opendous.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *                                                                         *
 *   Copyright (C) 2009 by Cahya Wirawan <cahya@gmx.at>                    *
 *   Based on opendous driver by Vladimir Fonov                            *
 *                                                                         *
 *   Copyright (C) 2009 by Vladimir Fonov <vladimir.fonov@gmai.com>        *
 *   Based on J-link driver by  Juergen Stuber                             *
 *                                                                         *
 *   Copyright (C) 2007 by Juergen Stuber <juergen@jstuber.net>            *
 *   based on Dominic Rath's and Benedikt Sauter's usbprog.c               *
 *                                                                         *
 *   Copyright (C) 2008 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 ***************************************************************************/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <jtag/interface.h>
#include <jtag/commands.h>
#include "libusb_helper.h"
#include <string.h>
#include <time.h>
 
#define OPENDOUS_MAX_VIDS_PIDS 4
/* define some probes with similar interface */
struct opendous_probe {
    const char *name;
    uint16_t VID[OPENDOUS_MAX_VIDS_PIDS];
    uint16_t PID[OPENDOUS_MAX_VIDS_PIDS];
    uint8_t READ_EP;
    uint8_t WRITE_EP;
    uint8_t CONTROL_TRANSFER;
    int BUFFERSIZE;
};
 
static const struct opendous_probe opendous_probes[] = {
    {"usbprog-jtag",    {0x1781, 0},            {0x0C63, 0},            0x82, 0x02, 0x00, 510 },
    {"opendous",        {0x1781, 0x03EB, 0},    {0xC0C0, 0x204F, 0},    0x81, 0x02, 0x00, 360 },
    {"usbvlab",         {0x16C0, 0},            {0x05DC, 0},            0x81, 0x02, 0x01, 360 },
    {NULL,              {0x0000},               {0x0000},               0x00, 0x00, 0x00,   0 }
};
 
#define OPENDOUS_WRITE_ENDPOINT   (opendous_probe->WRITE_EP)
#define OPENDOUS_READ_ENDPOINT    (opendous_probe->READ_EP)
 
static unsigned int opendous_hw_jtag_version = 1;
 
#define OPENDOUS_USB_TIMEOUT      1000
 
#define OPENDOUS_USB_BUFFER_SIZE  (opendous_probe->BUFFERSIZE)
#define OPENDOUS_IN_BUFFER_SIZE   (OPENDOUS_USB_BUFFER_SIZE)
#define OPENDOUS_OUT_BUFFER_SIZE  (OPENDOUS_USB_BUFFER_SIZE)
 
/* Global USB buffers */
static uint8_t *usb_in_buffer;
static uint8_t *usb_out_buffer;
 
/* Constants for OPENDOUS command */
 
#define OPENDOUS_MAX_SPEED          66
#define OPENDOUS_MAX_TAP_TRANSMIT   ((opendous_probe->BUFFERSIZE)-10)
#define OPENDOUS_MAX_INPUT_DATA     (OPENDOUS_MAX_TAP_TRANSMIT*4)
 
/* TAP */
#define OPENDOUS_TAP_BUFFER_SIZE 65536
 
struct pending_scan_result {
    int first;  /* First bit position in tdo_buffer to read */
    int length; /* Number of bits to read */
    struct scan_command *command; /* Corresponding scan command */
    uint8_t *buffer;
};
 
static int pending_scan_results_length;
static struct pending_scan_result *pending_scan_results_buffer;
 
#define MAX_PENDING_SCAN_RESULTS (OPENDOUS_MAX_INPUT_DATA)
 
/* JTAG usb commands */
#define JTAG_CMD_TAP_OUTPUT     0x0
#define JTAG_CMD_SET_TRST       0x1
#define JTAG_CMD_SET_SRST       0x2
#define JTAG_CMD_READ_INPUT     0x3
#define JTAG_CMD_TAP_OUTPUT_EMU 0x4
#define JTAG_CMD_SET_DELAY      0x5
#define JTAG_CMD_SET_SRST_TRST  0x6
#define JTAG_CMD_READ_CONFIG    0x7
 
/* usbvlab control transfer */
#define FUNC_START_BOOTLOADER 30
#define FUNC_WRITE_DATA       0x50
#define FUNC_READ_DATA        0x51
 
static char *opendous_type;
static const struct opendous_probe *opendous_probe;
 
/* External interface functions */
static int opendous_execute_queue(struct jtag_command *cmd_queue);
static int opendous_init(void);
static int opendous_quit(void);
 
/* Queue command functions */
static void opendous_end_state(enum tap_state state);
static void opendous_state_move(void);
static void opendous_path_move(unsigned int num_states, enum tap_state *path);
static void opendous_runtest(unsigned int num_cycles);
static void opendous_scan(int ir_scan, enum scan_type type, uint8_t *buffer,
        int scan_size, struct scan_command *command);
static void opendous_reset(int trst, int srst);
static void opendous_simple_command(uint8_t command, uint8_t _data);
static int opendous_get_status(void);
 
/* opendous tap buffer functions */
static void opendous_tap_init(void);
static int opendous_tap_execute(void);
static void opendous_tap_ensure_space(int scans, int bits);
static void opendous_tap_append_step(int tms, int tdi);
static void opendous_tap_append_scan(int length, uint8_t *buffer, struct scan_command *command);
 
/* opendous lowlevel functions */
struct opendous_jtag {
    struct libusb_device_handle *usb_handle;
};
 
static struct opendous_jtag *opendous_usb_open(void);
static void opendous_usb_close(struct opendous_jtag *opendous_jtag);
static int opendous_usb_message(struct opendous_jtag *opendous_jtag, int out_length, int in_length);
static int opendous_usb_write(struct opendous_jtag *opendous_jtag, int out_length);
static int opendous_usb_read(struct opendous_jtag *opendous_jtag);
 
/* helper functions */
static int opendous_get_version_info(void);
 
#ifdef _DEBUG_USB_COMMS_
static void opendous_debug_buffer(uint8_t *buffer, int length);
#endif
 
static struct opendous_jtag *opendous_jtag_handle;
 
/***************************************************************************/
/* External interface implementation */
 
COMMAND_HANDLER(opendous_handle_opendous_type_command)
{
    if (CMD_ARGC == 0)
        return ERROR_OK;
 
    /* only if the cable name wasn't overwritten by cmdline */
    if (!opendous_type) {
        /* REVISIT first verify that it's listed in cables[] ... */
        opendous_type = strdup(CMD_ARGV[0]);
    }
 
    /* REVISIT it's probably worth returning the current value ... */
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(opendous_handle_opendous_info_command)
{
    if (opendous_get_version_info() == ERROR_OK) {
        /* attempt to get status */
        opendous_get_status();
    }
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(opendous_handle_opendous_hw_jtag_command)
{
    switch (CMD_ARGC) {
        case 0:
            command_print(CMD, "opendous hw jtag  %i", opendous_hw_jtag_version);
            break;
 
        case 1: {
            int request_version = atoi(CMD_ARGV[0]);
            switch (request_version) {
                case 2:
                case 3:
                    opendous_hw_jtag_version = request_version;
                    break;
 
            default:
                return ERROR_COMMAND_SYNTAX_ERROR;
            }
            break;
        }
 
        default:
            return ERROR_COMMAND_SYNTAX_ERROR;
    }
 
    return ERROR_OK;
}
 
static const struct command_registration opendous_command_handlers[] = {
    {
        .name = "opendous_info",
        .handler = &opendous_handle_opendous_info_command,
        .mode = COMMAND_EXEC,
        .help = "show opendous info",
        .usage = "",
    },
    {
        .name = "opendous_hw_jtag",
        .handler = &opendous_handle_opendous_hw_jtag_command,
        .mode = COMMAND_EXEC,
        .help = "access opendous HW JTAG command version",
        .usage = "[2|3]",
    },
    {
        .name = "opendous_type",
        .handler = &opendous_handle_opendous_type_command,
        .mode = COMMAND_CONFIG,
        .help = "set opendous type",
        .usage = "[usbvlab|usbprog-jtag|opendous]",
    },
    COMMAND_REGISTRATION_DONE
};
 
static struct jtag_interface opendous_interface = {
    .execute_queue = opendous_execute_queue,
};
 
struct adapter_driver opendous_adapter_driver = {
    .name = "opendous",
    .transport_ids = TRANSPORT_JTAG,
    .transport_preferred_id = TRANSPORT_JTAG,
    .commands = opendous_command_handlers,
 
    .init = opendous_init,
    .quit = opendous_quit,
 
    .jtag_ops = &opendous_interface,
};
 
static int opendous_execute_queue(struct jtag_command *cmd_queue)
{
    struct jtag_command *cmd = cmd_queue;
    int scan_size;
    enum scan_type type;
    uint8_t *buffer;
 
    while (cmd) {
        switch (cmd->type) {
            case JTAG_RUNTEST:
                LOG_DEBUG_IO("runtest %u cycles, end in %i", cmd->cmd.runtest->num_cycles,
                    cmd->cmd.runtest->end_state);
 
                if (cmd->cmd.runtest->end_state != -1)
                    opendous_end_state(cmd->cmd.runtest->end_state);
                opendous_runtest(cmd->cmd.runtest->num_cycles);
                break;
 
            case JTAG_TLR_RESET:
                LOG_DEBUG_IO("statemove end in %i", cmd->cmd.statemove->end_state);
 
                if (cmd->cmd.statemove->end_state != -1)
                    opendous_end_state(cmd->cmd.statemove->end_state);
                opendous_state_move();
                break;
 
            case JTAG_PATHMOVE:
                LOG_DEBUG_IO("pathmove: %u states, end in %i",
                    cmd->cmd.pathmove->num_states,
                    cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]);
 
                opendous_path_move(cmd->cmd.pathmove->num_states, cmd->cmd.pathmove->path);
                break;
 
            case JTAG_SCAN:
                LOG_DEBUG_IO("scan end in %i", cmd->cmd.scan->end_state);
 
                if (cmd->cmd.scan->end_state != -1)
                    opendous_end_state(cmd->cmd.scan->end_state);
 
                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
                LOG_DEBUG_IO("scan input, length = %d", scan_size);
 
#ifdef _DEBUG_USB_COMMS_
                opendous_debug_buffer(buffer, (scan_size + 7) / 8);
#endif
                type = jtag_scan_type(cmd->cmd.scan);
                opendous_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size, cmd->cmd.scan);
                break;
 
            case JTAG_RESET:
                LOG_DEBUG_IO("reset trst: %i srst %i", cmd->cmd.reset->trst, cmd->cmd.reset->srst);
 
                opendous_tap_execute();
 
                if (cmd->cmd.reset->trst == 1)
                    tap_set_state(TAP_RESET);
                opendous_reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
                break;
 
            case JTAG_SLEEP:
                LOG_DEBUG_IO("sleep %" PRIu32, cmd->cmd.sleep->us);
                opendous_tap_execute();
                jtag_sleep(cmd->cmd.sleep->us);
                break;
 
            default:
                LOG_ERROR("BUG: unknown JTAG command type encountered");
                exit(-1);
        }
        cmd = cmd->next;
    }
    return opendous_tap_execute();
}
 
static int opendous_init(void)
{
    int check_cnt;
    const struct opendous_probe *cur_opendous_probe;
 
    cur_opendous_probe = opendous_probes;
 
    if (!opendous_type) {
        opendous_type = strdup("opendous");
        LOG_WARNING("No opendous_type specified, using default 'opendous'");
    }
 
    while (cur_opendous_probe->name) {
        if (strcmp(cur_opendous_probe->name, opendous_type) == 0) {
            opendous_probe = cur_opendous_probe;
            break;
        }
        cur_opendous_probe++;
    }
 
    if (!opendous_probe) {
        LOG_ERROR("No matching cable found for %s", opendous_type);
        return ERROR_JTAG_INIT_FAILED;
    }
 
 
    usb_in_buffer = malloc(opendous_probe->BUFFERSIZE);
    usb_out_buffer = malloc(opendous_probe->BUFFERSIZE);
 
    pending_scan_results_buffer = malloc(
            MAX_PENDING_SCAN_RESULTS * sizeof(*pending_scan_results_buffer));
 
    opendous_jtag_handle = opendous_usb_open();
 
    if (!opendous_jtag_handle) {
        LOG_ERROR("Cannot find opendous Interface! Please check connection and permissions.");
        return ERROR_JTAG_INIT_FAILED;
    }
 
    check_cnt = 0;
    while (check_cnt < 3) {
        if (opendous_get_version_info() == ERROR_OK) {
            /* attempt to get status */
            opendous_get_status();
            break;
        }
 
        check_cnt++;
    }
 
    LOG_INFO("opendous JTAG Interface ready");
 
    opendous_reset(0, 0);
    opendous_tap_init();
 
    return ERROR_OK;
}
 
static int opendous_quit(void)
{
    opendous_usb_close(opendous_jtag_handle);
 
    free(usb_out_buffer);
    usb_out_buffer = NULL;
 
    free(usb_in_buffer);
    usb_in_buffer = NULL;
 
    free(pending_scan_results_buffer);
    pending_scan_results_buffer = NULL;
 
    free(opendous_type);
    opendous_type = NULL;
 
    return ERROR_OK;
}
 
/***************************************************************************/
/* Queue command implementations */
 
void opendous_end_state(enum tap_state state)
{
    if (tap_is_state_stable(state))
        tap_set_end_state(state);
    else {
        LOG_ERROR("BUG: %i is not a valid end state", state);
        exit(-1);
    }
}
 
/* Goes to the end state. */
void opendous_state_move(void)
{
    int i;
    int tms = 0;
    uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
    uint8_t tms_scan_bits = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
 
    for (i = 0; i < tms_scan_bits; i++) {
        tms = (tms_scan >> i) & 1;
        opendous_tap_append_step(tms, 0);
    }
 
    tap_set_state(tap_get_end_state());
}
 
void opendous_path_move(unsigned int num_states, enum tap_state *path)
{
    for (unsigned int i = 0; i < num_states; i++) {
        if (path[i] == tap_state_transition(tap_get_state(), false))
            opendous_tap_append_step(0, 0);
        else if (path[i] == tap_state_transition(tap_get_state(), true))
            opendous_tap_append_step(1, 0);
        else {
            LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition",
                    tap_state_name(tap_get_state()), tap_state_name(path[i]));
            exit(-1);
        }
 
        tap_set_state(path[i]);
    }
 
    tap_set_end_state(tap_get_state());
}
 
void opendous_runtest(unsigned int num_cycles)
{
    enum tap_state saved_end_state = tap_get_end_state();
 
    /* only do a state_move when we're not already in IDLE */
    if (tap_get_state() != TAP_IDLE) {
        opendous_end_state(TAP_IDLE);
        opendous_state_move();
    }
 
    /* execute num_cycles */
    for (unsigned int i = 0; i < num_cycles; i++)
        opendous_tap_append_step(0, 0);
 
    /* finish in end_state */
    opendous_end_state(saved_end_state);
    if (tap_get_state() != tap_get_end_state())
        opendous_state_move();
}
 
void opendous_scan(int ir_scan, enum scan_type type, uint8_t *buffer, int scan_size, struct scan_command *command)
{
    enum tap_state saved_end_state;
 
    opendous_tap_ensure_space(1, scan_size + 8);
 
    saved_end_state = tap_get_end_state();
 
    /* Move to appropriate scan state */
    opendous_end_state(ir_scan ? TAP_IRSHIFT : TAP_DRSHIFT);
 
    if (tap_get_state() != tap_get_end_state())
        opendous_state_move();
 
    opendous_end_state(saved_end_state);
 
    /* Scan */
    opendous_tap_append_scan(scan_size, buffer, command);
 
    /* We are in Exit1, go to Pause */
    opendous_tap_append_step(0, 0);
 
    tap_set_state(ir_scan ? TAP_IRPAUSE : TAP_DRPAUSE);
 
    if (tap_get_state() != tap_get_end_state())
        opendous_state_move();
}
 
void opendous_reset(int trst, int srst)
{
    LOG_DEBUG("trst: %i, srst: %i", trst, srst);
 
    /* Signals are active low */
#if 0
    if (srst == 0)
        opendous_simple_command(JTAG_CMD_SET_SRST, 1);
    else if (srst == 1)
        opendous_simple_command(JTAG_CMD_SET_SRST, 0);
 
    if (trst == 0)
        opendous_simple_command(JTAG_CMD_SET_TRST, 1);
    else if (trst == 1)
        opendous_simple_command(JTAG_CMD_SET_TRST, 0);
#endif
 
    srst = srst ? 0 : 1;
    trst = trst ? 0 : 2;
    opendous_simple_command(JTAG_CMD_SET_SRST_TRST, srst | trst);
}
 
void opendous_simple_command(uint8_t command, uint8_t _data)
{
    int result;
 
    LOG_DEBUG_IO("0x%02x 0x%02x", command, _data);
 
    usb_out_buffer[0] = 2;
    usb_out_buffer[1] = 0;
    usb_out_buffer[2] = command;
    usb_out_buffer[3] = _data;
 
    result = opendous_usb_message(opendous_jtag_handle, 4, 1);
    if (result != 1)
        LOG_ERROR("opendous command 0x%02x failed (%d)", command, result);
}
 
int opendous_get_status(void)
{
    return ERROR_OK;
}
 
static int opendous_get_version_info(void)
{
    return ERROR_OK;
}
 
/***************************************************************************/
/* Estick tap functions */
 
static int tap_length;
static uint8_t tms_buffer[OPENDOUS_TAP_BUFFER_SIZE];
static uint8_t tdo_buffer[OPENDOUS_TAP_BUFFER_SIZE];
 
static int last_tms;
 
void opendous_tap_init(void)
{
    tap_length = 0;
    pending_scan_results_length = 0;
}
 
void opendous_tap_ensure_space(int scans, int bits)
{
    int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
    int available_bits = OPENDOUS_TAP_BUFFER_SIZE / 2 - tap_length;
 
    if ((scans > available_scans) || (bits > available_bits))
        opendous_tap_execute();
}
 
void opendous_tap_append_step(int tms, int tdi)
{
    last_tms = tms;
    unsigned char _tms = tms ? 1 : 0;
    unsigned char _tdi = tdi ? 1 : 0;
 
    opendous_tap_ensure_space(0, 1);
 
    int tap_index =  tap_length / 4;
    int bits  = (tap_length % 4) * 2;
 
    if (tap_length < OPENDOUS_TAP_BUFFER_SIZE) {
        if (!bits)
            tms_buffer[tap_index] = 0;
 
        tms_buffer[tap_index] |= (_tdi << bits)|(_tms << (bits + 1));
        tap_length++;
    } else
        LOG_ERROR("opendous_tap_append_step, overflow");
}
 
void opendous_tap_append_scan(int length, uint8_t *buffer, struct scan_command *command)
{
    LOG_DEBUG_IO("append scan, length = %d", length);
 
    struct pending_scan_result *pending_scan_result = &pending_scan_results_buffer[pending_scan_results_length];
    int i;
 
    pending_scan_result->first = tap_length;
    pending_scan_result->length = length;
    pending_scan_result->command = command;
    pending_scan_result->buffer = buffer;
 
    for (i = 0; i < length; i++)
        opendous_tap_append_step((i < length-1 ? 0 : 1), (buffer[i / 8] >> (i % 8)) & 1);
    pending_scan_results_length++;
}
 
/* Pad and send a tap sequence to the device, and receive the answer.
 * For the purpose of padding we assume that we are in idle or pause state. */
int opendous_tap_execute(void)
{
    int byte_length;
    int i, j;
    int result;
 
#ifdef _DEBUG_USB_COMMS_
    int byte_length_out;
#endif
 
    if (tap_length > 0) {
 
        /* memset(tdo_buffer,0,OPENDOUS_TAP_BUFFER_SIZE); */
        /* LOG_INFO("OPENDOUS tap execute %d",tap_length); */
        byte_length = (tap_length + 3) / 4;
 
#ifdef _DEBUG_USB_COMMS_
        byte_length_out = (tap_length + 7) / 8;
        LOG_DEBUG("opendous is sending %d bytes", byte_length);
#endif
 
        for (j = 0, i = 0; j <  byte_length;) {
 
            int receive;
            int transmit = byte_length - j;
            if (transmit > OPENDOUS_MAX_TAP_TRANSMIT) {
                transmit = OPENDOUS_MAX_TAP_TRANSMIT;
                receive = (OPENDOUS_MAX_TAP_TRANSMIT) / 2;
                usb_out_buffer[2] = JTAG_CMD_TAP_OUTPUT;
            } else {
                usb_out_buffer[2] = JTAG_CMD_TAP_OUTPUT | ((tap_length % 4) << 4);
                receive = (transmit + 1) / 2;
            }
            usb_out_buffer[0] = (transmit + 1) & 0xff;
            usb_out_buffer[1] = ((transmit + 1) >> 8) & 0xff;
 
            memmove(usb_out_buffer + 3, tms_buffer + j, transmit);
            result = opendous_usb_message(opendous_jtag_handle, 3 + transmit, receive);
            if (result != receive) {
                LOG_ERROR("opendous_tap_execute, wrong result %d, expected %d", result, receive);
                return ERROR_JTAG_QUEUE_FAILED;
            }
 
            memmove(tdo_buffer + i, usb_in_buffer, receive);
            i += receive;
            j += transmit;
        }
 
#ifdef _DEBUG_USB_COMMS_
        LOG_DEBUG("opendous tap result %d", byte_length_out);
        opendous_debug_buffer(tdo_buffer, byte_length_out);
#endif
 
        /* LOG_INFO("eStick tap execute %d",tap_length); */
        for (i = 0; i < pending_scan_results_length; i++) {
 
            struct pending_scan_result *pending_scan_result = &pending_scan_results_buffer[i];
            uint8_t *buffer = pending_scan_result->buffer;
            int length = pending_scan_result->length;
            int first = pending_scan_result->first;
            struct scan_command *command = pending_scan_result->command;
 
            /* Copy to buffer */
            buf_set_buf(tdo_buffer, first, buffer, 0, length);
 
            LOG_DEBUG_IO("pending scan result, length = %d", length);
 
#ifdef _DEBUG_USB_COMMS_
            opendous_debug_buffer(buffer, byte_length_out);
#endif
 
            if (jtag_read_buffer(buffer, command) != ERROR_OK) {
                opendous_tap_init();
                return ERROR_JTAG_QUEUE_FAILED;
            }
 
            free(pending_scan_result->buffer);
        }
 
        opendous_tap_init();
    }
 
    return ERROR_OK;
}
 
/*****************************************************************************/
/* Estick USB low-level functions */
 
struct opendous_jtag *opendous_usb_open(void)
{
    struct opendous_jtag *result;
 
    struct libusb_device_handle *devh;
    if (jtag_libusb_open(opendous_probe->VID, opendous_probe->PID, NULL, &devh, NULL) != ERROR_OK)
        return NULL;
 
    jtag_libusb_set_configuration(devh, 0);
    libusb_claim_interface(devh, 0);
 
    result = malloc(sizeof(*result));
    result->usb_handle = devh;
    return result;
}
 
void opendous_usb_close(struct opendous_jtag *opendous_jtag)
{
    jtag_libusb_close(opendous_jtag->usb_handle);
    free(opendous_jtag);
}
 
/* Send a message and receive the reply. */
int opendous_usb_message(struct opendous_jtag *opendous_jtag, int out_length, int in_length)
{
    int result;
 
    result = opendous_usb_write(opendous_jtag, out_length);
    if (result == out_length) {
        result = opendous_usb_read(opendous_jtag);
        if (result == in_length)
            return result;
        else {
            LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)", in_length, result);
            return -1;
        }
    } else {
        LOG_ERROR("usb_bulk_write failed (requested=%d, result=%d)", out_length, result);
        return -1;
    }
}
 
/* Write data from out_buffer to USB. */
int opendous_usb_write(struct opendous_jtag *opendous_jtag, int out_length)
{
    int result, transferred;
 
    if (out_length > OPENDOUS_OUT_BUFFER_SIZE) {
        LOG_ERROR("opendous_jtag_write illegal out_length=%d (max=%d)", out_length, OPENDOUS_OUT_BUFFER_SIZE);
        return -1;
    }
 
#ifdef _DEBUG_USB_COMMS_
    LOG_DEBUG("USB write begin");
#endif
    if (opendous_probe->CONTROL_TRANSFER) {
        result = jtag_libusb_control_transfer(opendous_jtag->usb_handle,
            LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE | LIBUSB_ENDPOINT_OUT,
            FUNC_WRITE_DATA, 0, 0, (char *)usb_out_buffer, out_length, OPENDOUS_USB_TIMEOUT,
            &transferred);
        /* FIXME: propagate error separately from transferred */
        if (result == ERROR_OK)
            result = transferred;
    } else {
        jtag_libusb_bulk_write(opendous_jtag->usb_handle, OPENDOUS_WRITE_ENDPOINT,
            (char *)usb_out_buffer, out_length, OPENDOUS_USB_TIMEOUT, &result);
    }
#ifdef _DEBUG_USB_COMMS_
    LOG_DEBUG("USB write end: %d bytes", result);
#endif
 
    LOG_DEBUG_IO("opendous_usb_write, out_length = %d, result = %d", out_length, result);
 
#ifdef _DEBUG_USB_COMMS_
    opendous_debug_buffer(usb_out_buffer, out_length);
#endif
    return result;
}
 
/* Read data from USB into in_buffer. */
int opendous_usb_read(struct opendous_jtag *opendous_jtag)
{
    int transferred;
 
#ifdef _DEBUG_USB_COMMS_
    LOG_DEBUG("USB read begin");
#endif
    int result;
    if (opendous_probe->CONTROL_TRANSFER) {
        result = jtag_libusb_control_transfer(opendous_jtag->usb_handle,
            LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE | LIBUSB_ENDPOINT_IN,
            FUNC_READ_DATA, 0, 0, (char *)usb_in_buffer, OPENDOUS_IN_BUFFER_SIZE, OPENDOUS_USB_TIMEOUT,
            &transferred);
        /* FIXME: propagate error separately from transferred */
        if (result == ERROR_OK)
            result = transferred;
    } else {
        jtag_libusb_bulk_read(opendous_jtag->usb_handle, OPENDOUS_READ_ENDPOINT,
            (char *)usb_in_buffer, OPENDOUS_IN_BUFFER_SIZE, OPENDOUS_USB_TIMEOUT, &result);
    }
#ifdef _DEBUG_USB_COMMS_
    LOG_DEBUG("USB read end: %d bytes", result);
#endif
    LOG_DEBUG_IO("opendous_usb_read, result = %d", result);
 
#ifdef _DEBUG_USB_COMMS_
    opendous_debug_buffer(usb_in_buffer, result);
#endif
    return result;
}
 
#ifdef _DEBUG_USB_COMMS_
#define BYTES_PER_LINE  16
 
void opendous_debug_buffer(uint8_t *buffer, int length)
{
    char line[8 + 3 * BYTES_PER_LINE + 1];
 
    for (int i = 0; i < length; i += BYTES_PER_LINE) {
        int n = snprintf(line, 9, "%04x", i);
        for (int j = i; j < i + BYTES_PER_LINE && j < length; j++)
            n += snprintf(line + n, 4, " %02x", buffer[j]);
        LOG_DEBUG("%s", line);
    }
}
#endif