// SPDX-License-Identifier: GPL-2.0

/* Driver for ETAS GmbH ES58X USB CAN(-FD) Bus Interfaces.
 *
 * File es58x_core.c: Core logic to manage the network devices and the
 * USB interface.
 *
 * Copyright (c) 2019 Robert Bosch Engineering and Business Solutions. All rights reserved.
 * Copyright (c) 2020 ETAS K.K.. All rights reserved.
 * Copyright (c) 2020, 2021 Vincent Mailhol <mailhol.vincent@wanadoo.fr>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/crc16.h>
#include <asm/unaligned.h>

#include "es58x_core.h"

#define DRV_VERSION "1.00"
MODULE_AUTHOR("Mailhol Vincent <mailhol.vincent@wanadoo.fr>");
MODULE_AUTHOR("Arunachalam Santhanam <arunachalam.santhanam@in.bosch.com>");
MODULE_DESCRIPTION("Socket CAN driver for ETAS ES58X USB adapters");
MODULE_VERSION(DRV_VERSION);
MODULE_LICENSE("GPL v2");

#define ES58X_MODULE_NAME "etas_es58x"
#define ES58X_VENDOR_ID 0x108C
#define ES581_4_PRODUCT_ID 0x0159
#define ES582_1_PRODUCT_ID 0x0168
#define ES584_1_PRODUCT_ID 0x0169

/* ES58X FD has some interface protocols unsupported by this driver. */
#define ES58X_FD_INTERFACE_PROTOCOL 0

/* Table of devices which work with this driver. */
static const struct usb_device_id es58x_id_table[] = {
        {
                /* ETAS GmbH ES581.4 USB dual-channel CAN Bus Interface module. */
                USB_DEVICE(ES58X_VENDOR_ID, ES581_4_PRODUCT_ID),
                .driver_info = ES58X_DUAL_CHANNEL
        }, {
                /* ETAS GmbH ES582.1 USB dual-channel CAN FD Bus Interface module. */
                USB_DEVICE_INTERFACE_PROTOCOL(ES58X_VENDOR_ID, ES582_1_PRODUCT_ID,
                                              ES58X_FD_INTERFACE_PROTOCOL),
                .driver_info = ES58X_DUAL_CHANNEL | ES58X_FD_FAMILY
        }, {
                /* ETAS GmbH ES584.1 USB single-channel CAN FD Bus Interface module. */
                USB_DEVICE_INTERFACE_PROTOCOL(ES58X_VENDOR_ID, ES584_1_PRODUCT_ID,
                                              ES58X_FD_INTERFACE_PROTOCOL),
                .driver_info = ES58X_FD_FAMILY
        }, {
                /* Terminating entry */
        }
};

MODULE_DEVICE_TABLE(usb, es58x_id_table);

#define es58x_print_hex_dump(buf, len)                                  \
        print_hex_dump(KERN_DEBUG,                                      \
                       ES58X_MODULE_NAME " " __stringify(buf) ": ",     \
                       DUMP_PREFIX_NONE, 16, 1, buf, len, false)

#define es58x_print_hex_dump_debug(buf, len)                             \
        print_hex_dump_debug(ES58X_MODULE_NAME " " __stringify(buf) ": ",\
                             DUMP_PREFIX_NONE, 16, 1, buf, len, false)

/* The last two bytes of an ES58X command is a CRC16. The first two
 * bytes (the start of frame) are skipped and the CRC calculation
 * starts on the third byte.
 */
#define ES58X_CRC_CALC_OFFSET 2

/**
 * es58x_calculate_crc() - Compute the crc16 of a given URB.
 * @urb_cmd: The URB command for which we want to calculate the CRC.
 * @urb_len: Length of @urb_cmd. Must be at least bigger than 4
 *      (ES58X_CRC_CALC_OFFSET + sizeof(crc))
 *
 * Return: crc16 value.
 */
static u16 es58x_calculate_crc(const union es58x_urb_cmd *urb_cmd, u16 urb_len)
{
        u16 crc;
        ssize_t len = urb_len - ES58X_CRC_CALC_OFFSET - sizeof(crc);

        crc = crc16(0, &urb_cmd->raw_cmd[ES58X_CRC_CALC_OFFSET], len);
        return crc;
}

/**
 * es58x_get_crc() - Get the CRC value of a given URB.
 * @urb_cmd: The URB command for which we want to get the CRC.
 * @urb_len: Length of @urb_cmd. Must be at least bigger than 4
 *      (ES58X_CRC_CALC_OFFSET + sizeof(crc))
 *
 * Return: crc16 value.
 */
static u16 es58x_get_crc(const union es58x_urb_cmd *urb_cmd, u16 urb_len)
{
        u16 crc;
        const __le16 *crc_addr;

        crc_addr = (__le16 *)&urb_cmd->raw_cmd[urb_len - sizeof(crc)];
        crc = get_unaligned_le16(crc_addr);
        return crc;
}

/**
 * es58x_set_crc() - Set the CRC value of a given URB.
 * @urb_cmd: The URB command for which we want to get the CRC.
 * @urb_len: Length of @urb_cmd. Must be at least bigger than 4
 *      (ES58X_CRC_CALC_OFFSET + sizeof(crc))
 */
static void es58x_set_crc(union es58x_urb_cmd *urb_cmd, u16 urb_len)
{
        u16 crc;
        __le16 *crc_addr;

        crc = es58x_calculate_crc(urb_cmd, urb_len);
        crc_addr = (__le16 *)&urb_cmd->raw_cmd[urb_len - sizeof(crc)];
        put_unaligned_le16(crc, crc_addr);
}

/**
 * es58x_check_crc() - Validate the CRC value of a given URB.
 * @es58x_dev: ES58X device.
 * @urb_cmd: The URB command for which we want to check the CRC.
 * @urb_len: Length of @urb_cmd. Must be at least bigger than 4
 *      (ES58X_CRC_CALC_OFFSET + sizeof(crc))
 *
 * Return: zero on success, -EBADMSG if the CRC check fails.
 */
static int es58x_check_crc(struct es58x_device *es58x_dev,
                           const union es58x_urb_cmd *urb_cmd, u16 urb_len)
{
        u16 calculated_crc = es58x_calculate_crc(urb_cmd, urb_len);
        u16 expected_crc = es58x_get_crc(urb_cmd, urb_len);

        if (expected_crc != calculated_crc) {
                dev_err_ratelimited(es58x_dev->dev,
                                    "%s: Bad CRC, urb_len: %d\n",
                                    __func__, urb_len);
                return -EBADMSG;
        }

        return 0;
}

/**
 * es58x_timestamp_to_ns() - Convert a timestamp value received from a
 *      ES58X device to nanoseconds.
 * @timestamp: Timestamp received from a ES58X device.
 *
 * The timestamp received from ES58X is expressed in multiples of 0.5
 * micro seconds. This function converts it in to nanoseconds.
 *
 * Return: Timestamp value in nanoseconds.
 */
static u64 es58x_timestamp_to_ns(u64 timestamp)
{
        const u64 es58x_timestamp_ns_mult_coef = 500ULL;

        return es58x_timestamp_ns_mult_coef * timestamp;
}

/**
 * es58x_set_skb_timestamp() - Set the hardware timestamp of an skb.
 * @netdev: CAN network device.
 * @skb: socket buffer of a CAN message.
 * @timestamp: Timestamp received from an ES58X device.
 *
 * Used for both received and echo messages.
 */
static void es58x_set_skb_timestamp(struct net_device *netdev,
                                    struct sk_buff *skb, u64 timestamp)
{
        struct es58x_device *es58x_dev = es58x_priv(netdev)->es58x_dev;
        struct skb_shared_hwtstamps *hwts;

        hwts = skb_hwtstamps(skb);
        /* Ignoring overflow (overflow on 64 bits timestamp with nano
         * second precision would occur after more than 500 years).
         */
        hwts->hwtstamp = ns_to_ktime(es58x_timestamp_to_ns(timestamp) +
                                     es58x_dev->realtime_diff_ns);
}

/**
 * es58x_rx_timestamp() - Handle a received timestamp.
 * @es58x_dev: ES58X device.
 * @timestamp: Timestamp received from a ES58X device.
 *
 * Calculate the difference between the ES58X device and the kernel
 * internal clocks. This difference will be later used as an offset to
 * convert the timestamps of RX and echo messages to match the kernel
 * system time (e.g. convert to UNIX time).
 */
void es58x_rx_timestamp(struct es58x_device *es58x_dev, u64 timestamp)
{
        u64 ktime_real_ns = ktime_get_real_ns();
        u64 device_timestamp = es58x_timestamp_to_ns(timestamp);

        dev_dbg(es58x_dev->dev, "%s: request round-trip time: %llu ns\n",
                __func__, ktime_real_ns - es58x_dev->ktime_req_ns);

        es58x_dev->realtime_diff_ns =
            (es58x_dev->ktime_req_ns + ktime_real_ns) / 2 - device_timestamp;
        es58x_dev->ktime_req_ns = 0;

        dev_dbg(es58x_dev->dev,
                "%s: Device timestamp: %llu, diff with kernel: %llu\n",
                __func__, device_timestamp, es58x_dev->realtime_diff_ns);
}

/**
 * es58x_set_realtime_diff_ns() - Calculate difference between the
 *      clocks of the ES58X device and the kernel
 * @es58x_dev: ES58X device.
 *
 * Request a timestamp from the ES58X device. Once the answer is
 * received, the timestamp difference will be set by the callback
 * function es58x_rx_timestamp().
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_set_realtime_diff_ns(struct es58x_device *es58x_dev)
{
        if (es58x_dev->ktime_req_ns) {
                dev_warn(es58x_dev->dev,
                         "%s: Previous request to set timestamp has not completed yet\n",
                         __func__);
                return -EBUSY;
        }

        es58x_dev->ktime_req_ns = ktime_get_real_ns();
        return es58x_dev->ops->get_timestamp(es58x_dev);
}

/**
 * es58x_is_can_state_active() - Is the network device in an active
 *      CAN state?
 * @netdev: CAN network device.
 *
 * The device is considered active if it is able to send or receive
 * CAN frames, that is to say if it is in any of
 * CAN_STATE_ERROR_ACTIVE, CAN_STATE_ERROR_WARNING or
 * CAN_STATE_ERROR_PASSIVE states.
 *
 * Caution: when recovering from a bus-off,
 * net/core/dev.c#can_restart() will call
 * net/core/dev.c#can_flush_echo_skb() without using any kind of
 * locks. For this reason, it is critical to guarantee that no TX or
 * echo operations (i.e. any access to priv->echo_skb[]) can be done
 * while this function is returning false.
 *
 * Return: true if the device is active, else returns false.
 */
static bool es58x_is_can_state_active(struct net_device *netdev)
{
        return es58x_priv(netdev)->can.state < CAN_STATE_BUS_OFF;
}

/**
 * es58x_is_echo_skb_threshold_reached() - Determine the limit of how
 *      many skb slots can be taken before we should stop the network
 *      queue.
 * @priv: ES58X private parameters related to the network device.
 *
 * We need to save enough free skb slots in order to be able to do
 * bulk send. This function can be used to determine when to wake or
 * stop the network queue in regard to the number of skb slots already
 * taken if the echo FIFO.
 *
 * Return: boolean.
 */
static bool es58x_is_echo_skb_threshold_reached(struct es58x_priv *priv)
{
        u32 num_echo_skb =  priv->tx_head - priv->tx_tail;
        u32 threshold = priv->can.echo_skb_max -
                priv->es58x_dev->param->tx_bulk_max + 1;

        return num_echo_skb >= threshold;
}

/**
 * es58x_can_free_echo_skb_tail() - Remove the oldest echo skb of the
 *      echo FIFO.
 * @netdev: CAN network device.
 *
 * Naming convention: the tail is the beginning of the FIFO, i.e. the
 * first skb to have entered the FIFO.
 */
static void es58x_can_free_echo_skb_tail(struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        u16 fifo_mask = priv->es58x_dev->param->fifo_mask;
        unsigned int frame_len = 0;

        can_free_echo_skb(netdev, priv->tx_tail & fifo_mask, &frame_len);
        netdev_completed_queue(netdev, 1, frame_len);

        priv->tx_tail++;

        netdev->stats.tx_dropped++;
}

/**
 * es58x_can_get_echo_skb_recovery() - Try to re-sync the echo FIFO.
 * @netdev: CAN network device.
 * @rcv_packet_idx: Index
 *
 * This function should not be called under normal circumstances. In
 * the unlikely case that one or several URB packages get dropped by
 * the device, the index will get out of sync. Try to recover by
 * dropping the echo skb packets with older indexes.
 *
 * Return: zero if recovery was successful, -EINVAL otherwise.
 */
static int es58x_can_get_echo_skb_recovery(struct net_device *netdev,
                                           u32 rcv_packet_idx)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        int ret = 0;

        netdev->stats.tx_errors++;

        if (net_ratelimit())
                netdev_warn(netdev,
                            "Bad echo packet index: %u. First index: %u, end index %u, num_echo_skb: %02u/%02u\n",
                            rcv_packet_idx, priv->tx_tail, priv->tx_head,
                            priv->tx_head - priv->tx_tail,
                            priv->can.echo_skb_max);

        if ((s32)(rcv_packet_idx - priv->tx_tail) < 0) {
                if (net_ratelimit())
                        netdev_warn(netdev,
                                    "Received echo index is from the past. Ignoring it\n");
                ret = -EINVAL;
        } else if ((s32)(rcv_packet_idx - priv->tx_head) >= 0) {
                if (net_ratelimit())
                        netdev_err(netdev,
                                   "Received echo index is from the future. Ignoring it\n");
                ret = -EINVAL;
        } else {
                if (net_ratelimit())
                        netdev_warn(netdev,
                                    "Recovery: dropping %u echo skb from index %u to %u\n",
                                    rcv_packet_idx - priv->tx_tail,
                                    priv->tx_tail, rcv_packet_idx - 1);
                while (priv->tx_tail != rcv_packet_idx) {
                        if (priv->tx_tail == priv->tx_head)
                                return -EINVAL;
                        es58x_can_free_echo_skb_tail(netdev);
                }
        }
        return ret;
}

/**
 * es58x_can_get_echo_skb() - Get the skb from the echo FIFO and loop
 *      it back locally.
 * @netdev: CAN network device.
 * @rcv_packet_idx: Index of the first packet received from the device.
 * @tstamps: Array of hardware timestamps received from a ES58X device.
 * @pkts: Number of packets (and so, length of @tstamps).
 *
 * Callback function for when we receive a self reception
 * acknowledgment.  Retrieves the skb from the echo FIFO, sets its
 * hardware timestamp (the actual time it was sent) and loops it back
 * locally.
 *
 * The device has to be active (i.e. network interface UP and not in
 * bus off state or restarting).
 *
 * Packet indexes must be consecutive (i.e. index of first packet is
 * @rcv_packet_idx, index of second packet is @rcv_packet_idx + 1 and
 * index of last packet is @rcv_packet_idx + @pkts - 1).
 *
 * Return: zero on success.
 */
int es58x_can_get_echo_skb(struct net_device *netdev, u32 rcv_packet_idx,
                           u64 *tstamps, unsigned int pkts)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        unsigned int rx_total_frame_len = 0;
        unsigned int num_echo_skb = priv->tx_head - priv->tx_tail;
        int i;
        u16 fifo_mask = priv->es58x_dev->param->fifo_mask;

        if (!netif_running(netdev)) {
                if (net_ratelimit())
                        netdev_info(netdev,
                                    "%s: %s is down, dropping %d echo packets\n",
                                    __func__, netdev->name, pkts);
                netdev->stats.tx_dropped += pkts;
                return 0;
        } else if (!es58x_is_can_state_active(netdev)) {
                if (net_ratelimit())
                        netdev_dbg(netdev,
                                   "Bus is off or device is restarting. Ignoring %u echo packets from index %u\n",
                                   pkts, rcv_packet_idx);
                /* stats.tx_dropped will be (or was already)
                 * incremented by
                 * drivers/net/can/net/dev.c:can_flush_echo_skb().
                 */
                return 0;
        } else if (num_echo_skb == 0) {
                if (net_ratelimit())
                        netdev_warn(netdev,
                                    "Received %u echo packets from index: %u but echo skb queue is empty.\n",
                                    pkts, rcv_packet_idx);
                netdev->stats.tx_dropped += pkts;
                return 0;
        }

        if (priv->tx_tail != rcv_packet_idx) {
                if (es58x_can_get_echo_skb_recovery(netdev, rcv_packet_idx) < 0) {
                        if (net_ratelimit())
                                netdev_warn(netdev,
                                            "Could not find echo skb for echo packet index: %u\n",
                                            rcv_packet_idx);
                        return 0;
                }
        }
        if (num_echo_skb < pkts) {
                int pkts_drop = pkts - num_echo_skb;

                if (net_ratelimit())
                        netdev_err(netdev,
                                   "Received %u echo packets but have only %d echo skb. Dropping %d echo skb\n",
                                   pkts, num_echo_skb, pkts_drop);
                netdev->stats.tx_dropped += pkts_drop;
                pkts -= pkts_drop;
        }

        for (i = 0; i < pkts; i++) {
                unsigned int skb_idx = priv->tx_tail & fifo_mask;
                struct sk_buff *skb = priv->can.echo_skb[skb_idx];
                unsigned int frame_len = 0;

                if (skb)
                        es58x_set_skb_timestamp(netdev, skb, tstamps[i]);

                netdev->stats.tx_bytes += can_get_echo_skb(netdev, skb_idx,
                                                           &frame_len);
                rx_total_frame_len += frame_len;

                priv->tx_tail++;
        }

        netdev_completed_queue(netdev, pkts, rx_total_frame_len);
        netdev->stats.tx_packets += pkts;

        priv->err_passive_before_rtx_success = 0;
        if (!es58x_is_echo_skb_threshold_reached(priv))
                netif_wake_queue(netdev);

        return 0;
}

/**
 * es58x_can_reset_echo_fifo() - Reset the echo FIFO.
 * @netdev: CAN network device.
 *
 * The echo_skb array of struct can_priv will be flushed by
 * drivers/net/can/dev.c:can_flush_echo_skb(). This function resets
 * the parameters of the struct es58x_priv of our device and reset the
 * queue (c.f. BQL).
 */
static void es58x_can_reset_echo_fifo(struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);

        priv->tx_tail = 0;
        priv->tx_head = 0;
        priv->tx_urb = NULL;
        priv->err_passive_before_rtx_success = 0;
        netdev_reset_queue(netdev);
}

/**
 * es58x_flush_pending_tx_msg() - Reset the buffer for transmission messages.
 * @netdev: CAN network device.
 *
 * es58x_start_xmit() will queue up to tx_bulk_max messages in
 * &tx_urb buffer and do a bulk send of all messages in one single URB
 * (c.f. xmit_more flag). When the device recovers from a bus off
 * state or when the device stops, the tx_urb buffer might still have
 * pending messages in it and thus need to be flushed.
 */
static void es58x_flush_pending_tx_msg(struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        struct es58x_device *es58x_dev = priv->es58x_dev;

        if (priv->tx_urb) {
                netdev_warn(netdev, "%s: dropping %d TX messages\n",
                            __func__, priv->tx_can_msg_cnt);
                netdev->stats.tx_dropped += priv->tx_can_msg_cnt;
                while (priv->tx_can_msg_cnt > 0) {
                        unsigned int frame_len = 0;
                        u16 fifo_mask = priv->es58x_dev->param->fifo_mask;

                        priv->tx_head--;
                        priv->tx_can_msg_cnt--;
                        can_free_echo_skb(netdev, priv->tx_head & fifo_mask,
                                          &frame_len);
                        netdev_completed_queue(netdev, 1, frame_len);
                }
                usb_anchor_urb(priv->tx_urb, &priv->es58x_dev->tx_urbs_idle);
                atomic_inc(&es58x_dev->tx_urbs_idle_cnt);
                usb_free_urb(priv->tx_urb);
        }
        priv->tx_urb = NULL;
}

/**
 * es58x_tx_ack_msg() - Handle acknowledgment messages.
 * @netdev: CAN network device.
 * @tx_free_entries: Number of free entries in the device transmit FIFO.
 * @rx_cmd_ret_u32: error code as returned by the ES58X device.
 *
 * ES58X sends an acknowledgment message after a transmission request
 * is done. This is mandatory for the ES581.4 but is optional (and
 * deactivated in this driver) for the ES58X_FD family.
 *
 * Under normal circumstances, this function should never throw an
 * error message.
 *
 * Return: zero on success, errno when any error occurs.
 */
int es58x_tx_ack_msg(struct net_device *netdev, u16 tx_free_entries,
                     enum es58x_ret_u32 rx_cmd_ret_u32)
{
        struct es58x_priv *priv = es58x_priv(netdev);

        if (tx_free_entries <= priv->es58x_dev->param->tx_bulk_max) {
                if (net_ratelimit())
                        netdev_err(netdev,
                                   "Only %d entries left in device queue, num_echo_skb: %d/%d\n",
                                   tx_free_entries,
                                   priv->tx_head - priv->tx_tail,
                                   priv->can.echo_skb_max);
                netif_stop_queue(netdev);
        }

        return es58x_rx_cmd_ret_u32(netdev, ES58X_RET_TYPE_TX_MSG,
                                    rx_cmd_ret_u32);
}

/**
 * es58x_rx_can_msg() - Handle a received a CAN message.
 * @netdev: CAN network device.
 * @timestamp: Hardware time stamp (only relevant in rx branches).
 * @data: CAN payload.
 * @can_id: CAN ID.
 * @es58x_flags: Please refer to enum es58x_flag.
 * @dlc: Data Length Code (raw value).
 *
 * Fill up a CAN skb and post it.
 *
 * This function handles the case where the DLC of a classical CAN
 * frame is greater than CAN_MAX_DLEN (c.f. the len8_dlc field of
 * struct can_frame).
 *
 * Return: zero on success.
 */
int es58x_rx_can_msg(struct net_device *netdev, u64 timestamp, const u8 *data,
                     canid_t can_id, enum es58x_flag es58x_flags, u8 dlc)
{
        struct canfd_frame *cfd;
        struct can_frame *ccf;
        struct sk_buff *skb;
        u8 len;
        bool is_can_fd = !!(es58x_flags & ES58X_FLAG_FD_DATA);

        if (dlc > CAN_MAX_RAW_DLC) {
                netdev_err(netdev,
                           "%s: DLC is %d but maximum should be %d\n",
                           __func__, dlc, CAN_MAX_RAW_DLC);
                return -EMSGSIZE;
        }

        if (is_can_fd) {
                len = can_fd_dlc2len(dlc);
                skb = alloc_canfd_skb(netdev, &cfd);
        } else {
                len = can_cc_dlc2len(dlc);
                skb = alloc_can_skb(netdev, &ccf);
                cfd = (struct canfd_frame *)ccf;
        }
        if (!skb) {
                netdev->stats.rx_dropped++;
                return 0;
        }

        cfd->can_id = can_id;
        if (es58x_flags & ES58X_FLAG_EFF)
                cfd->can_id |= CAN_EFF_FLAG;
        if (is_can_fd) {
                cfd->len = len;
                if (es58x_flags & ES58X_FLAG_FD_BRS)
                        cfd->flags |= CANFD_BRS;
                if (es58x_flags & ES58X_FLAG_FD_ESI)
                        cfd->flags |= CANFD_ESI;
        } else {
                can_frame_set_cc_len(ccf, dlc, es58x_priv(netdev)->can.ctrlmode);
                if (es58x_flags & ES58X_FLAG_RTR) {
                        ccf->can_id |= CAN_RTR_FLAG;
                        len = 0;
                }
        }
        memcpy(cfd->data, data, len);
        netdev->stats.rx_packets++;
        netdev->stats.rx_bytes += len;

        es58x_set_skb_timestamp(netdev, skb, timestamp);
        netif_rx(skb);

        es58x_priv(netdev)->err_passive_before_rtx_success = 0;

        return 0;
}

/**
 * es58x_rx_err_msg() - Handle a received CAN event or error message.
 * @netdev: CAN network device.
 * @error: Error code.
 * @event: Event code.
 * @timestamp: Timestamp received from a ES58X device.
 *
 * Handle the errors and events received by the ES58X device, create
 * a CAN error skb and post it.
 *
 * In some rare cases the devices might get stuck alternating between
 * CAN_STATE_ERROR_PASSIVE and CAN_STATE_ERROR_WARNING. To prevent
 * this behavior, we force a bus off state if the device goes in
 * CAN_STATE_ERROR_WARNING for ES58X_MAX_CONSECUTIVE_WARN consecutive
 * times with no successful transmission or reception in between.
 *
 * Once the device is in bus off state, the only way to restart it is
 * through the drivers/net/can/dev.c:can_restart() function. The
 * device is technically capable to recover by itself under certain
 * circumstances, however, allowing self recovery would create
 * complex race conditions with drivers/net/can/dev.c:can_restart()
 * and thus was not implemented. To activate automatic restart, please
 * set the restart-ms parameter (e.g. ip link set can0 type can
 * restart-ms 100).
 *
 * If the bus is really instable, this function would try to send a
 * lot of log messages. Those are rate limited (i.e. you will see
 * messages such as "net_ratelimit: XXX callbacks suppressed" in
 * dmesg).
 *
 * Return: zero on success, errno when any error occurs.
 */
int es58x_rx_err_msg(struct net_device *netdev, enum es58x_err error,
                     enum es58x_event event, u64 timestamp)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        struct can_priv *can = netdev_priv(netdev);
        struct can_device_stats *can_stats = &can->can_stats;
        struct can_frame *cf = NULL;
        struct sk_buff *skb;
        int ret;

        if (!netif_running(netdev)) {
                if (net_ratelimit())
                        netdev_info(netdev, "%s: %s is down, dropping packet\n",
                                    __func__, netdev->name);
                netdev->stats.rx_dropped++;
                return 0;
        }

        if (error == ES58X_ERR_OK && event == ES58X_EVENT_OK) {
                netdev_err(netdev, "%s: Both error and event are zero\n",
                           __func__);
                return -EINVAL;
        }

        skb = alloc_can_err_skb(netdev, &cf);

        switch (error) {
        case ES58X_ERR_OK:      /* 0: No error */
                break;

        case ES58X_ERR_PROT_STUFF:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error BITSTUFF\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_STUFF;
                break;

        case ES58X_ERR_PROT_FORM:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error FORMAT\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_FORM;
                break;

        case ES58X_ERR_ACK:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error ACK\n");
                if (cf)
                        cf->can_id |= CAN_ERR_ACK;
                break;

        case ES58X_ERR_PROT_BIT:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error BIT\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_BIT;
                break;

        case ES58X_ERR_PROT_CRC:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error CRC\n");
                if (cf)
                        cf->data[3] |= CAN_ERR_PROT_LOC_CRC_SEQ;
                break;

        case ES58X_ERR_PROT_BIT1:
                if (net_ratelimit())
                        netdev_dbg(netdev,
                                   "Error: expected a recessive bit but monitored a dominant one\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_BIT1;
                break;

        case ES58X_ERR_PROT_BIT0:
                if (net_ratelimit())
                        netdev_dbg(netdev,
                                   "Error expected a dominant bit but monitored a recessive one\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_BIT0;
                break;

        case ES58X_ERR_PROT_OVERLOAD:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Error OVERLOAD\n");
                if (cf)
                        cf->data[2] |= CAN_ERR_PROT_OVERLOAD;
                break;

        case ES58X_ERR_PROT_UNSPEC:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Unspecified error\n");
                if (cf)
                        cf->can_id |= CAN_ERR_PROT;
                break;

        default:
                if (net_ratelimit())
                        netdev_err(netdev,
                                   "%s: Unspecified error code 0x%04X\n",
                                   __func__, (int)error);
                if (cf)
                        cf->can_id |= CAN_ERR_PROT;
                break;
        }

        switch (event) {
        case ES58X_EVENT_OK:    /* 0: No event */
                break;

        case ES58X_EVENT_CRTL_ACTIVE:
                if (can->state == CAN_STATE_BUS_OFF) {
                        netdev_err(netdev,
                                   "%s: state transition: BUS OFF -> ACTIVE\n",
                                   __func__);
                }
                if (net_ratelimit())
                        netdev_dbg(netdev, "Event CAN BUS ACTIVE\n");
                if (cf)
                        cf->data[1] |= CAN_ERR_CRTL_ACTIVE;
                can->state = CAN_STATE_ERROR_ACTIVE;
                break;

        case ES58X_EVENT_CRTL_PASSIVE:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Event CAN BUS PASSIVE\n");
                /* Either TX or RX error count reached passive state
                 * but we do not know which. Setting both flags by
                 * default.
                 */
                if (cf) {
                        cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
                        cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;
                }
                if (can->state < CAN_STATE_BUS_OFF)
                        can->state = CAN_STATE_ERROR_PASSIVE;
                can_stats->error_passive++;
                if (priv->err_passive_before_rtx_success < U8_MAX)
                        priv->err_passive_before_rtx_success++;
                break;

        case ES58X_EVENT_CRTL_WARNING:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Event CAN BUS WARNING\n");
                /* Either TX or RX error count reached warning state
                 * but we do not know which. Setting both flags by
                 * default.
                 */
                if (cf) {
                        cf->data[1] |= CAN_ERR_CRTL_RX_WARNING;
                        cf->data[1] |= CAN_ERR_CRTL_TX_WARNING;
                }
                if (can->state < CAN_STATE_BUS_OFF)
                        can->state = CAN_STATE_ERROR_WARNING;
                can_stats->error_warning++;
                break;

        case ES58X_EVENT_BUSOFF:
                if (net_ratelimit())
                        netdev_dbg(netdev, "Event CAN BUS OFF\n");
                if (cf)
                        cf->can_id |= CAN_ERR_BUSOFF;
                can_stats->bus_off++;
                netif_stop_queue(netdev);
                if (can->state != CAN_STATE_BUS_OFF) {
                        can->state = CAN_STATE_BUS_OFF;
                        can_bus_off(netdev);
                        ret = can->do_set_mode(netdev, CAN_MODE_STOP);
                        if (ret)
                                return ret;
                }
                break;

        case ES58X_EVENT_SINGLE_WIRE:
                if (net_ratelimit())
                        netdev_warn(netdev,
                                    "Lost connection on either CAN high or CAN low\n");
                /* Lost connection on either CAN high or CAN
                 * low. Setting both flags by default.
                 */
                if (cf) {
                        cf->data[4] |= CAN_ERR_TRX_CANH_NO_WIRE;
                        cf->data[4] |= CAN_ERR_TRX_CANL_NO_WIRE;
                }
                break;

        default:
                if (net_ratelimit())
                        netdev_err(netdev,
                                   "%s: Unspecified event code 0x%04X\n",
                                   __func__, (int)event);
                if (cf)
                        cf->can_id |= CAN_ERR_CRTL;
                break;
        }

        /* driver/net/can/dev.c:can_restart() takes in account error
         * messages in the RX stats. Doing the same here for
         * consistency.
         */
        netdev->stats.rx_packets++;
        netdev->stats.rx_bytes += CAN_ERR_DLC;

        if (cf) {
                if (cf->data[1])
                        cf->can_id |= CAN_ERR_CRTL;
                if (cf->data[2] || cf->data[3]) {
                        cf->can_id |= CAN_ERR_PROT;
                        can_stats->bus_error++;
                }
                if (cf->data[4])
                        cf->can_id |= CAN_ERR_TRX;

                es58x_set_skb_timestamp(netdev, skb, timestamp);
                netif_rx(skb);
        }

        if ((event & ES58X_EVENT_CRTL_PASSIVE) &&
            priv->err_passive_before_rtx_success == ES58X_CONSECUTIVE_ERR_PASSIVE_MAX) {
                netdev_info(netdev,
                            "Got %d consecutive warning events with no successful RX or TX. Forcing bus-off\n",
                            priv->err_passive_before_rtx_success);
                return es58x_rx_err_msg(netdev, ES58X_ERR_OK,
                                        ES58X_EVENT_BUSOFF, timestamp);
        }

        return 0;
}

/**
 * es58x_cmd_ret_desc() - Convert a command type to a string.
 * @cmd_ret_type: Type of the command which triggered the return code.
 *
 * The final line (return "<unknown>") should not be reached. If this
 * is the case, there is an implementation bug.
 *
 * Return: a readable description of the @cmd_ret_type.
 */
static const char *es58x_cmd_ret_desc(enum es58x_ret_type cmd_ret_type)
{
        switch (cmd_ret_type) {
        case ES58X_RET_TYPE_SET_BITTIMING:
                return "Set bittiming";
        case ES58X_RET_TYPE_ENABLE_CHANNEL:
                return "Enable channel";
        case ES58X_RET_TYPE_DISABLE_CHANNEL:
                return "Disable channel";
        case ES58X_RET_TYPE_TX_MSG:
                return "Transmit message";
        case ES58X_RET_TYPE_RESET_RX:
                return "Reset RX";
        case ES58X_RET_TYPE_RESET_TX:
                return "Reset TX";
        case ES58X_RET_TYPE_DEVICE_ERR:
                return "Device error";
        }

        return "<unknown>";
};

/**
 * es58x_rx_cmd_ret_u8() - Handle the command's return code received
 *      from the ES58X device.
 * @dev: Device, only used for the dev_XXX() print functions.
 * @cmd_ret_type: Type of the command which triggered the return code.
 * @rx_cmd_ret_u8: Command error code as returned by the ES58X device.
 *
 * Handles the 8 bits command return code. Those are specific to the
 * ES581.4 device. The return value will eventually be used by
 * es58x_handle_urb_cmd() function which will take proper actions in
 * case of critical issues such and memory errors or bad CRC values.
 *
 * In contrast with es58x_rx_cmd_ret_u32(), the network device is
 * unknown.
 *
 * Return: zero on success, return errno when any error occurs.
 */
int es58x_rx_cmd_ret_u8(struct device *dev,
                        enum es58x_ret_type cmd_ret_type,
                        enum es58x_ret_u8 rx_cmd_ret_u8)
{
        const char *ret_desc = es58x_cmd_ret_desc(cmd_ret_type);

        switch (rx_cmd_ret_u8) {
        case ES58X_RET_U8_OK:
                dev_dbg_ratelimited(dev, "%s: OK\n", ret_desc);
                return 0;

        case ES58X_RET_U8_ERR_UNSPECIFIED_FAILURE:
                dev_err(dev, "%s: unspecified failure\n", ret_desc);
                return -EBADMSG;

        case ES58X_RET_U8_ERR_NO_MEM:
                dev_err(dev, "%s: device ran out of memory\n", ret_desc);
                return -ENOMEM;

        case ES58X_RET_U8_ERR_BAD_CRC:
                dev_err(dev, "%s: CRC of previous command is incorrect\n",
                        ret_desc);
                return -EIO;

        default:
                dev_err(dev, "%s: returned unknown value: 0x%02X\n",
                        ret_desc, rx_cmd_ret_u8);
                return -EBADMSG;
        }
}

/**
 * es58x_rx_cmd_ret_u32() - Handle the command return code received
 *      from the ES58X device.
 * @netdev: CAN network device.
 * @cmd_ret_type: Type of the command which triggered the return code.
 * @rx_cmd_ret_u32: error code as returned by the ES58X device.
 *
 * Handles the 32 bits command return code. The return value will
 * eventually be used by es58x_handle_urb_cmd() function which will
 * take proper actions in case of critical issues such and memory
 * errors or bad CRC values.
 *
 * Return: zero on success, errno when any error occurs.
 */
int es58x_rx_cmd_ret_u32(struct net_device *netdev,
                         enum es58x_ret_type cmd_ret_type,
                         enum es58x_ret_u32 rx_cmd_ret_u32)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        const struct es58x_operators *ops = priv->es58x_dev->ops;
        const char *ret_desc = es58x_cmd_ret_desc(cmd_ret_type);

        switch (rx_cmd_ret_u32) {
        case ES58X_RET_U32_OK:
                switch (cmd_ret_type) {
                case ES58X_RET_TYPE_ENABLE_CHANNEL:
                        es58x_can_reset_echo_fifo(netdev);
                        priv->can.state = CAN_STATE_ERROR_ACTIVE;
                        netif_wake_queue(netdev);
                        netdev_info(netdev,
                                    "%s: %s (Serial Number %s): CAN%d channel becomes ready\n",
                                    ret_desc, priv->es58x_dev->udev->product,
                                    priv->es58x_dev->udev->serial,
                                    priv->channel_idx + 1);
                        break;

                case ES58X_RET_TYPE_TX_MSG:
                        if (IS_ENABLED(CONFIG_VERBOSE_DEBUG) && net_ratelimit())
                                netdev_vdbg(netdev, "%s: OK\n", ret_desc);
                        break;

                default:
                        netdev_dbg(netdev, "%s: OK\n", ret_desc);
                        break;
                }
                return 0;

        case ES58X_RET_U32_ERR_UNSPECIFIED_FAILURE:
                if (cmd_ret_type == ES58X_RET_TYPE_ENABLE_CHANNEL) {
                        int ret;

                        netdev_warn(netdev,
                                    "%s: channel is already opened, closing and re-opening it to reflect new configuration\n",
                                    ret_desc);
                        ret = ops->disable_channel(es58x_priv(netdev));
                        if (ret)
                                return ret;
                        return ops->enable_channel(es58x_priv(netdev));
                }
                if (cmd_ret_type == ES58X_RET_TYPE_DISABLE_CHANNEL) {
                        netdev_info(netdev,
                                    "%s: channel is already closed\n", ret_desc);
                        return 0;
                }
                netdev_err(netdev,
                           "%s: unspecified failure\n", ret_desc);
                return -EBADMSG;

        case ES58X_RET_U32_ERR_NO_MEM:
                netdev_err(netdev, "%s: device ran out of memory\n", ret_desc);
                return -ENOMEM;

        case ES58X_RET_U32_WARN_PARAM_ADJUSTED:
                netdev_warn(netdev,
                            "%s: some incompatible parameters have been adjusted\n",
                            ret_desc);
                return 0;

        case ES58X_RET_U32_WARN_TX_MAYBE_REORDER:
                netdev_warn(netdev,
                            "%s: TX messages might have been reordered\n",
                            ret_desc);
                return 0;

        case ES58X_RET_U32_ERR_TIMEDOUT:
                netdev_err(netdev, "%s: command timed out\n", ret_desc);
                return -ETIMEDOUT;

        case ES58X_RET_U32_ERR_FIFO_FULL:
                netdev_warn(netdev, "%s: fifo is full\n", ret_desc);
                return 0;

        case ES58X_RET_U32_ERR_BAD_CONFIG:
                netdev_err(netdev, "%s: bad configuration\n", ret_desc);
                return -EINVAL;

        case ES58X_RET_U32_ERR_NO_RESOURCE:
                netdev_err(netdev, "%s: no resource available\n", ret_desc);
                return -EBUSY;

        default:
                netdev_err(netdev, "%s returned unknown value: 0x%08X\n",
                           ret_desc, rx_cmd_ret_u32);
                return -EBADMSG;
        }
}

/**
 * es58x_increment_rx_errors() - Increment the network devices' error
 *      count.
 * @es58x_dev: ES58X device.
 *
 * If an error occurs on the early stages on receiving an URB command,
 * we might not be able to figure out on which network device the
 * error occurred. In such case, we arbitrarily increment the error
 * count of all the network devices attached to our ES58X device.
 */
static void es58x_increment_rx_errors(struct es58x_device *es58x_dev)
{
        int i;

        for (i = 0; i < es58x_dev->num_can_ch; i++)
                if (es58x_dev->netdev[i])
                        es58x_dev->netdev[i]->stats.rx_errors++;
}

/**
 * es58x_handle_urb_cmd() - Handle the URB command
 * @es58x_dev: ES58X device.
 * @urb_cmd: The URB command received from the ES58X device, might not
 *      be aligned.
 *
 * Sends the URB command to the device specific function. Manages the
 * errors thrown back by those functions.
 */
static void es58x_handle_urb_cmd(struct es58x_device *es58x_dev,
                                 const union es58x_urb_cmd *urb_cmd)
{
        const struct es58x_operators *ops = es58x_dev->ops;
        size_t cmd_len;
        int i, ret;

        ret = ops->handle_urb_cmd(es58x_dev, urb_cmd);
        switch (ret) {
        case 0:         /* OK */
                return;

        case -ENODEV:
                dev_err_ratelimited(es58x_dev->dev, "Device is not ready\n");
                break;

        case -EINVAL:
        case -EMSGSIZE:
        case -EBADRQC:
        case -EBADMSG:
        case -ECHRNG:
        case -ETIMEDOUT:
                cmd_len = es58x_get_urb_cmd_len(es58x_dev,
                                                ops->get_msg_len(urb_cmd));
                dev_err(es58x_dev->dev,
                        "ops->handle_urb_cmd() returned error %pe",
                        ERR_PTR(ret));
                es58x_print_hex_dump(urb_cmd, cmd_len);
                break;

        case -EFAULT:
        case -ENOMEM:
        case -EIO:
        default:
                dev_crit(es58x_dev->dev,
                         "ops->handle_urb_cmd() returned error %pe, detaching all network devices\n",
                         ERR_PTR(ret));
                for (i = 0; i < es58x_dev->num_can_ch; i++)
                        if (es58x_dev->netdev[i])
                                netif_device_detach(es58x_dev->netdev[i]);
                if (es58x_dev->ops->reset_device)
                        es58x_dev->ops->reset_device(es58x_dev);
                break;
        }

        /* Because the urb command could not fully be parsed,
         * channel_id is not confirmed. Incrementing rx_errors count
         * of all channels.
         */
        es58x_increment_rx_errors(es58x_dev);
}

/**
 * es58x_check_rx_urb() - Check the length and format of the URB command.
 * @es58x_dev: ES58X device.
 * @urb_cmd: The URB command received from the ES58X device, might not
 *      be aligned.
 * @urb_actual_len: The actual length of the URB command.
 *
 * Check if the first message of the received urb is valid, that is to
 * say that both the header and the length are coherent.
 *
 * Return:
 * the length of the first message of the URB on success.
 *
 * -ENODATA if the URB command is incomplete (in which case, the URB
 * command should be buffered and combined with the next URB to try to
 * reconstitute the URB command).
 *
 * -EOVERFLOW if the length is bigger than the maximum expected one.
 *
 * -EBADRQC if the start of frame does not match the expected value.
 */
static signed int es58x_check_rx_urb(struct es58x_device *es58x_dev,
                                     const union es58x_urb_cmd *urb_cmd,
                                     u32 urb_actual_len)
{
        const struct device *dev = es58x_dev->dev;
        const struct es58x_parameters *param = es58x_dev->param;
        u16 sof, msg_len;
        signed int urb_cmd_len, ret;

        if (urb_actual_len < param->urb_cmd_header_len) {
                dev_vdbg(dev,
                         "%s: Received %d bytes [%*ph]: header incomplete\n",
                         __func__, urb_actual_len, urb_actual_len,
                         urb_cmd->raw_cmd);
                return -ENODATA;
        }

        sof = get_unaligned_le16(&urb_cmd->sof);
        if (sof != param->rx_start_of_frame) {
                dev_err_ratelimited(es58x_dev->dev,
                                    "%s: Expected sequence 0x%04X for start of frame but got 0x%04X.\n",
                                    __func__, param->rx_start_of_frame, sof);
                return -EBADRQC;
        }

        msg_len = es58x_dev->ops->get_msg_len(urb_cmd);
        urb_cmd_len = es58x_get_urb_cmd_len(es58x_dev, msg_len);
        if (urb_cmd_len > param->rx_urb_cmd_max_len) {
                dev_err_ratelimited(es58x_dev->dev,
                                    "%s: Biggest expected size for rx urb_cmd is %u but receive a command of size %d\n",
                                    __func__,
                                    param->rx_urb_cmd_max_len, urb_cmd_len);
                return -EOVERFLOW;
        } else if (urb_actual_len < urb_cmd_len) {
                dev_vdbg(dev, "%s: Received %02d/%02d bytes\n",
                         __func__, urb_actual_len, urb_cmd_len);
                return -ENODATA;
        }

        ret = es58x_check_crc(es58x_dev, urb_cmd, urb_cmd_len);
        if (ret)
                return ret;

        return urb_cmd_len;
}

/**
 * es58x_copy_to_cmd_buf() - Copy an array to the URB command buffer.
 * @es58x_dev: ES58X device.
 * @raw_cmd: the buffer we want to copy.
 * @raw_cmd_len: length of @raw_cmd.
 *
 * Concatenates @raw_cmd_len bytes of @raw_cmd to the end of the URB
 * command buffer.
 *
 * Return: zero on success, -EMSGSIZE if not enough space is available
 * to do the copy.
 */
static int es58x_copy_to_cmd_buf(struct es58x_device *es58x_dev,
                                 u8 *raw_cmd, int raw_cmd_len)
{
        if (es58x_dev->rx_cmd_buf_len + raw_cmd_len >
            es58x_dev->param->rx_urb_cmd_max_len)
                return -EMSGSIZE;

        memcpy(&es58x_dev->rx_cmd_buf.raw_cmd[es58x_dev->rx_cmd_buf_len],
               raw_cmd, raw_cmd_len);
        es58x_dev->rx_cmd_buf_len += raw_cmd_len;

        return 0;
}

/**
 * es58x_split_urb_try_recovery() - Try to recover bad URB sequences.
 * @es58x_dev: ES58X device.
 * @raw_cmd: pointer to the buffer we want to copy.
 * @raw_cmd_len: length of @raw_cmd.
 *
 * Under some rare conditions, we might get incorrect URBs from the
 * device. From our observations, one of the valid URB gets replaced
 * by one from the past. The full root cause is not identified.
 *
 * This function looks for the next start of frame in the urb buffer
 * in order to try to recover.
 *
 * Such behavior was not observed on the devices of the ES58X FD
 * family and only seems to impact the ES581.4.
 *
 * Return: the number of bytes dropped on success, -EBADMSG if recovery failed.
 */
static int es58x_split_urb_try_recovery(struct es58x_device *es58x_dev,
                                        u8 *raw_cmd, size_t raw_cmd_len)
{
        union es58x_urb_cmd *urb_cmd;
        signed int urb_cmd_len;
        u16 sof;
        int dropped_bytes = 0;

        es58x_increment_rx_errors(es58x_dev);

        while (raw_cmd_len > sizeof(sof)) {
                urb_cmd = (union es58x_urb_cmd *)raw_cmd;
                sof = get_unaligned_le16(&urb_cmd->sof);

                if (sof == es58x_dev->param->rx_start_of_frame) {
                        urb_cmd_len = es58x_check_rx_urb(es58x_dev,
                                                         urb_cmd, raw_cmd_len);
                        if ((urb_cmd_len == -ENODATA) || urb_cmd_len > 0) {
                                dev_info_ratelimited(es58x_dev->dev,
                                                     "Recovery successful! Dropped %d bytes (urb_cmd_len: %d)\n",
                                                     dropped_bytes,
                                                     urb_cmd_len);
                                return dropped_bytes;
                        }
                }
                raw_cmd++;
                raw_cmd_len--;
                dropped_bytes++;
        }

        dev_warn_ratelimited(es58x_dev->dev, "%s: Recovery failed\n", __func__);
        return -EBADMSG;
}

/**
 * es58x_handle_incomplete_cmd() - Reconstitute an URB command from
 *      different URB pieces.
 * @es58x_dev: ES58X device.
 * @urb: last urb buffer received.
 *
 * The device might split the URB commands in an arbitrary amount of
 * pieces. This function concatenates those in an URB buffer until a
 * full URB command is reconstituted and consume it.
 *
 * Return:
 * number of bytes consumed from @urb if successful.
 *
 * -ENODATA if the URB command is still incomplete.
 *
 * -EBADMSG if the URB command is incorrect.
 */
static signed int es58x_handle_incomplete_cmd(struct es58x_device *es58x_dev,
                                              struct urb *urb)
{
        size_t cpy_len;
        signed int urb_cmd_len, tmp_cmd_buf_len, ret;

        tmp_cmd_buf_len = es58x_dev->rx_cmd_buf_len;
        cpy_len = min_t(int, es58x_dev->param->rx_urb_cmd_max_len -
                        es58x_dev->rx_cmd_buf_len, urb->actual_length);
        ret = es58x_copy_to_cmd_buf(es58x_dev, urb->transfer_buffer, cpy_len);
        if (ret < 0)
                return ret;

        urb_cmd_len = es58x_check_rx_urb(es58x_dev, &es58x_dev->rx_cmd_buf,
                                         es58x_dev->rx_cmd_buf_len);
        if (urb_cmd_len == -ENODATA) {
                return -ENODATA;
        } else if (urb_cmd_len < 0) {
                dev_err_ratelimited(es58x_dev->dev,
                                    "Could not reconstitute incomplete command from previous URB, dropping %d bytes\n",
                                    tmp_cmd_buf_len + urb->actual_length);
                dev_err_ratelimited(es58x_dev->dev,
                                    "Error code: %pe, es58x_dev->rx_cmd_buf_len: %d, urb->actual_length: %u\n",
                                    ERR_PTR(urb_cmd_len),
                                    tmp_cmd_buf_len, urb->actual_length);
                es58x_print_hex_dump(&es58x_dev->rx_cmd_buf, tmp_cmd_buf_len);
                es58x_print_hex_dump(urb->transfer_buffer, urb->actual_length);
                return urb->actual_length;
        }

        es58x_handle_urb_cmd(es58x_dev, &es58x_dev->rx_cmd_buf);
        return urb_cmd_len - tmp_cmd_buf_len;   /* consumed length */
}

/**
 * es58x_split_urb() - Cut the received URB in individual URB commands.
 * @es58x_dev: ES58X device.
 * @urb: last urb buffer received.
 *
 * The device might send urb in bulk format (i.e. several URB commands
 * concatenated together). This function will split all the commands
 * contained in the urb.
 *
 * Return:
 * number of bytes consumed from @urb if successful.
 *
 * -ENODATA if the URB command is incomplete.
 *
 * -EBADMSG if the URB command is incorrect.
 */
static signed int es58x_split_urb(struct es58x_device *es58x_dev,
                                  struct urb *urb)
{
        union es58x_urb_cmd *urb_cmd;
        u8 *raw_cmd = urb->transfer_buffer;
        s32 raw_cmd_len = urb->actual_length;
        int ret;

        if (es58x_dev->rx_cmd_buf_len != 0) {
                ret = es58x_handle_incomplete_cmd(es58x_dev, urb);
                if (ret != -ENODATA)
                        es58x_dev->rx_cmd_buf_len = 0;
                if (ret < 0)
                        return ret;

                raw_cmd += ret;
                raw_cmd_len -= ret;
        }

        while (raw_cmd_len > 0) {
                if (raw_cmd[0] == ES58X_HEARTBEAT) {
                        raw_cmd++;
                        raw_cmd_len--;
                        continue;
                }
                urb_cmd = (union es58x_urb_cmd *)raw_cmd;
                ret = es58x_check_rx_urb(es58x_dev, urb_cmd, raw_cmd_len);
                if (ret > 0) {
                        es58x_handle_urb_cmd(es58x_dev, urb_cmd);
                } else if (ret == -ENODATA) {
                        es58x_copy_to_cmd_buf(es58x_dev, raw_cmd, raw_cmd_len);
                        return -ENODATA;
                } else if (ret < 0) {
                        ret = es58x_split_urb_try_recovery(es58x_dev, raw_cmd,
                                                           raw_cmd_len);
                        if (ret < 0)
                                return ret;
                }
                raw_cmd += ret;
                raw_cmd_len -= ret;
        }

        return 0;
}

/**
 * es58x_read_bulk_callback() - Callback for reading data from device.
 * @urb: last urb buffer received.
 *
 * This function gets eventually called each time an URB is received
 * from the ES58X device.
 *
 * Checks urb status, calls read function and resubmits urb read
 * operation.
 */
static void es58x_read_bulk_callback(struct urb *urb)
{
        struct es58x_device *es58x_dev = urb->context;
        const struct device *dev = es58x_dev->dev;
        int i, ret;

        switch (urb->status) {
        case 0:         /* success */
                break;

        case -EOVERFLOW:
                dev_err_ratelimited(dev, "%s: error %pe\n",
                                    __func__, ERR_PTR(urb->status));
                es58x_print_hex_dump_debug(urb->transfer_buffer,
                                           urb->transfer_buffer_length);
                goto resubmit_urb;

        case -EPROTO:
                dev_warn_ratelimited(dev, "%s: error %pe. Device unplugged?\n",
                                     __func__, ERR_PTR(urb->status));
                goto free_urb;

        case -ENOENT:
        case -EPIPE:
                dev_err_ratelimited(dev, "%s: error %pe\n",
                                    __func__, ERR_PTR(urb->status));
                goto free_urb;

        case -ESHUTDOWN:
                dev_dbg_ratelimited(dev, "%s: error %pe\n",
                                    __func__, ERR_PTR(urb->status));
                goto free_urb;

        default:
                dev_err_ratelimited(dev, "%s: error %pe\n",
                                    __func__, ERR_PTR(urb->status));
                goto resubmit_urb;
        }

        ret = es58x_split_urb(es58x_dev, urb);
        if ((ret != -ENODATA) && ret < 0) {
                dev_err(es58x_dev->dev, "es58x_split_urb() returned error %pe",
                        ERR_PTR(ret));
                es58x_print_hex_dump_debug(urb->transfer_buffer,
                                           urb->actual_length);

                /* Because the urb command could not be parsed,
                 * channel_id is not confirmed. Incrementing rx_errors
                 * count of all channels.
                 */
                es58x_increment_rx_errors(es58x_dev);
        }

 resubmit_urb:
        usb_fill_bulk_urb(urb, es58x_dev->udev, es58x_dev->rx_pipe,
                          urb->transfer_buffer, urb->transfer_buffer_length,
                          es58x_read_bulk_callback, es58x_dev);

        ret = usb_submit_urb(urb, GFP_ATOMIC);
        if (ret == -ENODEV) {
                for (i = 0; i < es58x_dev->num_can_ch; i++)
                        if (es58x_dev->netdev[i])
                                netif_device_detach(es58x_dev->netdev[i]);
        } else if (ret)
                dev_err_ratelimited(dev,
                                    "Failed resubmitting read bulk urb: %pe\n",
                                    ERR_PTR(ret));
        return;

 free_urb:
        usb_free_coherent(urb->dev, urb->transfer_buffer_length,
                          urb->transfer_buffer, urb->transfer_dma);
}

/**
 * es58x_write_bulk_callback() - Callback after writing data to the device.
 * @urb: urb buffer which was previously submitted.
 *
 * This function gets eventually called each time an URB was sent to
 * the ES58X device.
 *
 * Puts the @urb back to the urbs idle anchor and tries to restart the
 * network queue.
 */
static void es58x_write_bulk_callback(struct urb *urb)
{
        struct net_device *netdev = urb->context;
        struct es58x_device *es58x_dev = es58x_priv(netdev)->es58x_dev;

        switch (urb->status) {
        case 0:         /* success */
                break;

        case -EOVERFLOW:
                if (net_ratelimit())
                        netdev_err(netdev, "%s: error %pe\n",
                                   __func__, ERR_PTR(urb->status));
                es58x_print_hex_dump(urb->transfer_buffer,
                                     urb->transfer_buffer_length);
                break;

        case -ENOENT:
                if (net_ratelimit())
                        netdev_dbg(netdev, "%s: error %pe\n",
                                   __func__, ERR_PTR(urb->status));
                usb_free_coherent(urb->dev,
                                  es58x_dev->param->tx_urb_cmd_max_len,
                                  urb->transfer_buffer, urb->transfer_dma);
                return;

        default:
                if (net_ratelimit())
                        netdev_info(netdev, "%s: error %pe\n",
                                    __func__, ERR_PTR(urb->status));
                break;
        }

        usb_anchor_urb(urb, &es58x_dev->tx_urbs_idle);
        atomic_inc(&es58x_dev->tx_urbs_idle_cnt);
}

/**
 * es58x_alloc_urb() - Allocate memory for an URB and its transfer
 *      buffer.
 * @es58x_dev: ES58X device.
 * @urb: URB to be allocated.
 * @buf: used to return DMA address of buffer.
 * @buf_len: requested buffer size.
 * @mem_flags: affect whether allocation may block.
 *
 * Allocates an URB and its @transfer_buffer and set its @transfer_dma
 * address.
 *
 * This function is used at start-up to allocate all RX URBs at once
 * and during run time for TX URBs.
 *
 * Return: zero on success, -ENOMEM if no memory is available.
 */
static int es58x_alloc_urb(struct es58x_device *es58x_dev, struct urb **urb,
                           u8 **buf, size_t buf_len, gfp_t mem_flags)
{
        *urb = usb_alloc_urb(0, mem_flags);
        if (!*urb) {
                dev_err(es58x_dev->dev, "No memory left for URBs\n");
                return -ENOMEM;
        }

        *buf = usb_alloc_coherent(es58x_dev->udev, buf_len,
                                  mem_flags, &(*urb)->transfer_dma);
        if (!*buf) {
                dev_err(es58x_dev->dev, "No memory left for USB buffer\n");
                usb_free_urb(*urb);
                return -ENOMEM;
        }

        (*urb)->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

        return 0;
}

/**
 * es58x_get_tx_urb() - Get an URB for transmission.
 * @es58x_dev: ES58X device.
 *
 * Gets an URB from the idle urbs anchor or allocate a new one if the
 * anchor is empty.
 *
 * If there are more than ES58X_TX_URBS_MAX in the idle anchor, do
 * some garbage collection. The garbage collection is done here
 * instead of within es58x_write_bulk_callback() because
 * usb_free_coherent() should not be used in IRQ context:
 * c.f. WARN_ON(irqs_disabled()) in dma_free_attrs().
 *
 * Return: a pointer to an URB on success, NULL if no memory is
 * available.
 */
static struct urb *es58x_get_tx_urb(struct es58x_device *es58x_dev)
{
        atomic_t *idle_cnt = &es58x_dev->tx_urbs_idle_cnt;
        struct urb *urb = usb_get_from_anchor(&es58x_dev->tx_urbs_idle);

        if (!urb) {
                size_t tx_buf_len;
                u8 *buf;

                tx_buf_len = es58x_dev->param->tx_urb_cmd_max_len;
                if (es58x_alloc_urb(es58x_dev, &urb, &buf, tx_buf_len,
                                    GFP_ATOMIC))
                        return NULL;

                usb_fill_bulk_urb(urb, es58x_dev->udev, es58x_dev->tx_pipe,
                                  buf, tx_buf_len, NULL, NULL);
                return urb;
        }

        while (atomic_dec_return(idle_cnt) > ES58X_TX_URBS_MAX) {
                /* Garbage collector */
                struct urb *tmp = usb_get_from_anchor(&es58x_dev->tx_urbs_idle);

                if (!tmp)
                        break;
                usb_free_coherent(tmp->dev,
                                  es58x_dev->param->tx_urb_cmd_max_len,
                                  tmp->transfer_buffer, tmp->transfer_dma);
                usb_free_urb(tmp);
        }

        return urb;
}

/**
 * es58x_submit_urb() - Send data to the device.
 * @es58x_dev: ES58X device.
 * @urb: URB to be sent.
 * @netdev: CAN network device.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_submit_urb(struct es58x_device *es58x_dev, struct urb *urb,
                            struct net_device *netdev)
{
        int ret;

        es58x_set_crc(urb->transfer_buffer, urb->transfer_buffer_length);
        usb_fill_bulk_urb(urb, es58x_dev->udev, es58x_dev->tx_pipe,
                          urb->transfer_buffer, urb->transfer_buffer_length,
                          es58x_write_bulk_callback, netdev);
        usb_anchor_urb(urb, &es58x_dev->tx_urbs_busy);
        ret = usb_submit_urb(urb, GFP_ATOMIC);
        if (ret) {
                netdev_err(netdev, "%s: USB send urb failure: %pe\n",
                           __func__, ERR_PTR(ret));
                usb_unanchor_urb(urb);
                usb_free_coherent(urb->dev,
                                  es58x_dev->param->tx_urb_cmd_max_len,
                                  urb->transfer_buffer, urb->transfer_dma);
        }
        usb_free_urb(urb);

        return ret;
}

/**
 * es58x_send_msg() - Prepare an URB and submit it.
 * @es58x_dev: ES58X device.
 * @cmd_type: Command type.
 * @cmd_id: Command ID.
 * @msg: ES58X message to be sent.
 * @msg_len: Length of @msg.
 * @channel_idx: Index of the network device.
 *
 * Creates an URB command from a given message, sets the header and the
 * CRC and then submits it.
 *
 * Return: zero on success, errno when any error occurs.
 */
int es58x_send_msg(struct es58x_device *es58x_dev, u8 cmd_type, u8 cmd_id,
                   const void *msg, u16 msg_len, int channel_idx)
{
        struct net_device *netdev;
        union es58x_urb_cmd *urb_cmd;
        struct urb *urb;
        int urb_cmd_len;

        if (channel_idx == ES58X_CHANNEL_IDX_NA)
                netdev = es58x_dev->netdev[0];  /* Default to first channel */
        else
                netdev = es58x_dev->netdev[channel_idx];

        urb_cmd_len = es58x_get_urb_cmd_len(es58x_dev, msg_len);
        if (urb_cmd_len > es58x_dev->param->tx_urb_cmd_max_len)
                return -EOVERFLOW;

        urb = es58x_get_tx_urb(es58x_dev);
        if (!urb)
                return -ENOMEM;

        urb_cmd = urb->transfer_buffer;
        es58x_dev->ops->fill_urb_header(urb_cmd, cmd_type, cmd_id,
                                        channel_idx, msg_len);
        memcpy(&urb_cmd->raw_cmd[es58x_dev->param->urb_cmd_header_len],
               msg, msg_len);
        urb->transfer_buffer_length = urb_cmd_len;

        return es58x_submit_urb(es58x_dev, urb, netdev);
}

/**
 * es58x_alloc_rx_urbs() - Allocate RX URBs.
 * @es58x_dev: ES58X device.
 *
 * Allocate URBs for reception and anchor them.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_alloc_rx_urbs(struct es58x_device *es58x_dev)
{
        const struct device *dev = es58x_dev->dev;
        const struct es58x_parameters *param = es58x_dev->param;
        size_t rx_buf_len = es58x_dev->rx_max_packet_size;
        struct urb *urb;
        u8 *buf;
        int i;
        int ret = -EINVAL;

        for (i = 0; i < param->rx_urb_max; i++) {
                ret = es58x_alloc_urb(es58x_dev, &urb, &buf, rx_buf_len,
                                      GFP_KERNEL);
                if (ret)
                        break;

                usb_fill_bulk_urb(urb, es58x_dev->udev, es58x_dev->rx_pipe,
                                  buf, rx_buf_len, es58x_read_bulk_callback,
                                  es58x_dev);
                usb_anchor_urb(urb, &es58x_dev->rx_urbs);

                ret = usb_submit_urb(urb, GFP_KERNEL);
                if (ret) {
                        usb_unanchor_urb(urb);
                        usb_free_coherent(es58x_dev->udev, rx_buf_len,
                                          buf, urb->transfer_dma);
                        usb_free_urb(urb);
                        break;
                }
                usb_free_urb(urb);
        }

        if (i == 0) {
                dev_err(dev, "%s: Could not setup any rx URBs\n", __func__);
                return ret;
        }
        dev_dbg(dev, "%s: Allocated %d rx URBs each of size %zu\n",
                __func__, i, rx_buf_len);

        return ret;
}

/**
 * es58x_free_urbs() - Free all the TX and RX URBs.
 * @es58x_dev: ES58X device.
 */
static void es58x_free_urbs(struct es58x_device *es58x_dev)
{
        struct urb *urb;

        if (!usb_wait_anchor_empty_timeout(&es58x_dev->tx_urbs_busy, 1000)) {
                dev_err(es58x_dev->dev, "%s: Timeout, some TX urbs still remain\n",
                        __func__);
                usb_kill_anchored_urbs(&es58x_dev->tx_urbs_busy);
        }

        while ((urb = usb_get_from_anchor(&es58x_dev->tx_urbs_idle)) != NULL) {
                usb_free_coherent(urb->dev, es58x_dev->param->tx_urb_cmd_max_len,
                                  urb->transfer_buffer, urb->transfer_dma);
                usb_free_urb(urb);
                atomic_dec(&es58x_dev->tx_urbs_idle_cnt);
        }
        if (atomic_read(&es58x_dev->tx_urbs_idle_cnt))
                dev_err(es58x_dev->dev,
                        "All idle urbs were freed but tx_urb_idle_cnt is %d\n",
                        atomic_read(&es58x_dev->tx_urbs_idle_cnt));

        usb_kill_anchored_urbs(&es58x_dev->rx_urbs);
}

/**
 * es58x_open() - Enable the network device.
 * @netdev: CAN network device.
 *
 * Called when the network transitions to the up state. Allocate the
 * URB resources if needed and open the channel.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_open(struct net_device *netdev)
{
        struct es58x_device *es58x_dev = es58x_priv(netdev)->es58x_dev;
        int ret;

        if (atomic_inc_return(&es58x_dev->opened_channel_cnt) == 1) {
                ret = es58x_alloc_rx_urbs(es58x_dev);
                if (ret)
                        return ret;

                ret = es58x_set_realtime_diff_ns(es58x_dev);
                if (ret)
                        goto free_urbs;
        }

        ret = open_candev(netdev);
        if (ret)
                goto free_urbs;

        ret = es58x_dev->ops->enable_channel(es58x_priv(netdev));
        if (ret)
                goto free_urbs;

        netif_start_queue(netdev);

        return ret;

 free_urbs:
        if (atomic_dec_and_test(&es58x_dev->opened_channel_cnt))
                es58x_free_urbs(es58x_dev);
        netdev_err(netdev, "%s: Could not open the network device: %pe\n",
                   __func__, ERR_PTR(ret));

        return ret;
}

/**
 * es58x_stop() - Disable the network device.
 * @netdev: CAN network device.
 *
 * Called when the network transitions to the down state. If all the
 * channels of the device are closed, free the URB resources which are
 * not needed anymore.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_stop(struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        struct es58x_device *es58x_dev = priv->es58x_dev;
        int ret;

        netif_stop_queue(netdev);
        ret = es58x_dev->ops->disable_channel(priv);
        if (ret)
                return ret;

        priv->can.state = CAN_STATE_STOPPED;
        es58x_can_reset_echo_fifo(netdev);
        close_candev(netdev);

        es58x_flush_pending_tx_msg(netdev);

        if (atomic_dec_and_test(&es58x_dev->opened_channel_cnt))
                es58x_free_urbs(es58x_dev);

        return 0;
}

/**
 * es58x_xmit_commit() - Send the bulk urb.
 * @netdev: CAN network device.
 *
 * Do the bulk send. This function should be called only once by bulk
 * transmission.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_xmit_commit(struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        int ret;

        if (!es58x_is_can_state_active(netdev))
                return -ENETDOWN;

        if (es58x_is_echo_skb_threshold_reached(priv))
                netif_stop_queue(netdev);

        ret = es58x_submit_urb(priv->es58x_dev, priv->tx_urb, netdev);
        if (ret == 0)
                priv->tx_urb = NULL;

        return ret;
}

/**
 * es58x_xmit_more() - Can we put more packets?
 * @priv: ES58X private parameters related to the network device.
 *
 * Return: true if we can put more, false if it is time to send.
 */
static bool es58x_xmit_more(struct es58x_priv *priv)
{
        unsigned int free_slots =
            priv->can.echo_skb_max - (priv->tx_head - priv->tx_tail);

        return netdev_xmit_more() && free_slots > 0 &&
                priv->tx_can_msg_cnt < priv->es58x_dev->param->tx_bulk_max;
}

/**
 * es58x_start_xmit() - Transmit an skb.
 * @skb: socket buffer of a CAN message.
 * @netdev: CAN network device.
 *
 * Called when a packet needs to be transmitted.
 *
 * This function relies on Byte Queue Limits (BQL). The main benefit
 * is to increase the throughput by allowing bulk transfers
 * (c.f. xmit_more flag).
 *
 * Queues up to tx_bulk_max messages in &tx_urb buffer and does
 * a bulk send of all messages in one single URB.
 *
 * Return: NETDEV_TX_OK regardless of if we could transmit the @skb or
 *      had to drop it.
 */
static netdev_tx_t es58x_start_xmit(struct sk_buff *skb,
                                    struct net_device *netdev)
{
        struct es58x_priv *priv = es58x_priv(netdev);
        struct es58x_device *es58x_dev = priv->es58x_dev;
        unsigned int frame_len;
        int ret;

        if (can_dropped_invalid_skb(netdev, skb)) {
                if (priv->tx_urb)
                        goto xmit_commit;
                return NETDEV_TX_OK;
        }

        if (priv->tx_urb && priv->tx_can_msg_is_fd != can_is_canfd_skb(skb)) {
                /* Can not do bulk send with mixed CAN and CAN FD frames. */
                ret = es58x_xmit_commit(netdev);
                if (ret)
                        goto drop_skb;
        }

        if (!priv->tx_urb) {
                priv->tx_urb = es58x_get_tx_urb(es58x_dev);
                if (!priv->tx_urb) {
                        ret = -ENOMEM;
                        goto drop_skb;
                }
                priv->tx_can_msg_cnt = 0;
                priv->tx_can_msg_is_fd = can_is_canfd_skb(skb);
        }

        ret = es58x_dev->ops->tx_can_msg(priv, skb);
        if (ret)
                goto drop_skb;

        frame_len = can_skb_get_frame_len(skb);
        ret = can_put_echo_skb(skb, netdev,
                               priv->tx_head & es58x_dev->param->fifo_mask,
                               frame_len);
        if (ret)
                goto xmit_failure;
        netdev_sent_queue(netdev, frame_len);

        priv->tx_head++;
        priv->tx_can_msg_cnt++;

 xmit_commit:
        if (!es58x_xmit_more(priv)) {
                ret = es58x_xmit_commit(netdev);
                if (ret)
                        goto xmit_failure;
        }

        return NETDEV_TX_OK;

 drop_skb:
        dev_kfree_skb(skb);
        netdev->stats.tx_dropped++;
 xmit_failure:
        netdev_warn(netdev, "%s: send message failure: %pe\n",
                    __func__, ERR_PTR(ret));
        netdev->stats.tx_errors++;
        es58x_flush_pending_tx_msg(netdev);
        return NETDEV_TX_OK;
}

static const struct net_device_ops es58x_netdev_ops = {
        .ndo_open = es58x_open,
        .ndo_stop = es58x_stop,
        .ndo_start_xmit = es58x_start_xmit
};

/**
 * es58x_set_mode() - Change network device mode.
 * @netdev: CAN network device.
 * @mode: either %CAN_MODE_START, %CAN_MODE_STOP or %CAN_MODE_SLEEP
 *
 * Currently, this function is only used to stop and restart the
 * channel during a bus off event (c.f. es58x_rx_err_msg() and

 * drivers/net/can/dev.c:can_restart() which are the two only
 * callers).
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_set_mode(struct net_device *netdev, enum can_mode mode)
{
        struct es58x_priv *priv = es58x_priv(netdev);

        switch (mode) {
        case CAN_MODE_START:
                switch (priv->can.state) {
                case CAN_STATE_BUS_OFF:
                        return priv->es58x_dev->ops->enable_channel(priv);

                case CAN_STATE_STOPPED:
                        return es58x_open(netdev);

                case CAN_STATE_ERROR_ACTIVE:
                case CAN_STATE_ERROR_WARNING:
                case CAN_STATE_ERROR_PASSIVE:
                default:
                        return 0;
                }

        case CAN_MODE_STOP:
                switch (priv->can.state) {
                case CAN_STATE_STOPPED:
                        return 0;

                case CAN_STATE_ERROR_ACTIVE:
                case CAN_STATE_ERROR_WARNING:
                case CAN_STATE_ERROR_PASSIVE:
                case CAN_STATE_BUS_OFF:
                default:
                        return priv->es58x_dev->ops->disable_channel(priv);
                }

        case CAN_MODE_SLEEP:
        default:
                return -EOPNOTSUPP;
        }
}

/**
 * es58x_init_priv() - Initialize private parameters.
 * @es58x_dev: ES58X device.
 * @priv: ES58X private parameters related to the network device.
 * @channel_idx: Index of the network device.
 */
static void es58x_init_priv(struct es58x_device *es58x_dev,
                            struct es58x_priv *priv, int channel_idx)
{
        const struct es58x_parameters *param = es58x_dev->param;
        struct can_priv *can = &priv->can;

        priv->es58x_dev = es58x_dev;
        priv->channel_idx = channel_idx;
        priv->tx_urb = NULL;
        priv->tx_can_msg_cnt = 0;

        can->bittiming_const = param->bittiming_const;
        if (param->ctrlmode_supported & CAN_CTRLMODE_FD) {
                can->data_bittiming_const = param->data_bittiming_const;
                can->tdc_const = param->tdc_const;
        }
        can->bitrate_max = param->bitrate_max;
        can->clock = param->clock;
        can->state = CAN_STATE_STOPPED;
        can->ctrlmode_supported = param->ctrlmode_supported;
        can->do_set_mode = es58x_set_mode;
}

/**
 * es58x_init_netdev() - Initialize the network device.
 * @es58x_dev: ES58X device.
 * @channel_idx: Index of the network device.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_init_netdev(struct es58x_device *es58x_dev, int channel_idx)
{
        struct net_device *netdev;
        struct device *dev = es58x_dev->dev;
        int ret;

        netdev = alloc_candev(sizeof(struct es58x_priv),
                              es58x_dev->param->fifo_mask + 1);
        if (!netdev) {
                dev_err(dev, "Could not allocate candev\n");
                return -ENOMEM;
        }
        SET_NETDEV_DEV(netdev, dev);
        es58x_dev->netdev[channel_idx] = netdev;
        es58x_init_priv(es58x_dev, es58x_priv(netdev), channel_idx);

        netdev->netdev_ops = &es58x_netdev_ops;
        netdev->flags |= IFF_ECHO;      /* We support local echo */

        ret = register_candev(netdev);
        if (ret)
                return ret;

        netdev_queue_set_dql_min_limit(netdev_get_tx_queue(netdev, 0),
                                       es58x_dev->param->dql_min_limit);

        return ret;
}

/**
 * es58x_get_product_info() - Get the product information and print them.
 * @es58x_dev: ES58X device.
 *
 * Do a synchronous call to get the product information.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_get_product_info(struct es58x_device *es58x_dev)
{
        struct usb_device *udev = es58x_dev->udev;
        const int es58x_prod_info_idx = 6;
        /* Empirical tests show a prod_info length of maximum 83,
         * below should be more than enough.
         */
        const size_t prod_info_len = 127;
        char *prod_info;
        int ret;

        prod_info = kmalloc(prod_info_len, GFP_KERNEL);
        if (!prod_info)
                return -ENOMEM;

        ret = usb_string(udev, es58x_prod_info_idx, prod_info, prod_info_len);
        if (ret < 0) {
                dev_err(es58x_dev->dev,
                        "%s: Could not read the product info: %pe\n",
                        __func__, ERR_PTR(ret));
                goto out_free;
        }
        if (ret >= prod_info_len - 1) {
                dev_warn(es58x_dev->dev,
                         "%s: Buffer is too small, result might be truncated\n",
                         __func__);
        }
        dev_info(es58x_dev->dev, "Product info: %s\n", prod_info);

 out_free:
        kfree(prod_info);
        return ret < 0 ? ret : 0;
}

/**
 * es58x_init_es58x_dev() - Initialize the ES58X device.
 * @intf: USB interface.
 * @p_es58x_dev: pointer to the address of the ES58X device.
 * @driver_info: Quirks of the device.
 *
 * Return: zero on success, errno when any error occurs.
 */
static int es58x_init_es58x_dev(struct usb_interface *intf,
                                struct es58x_device **p_es58x_dev,
                                kernel_ulong_t driver_info)
{
        struct device *dev = &intf->dev;
        struct es58x_device *es58x_dev;
        const struct es58x_parameters *param;
        const struct es58x_operators *ops;
        struct usb_device *udev = interface_to_usbdev(intf);
        struct usb_endpoint_descriptor *ep_in, *ep_out;
        int ret;

        dev_info(dev,
                 "Starting %s %s (Serial Number %s) driver version %s\n",
                 udev->manufacturer, udev->product, udev->serial, DRV_VERSION);

        ret = usb_find_common_endpoints(intf->cur_altsetting, &ep_in, &ep_out,
                                        NULL, NULL);
        if (ret)
                return ret;

        if (driver_info & ES58X_FD_FAMILY) {
                param = &es58x_fd_param;
                ops = &es58x_fd_ops;
        } else {
                param = &es581_4_param;
                ops = &es581_4_ops;
        }

        es58x_dev = kzalloc(es58x_sizeof_es58x_device(param), GFP_KERNEL);
        if (!es58x_dev)
                return -ENOMEM;

        es58x_dev->param = param;
        es58x_dev->ops = ops;
        es58x_dev->dev = dev;
        es58x_dev->udev = udev;

        if (driver_info & ES58X_DUAL_CHANNEL)
                es58x_dev->num_can_ch = 2;
        else
                es58x_dev->num_can_ch = 1;

        init_usb_anchor(&es58x_dev->rx_urbs);
        init_usb_anchor(&es58x_dev->tx_urbs_idle);
        init_usb_anchor(&es58x_dev->tx_urbs_busy);
        atomic_set(&es58x_dev->tx_urbs_idle_cnt, 0);
        atomic_set(&es58x_dev->opened_channel_cnt, 0);
        usb_set_intfdata(intf, es58x_dev);

        es58x_dev->rx_pipe = usb_rcvbulkpipe(es58x_dev->udev,
                                             ep_in->bEndpointAddress);
        es58x_dev->tx_pipe = usb_sndbulkpipe(es58x_dev->udev,
                                             ep_out->bEndpointAddress);
        es58x_dev->rx_max_packet_size = le16_to_cpu(ep_in->wMaxPacketSize);

        *p_es58x_dev = es58x_dev;

        return 0;
}

/**
 * es58x_probe() - Initialize the USB device.
 * @intf: USB interface.
 * @id: USB device ID.
 *
 * Return: zero on success, -ENODEV if the interface is not supported
 * or errno when any other error occurs.
 */
static int es58x_probe(struct usb_interface *intf,
                       const struct usb_device_id *id)
{
        struct es58x_device *es58x_dev;
        int ch_idx, ret;

        ret = es58x_init_es58x_dev(intf, &es58x_dev, id->driver_info);
        if (ret)
                return ret;

        ret = es58x_get_product_info(es58x_dev);
        if (ret)
                goto cleanup_es58x_dev;

        for (ch_idx = 0; ch_idx < es58x_dev->num_can_ch; ch_idx++) {
                ret = es58x_init_netdev(es58x_dev, ch_idx);
                if (ret)
                        goto cleanup_candev;
        }

        return ret;

 cleanup_candev:
        for (ch_idx = 0; ch_idx < es58x_dev->num_can_ch; ch_idx++)
                if (es58x_dev->netdev[ch_idx]) {
                        unregister_candev(es58x_dev->netdev[ch_idx]);
                        free_candev(es58x_dev->netdev[ch_idx]);
                }
 cleanup_es58x_dev:
        kfree(es58x_dev);

        return ret;
}

/**
 * es58x_disconnect() - Disconnect the USB device.
 * @intf: USB interface
 *
 * Called by the usb core when driver is unloaded or device is
 * removed.
 */
static void es58x_disconnect(struct usb_interface *intf)
{
        struct es58x_device *es58x_dev = usb_get_intfdata(intf);
        struct net_device *netdev;
        int i;

        dev_info(&intf->dev, "Disconnecting %s %s\n",
                 es58x_dev->udev->manufacturer, es58x_dev->udev->product);

        for (i = 0; i < es58x_dev->num_can_ch; i++) {
                netdev = es58x_dev->netdev[i];
                if (!netdev)
                        continue;
                unregister_candev(netdev);
                es58x_dev->netdev[i] = NULL;
                free_candev(netdev);
        }

        es58x_free_urbs(es58x_dev);

        kfree(es58x_dev);
        usb_set_intfdata(intf, NULL);
}

static struct usb_driver es58x_driver = {
        .name = ES58X_MODULE_NAME,
        .probe = es58x_probe,
        .disconnect = es58x_disconnect,
        .id_table = es58x_id_table
};

module_usb_driver(es58x_driver);