Fix ft2232 TX buffer overflow

[openocd.git] / src / jtag / arm-jtag-ew.c

// vim:ts=4 sw=4: 

/***************************************************************************
 *   Copyright (C) 2009 by Dimitar Dimitrov <dinuxbg@gmail.com>            *
 *   based on Dominic Rath's and Benedikt Sauter's usbprog.c               *
 *                                                                         *
 *   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, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

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

#include "replacements.h"

#include "jtag.h"
#include <usb.h>
#include <string.h>
#include <ctype.h>

/* system includes */

#include "log.h"

#define USB_VID                                         0x15ba
#define USB_PID                                         0x001e

#define ARMJTAGEW_EPT_BULK_OUT          0x01u
#define ARMJTAGEW_EPT_BULK_IN           0x82u

#define ARMJTAGEW_USB_TIMEOUT           2000

#define ARMJTAGEW_IN_BUFFER_SIZE        (4*1024)
#define ARMJTAGEW_OUT_BUFFER_SIZE       (4*1024)


/* USB command request codes. */
#define CMD_GET_VERSION                         0x00
#define CMD_SELECT_DPIMPL                       0x10
#define CMD_SET_TCK_FREQUENCY           0x11
#define CMD_GET_TCK_FREQUENCY           0x12
#define CMD_MEASURE_MAX_TCK_FREQ        0x15
#define CMD_MEASURE_RTCK_RESPONSE       0x16
#define CMD_TAP_SHIFT                           0x17
#define CMD_SET_TAPHW_STATE                     0x20
#define CMD_GET_TAPHW_STATE                     0x21
#define CMD_TGPWR_SETUP                         0x22

/* Global USB buffers */
static u8 usb_in_buffer[ARMJTAGEW_IN_BUFFER_SIZE];
static u8 usb_out_buffer[ARMJTAGEW_OUT_BUFFER_SIZE];

/* External interface functions */
static int armjtagew_execute_queue(void);
static int armjtagew_speed(int speed);
static int armjtagew_khz(int khz, int *jtag_speed);
static int armjtagew_register_commands(struct command_context_s *cmd_ctx);
static int armjtagew_init(void);
static int armjtagew_quit(void);

/* CLI command handler functions */
static int armjtagew_handle_armjtagew_info_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);

/* Queue command functions */
static void armjtagew_end_state(tap_state_t state);
static void armjtagew_state_move(void);
static void armjtagew_path_move(int num_states, tap_state_t *path);
static void armjtagew_runtest(int num_cycles);
static void armjtagew_scan(int ir_scan, enum scan_type type, u8 *buffer, int scan_size, scan_command_t *command);
static void armjtagew_reset(int trst, int srst);
//static void armjtagew_simple_command(u8 command);
static int armjtagew_get_status(void);

/* tap buffer functions */
static void armjtagew_tap_init(void);
static int armjtagew_tap_execute(void);
static void armjtagew_tap_ensure_space(int scans, int bits);
static void armjtagew_tap_append_step(int tms, int tdi);
static void armjtagew_tap_append_scan(int length, u8 *buffer, scan_command_t *command);

/* ARM-JTAG-EW lowlevel functions */
typedef struct armjtagew_jtag
{
        struct usb_dev_handle* usb_handle;
} armjtagew_jtag_t;

static armjtagew_jtag_t *armjtagew_usb_open(void);
static void armjtagew_usb_close(armjtagew_jtag_t *armjtagew_jtag);
static int armjtagew_usb_message(armjtagew_jtag_t *armjtagew_jtag, int out_length, int in_length);
static int armjtagew_usb_write(armjtagew_jtag_t *armjtagew_jtag, int out_length);
static int armjtagew_usb_read(armjtagew_jtag_t *armjtagew_jtag, int exp_in_length);

/* helper functions */
static int armjtagew_get_version_info(void);

#ifdef _DEBUG_USB_COMMS_
static void armjtagew_debug_buffer(u8 *buffer, int length);
#endif

static armjtagew_jtag_t* armjtagew_jtag_handle;



/***************************************************************************/
/* External interface implementation */

jtag_interface_t armjtagew_interface =
{
        .name = "arm-jtag-ew",
        .execute_queue = armjtagew_execute_queue,
        .speed = armjtagew_speed,
        .khz = armjtagew_khz,
        .register_commands = armjtagew_register_commands,
        .init = armjtagew_init,
        .quit = armjtagew_quit
};


static int armjtagew_execute_queue(void)
{
        jtag_command_t *cmd = jtag_command_queue;
        int scan_size;
        enum scan_type type;
        u8 *buffer;

        while (cmd != NULL)
        {
                switch (cmd->type)
                {
                        case JTAG_END_STATE:
                                DEBUG_JTAG_IO("end_state: %i", cmd->cmd.end_state->end_state);

                                if (cmd->cmd.end_state->end_state != TAP_INVALID)
                                {
                                        armjtagew_end_state(cmd->cmd.end_state->end_state);
                                }
                                break;

                        case JTAG_RUNTEST:
                                DEBUG_JTAG_IO( "runtest %i cycles, end in %i", cmd->cmd.runtest->num_cycles, \
                                        cmd->cmd.runtest->end_state);

                                if (cmd->cmd.runtest->end_state != TAP_INVALID)
                                {
                                        armjtagew_end_state(cmd->cmd.runtest->end_state);
                                }
                                armjtagew_runtest(cmd->cmd.runtest->num_cycles);
                                break;

                        case JTAG_STATEMOVE:
                                DEBUG_JTAG_IO("statemove end in %i", cmd->cmd.statemove->end_state);

                                if (cmd->cmd.statemove->end_state != TAP_INVALID)
                                {
                                        armjtagew_end_state(cmd->cmd.statemove->end_state);
                                }
                                armjtagew_state_move();
                                break;

                        case JTAG_PATHMOVE:
                                DEBUG_JTAG_IO("pathmove: %i states, end in %i", \
                                        cmd->cmd.pathmove->num_states, \
                                        cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]);

                                armjtagew_path_move(cmd->cmd.pathmove->num_states, cmd->cmd.pathmove->path);
                                break;

                        case JTAG_SCAN:
                                DEBUG_JTAG_IO("scan end in %i", cmd->cmd.scan->end_state);

                                if (cmd->cmd.scan->end_state != TAP_INVALID)
                                {
                                        armjtagew_end_state(cmd->cmd.scan->end_state);
                                }

                                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
                                DEBUG_JTAG_IO("scan input, length = %d", scan_size);

#ifdef _DEBUG_USB_COMMS_
                                armjtagew_debug_buffer(buffer, (scan_size + 7) / 8);
#endif
                                type = jtag_scan_type(cmd->cmd.scan);
                                armjtagew_scan(cmd->cmd.scan->ir_scan, type, buffer, scan_size, cmd->cmd.scan);
                                break;

                        case JTAG_RESET:
                                DEBUG_JTAG_IO("reset trst: %i srst %i", cmd->cmd.reset->trst, cmd->cmd.reset->srst);

                                armjtagew_tap_execute();

                                if (cmd->cmd.reset->trst == 1)
                                {
                                        tap_set_state(TAP_RESET);
                                }
                                armjtagew_reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
                                break;

                        case JTAG_SLEEP:
                                DEBUG_JTAG_IO("sleep %i", cmd->cmd.sleep->us);
                                armjtagew_tap_execute();
                                jtag_sleep(cmd->cmd.sleep->us);
                                break;

                        default:
                                LOG_ERROR("BUG: unknown JTAG command type encountered");
                                exit(-1);
                }
                cmd = cmd->next;
        }

        return armjtagew_tap_execute();
}


/* Sets speed in kHz. */
static int armjtagew_speed(int speed)
{
    int result;
    int speed_real;


    usb_out_buffer[0] = CMD_SET_TCK_FREQUENCY;
        buf_set_u32(usb_out_buffer+1, 0, 32, speed);

    result = armjtagew_usb_message(armjtagew_jtag_handle, 4, 4);

    if (result < 0)
    {
        LOG_ERROR("ARM-JTAG-EW setting speed failed (%d)", result);
        return ERROR_JTAG_DEVICE_ERROR;
    }

        usb_out_buffer[0] = CMD_GET_TCK_FREQUENCY;
    result = armjtagew_usb_message(armjtagew_jtag_handle, 1, 4);
        speed_real = (int)buf_get_u32(usb_in_buffer,0,32);
        if(result < 0) 
        {
        LOG_ERROR("ARM-JTAG-EW getting speed failed (%d)", result);
        return ERROR_JTAG_DEVICE_ERROR;
        } 
        else
        {
        LOG_INFO("Requested speed %dkHz, emulator reported %dkHz.", speed, speed_real);
        }

    return ERROR_OK;
}


static int armjtagew_khz(int khz, int *jtag_speed)
{
        *jtag_speed = khz;

        return ERROR_OK;
}

static int armjtagew_register_commands(struct command_context_s *cmd_ctx)
{
        register_command(cmd_ctx, NULL, "armjtagew_info", armjtagew_handle_armjtagew_info_command, COMMAND_EXEC,
                "query armjtagew info");
        return ERROR_OK;
}

static int armjtagew_init(void)
{
        int check_cnt;

        armjtagew_jtag_handle = armjtagew_usb_open();

        if (armjtagew_jtag_handle == 0)
        {
                LOG_ERROR("Cannot find ARM-JTAG-EW Interface! Please check connection and permissions.");
                return ERROR_JTAG_INIT_FAILED;
        }

        check_cnt = 0;
        while (check_cnt < 3)
        {
                if (armjtagew_get_version_info() == ERROR_OK)
                {
                        /* attempt to get status */
                        armjtagew_get_status();
                        break;
                }

                check_cnt++;
        }

        if (check_cnt == 3)
        {
                LOG_INFO("ARM-JTAG-EW initial read failed, don't worry");
        }

        LOG_INFO("ARM-JTAG-EW JTAG Interface ready");

        armjtagew_reset(0, 0);
        armjtagew_tap_init();

        return ERROR_OK;
}

static int armjtagew_quit(void)
{
        armjtagew_usb_close(armjtagew_jtag_handle);
        return ERROR_OK;
}

/***************************************************************************/
/* Queue command implementations */

static void armjtagew_end_state(tap_state_t 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. */
static void armjtagew_state_move(void)
{
        int i;
        int tms = 0;
        u8 tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());

        for (i = 0; i < 7; i++)
        {
                tms = (tms_scan >> i) & 1;
                armjtagew_tap_append_step(tms, 0);
        }

        tap_set_state(tap_get_end_state());
}

static void armjtagew_path_move(int num_states, tap_state_t *path)
{
        int i;

        for (i = 0; i < num_states; i++)
        {
                /*
                 * TODO: The ARM-JTAG-EW hardware delays TDI with 3 TCK cycles when in RTCK mode. 
                 * Either handle that here, or update the documentation with examples
                 * how to fix that in the configuration files.
                 */
                if (path[i] == tap_state_transition(tap_get_state(), false))
                {
                        armjtagew_tap_append_step(0, 0);
                }
                else if (path[i] == tap_state_transition(tap_get_state(), true))
                {
                        armjtagew_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());
}

static void armjtagew_runtest(int num_cycles)
{
        int i;

        tap_state_t 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)
        {
                armjtagew_end_state(TAP_IDLE);
                armjtagew_state_move();
        }

        /* execute num_cycles */
        for (i = 0; i < num_cycles; i++)
        {
                armjtagew_tap_append_step(0, 0);
        }

        /* finish in end_state */
        armjtagew_end_state(saved_end_state);
        if (tap_get_state() != tap_get_end_state())
        {
                armjtagew_state_move();
        }
}

static void armjtagew_scan(int ir_scan, enum scan_type type, u8 *buffer, int scan_size, scan_command_t *command)
{
        tap_state_t saved_end_state;

        armjtagew_tap_ensure_space(1, scan_size + 8);

        saved_end_state = tap_get_end_state();

        /* Move to appropriate scan state */
        armjtagew_end_state(ir_scan ? TAP_IRSHIFT : TAP_DRSHIFT);

        armjtagew_state_move();
        armjtagew_end_state(saved_end_state);

        /* Scan */
        armjtagew_tap_append_scan(scan_size, buffer, command);

        /* We are in Exit1, go to Pause */
        armjtagew_tap_append_step(0, 0);

        tap_set_state(ir_scan ? TAP_IRPAUSE : TAP_DRPAUSE);

        if (tap_get_state() != tap_get_end_state())
        {
                armjtagew_state_move();
        }
}

static void armjtagew_reset(int trst, int srst)
{
        const u8 trst_mask = (1u<<5);
        const u8 srst_mask = (1u<<6);
        u8 val = 0;
        u8 outp_en = 0;
        u8 change_mask = 0;
        int result;

        LOG_DEBUG("trst: %i, srst: %i", trst, srst);

        if (srst == 0)
        {
                val |= srst_mask;
                outp_en &= ~srst_mask;          /* tristate */
                change_mask |= srst_mask;
        }
        else if (srst == 1)
        {
                val &= ~srst_mask;
                outp_en |= srst_mask;
                change_mask |= srst_mask;
        }

        if (trst == 0)
        {
                val |= trst_mask;
                outp_en &= ~trst_mask;          /* tristate */
                change_mask |= trst_mask;
        }
        else if (trst == 1)
        {
                val &= ~trst_mask;
                outp_en |= trst_mask;
                change_mask |= trst_mask;
        }

        usb_out_buffer[0] = CMD_SET_TAPHW_STATE;
        usb_out_buffer[1] = val;
        usb_out_buffer[2] = outp_en;
        usb_out_buffer[3] = change_mask;
        result = armjtagew_usb_write(armjtagew_jtag_handle, 4);
        if (result != 4)
        {
                LOG_ERROR("ARM-JTAG-EW TRST/SRST pin set failed failed (%d)", result);
        }
}


static int armjtagew_get_status(void)
{
        int result;

        usb_out_buffer[0] = CMD_GET_TAPHW_STATE;
        result = armjtagew_usb_message(armjtagew_jtag_handle, 1, 12);

        if (result == 0)
        {
                unsigned int u_tg = buf_get_u32(usb_in_buffer, 0, 16);
                LOG_INFO("U_tg = %d mV, U_aux = %d mV, U_tgpwr = %d mV, I_tgpwr = %d mA, D1 = %d, Target power %s %s\n", \
                        buf_get_u32(usb_in_buffer + 0, 0, 16), \
                        buf_get_u32(usb_in_buffer + 2, 0, 16), \
                        buf_get_u32(usb_in_buffer + 4, 0, 16), \
                        buf_get_u32(usb_in_buffer + 6, 0, 16), \
                        usb_in_buffer[9], \
                        usb_in_buffer[11] ? "OVERCURRENT" : "OK", \
                        usb_in_buffer[10] ? "enabled" : "disabled");

                if (u_tg < 1500)
                {
                        LOG_ERROR("Vref too low. Check Target Power\n");
                }
        }
        else
        {
                LOG_ERROR("ARM-JTAG-EW command CMD_GET_TAPHW_STATE failed (%d)\n", result);
        }

        return ERROR_OK;
}

static int armjtagew_get_version_info(void)
{
        int result;
        char sn[16];
        char auxinfo[257];

        /* query hardware version */
        usb_out_buffer[0] = CMD_GET_VERSION;
        result = armjtagew_usb_message(armjtagew_jtag_handle, 1, 4+15+256);

        if (result != 0) 
        {
                LOG_ERROR("ARM-JTAG-EW command CMD_GET_VERSION failed (%d)\n", result);
                return ERROR_JTAG_DEVICE_ERROR;
        }


        memcpy(sn, usb_in_buffer+4, 15);
        sn[15] = '\0';
        memcpy(auxinfo, usb_in_buffer+4+15, 256);
        auxinfo[256] = '\0';

        LOG_INFO("ARM-JTAG-EW firmware version %d.%d, hardware revision %c, SN=%s, Additional info: %s", \
                        usb_in_buffer[1], usb_in_buffer[0], \
                        isgraph(usb_in_buffer[2]) ? usb_in_buffer[2] : 'X', \
                        sn, auxinfo);
        return ERROR_OK;
}

static int armjtagew_handle_armjtagew_info_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
        if (armjtagew_get_version_info() == ERROR_OK)
        {
                /* attempt to get status */
                armjtagew_get_status();
        }

        return ERROR_OK;
}

/***************************************************************************/
/* ARM-JTAG-EW tap functions */

/* 2048 is the max value we can use here */
#define ARMJTAGEW_TAP_BUFFER_SIZE 2048

static int tap_length;
static u8 tms_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];
static u8 tdi_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];
static u8 tdo_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];

typedef struct
{
        int first;      /* First bit position in tdo_buffer to read */
        int length; /* Number of bits to read */
        scan_command_t *command; /* Corresponding scan command */
        u8 *buffer;
} pending_scan_result_t;

#define MAX_PENDING_SCAN_RESULTS 256

static int pending_scan_results_length;
static pending_scan_result_t pending_scan_results_buffer[MAX_PENDING_SCAN_RESULTS];

static int last_tms;

static void armjtagew_tap_init(void)
{
        tap_length = 0;
        pending_scan_results_length = 0;
}

static void armjtagew_tap_ensure_space(int scans, int bits)
{
        int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
        int available_bits = ARMJTAGEW_TAP_BUFFER_SIZE * 8 - tap_length;

        if (scans > available_scans || bits > available_bits)
        {
                armjtagew_tap_execute();
        }
}

static void armjtagew_tap_append_step(int tms, int tdi)
{
        last_tms = tms;
        int index = tap_length / 8;

        if (index < ARMJTAGEW_TAP_BUFFER_SIZE)
        {
                int bit_index = tap_length % 8;
                u8 bit = 1 << bit_index;

                if (tms)
                {
                        tms_buffer[index] |= bit;
                }
                else
                {
                        tms_buffer[index] &= ~bit;
                }

                if (tdi)
                {
                        tdi_buffer[index] |= bit;
                }
                else
                {
                        tdi_buffer[index] &= ~bit;
                }

                tap_length++;
        }
        else
        {
                LOG_ERROR("armjtagew_tap_append_step, overflow");
        }
}

void armjtagew_tap_append_scan(int length, u8 *buffer, scan_command_t *command)
{
        pending_scan_result_t *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++)
        {
                armjtagew_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. */
static int armjtagew_tap_execute(void)
{
        int byte_length;
        int tms_offset;
        int tdi_offset;
        int i;
        int result;

        if (tap_length > 0)
        {
                /* Pad last byte so that tap_length is divisible by 8 */
                while (tap_length % 8 != 0)
                {
                        /* More of the last TMS value keeps us in the same state,
                         * analogous to free-running JTAG interfaces. */
                        armjtagew_tap_append_step(last_tms, 0);
                }

                byte_length = tap_length / 8;

                usb_out_buffer[0] = CMD_TAP_SHIFT;
                buf_set_u32(usb_out_buffer+1, 0, 16, byte_length);

                tms_offset = 3;
                for (i = 0; i < byte_length; i++)
                {
                        usb_out_buffer[tms_offset + i] = flip_u32(tms_buffer[i],8);
                }

                tdi_offset = tms_offset + byte_length;
                for (i = 0; i < byte_length; i++)
                {
                        usb_out_buffer[tdi_offset + i] = flip_u32(tdi_buffer[i],8);
                }

                result = armjtagew_usb_message(armjtagew_jtag_handle, 3 + 2 * byte_length, byte_length + 4);

                if (result == 0)
                {
                        int stat;

                        stat = (int)buf_get_u32(usb_in_buffer + byte_length, 0, 32);
                        if(stat) {
                                LOG_ERROR("armjtagew_tap_execute, emulator returned error code %d for a CMD_TAP_SHIFT command", stat);
                                return ERROR_JTAG_QUEUE_FAILED;
                        }

                        for (i = 0; i < byte_length; i++)
                        {
                                tdo_buffer[i] = flip_u32(usb_in_buffer[i],8);
                        }

                        for (i = 0; i < pending_scan_results_length; i++)
                        {
                                pending_scan_result_t *pending_scan_result = &pending_scan_results_buffer[i];
                                u8 *buffer = pending_scan_result->buffer;
                                int length = pending_scan_result->length;
                                int first = pending_scan_result->first;
                                scan_command_t *command = pending_scan_result->command;

                                /* Copy to buffer */
                                buf_set_buf(tdo_buffer, first, buffer, 0, length);

                                DEBUG_JTAG_IO("pending scan result, length = %d", length);

#ifdef _DEBUG_USB_COMMS_
                                armjtagew_debug_buffer(buffer, byte_length);
#endif

                                if (jtag_read_buffer(buffer, command) != ERROR_OK)
                                {
                                        armjtagew_tap_init();
                                        return ERROR_JTAG_QUEUE_FAILED;
                                }

                                if (pending_scan_result->buffer != NULL)
                                {
                                        free(pending_scan_result->buffer);
                                }
                        }
                }
                else
                {
                        LOG_ERROR("armjtagew_tap_execute, wrong result %d, expected %d", result, byte_length);
                        return ERROR_JTAG_QUEUE_FAILED;
                }

                armjtagew_tap_init();
        }

        return ERROR_OK;
}

/*****************************************************************************/
/* JLink USB low-level functions */

static armjtagew_jtag_t* armjtagew_usb_open()
{
        struct usb_bus *busses;
        struct usb_bus *bus;
        struct usb_device *dev;

        armjtagew_jtag_t *result;

        result = (armjtagew_jtag_t*) malloc(sizeof(armjtagew_jtag_t));

        usb_init();
        usb_find_busses();
        usb_find_devices();

        busses = usb_get_busses();

        /* find armjtagew_jtag device in usb bus */

        for (bus = busses; bus; bus = bus->next)
        {
                for (dev = bus->devices; dev; dev = dev->next)
                {
                        if ((dev->descriptor.idVendor == USB_VID) && (dev->descriptor.idProduct == USB_PID))
                        {
                                result->usb_handle = usb_open(dev);

#if 0
                                /* usb_set_configuration required under win32 */
                                usb_set_configuration(result->usb_handle, dev->config[0].bConfigurationValue);
#endif
                                usb_claim_interface(result->usb_handle, 0);

#if 0
                                /*
                                 * This makes problems under Mac OS X. And is not needed
                                 * under Windows. Hopefully this will not break a linux build
                                 */
                                usb_set_altinterface(result->usb_handle, 0);
#endif
                                return result;
                        }
                }
        }

        free(result);
        return NULL;
}

static void armjtagew_usb_close(armjtagew_jtag_t *armjtagew_jtag)
{
        usb_close(armjtagew_jtag->usb_handle);
        free(armjtagew_jtag);
}

/* Send a message and receive the reply. */
static int armjtagew_usb_message(armjtagew_jtag_t *armjtagew_jtag, int out_length, int in_length)
{
        int result;

        result = armjtagew_usb_write(armjtagew_jtag, out_length);
        if (result == out_length)
        {
                result = armjtagew_usb_read(armjtagew_jtag, in_length);
                if (result != in_length) 
                {
                        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;
        }
        return 0;
}

/* Write data from out_buffer to USB. */
static int armjtagew_usb_write(armjtagew_jtag_t *armjtagew_jtag, int out_length)
{
        int result;

        if (out_length > ARMJTAGEW_OUT_BUFFER_SIZE)
        {
                LOG_ERROR("armjtagew_jtag_write illegal out_length=%d (max=%d)", out_length, ARMJTAGEW_OUT_BUFFER_SIZE);
                return -1;
        }

        result = usb_bulk_write(armjtagew_jtag->usb_handle, ARMJTAGEW_EPT_BULK_OUT, \
                (char*)usb_out_buffer, out_length, ARMJTAGEW_USB_TIMEOUT);

        DEBUG_JTAG_IO("armjtagew_usb_write, out_length = %d, result = %d", out_length, result);

#ifdef _DEBUG_USB_COMMS_
        armjtagew_debug_buffer(usb_out_buffer, out_length);
#endif
        return result;
}

/* Read data from USB into in_buffer. */
static int armjtagew_usb_read(armjtagew_jtag_t *armjtagew_jtag, int exp_in_length)
{
        int result = usb_bulk_read(armjtagew_jtag->usb_handle, ARMJTAGEW_EPT_BULK_IN, \
                (char*)usb_in_buffer, exp_in_length, ARMJTAGEW_USB_TIMEOUT);

        DEBUG_JTAG_IO("armjtagew_usb_read, result = %d", result);

#ifdef _DEBUG_USB_COMMS_
        armjtagew_debug_buffer(usb_in_buffer, result);
#endif
        return result;
}


#ifdef _DEBUG_USB_COMMS_
#define BYTES_PER_LINE  16

static void armjtagew_debug_buffer(u8 *buffer, int length)
{
        char line[81];
        char s[4];
        int i;
        int j;

        for (i = 0; i < length; i += BYTES_PER_LINE)
        {
                snprintf(line, 5, "%04x", i);
                for (j = i; j < i + BYTES_PER_LINE && j < length; j++)
                {
                        snprintf(s, 4, " %02x", buffer[j]);
                        strcat(line, s);
                }
                LOG_DEBUG("%s", line);
        }
}
#endif