drivers/ulink: Group adapter commands

[openocd.git] / src / jtag / drivers / ulink.c

/***************************************************************************
 *   Copyright (C) 2011-2013 by Martin Schmoelzer                          *
 *   <martin.schmoelzer@student.tuwien.ac.at>                              *
 *                                                                         *
 *   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; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <math.h>
#include "helper/system.h"
#include <jtag/interface.h>
#include <jtag/commands.h>
#include <target/image.h>
#include <libusb.h>
#include "libusb_helper.h"
#include "OpenULINK/include/msgtypes.h"

/** USB Vendor ID of ULINK device in unconfigured state (no firmware loaded
 *  yet) or with OpenULINK firmware. */
#define ULINK_VID                0xC251

/** USB Product ID of ULINK device in unconfigured state (no firmware loaded
 *  yet) or with OpenULINK firmware. */
#define ULINK_PID                0x2710

/** Address of EZ-USB CPU Control & Status register. This register can be
 *  written by issuing a Control EP0 vendor request. */
#define CPUCS_REG                0x7F92

/** USB Control EP0 bRequest: "Firmware Load". */
#define REQUEST_FIRMWARE_LOAD    0xA0

/** Value to write into CPUCS to put EZ-USB into reset. */
#define CPU_RESET                0x01

/** Value to write into CPUCS to put EZ-USB out of reset. */
#define CPU_START                0x00

/** Base address of firmware in EZ-USB code space. */
#define FIRMWARE_ADDR            0x0000

/** USB interface number */
#define USB_INTERFACE            0

/** libusb timeout in ms */
#define USB_TIMEOUT              5000

/** Delay (in microseconds) to wait while EZ-USB performs ReNumeration. */
#define ULINK_RENUMERATION_DELAY 1500000

/** Default location of OpenULINK firmware image. */
#define ULINK_FIRMWARE_FILE      PKGDATADIR "/OpenULINK/ulink_firmware.hex"

/** Maximum size of a single firmware section. Entire EZ-USB code space = 8kB */
#define SECTION_BUFFERSIZE       8192

/** Tuning of OpenOCD SCAN commands split into multiple OpenULINK commands. */
#define SPLIT_SCAN_THRESHOLD     10

/** ULINK hardware type */
enum ulink_type {
        /** Original ULINK adapter, based on Cypress EZ-USB (AN2131):
         *  Full JTAG support, no SWD support. */
        ULINK_1,

        /** Newer ULINK adapter, based on NXP LPC2148. Currently unsupported. */
        ULINK_2,

        /** Newer ULINK adapter, based on EZ-USB FX2 + FPGA. Currently unsupported. */
        ULINK_PRO,

        /** Newer ULINK adapter, possibly based on ULINK 2. Currently unsupported. */
        ULINK_ME
};

enum ulink_payload_direction {
        PAYLOAD_DIRECTION_OUT,
        PAYLOAD_DIRECTION_IN
};

enum ulink_delay_type {
        DELAY_CLOCK_TCK,
        DELAY_CLOCK_TMS,
        DELAY_SCAN_IN,
        DELAY_SCAN_OUT,
        DELAY_SCAN_IO
};

/**
 * OpenULINK command (OpenULINK command queue element).
 *
 * For the OUT direction payload, things are quite easy: Payload is stored
 * in a rather small array (up to 63 bytes), the payload is always allocated
 * by the function generating the command and freed by ulink_clear_queue().
 *
 * For the IN direction payload, things get a little bit more complicated:
 * The maximum IN payload size for a single command is 64 bytes. Assume that
 * a single OpenOCD command needs to scan 256 bytes. This results in the
 * generation of four OpenULINK commands. The function generating these
 * commands shall allocate an uint8_t[256] array. Each command's #payload_in
 * pointer shall point to the corresponding offset where IN data shall be
 * placed, while #payload_in_start shall point to the first element of the 256
 * byte array.
 * - first command:  #payload_in_start + 0
 * - second command: #payload_in_start + 64
 * - third command:  #payload_in_start + 128
 * - fourth command: #payload_in_start + 192
 *
 * The last command sets #needs_postprocessing to true.
 */
struct ulink_cmd {
        uint8_t id;                     /**< ULINK command ID */

        uint8_t *payload_out;           /**< OUT direction payload data */
        uint8_t payload_out_size;       /**< OUT direction payload size for this command */

        uint8_t *payload_in_start;      /**< Pointer to first element of IN payload array */
        uint8_t *payload_in;            /**< Pointer where IN payload shall be stored */
        uint8_t payload_in_size;        /**< IN direction payload size for this command */

        /** Indicates if this command needs post-processing */
        bool needs_postprocessing;

        /** Indicates if ulink_clear_queue() should free payload_in_start  */
        bool free_payload_in_start;

        /** Pointer to corresponding OpenOCD command for post-processing */
        struct jtag_command *cmd_origin;

        struct ulink_cmd *next;         /**< Pointer to next command (linked list) */
};

/** Describes one driver instance */
struct ulink {
        struct libusb_context *libusb_ctx;
        struct libusb_device_handle *usb_device_handle;
        enum ulink_type type;

        unsigned int ep_in;             /**< IN endpoint number */
        unsigned int ep_out;            /**< OUT endpoint number */

        int delay_scan_in;      /**< Delay value for SCAN_IN commands */
        int delay_scan_out;     /**< Delay value for SCAN_OUT commands */
        int delay_scan_io;      /**< Delay value for SCAN_IO commands */
        int delay_clock_tck;    /**< Delay value for CLOCK_TMS commands */
        int delay_clock_tms;    /**< Delay value for CLOCK_TCK commands */

        int commands_in_queue;          /**< Number of commands in queue */
        struct ulink_cmd *queue_start;  /**< Pointer to first command in queue */
        struct ulink_cmd *queue_end;    /**< Pointer to last command in queue */
};

/**************************** Function Prototypes *****************************/

/* USB helper functions */
static int ulink_usb_open(struct ulink **device);
static int ulink_usb_close(struct ulink **device);

/* ULINK MCU (Cypress EZ-USB) specific functions */
static int ulink_cpu_reset(struct ulink *device, unsigned char reset_bit);
static int ulink_load_firmware_and_renumerate(struct ulink **device, const char *filename,
                uint32_t delay);
static int ulink_load_firmware(struct ulink *device, const char *filename);
static int ulink_write_firmware_section(struct ulink *device,
                struct image *firmware_image, int section_index);

/* Generic helper functions */
static void ulink_print_signal_states(uint8_t input_signals, uint8_t output_signals);

/* OpenULINK command generation helper functions */
static int ulink_allocate_payload(struct ulink_cmd *ulink_cmd, int size,
                enum ulink_payload_direction direction);

/* OpenULINK command queue helper functions */
static int ulink_get_queue_size(struct ulink *device,
                enum ulink_payload_direction direction);
static void ulink_clear_queue(struct ulink *device);
static int ulink_append_queue(struct ulink *device, struct ulink_cmd *ulink_cmd);
static int ulink_execute_queued_commands(struct ulink *device, int timeout);

static void ulink_print_queue(struct ulink *device);

static int ulink_append_scan_cmd(struct ulink *device,
                enum scan_type scan_type,
                int scan_size_bits,
                uint8_t *tdi,
                uint8_t *tdo_start,
                uint8_t *tdo,
                uint8_t tms_count_start,
                uint8_t tms_sequence_start,
                uint8_t tms_count_end,
                uint8_t tms_sequence_end,
                struct jtag_command *origin,
                bool postprocess);
static int ulink_append_clock_tms_cmd(struct ulink *device, uint8_t count,
                uint8_t sequence);
static int ulink_append_clock_tck_cmd(struct ulink *device, uint16_t count);
static int ulink_append_get_signals_cmd(struct ulink *device);
static int ulink_append_set_signals_cmd(struct ulink *device, uint8_t low,
                uint8_t high);
static int ulink_append_sleep_cmd(struct ulink *device, uint32_t us);
static int ulink_append_configure_tck_cmd(struct ulink *device,
                int delay_scan_in,
                int delay_scan_out,
                int delay_scan_io,
                int delay_tck,
                int delay_tms);
static int __attribute__((unused)) ulink_append_led_cmd(struct ulink *device, uint8_t led_state);
static int ulink_append_test_cmd(struct ulink *device);

/* OpenULINK TCK frequency helper functions */
static int ulink_calculate_delay(enum ulink_delay_type type, long f, int *delay);

/* Interface between OpenULINK and OpenOCD */
static void ulink_set_end_state(tap_state_t endstate);
static int ulink_queue_statemove(struct ulink *device);

static int ulink_queue_scan(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_tlr_reset(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_runtest(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_reset(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_pathmove(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_sleep(struct ulink *device, struct jtag_command *cmd);
static int ulink_queue_stableclocks(struct ulink *device, struct jtag_command *cmd);

static int ulink_post_process_scan(struct ulink_cmd *ulink_cmd);
static int ulink_post_process_queue(struct ulink *device);

/* adapter driver functions */
static int ulink_execute_queue(void);
static int ulink_khz(int khz, int *jtag_speed);
static int ulink_speed(int speed);
static int ulink_speed_div(int speed, int *khz);
static int ulink_init(void);
static int ulink_quit(void);

/****************************** Global Variables ******************************/

static struct ulink *ulink_handle;

/**************************** USB helper functions ****************************/

/**
 * Opens the ULINK device
 *
 * Currently, only the original ULINK is supported
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_usb_open(struct ulink **device)
{
        ssize_t num_devices, i;
        bool found;
        struct libusb_device **usb_devices;
        struct libusb_device_descriptor usb_desc;
        struct libusb_device_handle *usb_device_handle;

        num_devices = libusb_get_device_list((*device)->libusb_ctx, &usb_devices);

        if (num_devices <= 0)
                return ERROR_FAIL;

        found = false;
        for (i = 0; i < num_devices; i++) {
                if (libusb_get_device_descriptor(usb_devices[i], &usb_desc) != 0)
                        continue;
                else if (usb_desc.idVendor == ULINK_VID && usb_desc.idProduct == ULINK_PID) {
                        found = true;
                        break;
                }
        }

        if (!found)
                return ERROR_FAIL;

        if (libusb_open(usb_devices[i], &usb_device_handle) != 0)
                return ERROR_FAIL;
        libusb_free_device_list(usb_devices, 1);

        (*device)->usb_device_handle = usb_device_handle;
        (*device)->type = ULINK_1;

        return ERROR_OK;
}

/**
 * Releases the ULINK interface and closes the USB device handle.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_usb_close(struct ulink **device)
{
        if (libusb_release_interface((*device)->usb_device_handle, 0) != 0)
                return ERROR_FAIL;

        libusb_close((*device)->usb_device_handle);

        (*device)->usb_device_handle = NULL;

        return ERROR_OK;
}

/******************* ULINK CPU (EZ-USB) specific functions ********************/

/**
 * Writes '0' or '1' to the CPUCS register, putting the EZ-USB CPU into reset
 * or out of reset.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param reset_bit 0 to put CPU into reset, 1 to put CPU out of reset.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_cpu_reset(struct ulink *device, unsigned char reset_bit)
{
        int ret;

        ret = libusb_control_transfer(device->usb_device_handle,
                        (LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE),
                        REQUEST_FIRMWARE_LOAD, CPUCS_REG, 0, &reset_bit, 1, USB_TIMEOUT);

        /* usb_control_msg() returns the number of bytes transferred during the
         * DATA stage of the control transfer - must be exactly 1 in this case! */
        if (ret != 1)
                return ERROR_FAIL;
        return ERROR_OK;
}

/**
 * Puts the ULINK's EZ-USB microcontroller into reset state, downloads
 * the firmware image, resumes the microcontroller and re-enumerates
 * USB devices.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 *  The usb_handle member will be modified during re-enumeration.
 * @param filename path to the Intel HEX file containing the firmware image.
 * @param delay the delay to wait for the device to re-enumerate.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_load_firmware_and_renumerate(struct ulink **device,
        const char *filename, uint32_t delay)
{
        int ret;

        /* Basic process: After downloading the firmware, the ULINK will disconnect
         * itself and re-connect after a short amount of time so we have to close
         * the handle and re-enumerate USB devices */

        ret = ulink_load_firmware(*device, filename);
        if (ret != ERROR_OK)
                return ret;

        ret = ulink_usb_close(device);
        if (ret != ERROR_OK)
                return ret;

        usleep(delay);

        ret = ulink_usb_open(device);
        if (ret != ERROR_OK)
                return ret;

        return ERROR_OK;
}

/**
 * Downloads a firmware image to the ULINK's EZ-USB microcontroller
 * over the USB bus.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param filename an absolute or relative path to the Intel HEX file
 *  containing the firmware image.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_load_firmware(struct ulink *device, const char *filename)
{
        struct image ulink_firmware_image;
        int ret;

        ret = ulink_cpu_reset(device, CPU_RESET);
        if (ret != ERROR_OK) {
                LOG_ERROR("Could not halt ULINK CPU");
                return ret;
        }

        ulink_firmware_image.base_address = 0;
        ulink_firmware_image.base_address_set = false;

        ret = image_open(&ulink_firmware_image, filename, "ihex");
        if (ret != ERROR_OK) {
                LOG_ERROR("Could not load firmware image");
                return ret;
        }

        /* Download all sections in the image to ULINK */
        for (unsigned int i = 0; i < ulink_firmware_image.num_sections; i++) {
                ret = ulink_write_firmware_section(device, &ulink_firmware_image, i);
                if (ret != ERROR_OK)
                        return ret;
        }

        image_close(&ulink_firmware_image);

        ret = ulink_cpu_reset(device, CPU_START);
        if (ret != ERROR_OK) {
                LOG_ERROR("Could not restart ULINK CPU");
                return ret;
        }

        return ERROR_OK;
}

/**
 * Send one contiguous firmware section to the ULINK's EZ-USB microcontroller
 * over the USB bus.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param firmware_image pointer to the firmware image that contains the section
 *  which should be sent to the ULINK's EZ-USB microcontroller.
 * @param section_index index of the section within the firmware image.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_write_firmware_section(struct ulink *device,
        struct image *firmware_image, int section_index)
{
        uint16_t addr, size, bytes_remaining, chunk_size;
        uint8_t data[SECTION_BUFFERSIZE];
        uint8_t *data_ptr = data;
        size_t size_read;
        int ret;

        size = (uint16_t)firmware_image->sections[section_index].size;
        addr = (uint16_t)firmware_image->sections[section_index].base_address;

        LOG_DEBUG("section %02i at addr 0x%04x (size 0x%04x)", section_index, addr,
                size);

        /* Copy section contents to local buffer */
        ret = image_read_section(firmware_image, section_index, 0, size, data,
                        &size_read);

        if ((ret != ERROR_OK) || (size_read != size)) {
                /* Propagating the return code would return '0' (misleadingly indicating
                 * successful execution of the function) if only the size check fails. */
                return ERROR_FAIL;
        }

        bytes_remaining = size;

        /* Send section data in chunks of up to 64 bytes to ULINK */
        while (bytes_remaining > 0) {
                if (bytes_remaining > 64)
                        chunk_size = 64;
                else
                        chunk_size = bytes_remaining;

                ret = libusb_control_transfer(device->usb_device_handle,
                                (LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE),
                                REQUEST_FIRMWARE_LOAD, addr, FIRMWARE_ADDR, (unsigned char *)data_ptr,
                                chunk_size, USB_TIMEOUT);

                if (ret != (int)chunk_size) {
                        /* Abort if libusb sent less data than requested */
                        return ERROR_FAIL;
                }

                bytes_remaining -= chunk_size;
                addr += chunk_size;
                data_ptr += chunk_size;
        }

        return ERROR_OK;
}

/************************** Generic helper functions **************************/

/**
 * Print state of interesting signals via LOG_INFO().
 *
 * @param input_signals input signal states as returned by CMD_GET_SIGNALS
 * @param output_signals output signal states as returned by CMD_GET_SIGNALS
 */
static void ulink_print_signal_states(uint8_t input_signals, uint8_t output_signals)
{
        LOG_INFO("ULINK signal states: TDI: %i, TDO: %i, TMS: %i, TCK: %i, TRST: %i,"
                " SRST: %i",
                (output_signals & SIGNAL_TDI   ? 1 : 0),
                (input_signals  & SIGNAL_TDO   ? 1 : 0),
                (output_signals & SIGNAL_TMS   ? 1 : 0),
                (output_signals & SIGNAL_TCK   ? 1 : 0),
                (output_signals & SIGNAL_TRST  ? 0 : 1),        /* Inverted by hardware */
                (output_signals & SIGNAL_RESET ? 0 : 1));       /* Inverted by hardware */
}

/**************** OpenULINK command generation helper functions ***************/

/**
 * Allocate and initialize space in memory for OpenULINK command payload.
 *
 * @param ulink_cmd pointer to command whose payload should be allocated.
 * @param size the amount of memory to allocate (bytes).
 * @param direction which payload to allocate.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_allocate_payload(struct ulink_cmd *ulink_cmd, int size,
        enum ulink_payload_direction direction)
{
        uint8_t *payload;

        payload = calloc(size, sizeof(uint8_t));

        if (!payload) {
                LOG_ERROR("Could not allocate OpenULINK command payload: out of memory");
                return ERROR_FAIL;
        }

        switch (direction) {
            case PAYLOAD_DIRECTION_OUT:
                    if (ulink_cmd->payload_out) {
                            LOG_ERROR("BUG: Duplicate payload allocation for OpenULINK command");
                            free(payload);
                            return ERROR_FAIL;
                    } else {
                            ulink_cmd->payload_out = payload;
                            ulink_cmd->payload_out_size = size;
                    }
                    break;
            case PAYLOAD_DIRECTION_IN:
                    if (ulink_cmd->payload_in_start) {
                            LOG_ERROR("BUG: Duplicate payload allocation for OpenULINK command");
                            free(payload);
                            return ERROR_FAIL;
                    } else {
                            ulink_cmd->payload_in_start = payload;
                            ulink_cmd->payload_in = payload;
                            ulink_cmd->payload_in_size = size;

                                /* By default, free payload_in_start in ulink_clear_queue(). Commands
                                 * that do not want this behavior (e. g. split scans) must turn it off
                                 * separately! */
                            ulink_cmd->free_payload_in_start = true;
                    }
                    break;
        }

        return ERROR_OK;
}

/****************** OpenULINK command queue helper functions ******************/

/**
 * Get the current number of bytes in the queue, including command IDs.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param direction the transfer direction for which to get byte count.
 * @return the number of bytes currently stored in the queue for the specified
 *  direction.
 */
static int ulink_get_queue_size(struct ulink *device,
        enum ulink_payload_direction direction)
{
        struct ulink_cmd *current = device->queue_start;
        int sum = 0;

        while (current) {
                switch (direction) {
                    case PAYLOAD_DIRECTION_OUT:
                            sum += current->payload_out_size + 1;       /* + 1 byte for Command ID */
                            break;
                    case PAYLOAD_DIRECTION_IN:
                            sum += current->payload_in_size;
                            break;
                }

                current = current->next;
        }

        return sum;
}

/**
 * Clear the OpenULINK command queue.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static void ulink_clear_queue(struct ulink *device)
{
        struct ulink_cmd *current = device->queue_start;
        struct ulink_cmd *next = NULL;

        while (current) {
                /* Save pointer to next element */
                next = current->next;

                /* Free payloads: OUT payload can be freed immediately */
                free(current->payload_out);
                current->payload_out = NULL;

                /* IN payload MUST be freed ONLY if no other commands use the
                 * payload_in_start buffer */
                if (current->free_payload_in_start == true) {
                        free(current->payload_in_start);
                        current->payload_in_start = NULL;
                        current->payload_in = NULL;
                }

                /* Free queue element */
                free(current);

                /* Proceed with next element */
                current = next;
        }

        device->commands_in_queue = 0;
        device->queue_start = NULL;
        device->queue_end = NULL;
}

/**
 * Add a command to the OpenULINK command queue.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param ulink_cmd pointer to command that shall be appended to the OpenULINK
 *  command queue.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_queue(struct ulink *device, struct ulink_cmd *ulink_cmd)
{
        int newsize_out, newsize_in;
        int ret = ERROR_OK;

        newsize_out = ulink_get_queue_size(device, PAYLOAD_DIRECTION_OUT) + 1
                + ulink_cmd->payload_out_size;

        newsize_in = ulink_get_queue_size(device, PAYLOAD_DIRECTION_IN)
                + ulink_cmd->payload_in_size;

        /* Check if the current command can be appended to the queue */
        if ((newsize_out > 64) || (newsize_in > 64)) {
                /* New command does not fit. Execute all commands in queue before starting
                 * new queue with the current command as first entry. */
                ret = ulink_execute_queued_commands(device, USB_TIMEOUT);

                if (ret == ERROR_OK)
                        ret = ulink_post_process_queue(device);

                if (ret == ERROR_OK)
                        ulink_clear_queue(device);
        }

        if (!device->queue_start) {
                /* Queue was empty */
                device->commands_in_queue = 1;

                device->queue_start = ulink_cmd;
                device->queue_end = ulink_cmd;
        } else {
                /* There are already commands in the queue */
                device->commands_in_queue++;

                device->queue_end->next = ulink_cmd;
                device->queue_end = ulink_cmd;
        }

        if (ret != ERROR_OK)
                ulink_clear_queue(device);

        return ret;
}

/**
 * Sends all queued OpenULINK commands to the ULINK for execution.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param timeout
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_execute_queued_commands(struct ulink *device, int timeout)
{
        struct ulink_cmd *current;
        int ret, i, index_out, index_in, count_out, count_in, transferred;
        uint8_t buffer[64];

        if (LOG_LEVEL_IS(LOG_LVL_DEBUG_IO))
                ulink_print_queue(device);

        index_out = 0;
        count_out = 0;
        count_in = 0;

        for (current = device->queue_start; current; current = current->next) {
                /* Add command to packet */
                buffer[index_out] = current->id;
                index_out++;
                count_out++;

                for (i = 0; i < current->payload_out_size; i++)
                        buffer[index_out + i] = current->payload_out[i];
                index_out += current->payload_out_size;
                count_in += current->payload_in_size;
                count_out += current->payload_out_size;
        }

        /* Send packet to ULINK */
        ret = libusb_bulk_transfer(device->usb_device_handle, device->ep_out,
                        (unsigned char *)buffer, count_out, &transferred, timeout);
        if (ret != 0)
                return ERROR_FAIL;
        if (transferred != count_out)
                return ERROR_FAIL;

        /* Wait for response if commands contain IN payload data */
        if (count_in > 0) {
                ret = libusb_bulk_transfer(device->usb_device_handle, device->ep_in,
                                (unsigned char *)buffer, 64, &transferred, timeout);
                if (ret != 0)
                        return ERROR_FAIL;
                if (transferred != count_in)
                        return ERROR_FAIL;

                /* Write back IN payload data */
                index_in = 0;
                for (current = device->queue_start; current; current = current->next) {
                        for (i = 0; i < current->payload_in_size; i++) {
                                current->payload_in[i] = buffer[index_in];
                                index_in++;
                        }
                }
        }

        return ERROR_OK;
}

/**
 * Convert an OpenULINK command ID (\a id) to a human-readable string.
 *
 * @param id the OpenULINK command ID.
 * @return the corresponding human-readable string.
 */
static const char *ulink_cmd_id_string(uint8_t id)
{
        switch (id) {
        case CMD_SCAN_IN:
                return "CMD_SCAN_IN";
        case CMD_SLOW_SCAN_IN:
                return "CMD_SLOW_SCAN_IN";
        case CMD_SCAN_OUT:
                return "CMD_SCAN_OUT";
        case CMD_SLOW_SCAN_OUT:
                return "CMD_SLOW_SCAN_OUT";
        case CMD_SCAN_IO:
                return "CMD_SCAN_IO";
        case CMD_SLOW_SCAN_IO:
                return "CMD_SLOW_SCAN_IO";
        case CMD_CLOCK_TMS:
                return "CMD_CLOCK_TMS";
        case CMD_SLOW_CLOCK_TMS:
                return "CMD_SLOW_CLOCK_TMS";
        case CMD_CLOCK_TCK:
                return "CMD_CLOCK_TCK";
        case CMD_SLOW_CLOCK_TCK:
                return "CMD_SLOW_CLOCK_TCK";
        case CMD_SLEEP_US:
                return "CMD_SLEEP_US";
        case CMD_SLEEP_MS:
                return "CMD_SLEEP_MS";
        case CMD_GET_SIGNALS:
                return "CMD_GET_SIGNALS";
        case CMD_SET_SIGNALS:
                return "CMD_SET_SIGNALS";
        case CMD_CONFIGURE_TCK_FREQ:
                return "CMD_CONFIGURE_TCK_FREQ";
        case CMD_SET_LEDS:
                return "CMD_SET_LEDS";
        case CMD_TEST:
                return "CMD_TEST";
        default:
                return "CMD_UNKNOWN";
        }
}

/**
 * Print one OpenULINK command to stdout.
 *
 * @param ulink_cmd pointer to OpenULINK command.
 */
static void ulink_print_command(struct ulink_cmd *ulink_cmd)
{
        int i;

        printf("  %-22s | OUT size = %i, bytes = 0x",
                ulink_cmd_id_string(ulink_cmd->id), ulink_cmd->payload_out_size);

        for (i = 0; i < ulink_cmd->payload_out_size; i++)
                printf("%02X ", ulink_cmd->payload_out[i]);
        printf("\n                         | IN size  = %i\n",
                ulink_cmd->payload_in_size);
}

/**
 * Print the OpenULINK command queue to stdout.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 */
static void ulink_print_queue(struct ulink *device)
{
        struct ulink_cmd *current;

        printf("OpenULINK command queue:\n");

        for (current = device->queue_start; current; current = current->next)
                ulink_print_command(current);
}

/**
 * Perform JTAG scan
 *
 * Creates and appends a JTAG scan command to the OpenULINK command queue.
 * A JTAG scan consists of three steps:
 * - Move to the desired SHIFT state, depending on scan type (IR/DR scan).
 * - Shift TDI data into the JTAG chain, optionally reading the TDO pin.
 * - Move to the desired end state.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param scan_type the type of the scan (IN, OUT, IO (bidirectional)).
 * @param scan_size_bits number of bits to shift into the JTAG chain.
 * @param tdi pointer to array containing TDI data.
 * @param tdo_start pointer to first element of array where TDO data shall be
 *  stored. See #ulink_cmd for details.
 * @param tdo pointer to array where TDO data shall be stored
 * @param tms_count_start number of TMS state transitions to perform BEFORE
 *  shifting data into the JTAG chain.
 * @param tms_sequence_start sequence of TMS state transitions that will be
 *  performed BEFORE shifting data into the JTAG chain.
 * @param tms_count_end number of TMS state transitions to perform AFTER
 *  shifting data into the JTAG chain.
 * @param tms_sequence_end sequence of TMS state transitions that will be
 *  performed AFTER shifting data into the JTAG chain.
 * @param origin pointer to OpenOCD command that generated this scan command.
 * @param postprocess whether this command needs to be post-processed after
 *  execution.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_scan_cmd(struct ulink *device, enum scan_type scan_type,
        int scan_size_bits, uint8_t *tdi, uint8_t *tdo_start, uint8_t *tdo,
        uint8_t tms_count_start, uint8_t tms_sequence_start, uint8_t tms_count_end,
        uint8_t tms_sequence_end, struct jtag_command *origin, bool postprocess)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret, i, scan_size_bytes;
        uint8_t bits_last_byte;

        if (!cmd)
                return ERROR_FAIL;

        /* Check size of command. USB buffer can hold 64 bytes, 1 byte is command ID,
         * 5 bytes are setup data -> 58 remaining payload bytes for TDI data */
        if (scan_size_bits > (58 * 8)) {
                LOG_ERROR("BUG: Tried to create CMD_SCAN_IO OpenULINK command with too"
                        " large payload");
                free(cmd);
                return ERROR_FAIL;
        }

        scan_size_bytes = DIV_ROUND_UP(scan_size_bits, 8);

        bits_last_byte = scan_size_bits % 8;
        if (bits_last_byte == 0)
                bits_last_byte = 8;

        /* Allocate out_payload depending on scan type */
        switch (scan_type) {
            case SCAN_IN:
                    if (device->delay_scan_in < 0)
                            cmd->id = CMD_SCAN_IN;
                    else
                            cmd->id = CMD_SLOW_SCAN_IN;
                    ret = ulink_allocate_payload(cmd, 5, PAYLOAD_DIRECTION_OUT);
                    break;
            case SCAN_OUT:
                    if (device->delay_scan_out < 0)
                            cmd->id = CMD_SCAN_OUT;
                    else
                            cmd->id = CMD_SLOW_SCAN_OUT;
                    ret = ulink_allocate_payload(cmd, scan_size_bytes + 5, PAYLOAD_DIRECTION_OUT);
                    break;
            case SCAN_IO:
                    if (device->delay_scan_io < 0)
                            cmd->id = CMD_SCAN_IO;
                    else
                            cmd->id = CMD_SLOW_SCAN_IO;
                    ret = ulink_allocate_payload(cmd, scan_size_bytes + 5, PAYLOAD_DIRECTION_OUT);
                    break;
            default:
                    LOG_ERROR("BUG: ulink_append_scan_cmd() encountered an unknown scan type");
                    ret = ERROR_FAIL;
                    break;
        }

        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        /* Build payload_out that is common to all scan types */
        cmd->payload_out[0] = scan_size_bytes & 0xFF;
        cmd->payload_out[1] = bits_last_byte & 0xFF;
        cmd->payload_out[2] = ((tms_count_start & 0x0F) << 4) | (tms_count_end & 0x0F);
        cmd->payload_out[3] = tms_sequence_start;
        cmd->payload_out[4] = tms_sequence_end;

        /* Setup payload_out for types with OUT transfer */
        if ((scan_type == SCAN_OUT) || (scan_type == SCAN_IO)) {
                for (i = 0; i < scan_size_bytes; i++)
                        cmd->payload_out[i + 5] = tdi[i];
        }

        /* Setup payload_in pointers for types with IN transfer */
        if ((scan_type == SCAN_IN) || (scan_type == SCAN_IO)) {
                cmd->payload_in_start = tdo_start;
                cmd->payload_in = tdo;
                cmd->payload_in_size = scan_size_bytes;
        }

        cmd->needs_postprocessing = postprocess;
        cmd->cmd_origin = origin;

        /* For scan commands, we free payload_in_start only when the command is
         * the last in a series of split commands or a stand-alone command */
        cmd->free_payload_in_start = postprocess;

        return ulink_append_queue(device, cmd);
}

/**
 * Perform TAP state transitions
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param count defines the number of TCK clock cycles generated (up to 8).
 * @param sequence defines the TMS pin levels for each state transition. The
 *  Least-Significant Bit is read first.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_clock_tms_cmd(struct ulink *device, uint8_t count,
        uint8_t sequence)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        if (device->delay_clock_tms < 0)
                cmd->id = CMD_CLOCK_TMS;
        else
                cmd->id = CMD_SLOW_CLOCK_TMS;

        /* CMD_CLOCK_TMS has two OUT payload bytes and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 2, PAYLOAD_DIRECTION_OUT);
        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = count;
        cmd->payload_out[1] = sequence;

        return ulink_append_queue(device, cmd);
}

/**
 * Generate a defined amount of TCK clock cycles
 *
 * All other JTAG signals are left unchanged.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param count the number of TCK clock cycles to generate.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_clock_tck_cmd(struct ulink *device, uint16_t count)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        if (device->delay_clock_tck < 0)
                cmd->id = CMD_CLOCK_TCK;
        else
                cmd->id = CMD_SLOW_CLOCK_TCK;

        /* CMD_CLOCK_TCK has two OUT payload bytes and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 2, PAYLOAD_DIRECTION_OUT);
        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = count & 0xff;
        cmd->payload_out[1] = (count >> 8) & 0xff;

        return ulink_append_queue(device, cmd);
}

/**
 * Read JTAG signals.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_get_signals_cmd(struct ulink *device)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_GET_SIGNALS;
        cmd->needs_postprocessing = true;

        /* CMD_GET_SIGNALS has two IN payload bytes */
        ret = ulink_allocate_payload(cmd, 2, PAYLOAD_DIRECTION_IN);

        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        return ulink_append_queue(device, cmd);
}

/**
 * Arbitrarily set JTAG output signals.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param low defines which signals will be de-asserted. Each bit corresponds
 *  to a JTAG signal:
 *  - SIGNAL_TDI
 *  - SIGNAL_TMS
 *  - SIGNAL_TCK
 *  - SIGNAL_TRST
 *  - SIGNAL_BRKIN
 *  - SIGNAL_RESET
 *  - SIGNAL_OCDSE
 * @param high defines which signals will be asserted.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_set_signals_cmd(struct ulink *device, uint8_t low,
        uint8_t high)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_SET_SIGNALS;

        /* CMD_SET_SIGNALS has two OUT payload bytes and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 2, PAYLOAD_DIRECTION_OUT);

        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = low;
        cmd->payload_out[1] = high;

        return ulink_append_queue(device, cmd);
}

/**
 * Sleep for a pre-defined number of microseconds
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param us the number microseconds to sleep.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_sleep_cmd(struct ulink *device, uint32_t us)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_SLEEP_US;

        /* CMD_SLEEP_US has two OUT payload bytes and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 2, PAYLOAD_DIRECTION_OUT);

        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = us & 0x00ff;
        cmd->payload_out[1] = (us >> 8) & 0x00ff;

        return ulink_append_queue(device, cmd);
}

/**
 * Set TCK delay counters
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param delay_scan_in delay count top value in jtag_slow_scan_in() function.
 * @param delay_scan_out delay count top value in jtag_slow_scan_out() function.
 * @param delay_scan_io delay count top value in jtag_slow_scan_io() function.
 * @param delay_tck delay count top value in jtag_clock_tck() function.
 * @param delay_tms delay count top value in jtag_slow_clock_tms() function.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_configure_tck_cmd(struct ulink *device, int delay_scan_in,
        int delay_scan_out, int delay_scan_io, int delay_tck, int delay_tms)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_CONFIGURE_TCK_FREQ;

        /* CMD_CONFIGURE_TCK_FREQ has five OUT payload bytes and zero
         * IN payload bytes */
        ret = ulink_allocate_payload(cmd, 5, PAYLOAD_DIRECTION_OUT);
        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        if (delay_scan_in < 0)
                cmd->payload_out[0] = 0;
        else
                cmd->payload_out[0] = (uint8_t)delay_scan_in;

        if (delay_scan_out < 0)
                cmd->payload_out[1] = 0;
        else
                cmd->payload_out[1] = (uint8_t)delay_scan_out;

        if (delay_scan_io < 0)
                cmd->payload_out[2] = 0;
        else
                cmd->payload_out[2] = (uint8_t)delay_scan_io;

        if (delay_tck < 0)
                cmd->payload_out[3] = 0;
        else
                cmd->payload_out[3] = (uint8_t)delay_tck;

        if (delay_tms < 0)
                cmd->payload_out[4] = 0;
        else
                cmd->payload_out[4] = (uint8_t)delay_tms;

        return ulink_append_queue(device, cmd);
}

/**
 * Turn on/off ULINK LEDs.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param led_state which LED(s) to turn on or off. The following bits
 *  influence the LEDS:
 *  - Bit 0: Turn COM LED on
 *  - Bit 1: Turn RUN LED on
 *  - Bit 2: Turn COM LED off
 *  - Bit 3: Turn RUN LED off
 *  If both the on-bit and the off-bit for the same LED is set, the LED is
 *  turned off.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_led_cmd(struct ulink *device, uint8_t led_state)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_SET_LEDS;

        /* CMD_SET_LEDS has one OUT payload byte and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 1, PAYLOAD_DIRECTION_OUT);
        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = led_state;

        return ulink_append_queue(device, cmd);
}

/**
 * Test command. Used to check if the ULINK device is ready to accept new
 * commands.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_append_test_cmd(struct ulink *device)
{
        struct ulink_cmd *cmd = calloc(1, sizeof(struct ulink_cmd));
        int ret;

        if (!cmd)
                return ERROR_FAIL;

        cmd->id = CMD_TEST;

        /* CMD_TEST has one OUT payload byte and zero IN payload bytes */
        ret = ulink_allocate_payload(cmd, 1, PAYLOAD_DIRECTION_OUT);
        if (ret != ERROR_OK) {
                free(cmd);
                return ret;
        }

        cmd->payload_out[0] = 0xAA;

        return ulink_append_queue(device, cmd);
}

/****************** OpenULINK TCK frequency helper functions ******************/

/**
 * Calculate delay values for a given TCK frequency.
 *
 * The OpenULINK firmware uses five different speed values for different
 * commands. These speed values are calculated in these functions.
 *
 * The five different commands which support variable TCK frequency are
 * implemented twice in the firmware:
 *   1. Maximum possible frequency without any artificial delay
 *   2. Variable frequency with artificial linear delay loop
 *
 * To set the ULINK to maximum frequency, it is only necessary to use the
 * corresponding command IDs. To set the ULINK to a lower frequency, the
 * delay loop top values have to be calculated first. Then, a
 * CMD_CONFIGURE_TCK_FREQ command needs to be sent to the ULINK device.
 *
 * The delay values are described by linear equations:
 *    t = k * x + d
 *    (t = period, k = constant, x = delay value, d = constant)
 *
 * Thus, the delay can be calculated as in the following equation:
 *    x = (t - d) / k
 *
 * The constants in these equations have been determined and validated by
 * measuring the frequency resulting from different delay values.
 *
 * @param type for which command to calculate the delay value.
 * @param f TCK frequency for which to calculate the delay value in Hz.
 * @param delay where to store resulting delay value.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_calculate_delay(enum ulink_delay_type type, long f, int *delay)
{
        float t, x, x_ceil;

        /* Calculate period of requested TCK frequency */
        t = 1.0 / (float)(f);

        switch (type) {
            case DELAY_CLOCK_TCK:
                    x = (t - (float)(6E-6)) / (float)(4E-6);
                    break;
            case DELAY_CLOCK_TMS:
                    x = (t - (float)(8.5E-6)) / (float)(4E-6);
                    break;
            case DELAY_SCAN_IN:
                    x = (t - (float)(8.8308E-6)) / (float)(4E-6);
                    break;
            case DELAY_SCAN_OUT:
                    x = (t - (float)(1.0527E-5)) / (float)(4E-6);
                    break;
            case DELAY_SCAN_IO:
                    x = (t - (float)(1.3132E-5)) / (float)(4E-6);
                    break;
            default:
                    return ERROR_FAIL;
                    break;
        }

        /* Check if the delay value is negative. This happens when a frequency is
         * requested that is too high for the delay loop implementation. In this
         * case, set delay value to zero. */
        if (x < 0)
                x = 0;

        /* We need to convert the exact delay value to an integer. Therefore, we
         * round the exact value UP to ensure that the resulting frequency is NOT
         * higher than the requested frequency. */
        x_ceil = ceilf(x);

        /* Check if the value is within limits */
        if (x_ceil > 255)
                return ERROR_FAIL;

        *delay = (int)x_ceil;

        return ERROR_OK;
}

/**
 * Calculate frequency for a given delay value.
 *
 * Similar to the #ulink_calculate_delay function, this function calculates the
 * TCK frequency for a given delay value by using linear equations of the form:
 *    t = k * x + d
 *    (t = period, k = constant, x = delay value, d = constant)
 *
 * @param type for which command to calculate the delay value.
 * @param delay delay value for which to calculate the resulting TCK frequency.
 * @return the resulting TCK frequency
 */
static long ulink_calculate_frequency(enum ulink_delay_type type, int delay)
{
        float t, f_float;

        if (delay > 255)
                return 0;

        switch (type) {
            case DELAY_CLOCK_TCK:
                    if (delay < 0)
                            t = (float)(2.666E-6);
                    else
                            t = (float)(4E-6) * (float)(delay) + (float)(6E-6);
                    break;
            case DELAY_CLOCK_TMS:
                    if (delay < 0)
                            t = (float)(5.666E-6);
                    else
                            t = (float)(4E-6) * (float)(delay) + (float)(8.5E-6);
                    break;
            case DELAY_SCAN_IN:
                    if (delay < 0)
                            t = (float)(5.5E-6);
                    else
                            t = (float)(4E-6) * (float)(delay) + (float)(8.8308E-6);
                    break;
            case DELAY_SCAN_OUT:
                    if (delay < 0)
                            t = (float)(7.0E-6);
                    else
                            t = (float)(4E-6) * (float)(delay) + (float)(1.0527E-5);
                    break;
            case DELAY_SCAN_IO:
                    if (delay < 0)
                            t = (float)(9.926E-6);
                    else
                            t = (float)(4E-6) * (float)(delay) + (float)(1.3132E-5);
                    break;
            default:
                    return 0;
        }

        f_float = 1.0 / t;
        return roundf(f_float);
}

/******************* Interface between OpenULINK and OpenOCD ******************/

/**
 * Sets the end state follower (see interface.h) if \a endstate is a stable
 * state.
 *
 * @param endstate the state the end state follower should be set to.
 */
static void ulink_set_end_state(tap_state_t endstate)
{
        if (tap_is_state_stable(endstate))
                tap_set_end_state(endstate);
        else {
                LOG_ERROR("BUG: %s is not a valid end state", tap_state_name(endstate));
                exit(EXIT_FAILURE);
        }
}

/**
 * Move from the current TAP state to the current TAP end state.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_statemove(struct ulink *device)
{
        uint8_t tms_sequence, tms_count;
        int ret;

        if (tap_get_state() == tap_get_end_state()) {
                /* Do nothing if we are already there */
                return ERROR_OK;
        }

        tms_sequence = tap_get_tms_path(tap_get_state(), tap_get_end_state());
        tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());

        ret = ulink_append_clock_tms_cmd(device, tms_count, tms_sequence);

        if (ret == ERROR_OK)
                tap_set_state(tap_get_end_state());

        return ret;
}

/**
 * Perform a scan operation on a JTAG register.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_scan(struct ulink *device, struct jtag_command *cmd)
{
        uint32_t scan_size_bits, scan_size_bytes, bits_last_scan;
        uint32_t scans_max_payload, bytecount;
        uint8_t *tdi_buffer_start = NULL, *tdi_buffer = NULL;
        uint8_t *tdo_buffer_start = NULL, *tdo_buffer = NULL;

        uint8_t first_tms_count, first_tms_sequence;
        uint8_t last_tms_count, last_tms_sequence;

        uint8_t tms_count_pause, tms_sequence_pause;
        uint8_t tms_count_resume, tms_sequence_resume;

        uint8_t tms_count_start, tms_sequence_start;
        uint8_t tms_count_end, tms_sequence_end;

        enum scan_type type;
        int ret;

        /* Determine scan size */
        scan_size_bits = jtag_scan_size(cmd->cmd.scan);
        scan_size_bytes = DIV_ROUND_UP(scan_size_bits, 8);

        /* Determine scan type (IN/OUT/IO) */
        type = jtag_scan_type(cmd->cmd.scan);

        /* Determine number of scan commands with maximum payload */
        scans_max_payload = scan_size_bytes / 58;

        /* Determine size of last shift command */
        bits_last_scan = scan_size_bits - (scans_max_payload * 58 * 8);

        /* Allocate TDO buffer if required */
        if ((type == SCAN_IN) || (type == SCAN_IO)) {
                tdo_buffer_start = calloc(sizeof(uint8_t), scan_size_bytes);

                if (!tdo_buffer_start)
                        return ERROR_FAIL;

                tdo_buffer = tdo_buffer_start;
        }

        /* Fill TDI buffer if required */
        if ((type == SCAN_OUT) || (type == SCAN_IO)) {
                jtag_build_buffer(cmd->cmd.scan, &tdi_buffer_start);
                tdi_buffer = tdi_buffer_start;
        }

        /* Get TAP state transitions */
        if (cmd->cmd.scan->ir_scan) {
                ulink_set_end_state(TAP_IRSHIFT);
                first_tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
                first_tms_sequence = tap_get_tms_path(tap_get_state(), tap_get_end_state());

                tap_set_state(TAP_IRSHIFT);
                tap_set_end_state(cmd->cmd.scan->end_state);
                last_tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
                last_tms_sequence = tap_get_tms_path(tap_get_state(), tap_get_end_state());

                /* TAP state transitions for split scans */
                tms_count_pause = tap_get_tms_path_len(TAP_IRSHIFT, TAP_IRPAUSE);
                tms_sequence_pause = tap_get_tms_path(TAP_IRSHIFT, TAP_IRPAUSE);
                tms_count_resume = tap_get_tms_path_len(TAP_IRPAUSE, TAP_IRSHIFT);
                tms_sequence_resume = tap_get_tms_path(TAP_IRPAUSE, TAP_IRSHIFT);
        } else {
                ulink_set_end_state(TAP_DRSHIFT);
                first_tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
                first_tms_sequence = tap_get_tms_path(tap_get_state(), tap_get_end_state());

                tap_set_state(TAP_DRSHIFT);
                tap_set_end_state(cmd->cmd.scan->end_state);
                last_tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
                last_tms_sequence = tap_get_tms_path(tap_get_state(), tap_get_end_state());

                /* TAP state transitions for split scans */
                tms_count_pause = tap_get_tms_path_len(TAP_DRSHIFT, TAP_DRPAUSE);
                tms_sequence_pause = tap_get_tms_path(TAP_DRSHIFT, TAP_DRPAUSE);
                tms_count_resume = tap_get_tms_path_len(TAP_DRPAUSE, TAP_DRSHIFT);
                tms_sequence_resume = tap_get_tms_path(TAP_DRPAUSE, TAP_DRSHIFT);
        }

        /* Generate scan commands */
        bytecount = scan_size_bytes;
        while (bytecount > 0) {
                if (bytecount == scan_size_bytes) {
                        /* This is the first scan */
                        tms_count_start = first_tms_count;
                        tms_sequence_start = first_tms_sequence;
                } else {
                        /* Resume from previous scan */
                        tms_count_start = tms_count_resume;
                        tms_sequence_start = tms_sequence_resume;
                }

                if (bytecount > 58) {   /* Full scan, at least one scan will follow */
                        tms_count_end = tms_count_pause;
                        tms_sequence_end = tms_sequence_pause;

                        ret = ulink_append_scan_cmd(device,
                                        type,
                                        58 * 8,
                                        tdi_buffer,
                                        tdo_buffer_start,
                                        tdo_buffer,
                                        tms_count_start,
                                        tms_sequence_start,
                                        tms_count_end,
                                        tms_sequence_end,
                                        cmd,
                                        false);

                        bytecount -= 58;

                        /* Update TDI and TDO buffer pointers */
                        if (tdi_buffer_start)
                                tdi_buffer += 58;
                        if (tdo_buffer_start)
                                tdo_buffer += 58;
                } else if (bytecount == 58) {   /* Full scan, no further scans */
                        tms_count_end = last_tms_count;
                        tms_sequence_end = last_tms_sequence;

                        ret = ulink_append_scan_cmd(device,
                                        type,
                                        58 * 8,
                                        tdi_buffer,
                                        tdo_buffer_start,
                                        tdo_buffer,
                                        tms_count_start,
                                        tms_sequence_start,
                                        tms_count_end,
                                        tms_sequence_end,
                                        cmd,
                                        true);

                        bytecount = 0;
                } else {/* Scan with less than maximum payload, no further scans */
                        tms_count_end = last_tms_count;
                        tms_sequence_end = last_tms_sequence;

                        ret = ulink_append_scan_cmd(device,
                                        type,
                                        bits_last_scan,
                                        tdi_buffer,
                                        tdo_buffer_start,
                                        tdo_buffer,
                                        tms_count_start,
                                        tms_sequence_start,
                                        tms_count_end,
                                        tms_sequence_end,
                                        cmd,
                                        true);

                        bytecount = 0;
                }

                if (ret != ERROR_OK) {
                        free(tdi_buffer_start);
                        free(tdo_buffer_start);
                        return ret;
                }
        }

        free(tdi_buffer_start);

        /* Set current state to the end state requested by the command */
        tap_set_state(cmd->cmd.scan->end_state);

        return ERROR_OK;
}

/**
 * Move the TAP into the Test Logic Reset state.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_tlr_reset(struct ulink *device, struct jtag_command *cmd)
{
        int ret;

        ret = ulink_append_clock_tms_cmd(device, 5, 0xff);

        if (ret == ERROR_OK)
                tap_set_state(TAP_RESET);

        return ret;
}

/**
 * Run Test.
 *
 * Generate TCK clock cycles while remaining
 * in the Run-Test/Idle state.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_runtest(struct ulink *device, struct jtag_command *cmd)
{
        int ret;

        /* Only perform statemove if the TAP currently isn't in the TAP_IDLE state */
        if (tap_get_state() != TAP_IDLE) {
                ulink_set_end_state(TAP_IDLE);
                ulink_queue_statemove(device);
        }

        /* Generate the clock cycles */
        ret = ulink_append_clock_tck_cmd(device, cmd->cmd.runtest->num_cycles);
        if (ret != ERROR_OK)
                return ret;

        /* Move to end state specified in command */
        if (cmd->cmd.runtest->end_state != tap_get_state()) {
                tap_set_end_state(cmd->cmd.runtest->end_state);
                ulink_queue_statemove(device);
        }

        return ERROR_OK;
}

/**
 * Execute a JTAG_RESET command
 *
 * @param device
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_reset(struct ulink *device, struct jtag_command *cmd)
{
        uint8_t low = 0, high = 0;

        if (cmd->cmd.reset->trst) {
                tap_set_state(TAP_RESET);
                high |= SIGNAL_TRST;
        } else
                low |= SIGNAL_TRST;

        if (cmd->cmd.reset->srst)
                high |= SIGNAL_RESET;
        else
                low |= SIGNAL_RESET;

        return ulink_append_set_signals_cmd(device, low, high);
}

/**
 * Move to one TAP state or several states in succession.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_pathmove(struct ulink *device, struct jtag_command *cmd)
{
        int ret, i, num_states, batch_size, state_count;
        tap_state_t *path;
        uint8_t tms_sequence;

        num_states = cmd->cmd.pathmove->num_states;
        path = cmd->cmd.pathmove->path;
        state_count = 0;

        while (num_states > 0) {
                tms_sequence = 0;

                /* Determine batch size */
                if (num_states >= 8)
                        batch_size = 8;
                else
                        batch_size = num_states;

                for (i = 0; i < batch_size; i++) {
                        if (tap_state_transition(tap_get_state(), false) == path[state_count]) {
                                /* Append '0' transition: clear bit 'i' in tms_sequence */
                                buf_set_u32(&tms_sequence, i, 1, 0x0);
                        } else if (tap_state_transition(tap_get_state(), true)
                                   == path[state_count]) {
                                /* Append '1' transition: set bit 'i' in tms_sequence */
                                buf_set_u32(&tms_sequence, i, 1, 0x1);
                        } else {
                                /* Invalid state transition */
                                LOG_ERROR("BUG: %s -> %s isn't a valid TAP state transition",
                                        tap_state_name(tap_get_state()),
                                        tap_state_name(path[state_count]));
                                return ERROR_FAIL;
                        }

                        tap_set_state(path[state_count]);
                        state_count++;
                        num_states--;
                }

                /* Append CLOCK_TMS command to OpenULINK command queue */
                LOG_INFO(
                        "pathmove batch: count = %i, sequence = 0x%x", batch_size, tms_sequence);
                ret = ulink_append_clock_tms_cmd(ulink_handle, batch_size, tms_sequence);
                if (ret != ERROR_OK)
                        return ret;
        }

        return ERROR_OK;
}

/**
 * Sleep for a specific amount of time.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_queue_sleep(struct ulink *device, struct jtag_command *cmd)
{
        /* IMPORTANT! Due to the time offset in command execution introduced by
         * command queueing, this needs to be implemented in the ULINK device */
        return ulink_append_sleep_cmd(device, cmd->cmd.sleep->us);
}

/**
 * Generate TCK cycles while remaining in a stable state.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @param cmd pointer to the command that shall be executed.
 */
static int ulink_queue_stableclocks(struct ulink *device, struct jtag_command *cmd)
{
        int ret;
        unsigned num_cycles;

        if (!tap_is_state_stable(tap_get_state())) {
                LOG_ERROR("JTAG_STABLECLOCKS: state not stable");
                return ERROR_FAIL;
        }

        num_cycles = cmd->cmd.stableclocks->num_cycles;

        /* TMS stays either high (Test Logic Reset state) or low (all other states) */
        if (tap_get_state() == TAP_RESET)
                ret = ulink_append_set_signals_cmd(device, 0, SIGNAL_TMS);
        else
                ret = ulink_append_set_signals_cmd(device, SIGNAL_TMS, 0);

        if (ret != ERROR_OK)
                return ret;

        while (num_cycles > 0) {
                if (num_cycles > 0xFFFF) {
                        /* OpenULINK CMD_CLOCK_TCK can generate up to 0xFFFF (uint16_t) cycles */
                        ret = ulink_append_clock_tck_cmd(device, 0xFFFF);
                        num_cycles -= 0xFFFF;
                } else {
                        ret = ulink_append_clock_tck_cmd(device, num_cycles);
                        num_cycles = 0;
                }

                if (ret != ERROR_OK)
                        return ret;
        }

        return ERROR_OK;
}

/**
 * Post-process JTAG_SCAN command
 *
 * @param ulink_cmd pointer to OpenULINK command that shall be processed.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_post_process_scan(struct ulink_cmd *ulink_cmd)
{
        struct jtag_command *cmd = ulink_cmd->cmd_origin;
        int ret;

        switch (jtag_scan_type(cmd->cmd.scan)) {
            case SCAN_IN:
            case SCAN_IO:
                    ret = jtag_read_buffer(ulink_cmd->payload_in_start, cmd->cmd.scan);
                    break;
            case SCAN_OUT:
                        /* Nothing to do for OUT scans */
                    ret = ERROR_OK;
                    break;
            default:
                    LOG_ERROR("BUG: ulink_post_process_scan() encountered an unknown"
                        " JTAG scan type");
                    ret = ERROR_FAIL;
                    break;
        }

        return ret;
}

/**
 * Perform post-processing of commands after OpenULINK queue has been executed.
 *
 * @param device pointer to struct ulink identifying ULINK driver instance.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_post_process_queue(struct ulink *device)
{
        struct ulink_cmd *current;
        struct jtag_command *openocd_cmd;
        int ret;

        current = device->queue_start;

        while (current) {
                openocd_cmd = current->cmd_origin;

                /* Check if a corresponding OpenOCD command is stored for this
                 * OpenULINK command */
                if ((current->needs_postprocessing == true) && (openocd_cmd)) {
                        switch (openocd_cmd->type) {
                            case JTAG_SCAN:
                                    ret = ulink_post_process_scan(current);
                                    break;
                            case JTAG_TLR_RESET:
                            case JTAG_RUNTEST:
                            case JTAG_RESET:
                            case JTAG_PATHMOVE:
                            case JTAG_SLEEP:
                            case JTAG_STABLECLOCKS:
                                        /* Nothing to do for these commands */
                                    ret = ERROR_OK;
                                    break;
                            default:
                                    ret = ERROR_FAIL;
                                    LOG_ERROR("BUG: ulink_post_process_queue() encountered unknown JTAG "
                                        "command type");
                                    break;
                        }

                        if (ret != ERROR_OK)
                                return ret;
                }

                current = current->next;
        }

        return ERROR_OK;
}

/**************************** JTAG driver functions ***************************/

/**
 * Executes the JTAG Command Queue.
 *
 * This is done in three stages: First, all OpenOCD commands are processed into
 * queued OpenULINK commands. Next, the OpenULINK command queue is sent to the
 * ULINK device and data received from the ULINK device is cached. Finally,
 * the post-processing function writes back data to the corresponding OpenOCD
 * commands.
 *
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_execute_queue(void)
{
        struct jtag_command *cmd = jtag_command_queue;
        int ret;

        while (cmd) {
                switch (cmd->type) {
                    case JTAG_SCAN:
                            ret = ulink_queue_scan(ulink_handle, cmd);
                            break;
                    case JTAG_TLR_RESET:
                            ret = ulink_queue_tlr_reset(ulink_handle, cmd);
                            break;
                    case JTAG_RUNTEST:
                            ret = ulink_queue_runtest(ulink_handle, cmd);
                            break;
                    case JTAG_RESET:
                            ret = ulink_queue_reset(ulink_handle, cmd);
                            break;
                    case JTAG_PATHMOVE:
                            ret = ulink_queue_pathmove(ulink_handle, cmd);
                            break;
                    case JTAG_SLEEP:
                            ret = ulink_queue_sleep(ulink_handle, cmd);
                            break;
                    case JTAG_STABLECLOCKS:
                            ret = ulink_queue_stableclocks(ulink_handle, cmd);
                            break;
                    default:
                            ret = ERROR_FAIL;
                            LOG_ERROR("BUG: encountered unknown JTAG command type");
                            break;
                }

                if (ret != ERROR_OK)
                        return ret;

                cmd = cmd->next;
        }

        if (ulink_handle->commands_in_queue > 0) {
                ret = ulink_execute_queued_commands(ulink_handle, USB_TIMEOUT);
                if (ret != ERROR_OK)
                        return ret;

                ret = ulink_post_process_queue(ulink_handle);
                if (ret != ERROR_OK)
                        return ret;

                ulink_clear_queue(ulink_handle);
        }

        return ERROR_OK;
}

/**
 * Set the TCK frequency of the ULINK adapter.
 *
 * @param khz desired JTAG TCK frequency.
 * @param jtag_speed where to store corresponding adapter-specific speed value.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_khz(int khz, int *jtag_speed)
{
        int ret;

        if (khz == 0) {
                LOG_ERROR("RCLK not supported");
                return ERROR_FAIL;
        }

        /* CLOCK_TCK commands are decoupled from others. Therefore, the frequency
         * setting can be done independently from all other commands. */
        if (khz >= 375)
                ulink_handle->delay_clock_tck = -1;
        else {
                ret = ulink_calculate_delay(DELAY_CLOCK_TCK, khz * 1000,
                                &ulink_handle->delay_clock_tck);
                if (ret != ERROR_OK)
                        return ret;
        }

        /* SCAN_{IN,OUT,IO} commands invoke CLOCK_TMS commands. Therefore, if the
         * requested frequency goes below the maximum frequency for SLOW_CLOCK_TMS
         * commands, all SCAN commands MUST also use the variable frequency
         * implementation! */
        if (khz >= 176) {
                ulink_handle->delay_clock_tms = -1;
                ulink_handle->delay_scan_in = -1;
                ulink_handle->delay_scan_out = -1;
                ulink_handle->delay_scan_io = -1;
        } else {
                ret = ulink_calculate_delay(DELAY_CLOCK_TMS, khz * 1000,
                                &ulink_handle->delay_clock_tms);
                if (ret != ERROR_OK)
                        return ret;

                ret = ulink_calculate_delay(DELAY_SCAN_IN, khz * 1000,
                                &ulink_handle->delay_scan_in);
                if (ret != ERROR_OK)
                        return ret;

                ret = ulink_calculate_delay(DELAY_SCAN_OUT, khz * 1000,
                                &ulink_handle->delay_scan_out);
                if (ret != ERROR_OK)
                        return ret;

                ret = ulink_calculate_delay(DELAY_SCAN_IO, khz * 1000,
                                &ulink_handle->delay_scan_io);
                if (ret != ERROR_OK)
                        return ret;
        }

        LOG_DEBUG_IO("ULINK TCK setup: delay_tck      = %i (%li Hz),",
                ulink_handle->delay_clock_tck,
                ulink_calculate_frequency(DELAY_CLOCK_TCK, ulink_handle->delay_clock_tck));
        LOG_DEBUG_IO("                 delay_tms      = %i (%li Hz),",
                ulink_handle->delay_clock_tms,
                ulink_calculate_frequency(DELAY_CLOCK_TMS, ulink_handle->delay_clock_tms));
        LOG_DEBUG_IO("                 delay_scan_in  = %i (%li Hz),",
                ulink_handle->delay_scan_in,
                ulink_calculate_frequency(DELAY_SCAN_IN, ulink_handle->delay_scan_in));
        LOG_DEBUG_IO("                 delay_scan_out = %i (%li Hz),",
                ulink_handle->delay_scan_out,
                ulink_calculate_frequency(DELAY_SCAN_OUT, ulink_handle->delay_scan_out));
        LOG_DEBUG_IO("                 delay_scan_io  = %i (%li Hz),",
                ulink_handle->delay_scan_io,
                ulink_calculate_frequency(DELAY_SCAN_IO, ulink_handle->delay_scan_io));

        /* Configure the ULINK device with the new delay values */
        ret = ulink_append_configure_tck_cmd(ulink_handle,
                        ulink_handle->delay_scan_in,
                        ulink_handle->delay_scan_out,
                        ulink_handle->delay_scan_io,
                        ulink_handle->delay_clock_tck,
                        ulink_handle->delay_clock_tms);

        if (ret != ERROR_OK)
                return ret;

        *jtag_speed = khz;

        return ERROR_OK;
}

/**
 * Set the TCK frequency of the ULINK adapter.
 *
 * Because of the way the TCK frequency is set up in the OpenULINK firmware,
 * there are five different speed settings. To simplify things, the
 * adapter-specific speed setting value is identical to the TCK frequency in
 * khz.
 *
 * @param speed desired adapter-specific speed value.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_speed(int speed)
{
        int dummy;

        return ulink_khz(speed, &dummy);
}

/**
 * Convert adapter-specific speed value to corresponding TCK frequency in kHz.
 *
 * Because of the way the TCK frequency is set up in the OpenULINK firmware,
 * there are five different speed settings. To simplify things, the
 * adapter-specific speed setting value is identical to the TCK frequency in
 * khz.
 *
 * @param speed adapter-specific speed value.
 * @param khz where to store corresponding TCK frequency in kHz.
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_speed_div(int speed, int *khz)
{
        *khz = speed;

        return ERROR_OK;
}

/**
 * Initiates the firmware download to the ULINK adapter and prepares
 * the USB handle.
 *
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_init(void)
{
        int ret, transferred;
        char str_manufacturer[20];
        bool download_firmware = false;
        unsigned char *dummy;
        uint8_t input_signals, output_signals;

        ulink_handle = calloc(1, sizeof(struct ulink));
        if (!ulink_handle)
                return ERROR_FAIL;

        libusb_init(&ulink_handle->libusb_ctx);

        ret = ulink_usb_open(&ulink_handle);
        if (ret != ERROR_OK) {
                LOG_ERROR("Could not open ULINK device");
                free(ulink_handle);
                ulink_handle = NULL;
                return ret;
        }

        /* Get String Descriptor to determine if firmware needs to be loaded */
        ret = libusb_get_string_descriptor_ascii(ulink_handle->usb_device_handle, 1, (unsigned char *)str_manufacturer, 20);
        if (ret < 0) {
                /* Could not get descriptor -> Unconfigured or original Keil firmware */
                download_firmware = true;
        } else {
                /* We got a String Descriptor, check if it is the correct one */
                if (strncmp(str_manufacturer, "OpenULINK", 9) != 0)
                        download_firmware = true;
        }

        if (download_firmware == true) {
                LOG_INFO("Loading OpenULINK firmware. This is reversible by power-cycling"
                        " ULINK device.");
                ret = ulink_load_firmware_and_renumerate(&ulink_handle,
                                ULINK_FIRMWARE_FILE, ULINK_RENUMERATION_DELAY);
                if (ret != ERROR_OK) {
                        LOG_ERROR("Could not download firmware and re-numerate ULINK");
                        free(ulink_handle);
                        ulink_handle = NULL;
                        return ret;
                }
        } else
                LOG_INFO("ULINK device is already running OpenULINK firmware");

        /* Get OpenULINK USB IN/OUT endpoints and claim the interface */
        ret = jtag_libusb_choose_interface(ulink_handle->usb_device_handle,
                &ulink_handle->ep_in, &ulink_handle->ep_out, -1, -1, -1, -1);
        if (ret != ERROR_OK)
                return ret;

        /* Initialize OpenULINK command queue */
        ulink_clear_queue(ulink_handle);

        /* Issue one test command with short timeout */
        ret = ulink_append_test_cmd(ulink_handle);
        if (ret != ERROR_OK)
                return ret;

        ret = ulink_execute_queued_commands(ulink_handle, 200);
        if (ret != ERROR_OK) {
                /* Sending test command failed. The ULINK device may be forever waiting for
                 * the host to fetch an USB Bulk IN packet (e. g. OpenOCD crashed or was
                 * shut down by the user via Ctrl-C. Try to retrieve this Bulk IN packet. */
                dummy = calloc(64, sizeof(uint8_t));

                ret = libusb_bulk_transfer(ulink_handle->usb_device_handle, ulink_handle->ep_in,
                                dummy, 64, &transferred, 200);

                free(dummy);

                if (ret != 0 || transferred == 0) {
                        /* Bulk IN transfer failed -> unrecoverable error condition */
                        LOG_ERROR("Cannot communicate with ULINK device. Disconnect ULINK from "
                                "the USB port and re-connect, then re-run OpenOCD");
                        free(ulink_handle);
                        ulink_handle = NULL;
                        return ERROR_FAIL;
                }
#ifdef _DEBUG_USB_COMMS_
                else {
                        /* Successfully received Bulk IN packet -> continue */
                        LOG_INFO("Recovered from lost Bulk IN packet");
                }
#endif
        }
        ulink_clear_queue(ulink_handle);

        ret = ulink_append_get_signals_cmd(ulink_handle);
        if (ret == ERROR_OK)
                ret = ulink_execute_queued_commands(ulink_handle, 200);

        if (ret == ERROR_OK) {
                /* Post-process the single CMD_GET_SIGNALS command */
                input_signals = ulink_handle->queue_start->payload_in[0];
                output_signals = ulink_handle->queue_start->payload_in[1];

                ulink_print_signal_states(input_signals, output_signals);
        }

        ulink_clear_queue(ulink_handle);

        return ERROR_OK;
}

/**
 * Closes the USB handle for the ULINK device.
 *
 * @return on success: ERROR_OK
 * @return on failure: ERROR_FAIL
 */
static int ulink_quit(void)
{
        int ret;

        ret = ulink_usb_close(&ulink_handle);
        free(ulink_handle);

        return ret;
}

/**
 * Set a custom path to ULINK firmware image and force downloading to ULINK.
 */
COMMAND_HANDLER(ulink_download_firmware_handler)
{
        int ret;

        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;


        LOG_INFO("Downloading ULINK firmware image %s", CMD_ARGV[0]);

        /* Download firmware image in CMD_ARGV[0] */
        ret = ulink_load_firmware_and_renumerate(&ulink_handle, CMD_ARGV[0],
                        ULINK_RENUMERATION_DELAY);

        return ret;
}

/*************************** Command Registration **************************/

static const struct command_registration ulink_subcommand_handlers[] = {
        {
                .name = "download_firmware",
                .handler = &ulink_download_firmware_handler,
                .mode = COMMAND_EXEC,
                .help = "download firmware image to ULINK device",
                .usage = "path/to/ulink_firmware.hex",
        },
        COMMAND_REGISTRATION_DONE,
};

static const struct command_registration ulink_command_handlers[] = {
        {
                .name = "ulink",
                .mode = COMMAND_ANY,
                .help = "perform ulink management",
                .chain = ulink_subcommand_handlers,
                .usage = "",
        },
        COMMAND_REGISTRATION_DONE
};

static struct jtag_interface ulink_interface = {
        .execute_queue = ulink_execute_queue,
};

struct adapter_driver ulink_adapter_driver = {
        .name = "ulink",
        .transports = jtag_only,
        .commands = ulink_command_handlers,

        .init = ulink_init,
        .quit = ulink_quit,
        .speed = ulink_speed,
        .khz = ulink_khz,
        .speed_div = ulink_speed_div,

        .jtag_ops = &ulink_interface,
};