libusb1_common, ftdi: clarify libusb_open error message

[openocd.git] / src / jtag / drivers / mpsse.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.           *
 ***************************************************************************/

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

#include "mpsse.h"
#include "helper/log.h"
#include <libusb-1.0/libusb.h>

/* Compatibility define for older libusb-1.0 */
#ifndef LIBUSB_CALL
#define LIBUSB_CALL
#endif

#ifdef _DEBUG_JTAG_IO_
#define DEBUG_IO(expr...) LOG_DEBUG(expr)
#define DEBUG_PRINT_BUF(buf, len) \
        do { \
                char buf_string[32 * 3 + 1]; \
                int buf_string_pos = 0; \
                for (int i = 0; i < len; i++) { \
                        buf_string_pos += sprintf(buf_string + buf_string_pos, " %02x", buf[i]); \
                        if (i % 32 == 32 - 1) { \
                                LOG_DEBUG("%s", buf_string); \
                                buf_string_pos = 0; \
                        } \
                } \
                if (buf_string_pos > 0) \
                        LOG_DEBUG("%s", buf_string);\
        } while (0)
#else
#define DEBUG_IO(expr...) do {} while (0)
#define DEBUG_PRINT_BUF(buf, len) do {} while (0)
#endif

#define FTDI_DEVICE_OUT_REQTYPE (LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE)
#define FTDI_DEVICE_IN_REQTYPE (0x80 | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE)

#define BITMODE_MPSSE 0x02

#define SIO_RESET_REQUEST             0x00
#define SIO_SET_LATENCY_TIMER_REQUEST 0x09
#define SIO_GET_LATENCY_TIMER_REQUEST 0x0A
#define SIO_SET_BITMODE_REQUEST       0x0B

#define SIO_RESET_SIO 0
#define SIO_RESET_PURGE_RX 1
#define SIO_RESET_PURGE_TX 2

struct mpsse_ctx {
        libusb_context *usb_ctx;
        libusb_device_handle *usb_dev;
        unsigned int usb_write_timeout;
        unsigned int usb_read_timeout;
        uint8_t in_ep;
        uint8_t out_ep;
        uint16_t max_packet_size;
        uint16_t index;
        uint8_t interface;
        enum ftdi_chip_type type;
        uint8_t *write_buffer;
        unsigned write_size;
        unsigned write_count;
        uint8_t *read_buffer;
        unsigned read_size;
        unsigned read_count;
        uint8_t *read_chunk;
        unsigned read_chunk_size;
        struct bit_copy_queue read_queue;
};

/* Returns true if the string descriptor indexed by str_index in device matches string */
static bool string_descriptor_equal(libusb_device_handle *device, uint8_t str_index,
        const char *string)
{
        int retval;
        char desc_string[256]; /* Max size of string descriptor */
        retval = libusb_get_string_descriptor_ascii(device, str_index, (unsigned char *)desc_string,
                        sizeof(desc_string));
        if (retval < 0) {
                LOG_ERROR("libusb_get_string_descriptor_ascii() failed with %d", retval);
                return false;
        }
        return strncmp(string, desc_string, sizeof(desc_string)) == 0;
}

/* Helper to open a libusb device that matches vid, pid, product string and/or serial string.
 * Set any field to 0 as a wildcard. If the device is found true is returned, with ctx containing
 * the already opened handle. ctx->interface must be set to the desired interface (channel) number
 * prior to calling this function. */
static bool open_matching_device(struct mpsse_ctx *ctx, const uint16_t *vid, const uint16_t *pid,
        const char *product, const char *serial)
{
        libusb_device **list;
        struct libusb_device_descriptor desc;
        struct libusb_config_descriptor *config0;
        int err;
        bool found = false;
        ssize_t cnt = libusb_get_device_list(ctx->usb_ctx, &list);
        if (cnt < 0)
                LOG_ERROR("libusb_get_device_list() failed with %zi", cnt);

        for (ssize_t i = 0; i < cnt; i++) {
                libusb_device *device = list[i];

                err = libusb_get_device_descriptor(device, &desc);
                if (err != LIBUSB_SUCCESS) {
                        LOG_ERROR("libusb_get_device_descriptor() failed with %d", err);
                        continue;
                }

                if (vid && *vid != desc.idVendor)
                        continue;
                if (pid && *pid != desc.idProduct)
                        continue;

                err = libusb_open(device, &ctx->usb_dev);
                if (err != LIBUSB_SUCCESS) {
                        LOG_ERROR("libusb_open() failed with %s",
                                  libusb_error_name(err));
                        continue;
                }

                if (product && !string_descriptor_equal(ctx->usb_dev, desc.iProduct, product)) {
                        libusb_close(ctx->usb_dev);
                        continue;
                }

                if (serial && !string_descriptor_equal(ctx->usb_dev, desc.iSerialNumber, serial)) {
                        libusb_close(ctx->usb_dev);
                        continue;
                }

                found = true;
                break;
        }

        libusb_free_device_list(list, 1);

        if (!found) {
                LOG_ERROR("no device found");
                return false;
        }

        err = libusb_get_config_descriptor(libusb_get_device(ctx->usb_dev), 0, &config0);
        if (err != LIBUSB_SUCCESS) {
                LOG_ERROR("libusb_get_config_descriptor() failed with %d", err);
                libusb_close(ctx->usb_dev);
                return false;
        }

        /* Make sure the first configuration is selected */
        int cfg;
        err = libusb_get_configuration(ctx->usb_dev, &cfg);
        if (err != LIBUSB_SUCCESS) {
                LOG_ERROR("libusb_get_configuration() failed with %d", err);
                goto error;
        }

        if (desc.bNumConfigurations > 0 && cfg != config0->bConfigurationValue) {
                err = libusb_set_configuration(ctx->usb_dev, config0->bConfigurationValue);
                if (err != LIBUSB_SUCCESS) {
                        LOG_ERROR("libusb_set_configuration() failed with %d", err);
                        goto error;
                }
        }

        /* Try to detach ftdi_sio kernel module */
        err = libusb_detach_kernel_driver(ctx->usb_dev, ctx->interface);
        if (err != LIBUSB_SUCCESS && err != LIBUSB_ERROR_NOT_FOUND
                        && err != LIBUSB_ERROR_NOT_SUPPORTED) {
                LOG_ERROR("libusb_detach_kernel_driver() failed with %d", err);
                goto error;
        }

        err = libusb_claim_interface(ctx->usb_dev, ctx->interface);
        if (err != LIBUSB_SUCCESS) {
                LOG_ERROR("libusb_claim_interface() failed with %d", err);
                goto error;
        }

        /* Reset FTDI device */
        err = libusb_control_transfer(ctx->usb_dev, FTDI_DEVICE_OUT_REQTYPE,
                        SIO_RESET_REQUEST, SIO_RESET_SIO,
                        ctx->index, NULL, 0, ctx->usb_write_timeout);
        if (err < 0) {
                LOG_ERROR("failed to reset FTDI device: %d", err);
                goto error;
        }

        switch (desc.bcdDevice) {
        case 0x500:
                ctx->type = TYPE_FT2232C;
                break;
        case 0x700:
                ctx->type = TYPE_FT2232H;
                break;
        case 0x800:
                ctx->type = TYPE_FT4232H;
                break;
        case 0x900:
                ctx->type = TYPE_FT232H;
                break;
        default:
                LOG_ERROR("unsupported FTDI chip type: 0x%04x", desc.bcdDevice);
                goto error;
        }

        /* Determine maximum packet size and endpoint addresses */
        if (!(desc.bNumConfigurations > 0 && ctx->interface < config0->bNumInterfaces
                        && config0->interface[ctx->interface].num_altsetting > 0))
                goto desc_error;

        const struct libusb_interface_descriptor *descriptor;
        descriptor = &config0->interface[ctx->interface].altsetting[0];
        if (descriptor->bNumEndpoints != 2)
                goto desc_error;

        ctx->in_ep = 0;
        ctx->out_ep = 0;
        for (int i = 0; i < descriptor->bNumEndpoints; i++) {
                if (descriptor->endpoint[i].bEndpointAddress & 0x80) {
                        ctx->in_ep = descriptor->endpoint[i].bEndpointAddress;
                        ctx->max_packet_size =
                                        descriptor->endpoint[i].wMaxPacketSize;
                } else {
                        ctx->out_ep = descriptor->endpoint[i].bEndpointAddress;
                }
        }

        if (ctx->in_ep == 0 || ctx->out_ep == 0)
                goto desc_error;

        libusb_free_config_descriptor(config0);
        return true;

desc_error:
        LOG_ERROR("unrecognized USB device descriptor");
error:
        libusb_free_config_descriptor(config0);
        libusb_close(ctx->usb_dev);
        return false;
}

struct mpsse_ctx *mpsse_open(const uint16_t *vid, const uint16_t *pid, const char *description,
        const char *serial, int channel)
{
        struct mpsse_ctx *ctx = calloc(1, sizeof(*ctx));
        int err;

        if (!ctx)
                return 0;

        bit_copy_queue_init(&ctx->read_queue);
        ctx->read_chunk_size = 16384;
        ctx->read_size = 16384;
        ctx->write_size = 16384;
        ctx->read_chunk = malloc(ctx->read_chunk_size);
        ctx->read_buffer = malloc(ctx->read_size);
        ctx->write_buffer = malloc(ctx->write_size);
        if (!ctx->read_chunk || !ctx->read_buffer || !ctx->write_buffer)
                goto error;

        ctx->interface = channel;
        ctx->index = channel + 1;
        ctx->usb_read_timeout = 5000;
        ctx->usb_write_timeout = 5000;

        err = libusb_init(&ctx->usb_ctx);
        if (err != LIBUSB_SUCCESS) {
                LOG_ERROR("libusb_init() failed with %d", err);
                goto error;
        }

        if (!open_matching_device(ctx, vid, pid, description, serial)) {
                /* Four hex digits plus terminating zero each */
                char vidstr[5];
                char pidstr[5];
                LOG_ERROR("unable to open ftdi device with vid %s, pid %s, description '%s' and "
                                "serial '%s'",
                                vid ? sprintf(vidstr, "%04x", *vid), vidstr : "*",
                                pid ? sprintf(pidstr, "%04x", *pid), pidstr : "*",
                                description ? description : "*",
                                serial ? serial : "*");
                ctx->usb_dev = 0;
                goto error;
        }

        err = libusb_control_transfer(ctx->usb_dev, FTDI_DEVICE_OUT_REQTYPE,
                        SIO_SET_LATENCY_TIMER_REQUEST, 255, ctx->index, NULL, 0,
                        ctx->usb_write_timeout);
        if (err < 0) {
                LOG_ERROR("unable to set latency timer: %d", err);
                goto error;
        }

        err = libusb_control_transfer(ctx->usb_dev,
                        FTDI_DEVICE_OUT_REQTYPE,
                        SIO_SET_BITMODE_REQUEST,
                        0x0b | (BITMODE_MPSSE << 8),
                        ctx->index,
                        NULL,
                        0,
                        ctx->usb_write_timeout);
        if (err < 0) {
                LOG_ERROR("unable to set MPSSE bitmode: %d", err);
                goto error;
        }

        mpsse_purge(ctx);

        return ctx;
error:
        mpsse_close(ctx);
        return 0;
}

void mpsse_close(struct mpsse_ctx *ctx)
{
        if (ctx->usb_dev)
                libusb_close(ctx->usb_dev);
        if (ctx->usb_ctx)
                libusb_exit(ctx->usb_ctx);
        bit_copy_discard(&ctx->read_queue);
        if (ctx->write_buffer)
                free(ctx->write_buffer);
        if (ctx->read_buffer)
                free(ctx->read_buffer);
        if (ctx->read_chunk)
                free(ctx->read_chunk);

        free(ctx);
}

bool mpsse_is_high_speed(struct mpsse_ctx *ctx)
{
        return ctx->type != TYPE_FT2232C;
}

void mpsse_purge(struct mpsse_ctx *ctx)
{
        int err;
        LOG_DEBUG("-");
        ctx->write_count = 0;
        ctx->read_count = 0;
        bit_copy_discard(&ctx->read_queue);
        err = libusb_control_transfer(ctx->usb_dev, FTDI_DEVICE_OUT_REQTYPE, SIO_RESET_REQUEST,
                        SIO_RESET_PURGE_RX, ctx->index, NULL, 0, ctx->usb_write_timeout);
        if (err < 0) {
                LOG_ERROR("unable to purge ftdi rx buffers: %d", err);
                return;
        }

        err = libusb_control_transfer(ctx->usb_dev, FTDI_DEVICE_OUT_REQTYPE, SIO_RESET_REQUEST,
                        SIO_RESET_PURGE_TX, ctx->index, NULL, 0, ctx->usb_write_timeout);
        if (err < 0) {
                LOG_ERROR("unable to purge ftdi tx buffers: %d", err);
                return;
        }
}

static unsigned buffer_write_space(struct mpsse_ctx *ctx)
{
        /* Reserve one byte for SEND_IMMEDIATE */
        return ctx->write_size - ctx->write_count - 1;
}

static unsigned buffer_read_space(struct mpsse_ctx *ctx)
{
        return ctx->read_size - ctx->read_count;
}

static void buffer_write_byte(struct mpsse_ctx *ctx, uint8_t data)
{
        DEBUG_IO("%02x", data);
        assert(ctx->write_count < ctx->write_size);
        ctx->write_buffer[ctx->write_count++] = data;
}

static unsigned buffer_write(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_offset,
        unsigned bit_count)
{
        DEBUG_IO("%d bits", bit_count);
        assert(ctx->write_count + DIV_ROUND_UP(bit_count, 8) <= ctx->write_size);
        bit_copy(ctx->write_buffer + ctx->write_count, 0, out, out_offset, bit_count);
        ctx->write_count += DIV_ROUND_UP(bit_count, 8);
        return bit_count;
}

static unsigned buffer_add_read(struct mpsse_ctx *ctx, uint8_t *in, unsigned in_offset,
        unsigned bit_count, unsigned offset)
{
        DEBUG_IO("%d bits, offset %d", bit_count, offset);
        assert(ctx->read_count + DIV_ROUND_UP(bit_count, 8) <= ctx->read_size);
        bit_copy_queued(&ctx->read_queue, in, in_offset, ctx->read_buffer + ctx->read_count, offset,
                bit_count);
        ctx->read_count += DIV_ROUND_UP(bit_count, 8);
        return bit_count;
}

int mpsse_clock_data_out(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_offset,
        unsigned length, uint8_t mode)
{
        return mpsse_clock_data(ctx, out, out_offset, 0, 0, length, mode);
}

int mpsse_clock_data_in(struct mpsse_ctx *ctx, uint8_t *in, unsigned in_offset, unsigned length,
        uint8_t mode)
{
        return mpsse_clock_data(ctx, 0, 0, in, in_offset, length, mode);
}

int mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_offset, uint8_t *in,
        unsigned in_offset, unsigned length, uint8_t mode)
{
        /* TODO: Fix MSB first modes */
        DEBUG_IO("%s%s %d bits", in ? "in" : "", out ? "out" : "", length);
        int retval = ERROR_OK;

        /* TODO: On H chips, use command 0x8E/0x8F if in and out are both 0 */
        if (out || (!out && !in))
                mode |= 0x10;
        if (in)
                mode |= 0x20;

        while (length > 0) {
                /* Guarantee buffer space enough for a minimum size transfer */
                if (buffer_write_space(ctx) + (length < 8) < (out || (!out && !in) ? 4 : 3)
                                || (in && buffer_read_space(ctx) < 1))
                        retval = mpsse_flush(ctx);

                if (length < 8) {
                        /* Transfer remaining bits in bit mode */
                        buffer_write_byte(ctx, 0x02 | mode);
                        buffer_write_byte(ctx, length - 1);
                        if (out)
                                out_offset += buffer_write(ctx, out, out_offset, length);
                        if (in)
                                in_offset += buffer_add_read(ctx, in, in_offset, length, 8 - length);
                        if (!out && !in)
                                buffer_write_byte(ctx, 0x00);
                        length = 0;
                } else {
                        /* Byte transfer */
                        unsigned this_bytes = length / 8;
                        /* MPSSE command limit */
                        if (this_bytes > 65536)
                                this_bytes = 65536;
                        /* Buffer space limit. We already made sure there's space for the minimum
                         * transfer. */
                        if ((out || (!out && !in)) && this_bytes + 3 > buffer_write_space(ctx))
                                this_bytes = buffer_write_space(ctx) - 3;
                        if (in && this_bytes > buffer_read_space(ctx))
                                this_bytes = buffer_read_space(ctx);

                        if (this_bytes > 0) {
                                buffer_write_byte(ctx, mode);
                                buffer_write_byte(ctx, (this_bytes - 1) & 0xff);
                                buffer_write_byte(ctx, (this_bytes - 1) >> 8);
                                if (out)
                                        out_offset += buffer_write(ctx,
                                                        out,
                                                        out_offset,
                                                        this_bytes * 8);
                                if (in)
                                        in_offset += buffer_add_read(ctx,
                                                        in,
                                                        in_offset,
                                                        this_bytes * 8,
                                                        0);
                                if (!out && !in)
                                        for (unsigned n = 0; n < this_bytes; n++)
                                                buffer_write_byte(ctx, 0x00);
                                length -= this_bytes * 8;
                        }
                }
        }
        return retval;
}

int mpsse_clock_tms_cs_out(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_offset,
        unsigned length, bool tdi, uint8_t mode)
{
        return mpsse_clock_tms_cs(ctx, out, out_offset, 0, 0, length, tdi, mode);
}

int mpsse_clock_tms_cs(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_offset, uint8_t *in,
        unsigned in_offset, unsigned length, bool tdi, uint8_t mode)
{
        DEBUG_IO("%sout %d bits, tdi=%d", in ? "in" : "", length, tdi);
        assert(out);
        int retval = ERROR_OK;

        mode |= 0x42;
        if (in)
                mode |= 0x20;

        while (length > 0) {
                /* Guarantee buffer space enough for a minimum size transfer */
                if (buffer_write_space(ctx) < 3 || (in && buffer_read_space(ctx) < 1))
                        retval = mpsse_flush(ctx);

                /* Byte transfer */
                unsigned this_bits = length;
                /* MPSSE command limit */
                /* NOTE: there's a report of an FT2232 bug in this area, where shifting
                 * exactly 7 bits can make problems with TMS signaling for the last
                 * clock cycle:
                 *
                 * http://developer.intra2net.com/mailarchive/html/libftdi/2009/msg00292.html
                 */
                if (this_bits > 7)
                        this_bits = 7;

                if (this_bits > 0) {
                        buffer_write_byte(ctx, mode);
                        buffer_write_byte(ctx, this_bits - 1);
                        uint8_t data = 0;
                        /* TODO: Fix MSB first, if allowed in MPSSE */
                        bit_copy(&data, 0, out, out_offset, this_bits);
                        out_offset += this_bits;
                        buffer_write_byte(ctx, data | (tdi ? 0x80 : 0x00));
                        if (in)
                                in_offset += buffer_add_read(ctx,
                                                in,
                                                in_offset,
                                                this_bits,
                                                8 - this_bits);
                        length -= this_bits;
                }
        }
        return retval;
}

int mpsse_set_data_bits_low_byte(struct mpsse_ctx *ctx, uint8_t data, uint8_t dir)
{
        DEBUG_IO("-");
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 3)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, 0x80);
        buffer_write_byte(ctx, data);
        buffer_write_byte(ctx, dir);

        return retval;
}

int mpsse_set_data_bits_high_byte(struct mpsse_ctx *ctx, uint8_t data, uint8_t dir)
{
        DEBUG_IO("-");
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 3)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, 0x82);
        buffer_write_byte(ctx, data);
        buffer_write_byte(ctx, dir);

        return retval;
}

int mpsse_read_data_bits_low_byte(struct mpsse_ctx *ctx, uint8_t *data)
{
        DEBUG_IO("-");
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 1)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, 0x81);
        buffer_add_read(ctx, data, 0, 8, 0);

        return retval;
}

int mpsse_read_data_bits_high_byte(struct mpsse_ctx *ctx, uint8_t *data)
{
        DEBUG_IO("-");
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 1)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, 0x83);
        buffer_add_read(ctx, data, 0, 8, 0);

        return retval;
}

static int single_byte_boolean_helper(struct mpsse_ctx *ctx, bool var, uint8_t val_if_true,
        uint8_t val_if_false)
{
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 1)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, var ? val_if_true : val_if_false);

        return retval;
}

int mpsse_loopback_config(struct mpsse_ctx *ctx, bool enable)
{
        LOG_DEBUG("%s", enable ? "on" : "off");
        return single_byte_boolean_helper(ctx, enable, 0x84, 0x85);
}

int mpsse_set_divisor(struct mpsse_ctx *ctx, uint16_t divisor)
{
        LOG_DEBUG("%d", divisor);
        int retval = ERROR_OK;

        if (buffer_write_space(ctx) < 3)
                retval = mpsse_flush(ctx);

        buffer_write_byte(ctx, 0x86);
        buffer_write_byte(ctx, divisor & 0xff);
        buffer_write_byte(ctx, divisor >> 8);

        return retval;
}

int mpsse_divide_by_5_config(struct mpsse_ctx *ctx, bool enable)
{
        if (!mpsse_is_high_speed(ctx))
                return ERROR_FAIL;

        LOG_DEBUG("%s", enable ? "on" : "off");

        return single_byte_boolean_helper(ctx, enable, 0x8b, 0x8a);
}

int mpsse_rtck_config(struct mpsse_ctx *ctx, bool enable)
{
        if (!mpsse_is_high_speed(ctx))
                return ERROR_FAIL;

        LOG_DEBUG("%s", enable ? "on" : "off");

        return single_byte_boolean_helper(ctx, enable, 0x96, 0x97);
}

int mpsse_set_frequency(struct mpsse_ctx *ctx, int frequency)
{
        LOG_DEBUG("target %d Hz", frequency);
        assert(frequency >= 0);
        int base_clock;

        if (frequency == 0)
                return mpsse_rtck_config(ctx, true);

        mpsse_rtck_config(ctx, false); /* just try */

        if (frequency > 60000000 / 2 / 65536 && mpsse_is_high_speed(ctx)) {
                int retval = mpsse_divide_by_5_config(ctx, false);
                if (retval != ERROR_OK)
                        return retval;
                base_clock = 60000000;
        } else {
                mpsse_divide_by_5_config(ctx, true); /* just try */
                base_clock = 12000000;
        }

        int divisor = (base_clock / 2 + frequency - 1) / frequency - 1;
        if (divisor > 65535)
                divisor = 65535;
        assert(divisor >= 0);

        int retval = mpsse_set_divisor(ctx, divisor);
        if (retval != ERROR_OK)
                return retval;

        frequency = base_clock / 2 / (1 + divisor);
        LOG_DEBUG("actually %d Hz", frequency);

        return frequency;
}

/* Context needed by the callbacks */
struct transfer_result {
        struct mpsse_ctx *ctx;
        bool done;
        unsigned transferred;
};

static LIBUSB_CALL void read_cb(struct libusb_transfer *transfer)
{
        struct transfer_result *res = (struct transfer_result *)transfer->user_data;
        struct mpsse_ctx *ctx = res->ctx;

        unsigned packet_size = ctx->max_packet_size;

        DEBUG_PRINT_BUF(transfer->buffer, transfer->actual_length);

        /* Strip the two status bytes sent at the beginning of each USB packet
         * while copying the chunk buffer to the read buffer */
        unsigned num_packets = DIV_ROUND_UP(transfer->actual_length, packet_size);
        unsigned chunk_remains = transfer->actual_length;
        for (unsigned i = 0; i < num_packets && chunk_remains > 2; i++) {
                unsigned this_size = packet_size - 2;
                if (this_size > chunk_remains - 2)
                        this_size = chunk_remains - 2;
                if (this_size > ctx->read_count - res->transferred)
                        this_size = ctx->read_count - res->transferred;
                memcpy(ctx->read_buffer + res->transferred,
                        ctx->read_chunk + packet_size * i + 2,
                        this_size);
                res->transferred += this_size;
                chunk_remains -= this_size + 2;
                if (res->transferred == ctx->read_count) {
                        res->done = true;
                        break;
                }
        }

        DEBUG_IO("raw chunk %d, transferred %d of %d", transfer->actual_length, res->transferred,
                ctx->read_count);

        if (!res->done)
                if (libusb_submit_transfer(transfer) != LIBUSB_SUCCESS)
                        res->done = true;
}

static LIBUSB_CALL void write_cb(struct libusb_transfer *transfer)
{
        struct transfer_result *res = (struct transfer_result *)transfer->user_data;
        struct mpsse_ctx *ctx = res->ctx;

        res->transferred += transfer->actual_length;

        DEBUG_IO("transferred %d of %d", res->transferred, ctx->write_count);

        DEBUG_PRINT_BUF(transfer->buffer, transfer->actual_length);

        if (res->transferred == ctx->write_count)
                res->done = true;
        else {
                transfer->length = ctx->write_count - res->transferred;
                transfer->buffer = ctx->write_buffer + res->transferred;
                if (libusb_submit_transfer(transfer) != LIBUSB_SUCCESS)
                        res->done = true;
        }
}

int mpsse_flush(struct mpsse_ctx *ctx)
{
        DEBUG_IO("write %d%s, read %d", ctx->write_count, ctx->read_count ? "+1" : "",
                        ctx->read_count);
        assert(ctx->write_count > 0 || ctx->read_count == 0); /* No read data without write data */
        int retval = ERROR_OK;

        if (ctx->write_count == 0)
                return retval;

        struct libusb_transfer *read_transfer = 0;
        struct transfer_result read_result = { .ctx = ctx, .done = true };
        if (ctx->read_count) {
                buffer_write_byte(ctx, 0x87); /* SEND_IMMEDIATE */
                read_result.done = false;
                /* delay read transaction to ensure the FTDI chip can support us with data
                   immediately after processing the MPSSE commands in the write transaction */
        }

        struct transfer_result write_result = { .ctx = ctx, .done = false };
        struct libusb_transfer *write_transfer = libusb_alloc_transfer(0);
        libusb_fill_bulk_transfer(write_transfer, ctx->usb_dev, ctx->out_ep, ctx->write_buffer,
                ctx->write_count, write_cb, &write_result, ctx->usb_write_timeout);
        retval = libusb_submit_transfer(write_transfer);

        if (ctx->read_count) {
                read_transfer = libusb_alloc_transfer(0);
                libusb_fill_bulk_transfer(read_transfer, ctx->usb_dev, ctx->in_ep, ctx->read_chunk,
                        ctx->read_chunk_size, read_cb, &read_result,
                        ctx->usb_read_timeout);
                retval = libusb_submit_transfer(read_transfer);
        }

        /* Polling loop, more or less taken from libftdi */
        while (!write_result.done || !read_result.done) {
                retval = libusb_handle_events(ctx->usb_ctx);
                keep_alive();
                if (retval != LIBUSB_SUCCESS && retval != LIBUSB_ERROR_INTERRUPTED) {
                        libusb_cancel_transfer(write_transfer);
                        if (read_transfer)
                                libusb_cancel_transfer(read_transfer);
                        while (!write_result.done || !read_result.done)
                                if (libusb_handle_events(ctx->usb_ctx) != LIBUSB_SUCCESS)
                                        break;
                }
        }

        if (retval != LIBUSB_SUCCESS) {
                LOG_ERROR("libusb_handle_events() failed with %d", retval);
                retval = ERROR_FAIL;
        } else if (write_result.transferred < ctx->write_count) {
                LOG_ERROR("ftdi device did not accept all data: %d, tried %d",
                        write_result.transferred,
                        ctx->write_count);
                retval = ERROR_FAIL;
        } else if (read_result.transferred < ctx->read_count) {
                LOG_ERROR("ftdi device did not return all data: %d, expected %d",
                        read_result.transferred,
                        ctx->read_count);
                retval = ERROR_FAIL;
        } else if (ctx->read_count) {
                ctx->write_count = 0;
                ctx->read_count = 0;
                bit_copy_execute(&ctx->read_queue);
                retval = ERROR_OK;
        } else {
                ctx->write_count = 0;
                bit_copy_discard(&ctx->read_queue);
                retval = ERROR_OK;
        }

        libusb_free_transfer(write_transfer);
        if (read_transfer)
                libusb_free_transfer(read_transfer);

        if (retval != ERROR_OK)
                mpsse_purge(ctx);

        return retval;
}