_set_bittiming->tq = cpu_to_le32(up->can.bittiming.tq);
        cmd_set_bittiming->brp = cpu_to_le16(up->can.bittiming.brp);
        cmd_set_bittiming->sample_point =
            cpu_to_le16(up->can.bittiming.sample_point);
        cmd_set_bittiming->prop_seg = up->can.bittiming.prop_seg;
        cmd_set_bittiming->phase_seg1 = up->can.bittiming.phase_seg1;
        cmd_set_bittiming->phase_seg2 = up->can.bittiming.phase_seg2;
        cmd_set_bittiming->sjw = up->can.bittiming.sjw;

        ret = ucan_ctrl_command_out(up, UCAN_COMMAND_SET_BITTIMING, 0,
                                    sizeof(*cmd_set_bittiming));
        return (ret < 0) ? ret : 0;
}

/* Restart the device to get it out of BUS-OFF state.
 * Called when the user runs "ip link set can1 type can restart".
 */
static int ucan_set_mode(struct net_device *netdev, enum can_mode mode)
{
        int ret;
        unsigned long flags;
        struct ucan_priv *up = netdev_priv(netdev);

        switch (mode) {
        case CAN_MODE_START:
                netdev_dbg(up->netdev, "restarting device\n");

                ret = ucan_ctrl_command_out(up, UCAN_COMMAND_RESTART, 0, 0);
                up->can.state = CAN_STATE_ERROR_ACTIVE;

                /* check if queue can be restarted,
                 * up->available_tx_urbs must be protected by the
                 * lock
                 */
                spin_lock_irqsave(&up->context_lock, flags);

                if (up->available_tx_urbs > 0)
                        netif_wake_queue(up->netdev);

                spin_unlock_irqrestore(&up->context_lock, flags);

                return ret;
        default:
                return -EOPNOTSUPP;
        }
}

/* Probe the device, reset it and gather general device information */
static int ucan_probe(struct usb_interface *intf,
                      const struct usb_device_id *id)
{
        int ret;
        int i;
        u32 protocol_version;
        struct usb_device *udev;
        struct net_device *netdev;
        struct usb_host_interface *iface_desc;
        struct ucan_priv *up;
        struct usb_endpoint_descriptor *ep;
        u16 in_ep_size;
        u16 out_ep_size;
        u8 in_ep_addr;
        u8 out_ep_addr;
        union ucan_ctl_payload *ctl_msg_buffer;
        char firmware_str[sizeof(union ucan_ctl_payload) + 1];

        udev = interface_to_usbdev(intf);

        /* Stage 1 - Interface Parsing
         * ---------------------------
         *
         * Identifie the device USB interface descriptor and its
         * endpoints. Probing is aborted on errors.
         */

        /* check if the interface is sane */
        iface_desc = intf->cur_altsetting;
        if (!iface_desc)
                return -ENODEV;

        dev_info(&udev->dev,
                 "%s: probing device on interface #%d\n",
                 UCAN_DRIVER_NAME,
                 iface_desc->desc.bInterfaceNumber);

        /* interface sanity check */
        if (iface_desc->desc.bNumEndpoints != 2) {
                dev_err(&udev->dev,
                        "%s: invalid EP count (%d)",
                        UCAN_DRIVER_NAME, iface_desc->desc.bNumEndpoints);
                goto err_firmware_needs_update;
        }

        /* check interface endpoints */
        in_ep_addr = 0;
        out_ep_addr = 0;
        in_ep_size = 0;
        out_ep_size = 0;
        for (i = 0; i < iface_desc->desc.bNumEndpoints; i++) {
                ep = &iface_desc->endpoint[i].desc;

                if (((ep->bEndpointAddress & USB_ENDPOINT_DIR_MASK) != 0) &&
                    ((ep->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) ==
                     USB_ENDPOINT_XFER_BULK)) {
                        /* In Endpoint */
                        in_ep_addr = ep->bEndpointAddress;
                        in_ep_addr &= USB_ENDPOINT_NUMBER_MASK;
                        in_ep_size = le16_to_cpu(ep->wMaxPacketSize);
                } else if (((ep->bEndpointAddress & USB_ENDPOINT_DIR_MASK) ==
                            0) &&
                           ((ep->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) ==
                            USB_ENDPOINT_XFER_BULK)) {
                        /* Out Endpoint */
                        out_ep_addr = ep->bEndpointAddress;
                        out_ep_addr &= USB_ENDPOINT_NUMBER_MASK;
                        out_ep_size = le16_to_cpu(ep->wMaxPacketSize);
                }
        }

        /* check if interface is sane */
        if (!in_ep_addr || !out_ep_addr) {
                dev_err(&udev->dev, "%s: invalid endpoint configuration\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }
        if (in_ep_size < sizeof(struct ucan_message_in)) {
                dev_err(&udev->dev, "%s: invalid in_ep MaxPacketSize\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }
        if (out_ep_size < sizeof(struct ucan_message_out)) {
                dev_err(&udev->dev, "%s: invalid out_ep MaxPacketSize\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }

        /* Stage 2 - Device Identification
         * -------------------------------
         *
         * The device interface seems to be a ucan device. Do further
         * compatibility checks. On error probing is aborted, on
         * success this stage leaves the ctl_msg_buffer with the
         * reported contents of a GET_INFO command (supported
         * bittimings, tx_fifo depth). This information is used in
         * Stage 3 for the final driver initialisation.
         */

        /* Prepare Memory for control transfers */
        ctl_msg_buffer = devm_kzalloc(&udev->dev,
                                      sizeof(union ucan_ctl_payload),
                                      GFP_KERNEL);
        if (!ctl_msg_buffer) {
                dev_err(&udev->dev,
                        "%s: failed to allocate control pipe memory\n",
                        UCAN_DRIVER_NAME);
                return -ENOMEM;
        }

        /* get protocol version
         *
         * note: ucan_ctrl_command_* wrappers cannot be used yet
         * because `up` is initialised in Stage 3
         */
        ret = usb_control_msg(udev,
                              usb_rcvctrlpipe(udev, 0),
                              UCAN_COMMAND_GET,
                              USB_DIR_IN | USB_TYPE_VENDOR |
                                        USB_RECIP_INTERFACE,
                              UCAN_COMMAND_GET_PROTOCOL_VERSION,
                              iface_desc->desc.bInterfaceNumber,
                              ctl_msg_buffer,
                              sizeof(union ucan_ctl_payload),
                              UCAN_USB_CTL_PIPE_TIMEOUT);

        /* older firmware version do not support this command - those
         * are not supported by this drive
         */
        if (ret != 4) {
                dev_err(&udev->dev,
                        "%s: could not read protocol version, ret=%d\n",
                        UCAN_DRIVER_NAME, ret);
                if (ret >= 0)
                        ret = -EINVAL;
                goto err_firmware_needs_update;
        }

        /* this driver currently supports protocol version 3 only */
        protocol_version =
                le32_to_cpu(ctl_msg_buffer->cmd_get_protocol_version.version);
        if (protocol_version < UCAN_PROTOCOL_VERSION_MIN ||
            protocol_version > UCAN_PROTOCOL_VERSION_MAX) {
                dev_err(&udev->dev,
                        "%s: device protocol version %d is not supported\n",
                        UCAN_DRIVER_NAME, protocol_version);
                goto err_firmware_needs_update;
        }

        /* request the device information and store it in ctl_msg_buffer
         *
         * note: ucan_ctrl_command_* wrappers cannot be used yet
         * because `up` is initialised in Stage 3
         */
        ret = usb_control_msg(udev,
                              usb_rcvctrlpipe(udev, 0),
                              UCAN_COMMAND_GET,
                              USB_DIR_IN | USB_TYPE_VENDOR |
                                        USB_RECIP_INTERFACE,
                              UCAN_COMMAND_GET_INFO,
                              iface_desc->desc.bInterfaceNumber,
                              ctl_msg_buffer,
                              sizeof(ctl_msg_buffer->cmd_get_device_info),
                              UCAN_USB_CTL_PIPE_TIMEOUT);

        if (ret < 0) {
                dev_err(&udev->dev, "%s: failed to retrieve device info\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }
        if (ret < sizeof(ctl_msg_buffer->cmd_get_device_info)) {
                dev_err(&udev->dev, "%s: device reported invalid device info\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }
        if (ctl_msg_buffer->cmd_get_device_info.tx_fifo == 0) {
                dev_err(&udev->dev,
                        "%s: device reported invalid tx-fifo size\n",
                        UCAN_DRIVER_NAME);
                goto err_firmware_needs_update;
        }

        /* Stage 3 - Driver Initialisation
         * -------------------------------
         *
         * Register device to Linux, prepare private structures and
         * reset the device.
         */

        /* allocate driver resources */
        netdev = alloc_candev(sizeof(struct ucan_priv),
                              ctl_msg_buffer->cmd_get_device_info.tx_fifo);
        if (!netdev) {
                dev_err(&udev->dev,
                        "%s: cannot allocate candev\n", UCAN_DRIVER_NAME);
                return -ENOMEM;
        }

        up = netdev_priv(netdev);

        /* initialize data */
        up->udev = udev;
        up->intf = intf;
        up->netdev = netdev;
        up->intf_index = iface_desc->desc.bInterfaceNumber;
        up->in_ep_addr = in_ep_addr;
        up->out_ep_addr = out_ep_addr;
        up->in_ep_size = in_ep_size;
        up->ctl_msg_buffer = ctl_msg_buffer;
        up->context_array = NULL;
        up->available_tx_urbs = 0;

        up->can.state = CAN_STATE_STOPPED;
        up->can.bittiming_const = &up->device_info.bittiming_const;
        up->can.do_set_bittiming = ucan_set_bittiming;
        up->can.do_set_mode = &ucan_set_mode;
        spin_lock_init(&up->context_lock);
        spin_lock_init(&up->echo_skb_lock);
        netdev->netdev_ops = &ucan_netdev_ops;

        usb_set_intfdata(intf, up);
        SET_NETDEV_DEV(netdev, &intf->dev);

        /* parse device information
         * the data retrieved in Stage 2 is still available in
         * up->ctl_msg_buffer
         */
        ucan_parse_device_info(up, &ctl_msg_buffer->cmd_get_device_info);

        /* just print some device information - if available */
        ret = ucan_device_request_in(up, UCAN_DEVICE_GET_FW_STRING, 0,
                                     sizeof(union ucan_ctl_payload));
        if (ret > 0) {
                /* copy string while ensuring zero termination */
                strncpy(firmware_str, up->ctl_msg_buffer->raw,
                        sizeof(union ucan_ctl_payload));
                firmware_str[sizeof(union ucan_ctl_payload)] = '\0';
        } else {
                strcpy(firmware_str, "unknown");
        }

        /* device is compatible, reset it */
        ret = ucan_ctrl_command_out(up, UCAN_COMMAND_RESET, 0, 0);
        if (ret < 0)
                goto err_free_candev;

        init_usb_anchor(&up->rx_urbs);
        init_usb_anchor(&up->tx_urbs);

        up->can.state = CAN_STATE_STOPPED;

        /* register the device */
        ret = register_candev(netdev);
        if (ret)
                goto err_free_candev;

        /* initialisation complete, log device info */
        netdev_info(up->netdev, "registered device\n");
        netdev_info(up->netdev, "firmware string: %s\n", firmware_str);

        /* success */
        return 0;

err_free_candev:
        free_candev(netdev);
        return ret;

err_firmware_needs_update:
        dev_err(&udev->dev,
                "%s: probe failed; try to update the device firmware\n",
                UCAN_DRIVER_NAME);
        return -ENODEV;
}

/* disconnect the device */
static void ucan_disconnect(struct usb_interface *intf)
{
        struct ucan_priv *up = usb_get_intfdata(intf);

        usb_set_intfdata(intf, NULL);

        if (up) {
                unregister_netdev(up->netdev);
                free_candev(up->netdev);
        }
}

static struct usb_device_id ucan_table[] = {
        /* Mule (soldered onto compute modules) */
        {USB_DEVICE_INTERFACE_NUMBER(0x2294, 0x425a, 0)},
        /* Seal (standalone USB stick) */
        {USB_DEVICE_INTERFACE_NUMBER(0x2294, 0x425b, 0)},
        {} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, ucan_table);
/* driver callbacks */
static struct usb_driver ucan_driver = {
        .name = UCAN_DRIVER_NAME,
        .probe = ucan_probe,
        .disconnect = ucan_disconnect,
        .id_table = ucan_table,
};

module_usb_driver(ucan_driver);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Martin Elshuber <martin.elshuber@theobroma-systems.com>");
MODULE_AUTHOR("Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>");
MODULE_DESCRIPTION("Driver for Theobroma Systems UCAN devices");