/*
 * CAN driver for PEAK System PCAN-USB adapter
 * Derived from the PCAN project file driver/src/pcan_usb.c
 *
 * Copyright (C) 2003-2010 PEAK System-Technik GmbH
 * Copyright (C) 2011-2012 Stephane Grosjean <s.grosjean@peak-system.com>
 *
 * Many thanks to Klaus Hitschler <klaus.hitschler@gmx.de>
 *
 * 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/netdevice.h>
#include <linux/usb.h>
#include <linux/module.h>

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include "pcan_usb_core.h"

MODULE_SUPPORTED_DEVICE("PEAK-System PCAN-USB adapter");

/* PCAN-USB Endpoints */
#define PCAN_USB_EP_CMDOUT              1
#define PCAN_USB_EP_CMDIN               (PCAN_USB_EP_CMDOUT | USB_DIR_IN)
#define PCAN_USB_EP_MSGOUT              2
#define PCAN_USB_EP_MSGIN               (PCAN_USB_EP_MSGOUT | USB_DIR_IN)

/* PCAN-USB command struct */
#define PCAN_USB_CMD_FUNC               0
#define PCAN_USB_CMD_NUM                1
#define PCAN_USB_CMD_ARGS               2
#define PCAN_USB_CMD_ARGS_LEN           14
#define PCAN_USB_CMD_LEN                (PCAN_USB_CMD_ARGS + \
                                         PCAN_USB_CMD_ARGS_LEN)

/* PCAN-USB commands */
#define PCAN_USB_CMD_BITRATE    1
#define PCAN_USB_CMD_SET_BUS    3
#define PCAN_USB_CMD_DEVID      4
#define PCAN_USB_CMD_SN         6
#define PCAN_USB_CMD_REGISTER   9
#define PCAN_USB_CMD_EXT_VCC    10
#define PCAN_USB_CMD_ERR_FR     11

/* PCAN_USB_CMD_SET_BUS number arg */
#define PCAN_USB_BUS_XCVER              2
#define PCAN_USB_BUS_SILENT_MODE        3

/* PCAN_USB_CMD_xxx functions */
#define PCAN_USB_GET            1
#define PCAN_USB_SET            2

/* PCAN-USB command timeout (ms.) */
#define PCAN_USB_COMMAND_TIMEOUT        1000

/* PCAN-USB startup timeout (ms.) */
#define PCAN_USB_STARTUP_TIMEOUT        10

/* PCAN-USB rx/tx buffers size */
#define PCAN_USB_RX_BUFFER_SIZE         64
#define PCAN_USB_TX_BUFFER_SIZE         64

#define PCAN_USB_MSG_HEADER_LEN         2

/* PCAN-USB adapter internal clock (MHz) */
#define PCAN_USB_CRYSTAL_HZ             16000000

/* PCAN-USB USB message record status/len field */
#define PCAN_USB_STATUSLEN_TIMESTAMP    (1 << 7)
#define PCAN_USB_STATUSLEN_INTERNAL     (1 << 6)
#define PCAN_USB_STATUSLEN_EXT_ID       (1 << 5)
#define PCAN_USB_STATUSLEN_RTR          (1 << 4)
#define PCAN_USB_STATUSLEN_DLC          (0xf)

/* PCAN-USB error flags */
#define PCAN_USB_ERROR_TXFULL           0x01
#define PCAN_USB_ERROR_RXQOVR           0x02
#define PCAN_USB_ERROR_BUS_LIGHT        0x04
#define PCAN_USB_ERROR_BUS_HEAVY        0x08
#define PCAN_USB_ERROR_BUS_OFF          0x10
#define PCAN_USB_ERROR_RXQEMPTY         0x20
#define PCAN_USB_ERROR_QOVR             0x40
#define PCAN_USB_ERROR_TXQFULL          0x80

#define PCAN_USB_ERROR_BUS              (PCAN_USB_ERROR_BUS_LIGHT | \
                                         PCAN_USB_ERROR_BUS_HEAVY | \
                                         PCAN_USB_ERROR_BUS_OFF)

/* SJA1000 modes */
#define SJA1000_MODE_NORMAL             0x00
#define SJA1000_MODE_INIT               0x01

/*
 * tick duration = 42.666 us =>
 * (tick_number * 44739243) >> 20 ~ (tick_number * 42666) / 1000
 * accuracy = 10^-7
 */
#define PCAN_USB_TS_DIV_SHIFTER         20
#define PCAN_USB_TS_US_PER_TICK         44739243

/* PCAN-USB messages record types */
#define PCAN_USB_REC_ERROR              1
#define PCAN_USB_REC_ANALOG             2
#define PCAN_USB_REC_BUSLOAD            3
#define PCAN_USB_REC_TS                 4
#define PCAN_USB_REC_BUSEVT             5

/* CAN bus events notifications selection mask */
#define PCAN_USB_ERR_RXERR              0x02    /* ask for rxerr counter */
#define PCAN_USB_ERR_TXERR              0x04    /* ask for txerr counter */

/* This mask generates an usb packet each time the state of the bus changes.
 * In other words, its interest is to know which side among rx and tx is
 * responsible of the change of the bus state.
 */
#define PCAN_USB_BERR_MASK      (PCAN_USB_ERR_RXERR | PCAN_USB_ERR_TXERR)

/* identify bus event packets with rx/tx error counters */
#define PCAN_USB_ERR_CNT                0x80

/* private to PCAN-USB adapter */
struct pcan_usb {
        struct peak_usb_device dev;
        struct peak_time_ref time_ref;
        struct timer_list restart_timer;
        struct can_berr_counter bec;
};

/* incoming message context for decoding */
struct pcan_usb_msg_context {
        u16 ts16;
        u8 prev_ts8;
        u8 *ptr;
        u8 *end;
        u8 rec_cnt;
        u8 rec_idx;
        u8 rec_ts_idx;
        struct net_device *netdev;
        struct pcan_usb *pdev;
};

/*
 * send a command
 */
static int pcan_usb_send_cmd(struct peak_usb_device *dev, u8 f, u8 n, u8 *p)
{
        int err;
        int actual_length;

        /* usb device unregistered? */
        if (!(dev->state & PCAN_USB_STATE_CONNECTED))
                return 0;

        dev->cmd_buf[PCAN_USB_CMD_FUNC] = f;
        dev->cmd_buf[PCAN_USB_CMD_NUM] = n;

        if (p)
                memcpy(dev->cmd_buf + PCAN_USB_CMD_ARGS,
                        p, PCAN_USB_CMD_ARGS_LEN);

        err = usb_bulk_msg(dev->udev,
                        usb_sndbulkpipe(dev->udev, PCAN_USB_EP_CMDOUT),
                        dev->cmd_buf, PCAN_USB_CMD_LEN, &actual_length,
                        PCAN_USB_COMMAND_TIMEOUT);
        if (err)
                netdev_err(dev->netdev,
                        "sending cmd f=0x%x n=0x%x failure: %d\n",
                        f, n, err);
        return err;
}

/*
 * send a command then wait for its response
 */
static int pcan_usb_wait_rsp(struct peak_usb_device *dev, u8 f, u8 n, u8 *p)
{
        int err;
        int actual_length;

        /* usb device unregistered? */
        if (!(dev->state & PCAN_USB_STATE_CONNECTED))
                return 0;

        /* first, send command */
        err = pcan_usb_send_cmd(dev, f, n, NULL);
        if (err)
                return err;

        err = usb_bulk_msg(dev->udev,
                usb_rcvbulkpipe(dev->udev, PCAN_USB_EP_CMDIN),
                dev->cmd_buf, PCAN_USB_CMD_LEN, &actual_length,
                PCAN_USB_COMMAND_TIMEOUT);
        if (err)
                netdev_err(dev->netdev,
                        "waiting rsp f=0x%x n=0x%x failure: %d\n", f, n, err);
        else if (p)
                memcpy(p, dev->cmd_buf + PCAN_USB_CMD_ARGS,
                        PCAN_USB_CMD_ARGS_LEN);

        return err;
}

static int pcan_usb_set_sja1000(struct peak_usb_device *dev, u8 mode)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN] = {
                [1] = mode,
        };

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_REGISTER, PCAN_USB_SET,
                                 args);
}

static int pcan_usb_set_bus(struct peak_usb_device *dev, u8 onoff)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN] = {
                [0] = !!onoff,
        };

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_SET_BUS, PCAN_USB_BUS_XCVER,
                                 args);
}

static int pcan_usb_set_silent(struct peak_usb_device *dev, u8 onoff)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN] = {
                [0] = !!onoff,
        };

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_SET_BUS,
                                 PCAN_USB_BUS_SILENT_MODE, args);
}

/* send the cmd to be notified from bus errors */
static int pcan_usb_set_err_frame(struct peak_usb_device *dev, u8 err_mask)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN] = {
                [0] = err_mask,
        };

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_ERR_FR, PCAN_USB_SET, args);
}

static int pcan_usb_set_ext_vcc(struct peak_usb_device *dev, u8 onoff)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN] = {
                [0] = !!onoff,
        };

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_EXT_VCC, PCAN_USB_SET, args);
}

/*
 * set bittiming value to can
 */
static int pcan_usb_set_bittiming(struct peak_usb_device *dev,
                                  struct can_bittiming *bt)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN];
        u8 btr0, btr1;

        btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
        btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
                (((bt->phase_seg2 - 1) & 0x7) << 4);
        if (dev->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
                btr1 |= 0x80;

        netdev_info(dev->netdev, "setting BTR0=0x%02x BTR1=0x%02x\n",
                btr0, btr1);

        args[0] = btr1;
        args[1] = btr0;

        return pcan_usb_send_cmd(dev, PCAN_USB_CMD_BITRATE, PCAN_USB_SET, args);
}

/*
 * init/reset can
 */
static int pcan_usb_write_mode(struct peak_usb_device *dev, u8 onoff)
{
        int err;

        err = pcan_usb_set_bus(dev, onoff);
        if (err)
                return err;

        if (!onoff) {
                err = pcan_usb_set_sja1000(dev, SJA1000_MODE_INIT);
        } else {
                /* the PCAN-USB needs time to init */
                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(msecs_to_jiffies(PCAN_USB_STARTUP_TIMEOUT));
        }

        return err;
}

/*
 * handle end of waiting for the device to reset
 */
static void pcan_usb_restart(struct timer_list *t)
{
        struct pcan_usb *pdev = from_timer(pdev, t, restart_timer);
        struct peak_usb_device *dev = &pdev->dev;

        /* notify candev and netdev */
        peak_usb_restart_complete(dev);
}

/*
 * handle the submission of the restart urb
 */
static void pcan_usb_restart_pending(struct urb *urb)
{
        struct pcan_usb *pdev = urb->context;

        /* the PCAN-USB needs time to restart */
        mod_timer(&pdev->restart_timer,
                        jiffies + msecs_to_jiffies(PCAN_USB_STARTUP_TIMEOUT));

        /* can delete usb resources */
        peak_usb_async_complete(urb);
}

/*
 * handle asynchronous restart
 */
static int pcan_usb_restart_async(struct peak_usb_device *dev, struct urb *urb,
                                  u8 *buf)
{
        struct pcan_usb *pdev = container_of(dev, struct pcan_usb, dev);

        if (timer_pending(&pdev->restart_timer))
                return -EBUSY;

        /* set bus on */
        buf[PCAN_USB_CMD_FUNC] = 3;
        buf[PCAN_USB_CMD_NUM] = 2;
        buf[PCAN_USB_CMD_ARGS] = 1;

        usb_fill_bulk_urb(urb, dev->udev,
                        usb_sndbulkpipe(dev->udev, PCAN_USB_EP_CMDOUT),
                        buf, PCAN_USB_CMD_LEN,
                        pcan_usb_restart_pending, pdev);

        return usb_submit_urb(urb, GFP_ATOMIC);
}

/*
 * read serial number from device
 */
static int pcan_usb_get_serial(struct peak_usb_device *dev, u32 *serial_number)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN];
        int err;

        err = pcan_usb_wait_rsp(dev, PCAN_USB_CMD_SN, PCAN_USB_GET, args);
        if (err) {
                netdev_err(dev->netdev, "getting serial failure: %d\n", err);
        } else if (serial_number) {
                __le32 tmp32;

                memcpy(&tmp32, args, 4);
                *serial_number = le32_to_cpu(tmp32);
        }

        return err;
}

/*
 * read device id from device
 */
static int pcan_usb_get_device_id(struct peak_usb_device *dev, u32 *device_id)
{
        u8 args[PCAN_USB_CMD_ARGS_LEN];
        int err;

        err = pcan_usb_wait_rsp(dev, PCAN_USB_CMD_DEVID, PCAN_USB_GET, args);
        if (err)
                netdev_err(dev->netdev, "getting device id failure: %d\n", err);
        else if (device_id)
                *device_id = args[0];

        return err;
}

/*
 * update current time ref with received timestamp
 */
static int pcan_usb_update_ts(struct pcan_usb_msg_context *mc)
{
        __le16 tmp16;

        if ((mc->ptr+2) > mc->end)
                return -EINVAL;

        memcpy(&tmp16, mc->ptr, 2);

        mc->ts16 = le16_to_cpu(tmp16);

        if (mc->rec_idx > 0)
                peak_usb_update_ts_now(&mc->pdev->time_ref, mc->ts16);
        else
                peak_usb_set_ts_now(&mc->pdev->time_ref, mc->ts16);

        return 0;
}

/*
 * decode received timestamp
 */
static int pcan_usb_decode_ts(struct pcan_usb_msg_context *mc, u8 first_packet)
{
        /* only 1st packet supplies a word timestamp */
        if (first_packet) {
                __le16 tmp16;

                if ((mc->ptr + 2) > mc->end)
                        return -EINVAL;

                memcpy(&tmp16, mc->ptr, 2);
                mc->ptr += 2;

                mc->ts16 = le16_to_cpu(tmp16);
                mc->prev_ts8 = mc->ts16 & 0x00ff;
        } else {
                u8 ts8;

                if ((mc->ptr + 1) > mc->end)
                        return -EINVAL;

                ts8 = *mc->ptr++;

                if (ts8 < mc->prev_ts8)
                        mc->ts16 += 0x100;

                mc->ts16 &= 0xff00;
                mc->ts16 |= ts8;
                mc->prev_ts8 = ts8;
        }

        return 0;
}

static int pcan_usb_decode_error(struct pcan_usb_msg_context *mc, u8 n,
                                 u8 status_len)
{
        struct sk_buff *skb;
        struct can_frame *cf;
        enum can_state new_state;

        /* ignore this error until 1st ts received */
        if (n == PCAN_USB_ERROR_QOVR)
                if (!mc->pdev->time_ref.tick_count)
                        return 0;

        new_state = mc->pdev->dev.can.state;

        switch (mc->pdev->dev.can.state) {
        case CAN_STATE_ERROR_ACTIVE:
                if (n & PCAN_USB_ERROR_BUS_LIGHT) {
                        new_state = CAN_STATE_ERROR_WARNING;
                        break;
                }
                /* fall through */

        case CAN_STATE_ERROR_WARNING:
                if (n & PCAN_USB_ERROR_BUS_HEAVY) {
                        new_state = CAN_STATE_ERROR_PASSIVE;
                        break;
                }
                if (n & PCAN_USB_ERROR_BUS_OFF) {
                        new_state = CAN_STATE_BUS_OFF;
                        break;
                }
                if (n & ~PCAN_USB_ERROR_BUS) {
                        /*
                         * trick to bypass next comparison and process other
                         * errors
                         */
                        new_state = CAN_STATE_MAX;
                        break;
                }
                if ((n & PCAN_USB_ERROR_BUS_LIGHT) == 0) {
                        /* no error (back to active state) */
                        new_state = CAN_STATE_ERROR_ACTIVE;
                        break;
                }
                break;

        case CAN_STATE_ERROR_PASSIVE:
                if (n & PCAN_USB_ERROR_BUS_OFF) {
                        new_state = CAN_STATE_BUS_OFF;
                        break;
                }
                if (n & PCAN_USB_ERROR_BUS_LIGHT) {
                        new_state = CAN_STATE_ERROR_WARNING;
                        break;
                }
                if (n & ~PCAN_USB_ERROR_BUS) {
                        /*
                         * trick to bypass next comparison and process other
                         * errors
                         */
                        new_state = CAN_STATE_MAX;
                        break;
                }

                if ((n & PCAN_USB_ERROR_BUS_HEAVY) == 0) {
                        /* no error (back to warning state) */
                        new_state = CAN_STATE_ERROR_WARNING;
                        break;
                }
                break;

        default:
                /* do nothing waiting for restart */
                return 0;
        }

        /* donot post any error if current state didn't change */
        if (mc->pdev->dev.can.state == new_state)
                return 0;

        /* allocate an skb to store the error frame */
        skb = alloc_can_err_skb(mc->netdev, &cf);
        if (!skb)
                return -ENOMEM;

        switch (new_state) {
        case CAN_STATE_BUS_OFF:
                cf->can_id |= CAN_ERR_BUSOFF;
                mc->pdev->dev.can.can_stats.bus_off++;
                can_bus_off(mc->netdev);
                break;

        case CAN_STATE_ERROR_PASSIVE:
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = (mc->pdev->bec.txerr > mc->pdev->bec.rxerr) ?
                                CAN_ERR_CRTL_TX_PASSIVE :
                                CAN_ERR_CRTL_RX_PASSIVE;
                cf->data[6] = mc->pdev->bec.txerr;
                cf->data[7] = mc->pdev->bec.rxerr;

                mc->pdev->dev.can.can_stats.error_passive++;
                break;

        case CAN_STATE_ERROR_WARNING:
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = (mc->pdev->bec.txerr > mc->pdev->bec.rxerr) ?
                                CAN_ERR_CRTL_TX_WARNING :
                                CAN_ERR_CRTL_RX_WARNING;
                cf->data[6] = mc->pdev->bec.txerr;
                cf->data[7] = mc->pdev->bec.rxerr;

                mc->pdev->dev.can.can_stats.error_warning++;
                break;

        case CAN_STATE_ERROR_ACTIVE:
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = CAN_ERR_CRTL_ACTIVE;

                /* sync local copies of rxerr/txerr counters */
                mc->pdev->bec.txerr = 0;
                mc->pdev->bec.rxerr = 0;
                break;

        default:
                /* CAN_STATE_MAX (trick to handle other errors) */
                if (n & PCAN_USB_ERROR_TXQFULL)
                        netdev_dbg(mc->netdev, "device Tx queue full)\n");

                if (n & PCAN_USB_ERROR_RXQOVR) {
                        netdev_dbg(mc->netdev, "data overrun interrupt\n");
                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] |= CAN_ERR_CRTL_RX_OVERFLOW;
                        mc->netdev->stats.rx_over_errors++;
                        mc->netdev->stats.rx_errors++;
                }

                cf->data[6] = mc->pdev->bec.txerr;
                cf->data[7] = mc->pdev->bec.rxerr;

                new_state = mc->pdev->dev.can.state;
                break;
        }

        mc->pdev->dev.can.state = new_state;

        if (status_len & PCAN_USB_STATUSLEN_TIMESTAMP) {
                struct skb_shared_hwtstamps *hwts = skb_hwtstamps(skb);

                peak_usb_get_ts_time(&mc->pdev->time_ref, mc->ts16,
                                     &hwts->hwtstamp);
        }

        mc->netdev->stats.rx_packets++;
        mc->netdev->stats.rx_bytes += cf->can_dlc;
        netif_rx(skb);

        return 0;
}

/* decode bus event usb packet: first byte contains rxerr while 2nd one contains
 * txerr.
 */
static int pcan_usb_handle_bus_evt(struct pcan_usb_msg_context *mc, u8 ir)
{
        struct pcan_usb *pdev = mc->pdev;

        /* acccording to the content of the packet */
        switch (ir) {
        case PCAN_USB_ERR_CNT:

                /* save rx/tx error counters from in the device context */
                pdev->bec.rxerr = mc->ptr[0];
                pdev->bec.txerr = mc->ptr[1];
                break;

        default:
                /* reserved */
                break;
        }

        return 0;
}

/*
 * decode non-data usb message
 */
static int pcan_usb_decode_status(struct pcan_usb_msg_context *mc,
                                  u8 status_len)
{
        u8 rec_len = status_len & PCAN_USB_STATUSLEN_DLC;
        u8 f, n;
        int err;

        /* check whether function and number can be read */
        if ((mc->ptr + 2) > mc->end)
                return -EINVAL;

        f = mc->ptr[PCAN_USB_CMD_FUNC];
        n = mc->ptr[PCAN_USB_CMD_NUM];
        mc->ptr += PCAN_USB_CMD_ARGS;

        if (status_len & PCAN_USB_STATUSLEN_TIMESTAMP) {
                int err = pcan_usb_decode_ts(mc, !mc->rec_ts_idx);

                if (err)
                        return err;

                /* Next packet in the buffer will have a timestamp on a single
                 * byte
                 */
                mc->rec_ts_idx++;
        }

        switch (f) {
        case PCAN_USB_REC_ERROR:
                err = pcan_usb_decode_error(mc, n, status_len);
                if (err)
                        return err;
                break;

        case PCAN_USB_REC_ANALOG:
                /* analog values (ignored) */
                rec_len = 2;
                break;

        case PCAN_USB_REC_BUSLOAD:
                /* bus load (ignored) */
                rec_len = 1;
                break;

        case PCAN_USB_REC_TS:
                /* only timestamp */
                if (pcan_usb_update_ts(mc))
                        return -EINVAL;
                break;

        case PCAN_USB_REC_BUSEVT:
                /* bus event notifications (get rxerr/txerr) */
                err = pcan_usb_handle_bus_evt(mc, n);
                if (err)
                        return err;
                break;
        default:
                netdev_err(mc->netdev, "unexpected function %u\n", f);
                break;
        }

        if ((mc->ptr + rec_len) > mc->end)
                return -EINVAL;

        mc->ptr += rec_len;

        return 0;
}

/*
 * decode data usb message
 */
static int pcan_usb_decode_data(struct pcan_usb_msg_context *mc, u8 status_len)
{
        u8 rec_len = status_len & PCAN_USB_STATUSLEN_DLC;
        struct sk_buff *skb;
        struct can_frame *cf;
        struct skb_shared_hwtstamps *hwts;

        skb = alloc_can_skb(mc->netdev, &cf);
        if (!skb)
                return -ENOMEM;

        if (status_len & PCAN_USB_STATUSLEN_EXT_ID) {
                __le32 tmp32;

                if ((mc->ptr + 4) > mc->end)
                        goto decode_failed;

                memcpy(&tmp32, mc->ptr, 4);
                mc->ptr += 4;

                cf->can_id = (le32_to_cpu(tmp32) >> 3) | CAN_EFF_FLAG;
        } else {
                __le16 tmp16;

                if ((mc->ptr + 2) > mc->end)
                        goto decode_failed;

                memcpy(&tmp16, mc->ptr, 2);
                mc->ptr += 2;

                cf->can_id = le16_to_cpu(tmp16) >> 5;
        }

        cf->can_dlc = get_can_dlc(rec_len);

        /* Only first packet timestamp is a word */
        if (pcan_usb_decode_ts(mc, !mc->rec_ts_idx))
                goto decode_failed;

        /* Next packet in the buffer will have a timestamp on a single byte */
        mc->rec_ts_idx++;

        /* read data */
        memset(cf->data, 0x0, sizeof(cf->data));
        if (status_len & PCAN_USB_STATUSLEN_RTR) {
                cf->can_id |= CAN_RTR_FLAG;
        } else {
                if ((mc->ptr + rec_len) > mc->end)
                        goto decode_failed;

                memcpy(cf->data, mc->ptr, cf->can_dlc);
                mc->ptr += rec_len;
        }

        /* convert timestamp into kernel time */
        hwts = skb_hwtstamps(skb);
        peak_usb_get_ts_time(&mc->pdev->time_ref, mc->ts16, &hwts->hwtstamp);

        /* update statistics */
        mc->netdev->stats.rx_packets++;
        mc->netdev->stats.rx_bytes += cf->can_dlc;
        /* push the skb */
        netif_rx(skb);

        return 0;

decode_failed:
        dev_kfree_skb(skb);
        return -EINVAL;
}

/*
 * process incoming message
 */
static int pcan_usb_decode_msg(struct peak_usb_device *dev, u8 *ibuf, u32 lbuf)
{
        struct pcan_usb_msg_context mc = {
                .rec_cnt = ibuf[1],
                .ptr = ibuf + PCAN_USB_MSG_HEADER_LEN,
                .end = ibuf + lbuf,
                .netdev = dev->netdev,
                .pdev = container_of(dev, struct pcan_usb, dev),
        };
        int err;

        for (err = 0; mc.rec_idx < mc.rec_cnt && !err; mc.rec_idx++) {
                u8 sl = *mc.ptr++;

                /* handle status and error frames here */
                if (sl & PCAN_USB_STATUSLEN_INTERNAL) {
                        err = pcan_usb_decode_status(&mc, sl);
                /* handle normal can frames here */
                } else {
                        err = pcan_usb_decode_data(&mc, sl);
                }
        }

        return err;
}

/*
 * process any incoming buffer
 */
static int pcan_usb_decode_buf(struct peak_usb_device *dev, struct urb *urb)
{
        int err = 0;

        if (urb->actual_length > PCAN_USB_MSG_HEADER_LEN) {
                err = pcan_usb_decode_msg(dev, urb->transfer_buffer,
                        urb->actual_length);

        } else if (urb->actual_length > 0) {
                netdev_err(dev->netdev, "usb message length error (%u)\n",
                        urb->actual_length);
                err = -EINVAL;
        }

        return err;
}

/*
 * process outgoing packet
 */
static int pcan_usb_encode_msg(struct peak_usb_device *dev, struct sk_buff *skb,
                               u8 *obuf, size_t *size)
{
        struct net_device *netdev = dev->netdev;
        struct net_device_stats *stats = &netdev->stats;
        struct can_frame *cf = (struct can_frame *)skb->data;
        u8 *pc;

        obuf[0] = 2;
        obuf[1] = 1;

        pc = obuf + PCAN_USB_MSG_HEADER_LEN;

        /* status/len byte */
        *pc = cf->can_dlc;
        if (cf->can_id & CAN_RTR_FLAG)
                *pc |= PCAN_USB_STATUSLEN_RTR;

        /* can id */
        if (cf->can_id & CAN_EFF_FLAG) {
                __le32 tmp32 = cpu_to_le32((cf->can_id & CAN_ERR_MASK) << 3);

                *pc |= PCAN_USB_STATUSLEN_EXT_ID;
                memcpy(++pc, &tmp32, 4);
                pc += 4;
        } else {
                __le16 tmp16 = cpu_to_le16((cf->can_id & CAN_ERR_MASK) << 5);

                memcpy(++pc, &tmp16, 2);
                pc += 2;
        }

        /* can data */
        if (!(cf->can_id & CAN_RTR_FLAG)) {
                memcpy(pc, cf->data, cf->can_dlc);
                pc += cf->can_dlc;
        }

        obuf[(*size)-1] = (u8)(stats->tx_packets & 0xff);

        return 0;
}

/* socket callback used to copy berr counters values received through USB */
static int pcan_usb_get_berr_counter(const struct net_device *netdev,
                                     struct can_berr_counter *bec)
{
        struct peak_usb_device *dev = netdev_priv(netdev);
        struct pcan_usb *pdev = container_of(dev, struct pcan_usb, dev);

        *bec = pdev->bec;

        /* must return 0 */
        return 0;
}

/*
 * start interface
 */
static int pcan_usb_start(struct peak_usb_device *dev)
{
        struct pcan_usb *pdev = container_of(dev, struct pcan_usb, dev);
        int err;

        /* number of bits used in timestamps read from adapter struct */
        peak_usb_init_time_ref(&pdev->time_ref, &pcan_usb);

        pdev->bec.rxerr = 0;
        pdev->bec.txerr = 0;

        /* be notified on error counter changes (if requested by user) */
        if (dev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) {
                err = pcan_usb_set_err_frame(dev, PCAN_USB_BERR_MASK);
                if (err)
                        netdev_warn(dev->netdev,
                                    "Asking for BERR reporting error %u\n",
                                    err);
        }

        /* if revision greater than 3, can put silent mode on/off */
        if (dev->device_rev > 3) {
                err = pcan_usb_set_silent(dev,
                                dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY);
                if (err)
                        return err;
        }

        return pcan_usb_set_ext_vcc(dev, 0);
}

static int pcan_usb_init(struct peak_usb_device *dev)
{
        struct pcan_usb *pdev = container_of(dev, struct pcan_usb, dev);
        u32 serial_number;
        int err;

        /* initialize a timer needed to wait for hardware restart */
        timer_setup(&pdev->restart_timer, pcan_usb_restart, 0);

        /*
         * explicit use of dev_xxx() instead of netdev_xxx() here:
         * information displayed are related to the device itself, not
         * to the canx netdevice.
         */
        err = pcan_usb_get_serial(dev, &serial_number);
        if (err) {
                dev_err(dev->netdev->dev.parent,
                        "unable to read %s serial number (err %d)\n",
                        pcan_usb.name, err);
                return err;
        }

        dev_info(dev->netdev->dev.parent,
                 "PEAK-System %s adapter hwrev %u serial %08X (%u channel)\n",
                 pcan_usb.name, dev->device_rev, serial_number,
                 pcan_usb.ctrl_count);

        return 0;
}

/*
 * probe function for new PCAN-USB usb interface
 */
static int pcan_usb_probe(struct usb_interface *intf)
{
        struct usb_host_interface *if_desc;
        int i;

        if_desc = intf->altsetting;

        /* check interface endpoint addresses */
        for (i = 0; i < if_desc->desc.bNumEndpoints; i++) {
                struct usb_endpoint_descriptor *ep = &if_desc->endpoint[i].desc;

                switch (ep->bEndpointAddress) {
                case PCAN_USB_EP_CMDOUT:
                case PCAN_USB_EP_CMDIN:
                case PCAN_USB_EP_MSGOUT:
                case PCAN_USB_EP_MSGIN:
                        break;
                default:
                        return -ENODEV;
                }
        }

        return 0;
}

/*
 * describe the PCAN-USB adapter
 */
static const struct can_bittiming_const pcan_usb_const = {
        .name = "pcan_usb",
        .tseg1_min = 1,
        .tseg1_max = 16,
        .tseg2_min = 1,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 64,
        .brp_inc = 1,
};

const struct peak_usb_adapter pcan_usb = {
        .name = "PCAN-USB",
        .device_id = PCAN_USB_PRODUCT_ID,

        .ctrl_count = 1,
        .ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES | CAN_CTRLMODE_LISTENONLY |
                              CAN_CTRLMODE_BERR_REPORTING,
        .clock = {
                .freq = PCAN_USB_CRYSTAL_HZ / 2 ,
        },
        .bittiming_const = &pcan_usb_const,

        /* size of device private data */
        .sizeof_dev_private = sizeof(struct pcan_usb),

        /* timestamps usage */
        .ts_used_bits = 16,
        .ts_period = 24575, /* calibration period in ts. */
        .us_per_ts_scale = PCAN_USB_TS_US_PER_TICK, /* us=(ts*scale) */
        .us_per_ts_shift = PCAN_USB_TS_DIV_SHIFTER, /*  >> shift     */

        /* give here messages in/out endpoints */
        .ep_msg_in = PCAN_USB_EP_MSGIN,
        .ep_msg_out = {PCAN_USB_EP_MSGOUT},

        /* size of rx/tx usb buffers */
        .rx_buffer_size = PCAN_USB_RX_BUFFER_SIZE,
        .tx_buffer_size = PCAN_USB_TX_BUFFER_SIZE,

        /* device callbacks */
        .intf_probe = pcan_usb_probe,
        .dev_init = pcan_usb_init,
        .dev_set_bus = pcan_usb_write_mode,
        .dev_set_bittiming = pcan_usb_set_bittiming,
        .dev_get_device_id = pcan_usb_get_device_id,
        .dev_decode_buf = pcan_usb_decode_buf,
        .dev_encode_msg = pcan_usb_encode_msg,
        .dev_start = pcan_usb_start,
        .dev_restart_async = pcan_usb_restart_async,
        .do_get_berr_counter = pcan_usb_get_berr_counter,
};