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

/**************************************************************************
*   Copyright (C) 2012 by Andreas Fritiofson                              *
*   andreas.fritiofson@gmail.com                                          *
*                                                                         *
*   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.,                                       *
*   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
***************************************************************************/

/**
 * @file
 * JTAG adapters based on the FT2232 full and high speed USB parts are
 * popular low cost JTAG debug solutions.  Many FT2232 based JTAG adapters
 * are discrete, but development boards may integrate them as alternatives
 * to more capable (and expensive) third party JTAG pods.
 *
 * JTAG uses only one of the two communications channels ("MPSSE engines")
 * on these devices.  Adapters based on FT4232 parts have four ports/channels
 * (A/B/C/D), instead of just two (A/B).
 *
 * Especially on development boards integrating one of these chips (as
 * opposed to discrete pods/dongles), the additional channels can be used
 * for a variety of purposes, but OpenOCD only uses one channel at a time.
 *
 *  - As a USB-to-serial adapter for the target's console UART ...
 *    which may be able to support ROM boot loaders that load initial
 *    firmware images to flash (or SRAM).
 *
 *  - On systems which support ARM's SWD in addition to JTAG, or instead
 *    of it, that second port can be used for reading SWV/SWO trace data.
 *
 *  - Additional JTAG links, e.g. to a CPLD or * FPGA.
 *
 * FT2232 based JTAG adapters are "dumb" not "smart", because most JTAG
 * request/response interactions involve round trips over the USB link.
 * A "smart" JTAG adapter has intelligence close to the scan chain, so it
 * can for example poll quickly for a status change (usually taking on the
 * order of microseconds not milliseconds) before beginning a queued
 * transaction which require the previous one to have completed.
 *
 * There are dozens of adapters of this type, differing in details which
 * this driver needs to understand.  Those "layout" details are required
 * as part of FT2232 driver configuration.
 *
 * This code uses information contained in the MPSSE specification which was
 * found here:
 * http://www.ftdichip.com/Documents/AppNotes/AN2232C-01_MPSSE_Cmnd.pdf
 * Hereafter this is called the "MPSSE Spec".
 *
 * The datasheet for the ftdichip.com's FT2232D part is here:
 * http://www.ftdichip.com/Documents/DataSheets/DS_FT2232D.pdf
 *
 * Also note the issue with code 0x4b (clock data to TMS) noted in
 * http://developer.intra2net.com/mailarchive/html/libftdi/2009/msg00292.html
 * which can affect longer JTAG state paths.
 */

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

/* project specific includes */
#include <jtag/interface.h>
#include <transport/transport.h>
#include <helper/time_support.h>

#if IS_CYGWIN == 1
#include <windows.h>
#endif

#include <assert.h>

/* FTDI access library includes */
#include "mpsse.h"

#define JTAG_MODE (LSB_FIRST | POS_EDGE_IN | NEG_EDGE_OUT)

static char *ftdi_device_desc;
static char *ftdi_serial;
static uint8_t ftdi_channel;

#define MAX_USB_IDS 8
/* vid = pid = 0 marks the end of the list */
static uint16_t ftdi_vid[MAX_USB_IDS + 1] = { 0 };
static uint16_t ftdi_pid[MAX_USB_IDS + 1] = { 0 };

static struct mpsse_ctx *mpsse_ctx;

struct signal {
        const char *name;
        uint16_t data_mask;
        uint16_t oe_mask;
        bool invert_data;
        bool invert_oe;
        struct signal *next;
};

static struct signal *signals;

static uint16_t output;
static uint16_t direction;

static struct signal *find_signal_by_name(const char *name)
{
        for (struct signal *sig = signals; sig; sig = sig->next) {
                if (strcmp(name, sig->name) == 0)
                        return sig;
        }
        return NULL;
}

static struct signal *create_signal(const char *name)
{
        struct signal **psig = &signals;
        while (*psig)
                psig = &(*psig)->next;

        *psig = calloc(1, sizeof(**psig));
        if (*psig == NULL)
                return NULL;

        (*psig)->name = strdup(name);
        if ((*psig)->name == NULL) {
                free(*psig);
                *psig = NULL;
        }
        return *psig;
}

static int ftdi_set_signal(const struct signal *s, char value)
{
        bool data;
        bool oe;

        if (s->data_mask == 0 && s->oe_mask == 0) {
                LOG_ERROR("interface doesn't provide signal '%s'", s->name);
                return ERROR_FAIL;
        }
        switch (value) {
        case '0':
                data = s->invert_data;
                oe = !s->invert_oe;
                break;
        case '1':
                if (s->data_mask == 0) {
                        LOG_ERROR("interface can't drive '%s' high", s->name);
                        return ERROR_FAIL;
                }
                data = !s->invert_data;
                oe = !s->invert_oe;
                break;
        case 'z':
        case 'Z':
                if (s->oe_mask == 0) {
                        LOG_ERROR("interface can't tri-state '%s'", s->name);
                        return ERROR_FAIL;
                }
                data = s->invert_data;
                oe = s->invert_oe;
                break;
        default:
                assert(0 && "invalid signal level specifier");
                return ERROR_FAIL;
        }

        uint16_t old_output = output;
        uint16_t old_direction = direction;

        output = data ? output | s->data_mask : output & ~s->data_mask;
        if (s->oe_mask == s->data_mask)
                direction = oe ? direction | s->oe_mask : direction & ~s->oe_mask;
        else
                output = oe ? output | s->oe_mask : output & ~s->oe_mask;

        if ((output & 0xff) != (old_output & 0xff) || (direction & 0xff) != (old_direction & 0xff))
                mpsse_set_data_bits_low_byte(mpsse_ctx, output & 0xff, direction & 0xff);
        if ((output >> 8 != old_output >> 8) || (direction >> 8 != old_direction >> 8))
                mpsse_set_data_bits_high_byte(mpsse_ctx, output >> 8, direction >> 8);

        return ERROR_OK;
}


/**
 * Function move_to_state
 * moves the TAP controller from the current state to a
 * \a goal_state through a path given by tap_get_tms_path().  State transition
 * logging is performed by delegation to clock_tms().
 *
 * @param goal_state is the destination state for the move.
 */
static void move_to_state(tap_state_t goal_state)
{
        tap_state_t start_state = tap_get_state();

        /*      goal_state is 1/2 of a tuple/pair of states which allow convenient
                lookup of the required TMS pattern to move to this state from the
                start state.
        */

        /* do the 2 lookups */
        uint8_t tms_bits  = tap_get_tms_path(start_state, goal_state);
        int tms_count = tap_get_tms_path_len(start_state, goal_state);
        assert(tms_count <= 8);

        DEBUG_JTAG_IO("start=%s goal=%s", tap_state_name(start_state), tap_state_name(goal_state));

        /* Track state transitions step by step */
        for (int i = 0; i < tms_count; i++)
                tap_set_state(tap_state_transition(tap_get_state(), (tms_bits >> i) & 1));

        mpsse_clock_tms_cs_out(mpsse_ctx,
                &tms_bits,
                0,
                tms_count,
                false,
                JTAG_MODE);
}

static int ftdi_speed(int speed)
{
        int retval;
        retval = mpsse_set_frequency(mpsse_ctx, speed);

        if (retval < 0) {
                LOG_ERROR("couldn't set FTDI TCK speed");
                return retval;
        }

        return ERROR_OK;
}

static int ftdi_speed_div(int speed, int *khz)
{
        *khz = speed / 1000;
        return ERROR_OK;
}

static int ftdi_khz(int khz, int *jtag_speed)
{
        if (khz == 0 && !mpsse_is_high_speed(mpsse_ctx)) {
                LOG_DEBUG("RCLK not supported");
                return ERROR_FAIL;
        }

        *jtag_speed = khz * 1000;
        return ERROR_OK;
}

static void ftdi_end_state(tap_state_t state)
{
        if (tap_is_state_stable(state))
                tap_set_end_state(state);
        else {
                LOG_ERROR("BUG: %s is not a stable end state", tap_state_name(state));
                exit(-1);
        }
}

static void ftdi_execute_runtest(struct jtag_command *cmd)
{
        int i;
        uint8_t zero = 0;

        DEBUG_JTAG_IO("runtest %i cycles, end in %s",
                cmd->cmd.runtest->num_cycles,
                tap_state_name(cmd->cmd.runtest->end_state));

        if (tap_get_state() != TAP_IDLE)
                move_to_state(TAP_IDLE);

        /* TODO: Reuse ftdi_execute_stableclocks */
        i = cmd->cmd.runtest->num_cycles;
        while (i > 0) {
                /* there are no state transitions in this code, so omit state tracking */
                unsigned this_len = i > 7 ? 7 : i;
                mpsse_clock_tms_cs_out(mpsse_ctx, &zero, 0, this_len, false, JTAG_MODE);
                i -= this_len;
        }

        ftdi_end_state(cmd->cmd.runtest->end_state);

        if (tap_get_state() != tap_get_end_state())
                move_to_state(tap_get_end_state());

        DEBUG_JTAG_IO("runtest: %i, end in %s",
                cmd->cmd.runtest->num_cycles,
                tap_state_name(tap_get_end_state()));
}

static void ftdi_execute_statemove(struct jtag_command *cmd)
{
        DEBUG_JTAG_IO("statemove end in %s",
                tap_state_name(cmd->cmd.statemove->end_state));

        ftdi_end_state(cmd->cmd.statemove->end_state);

        /* shortest-path move to desired end state */
        if (tap_get_state() != tap_get_end_state() || tap_get_end_state() == TAP_RESET)
                move_to_state(tap_get_end_state());
}

/**
 * Clock a bunch of TMS (or SWDIO) transitions, to change the JTAG
 * (or SWD) state machine. REVISIT: Not the best method, perhaps.
 */
static void ftdi_execute_tms(struct jtag_command *cmd)
{
        DEBUG_JTAG_IO("TMS: %d bits", cmd->cmd.tms->num_bits);

        /* TODO: Missing tap state tracking, also missing from ft2232.c! */
        mpsse_clock_tms_cs_out(mpsse_ctx,
                cmd->cmd.tms->bits,
                0,
                cmd->cmd.tms->num_bits,
                false,
                JTAG_MODE);
}

static void ftdi_execute_pathmove(struct jtag_command *cmd)
{
        tap_state_t *path = cmd->cmd.pathmove->path;
        int num_states  = cmd->cmd.pathmove->num_states;

        DEBUG_JTAG_IO("pathmove: %i states, current: %s  end: %s", num_states,
                tap_state_name(tap_get_state()),
                tap_state_name(path[num_states-1]));

        int state_count = 0;
        unsigned bit_count = 0;
        uint8_t tms_byte = 0;

        DEBUG_JTAG_IO("-");

        /* this loop verifies that the path is legal and logs each state in the path */
        while (num_states--) {

                /* either TMS=0 or TMS=1 must work ... */
                if (tap_state_transition(tap_get_state(), false)
                    == path[state_count])
                        buf_set_u32(&tms_byte, bit_count++, 1, 0x0);
                else if (tap_state_transition(tap_get_state(), true)
                         == path[state_count]) {
                        buf_set_u32(&tms_byte, bit_count++, 1, 0x1);

                        /* ... or else the caller goofed BADLY */
                } else {
                        LOG_ERROR("BUG: %s -> %s isn't a valid "
                                "TAP state transition",
                                tap_state_name(tap_get_state()),
                                tap_state_name(path[state_count]));
                        exit(-1);
                }

                tap_set_state(path[state_count]);
                state_count++;

                if (bit_count == 7 || num_states == 0) {
                        mpsse_clock_tms_cs_out(mpsse_ctx,
                                        &tms_byte,
                                        0,
                                        bit_count,
                                        false,
                                        JTAG_MODE);
                        bit_count = 0;
                }
        }
        tap_set_end_state(tap_get_state());
}

static void ftdi_execute_scan(struct jtag_command *cmd)
{
        DEBUG_JTAG_IO("%s type:%d", cmd->cmd.scan->ir_scan ? "IRSCAN" : "DRSCAN",
                jtag_scan_type(cmd->cmd.scan));

        /* Make sure there are no trailing fields with num_bits == 0, or the logic below will fail. */
        while (cmd->cmd.scan->num_fields > 0
                        && cmd->cmd.scan->fields[cmd->cmd.scan->num_fields - 1].num_bits == 0) {
                cmd->cmd.scan->num_fields--;
                LOG_DEBUG("discarding trailing empty field");
        }

        if (cmd->cmd.scan->num_fields == 0) {
                LOG_DEBUG("empty scan, doing nothing");
                return;
        }

        if (cmd->cmd.scan->ir_scan) {
                if (tap_get_state() != TAP_IRSHIFT)
                        move_to_state(TAP_IRSHIFT);
        } else {
                if (tap_get_state() != TAP_DRSHIFT)
                        move_to_state(TAP_DRSHIFT);
        }

        ftdi_end_state(cmd->cmd.scan->end_state);

        struct scan_field *field = cmd->cmd.scan->fields;
        unsigned scan_size = 0;

        for (int i = 0; i < cmd->cmd.scan->num_fields; i++, field++) {
                scan_size += field->num_bits;
                DEBUG_JTAG_IO("%s%s field %d/%d %d bits",
                        field->in_value ? "in" : "",
                        field->out_value ? "out" : "",
                        i,
                        cmd->cmd.scan->num_fields,
                        field->num_bits);

                if (i == cmd->cmd.scan->num_fields - 1 && tap_get_state() != tap_get_end_state()) {
                        /* Last field, and we're leaving IRSHIFT/DRSHIFT. Clock last bit during tap
                         * movement. This last field can't have length zero, it was checked above. */
                        mpsse_clock_data(mpsse_ctx,
                                field->out_value,
                                0,
                                field->in_value,
                                0,
                                field->num_bits - 1,
                                JTAG_MODE);
                        uint8_t last_bit = 0;
                        if (field->out_value)
                                bit_copy(&last_bit, 0, field->out_value, field->num_bits - 1, 1);
                        uint8_t tms_bits = 0x01;
                        mpsse_clock_tms_cs(mpsse_ctx,
                                        &tms_bits,
                                        0,
                                        field->in_value,
                                        field->num_bits - 1,
                                        1,
                                        last_bit,
                                        JTAG_MODE);
                        tap_set_state(tap_state_transition(tap_get_state(), 1));
                        mpsse_clock_tms_cs_out(mpsse_ctx,
                                        &tms_bits,
                                        1,
                                        1,
                                        last_bit,
                                        JTAG_MODE);
                        tap_set_state(tap_state_transition(tap_get_state(), 0));
                } else
                        mpsse_clock_data(mpsse_ctx,
                                field->out_value,
                                0,
                                field->in_value,
                                0,
                                field->num_bits,
                                JTAG_MODE);
        }

        if (tap_get_state() != tap_get_end_state())
                move_to_state(tap_get_end_state());

        DEBUG_JTAG_IO("%s scan, %i bits, end in %s",
                (cmd->cmd.scan->ir_scan) ? "IR" : "DR", scan_size,
                tap_state_name(tap_get_end_state()));
}

static void ftdi_execute_reset(struct jtag_command *cmd)
{
        DEBUG_JTAG_IO("reset trst: %i srst %i",
                cmd->cmd.reset->trst, cmd->cmd.reset->srst);

        if (cmd->cmd.reset->trst == 1
            || (cmd->cmd.reset->srst
                && (jtag_get_reset_config() & RESET_SRST_PULLS_TRST)))
                tap_set_state(TAP_RESET);

        struct signal *trst = find_signal_by_name("nTRST");
        if (cmd->cmd.reset->trst == 1) {
                if (trst)
                        ftdi_set_signal(trst, '0');
                else
                        LOG_ERROR("Can't assert TRST: nTRST signal is not defined");
        } else if (trst && cmd->cmd.reset->trst == 0) {
                if (jtag_get_reset_config() & RESET_TRST_OPEN_DRAIN)
                        ftdi_set_signal(trst, 'z');
                else
                        ftdi_set_signal(trst, '1');
        }

        struct signal *srst = find_signal_by_name("nSRST");
        if (cmd->cmd.reset->srst == 1) {
                if (srst)
                        ftdi_set_signal(srst, '0');
                else
                        LOG_ERROR("Can't assert SRST: nSRST signal is not defined");
        } else if (srst && cmd->cmd.reset->srst == 0) {
                if (jtag_get_reset_config() & RESET_SRST_PUSH_PULL)
                        ftdi_set_signal(srst, '1');
                else
                        ftdi_set_signal(srst, 'z');
        }

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

static void ftdi_execute_sleep(struct jtag_command *cmd)
{
        DEBUG_JTAG_IO("sleep %" PRIi32, cmd->cmd.sleep->us);

        mpsse_flush(mpsse_ctx);
        jtag_sleep(cmd->cmd.sleep->us);
        DEBUG_JTAG_IO("sleep %" PRIi32 " usec while in %s",
                cmd->cmd.sleep->us,
                tap_state_name(tap_get_state()));
}

static void ftdi_execute_stableclocks(struct jtag_command *cmd)
{
        /* this is only allowed while in a stable state.  A check for a stable
         * state was done in jtag_add_clocks()
         */
        int num_cycles = cmd->cmd.stableclocks->num_cycles;

        /* 7 bits of either ones or zeros. */
        uint8_t tms = tap_get_state() == TAP_RESET ? 0x7f : 0x00;

        /* TODO: Use mpsse_clock_data with in=out=0 for this, if TMS can be set to
         * the correct level and remain there during the scan */
        while (num_cycles > 0) {
                /* there are no state transitions in this code, so omit state tracking */
                unsigned this_len = num_cycles > 7 ? 7 : num_cycles;
                mpsse_clock_tms_cs_out(mpsse_ctx, &tms, 0, this_len, false, JTAG_MODE);
                num_cycles -= this_len;
        }

        DEBUG_JTAG_IO("clocks %i while in %s",
                cmd->cmd.stableclocks->num_cycles,
                tap_state_name(tap_get_state()));
}

static void ftdi_execute_command(struct jtag_command *cmd)
{
        switch (cmd->type) {
                case JTAG_RESET:
                        ftdi_execute_reset(cmd);
                        break;
                case JTAG_RUNTEST:
                        ftdi_execute_runtest(cmd);
                        break;
                case JTAG_TLR_RESET:
                        ftdi_execute_statemove(cmd);
                        break;
                case JTAG_PATHMOVE:
                        ftdi_execute_pathmove(cmd);
                        break;
                case JTAG_SCAN:
                        ftdi_execute_scan(cmd);
                        break;
                case JTAG_SLEEP:
                        ftdi_execute_sleep(cmd);
                        break;
                case JTAG_STABLECLOCKS:
                        ftdi_execute_stableclocks(cmd);
                        break;
                case JTAG_TMS:
                        ftdi_execute_tms(cmd);
                        break;
                default:
                        LOG_ERROR("BUG: unknown JTAG command type encountered: %d", cmd->type);
                        break;
        }
}

static int ftdi_execute_queue(void)
{
        /* blink, if the current layout has that feature */
        struct signal *led = find_signal_by_name("LED");
        if (led)
                ftdi_set_signal(led, '1');

        for (struct jtag_command *cmd = jtag_command_queue; cmd; cmd = cmd->next) {
                /* fill the write buffer with the desired command */
                ftdi_execute_command(cmd);
        }

        if (led)
                ftdi_set_signal(led, '0');

        int retval = mpsse_flush(mpsse_ctx);
        if (retval != ERROR_OK)
                LOG_ERROR("error while flushing MPSSE queue: %d", retval);

        return retval;
}

static int ftdi_initialize(void)
{
        if (tap_get_tms_path_len(TAP_IRPAUSE, TAP_IRPAUSE) == 7)
                LOG_DEBUG("ftdi interface using 7 step jtag state transitions");
        else
                LOG_DEBUG("ftdi interface using shortest path jtag state transitions");

        for (int i = 0; ftdi_vid[i] || ftdi_pid[i]; i++) {
                mpsse_ctx = mpsse_open(&ftdi_vid[i], &ftdi_pid[i], ftdi_device_desc,
                                ftdi_serial, ftdi_channel);
                if (mpsse_ctx)
                        break;
        }

        if (!mpsse_ctx)
                return ERROR_JTAG_INIT_FAILED;

        mpsse_set_data_bits_low_byte(mpsse_ctx, output & 0xff, direction & 0xff);
        mpsse_set_data_bits_high_byte(mpsse_ctx, output >> 8, direction >> 8);

        mpsse_loopback_config(mpsse_ctx, false);

        return mpsse_flush(mpsse_ctx);
}

static int ftdi_quit(void)
{
        mpsse_close(mpsse_ctx);

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_device_desc_command)
{
        if (CMD_ARGC == 1) {
                if (ftdi_device_desc)
                        free(ftdi_device_desc);
                ftdi_device_desc = strdup(CMD_ARGV[0]);
        } else {
                LOG_ERROR("expected exactly one argument to ftdi_device_desc <description>");
        }

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_serial_command)
{
        if (CMD_ARGC == 1) {
                if (ftdi_serial)
                        free(ftdi_serial);
                ftdi_serial = strdup(CMD_ARGV[0]);
        } else {
                return ERROR_COMMAND_SYNTAX_ERROR;
        }

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_channel_command)
{
        if (CMD_ARGC == 1)
                COMMAND_PARSE_NUMBER(u8, CMD_ARGV[0], ftdi_channel);
        else
                return ERROR_COMMAND_SYNTAX_ERROR;

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_layout_init_command)
{
        if (CMD_ARGC != 2)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[0], output);
        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[1], direction);

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_layout_signal_command)
{
        if (CMD_ARGC < 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        bool invert_data = false;
        uint16_t data_mask = 0;
        bool invert_oe = false;
        uint16_t oe_mask = 0;
        for (unsigned i = 1; i < CMD_ARGC; i += 2) {
                if (strcmp("-data", CMD_ARGV[i]) == 0) {
                        invert_data = false;
                        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], data_mask);
                } else if (strcmp("-ndata", CMD_ARGV[i]) == 0) {
                        invert_data = true;
                        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], data_mask);
                } else if (strcmp("-oe", CMD_ARGV[i]) == 0) {
                        invert_oe = false;
                        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], oe_mask);
                } else if (strcmp("-noe", CMD_ARGV[i]) == 0) {
                        invert_oe = true;
                        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], oe_mask);
                } else {
                        LOG_ERROR("unknown option '%s'", CMD_ARGV[i]);
                        return ERROR_COMMAND_SYNTAX_ERROR;
                }
        }

        struct signal *sig;
        sig = find_signal_by_name(CMD_ARGV[0]);
        if (!sig)
                sig = create_signal(CMD_ARGV[0]);
        if (!sig) {
                LOG_ERROR("failed to create signal %s", CMD_ARGV[0]);
                return ERROR_FAIL;
        }

        sig->invert_data = invert_data;
        sig->data_mask = data_mask;
        sig->invert_oe = invert_oe;
        sig->oe_mask = oe_mask;

        return ERROR_OK;
}

COMMAND_HANDLER(ftdi_handle_set_signal_command)
{
        if (CMD_ARGC < 2)
                return ERROR_COMMAND_SYNTAX_ERROR;

        struct signal *sig;
        sig = find_signal_by_name(CMD_ARGV[0]);
        if (!sig) {
                LOG_ERROR("interface configuration doesn't define signal '%s'", CMD_ARGV[0]);
                return ERROR_FAIL;
        }

        switch (*CMD_ARGV[1]) {
        case '0':
        case '1':
        case 'z':
        case 'Z':
                /* single character level specifier only */
                if (CMD_ARGV[1][1] == '\0') {
                        ftdi_set_signal(sig, *CMD_ARGV[1]);
                        break;
                }
        default:
                LOG_ERROR("unknown signal level '%s', use 0, 1 or z", CMD_ARGV[1]);
                return ERROR_COMMAND_SYNTAX_ERROR;
        }

        return mpsse_flush(mpsse_ctx);
}

COMMAND_HANDLER(ftdi_handle_vid_pid_command)
{
        if (CMD_ARGC > MAX_USB_IDS * 2) {
                LOG_WARNING("ignoring extra IDs in ftdi_vid_pid "
                        "(maximum is %d pairs)", MAX_USB_IDS);
                CMD_ARGC = MAX_USB_IDS * 2;
        }
        if (CMD_ARGC < 2 || (CMD_ARGC & 1)) {
                LOG_WARNING("incomplete ftdi_vid_pid configuration directive");
                if (CMD_ARGC < 2)
                        return ERROR_COMMAND_SYNTAX_ERROR;
                /* remove the incomplete trailing id */
                CMD_ARGC -= 1;
        }

        unsigned i;
        for (i = 0; i < CMD_ARGC; i += 2) {
                COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i], ftdi_vid[i >> 1]);
                COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], ftdi_pid[i >> 1]);
        }

        /*
         * Explicitly terminate, in case there are multiples instances of
         * ftdi_vid_pid.
         */
        ftdi_vid[i >> 1] = ftdi_pid[i >> 1] = 0;

        return ERROR_OK;
}

static const struct command_registration ftdi_command_handlers[] = {
        {
                .name = "ftdi_device_desc",
                .handler = &ftdi_handle_device_desc_command,
                .mode = COMMAND_CONFIG,
                .help = "set the USB device description of the FTDI device",
                .usage = "description_string",
        },
        {
                .name = "ftdi_serial",
                .handler = &ftdi_handle_serial_command,
                .mode = COMMAND_CONFIG,
                .help = "set the serial number of the FTDI device",
                .usage = "serial_string",
        },
        {
                .name = "ftdi_channel",
                .handler = &ftdi_handle_channel_command,
                .mode = COMMAND_CONFIG,
                .help = "set the channel of the FTDI device that is used as JTAG",
                .usage = "(0-3)",
        },
        {
                .name = "ftdi_layout_init",
                .handler = &ftdi_handle_layout_init_command,
                .mode = COMMAND_CONFIG,
                .help = "initialize the FTDI GPIO signals used "
                        "to control output-enables and reset signals",
                .usage = "data direction",
        },
        {
                .name = "ftdi_layout_signal",
                .handler = &ftdi_handle_layout_signal_command,
                .mode = COMMAND_ANY,
                .help = "define a signal controlled by one or more FTDI GPIO as data "
                        "and/or output enable",
                .usage = "name [-data mask|-ndata mask] [-oe mask|-noe mask]",
        },
        {
                .name = "ftdi_set_signal",
                .handler = &ftdi_handle_set_signal_command,
                .mode = COMMAND_EXEC,
                .help = "control a layout-specific signal",
                .usage = "name (1|0|z)",
        },
        {
                .name = "ftdi_vid_pid",
                .handler = &ftdi_handle_vid_pid_command,
                .mode = COMMAND_CONFIG,
                .help = "the vendor ID and product ID of the FTDI device",
                .usage = "(vid pid)* ",
        },
        COMMAND_REGISTRATION_DONE
};

struct jtag_interface ftdi_interface = {
        .name = "ftdi",
        .supported = DEBUG_CAP_TMS_SEQ,
        .commands = ftdi_command_handlers,
        .transports = jtag_only,

        .init = ftdi_initialize,
        .quit = ftdi_quit,
        .speed = ftdi_speed,
        .speed_div = ftdi_speed_div,
        .khz = ftdi_khz,
        .execute_queue = ftdi_execute_queue,
};