mpsse.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/**************************************************************************
 *   Copyright (C) 2012 by Andreas Fritiofson                              *
 *   andreas.fritiofson@gmail.com                                          *
 ***************************************************************************/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "mpsse.h"
#include "helper/log.h"
#include "helper/replacements.h"
#include "helper/time_support.h"
#include "libusb_helper.h"
#include <libusb.h>
 
/* Compatibility define for older libusb-1.0 */
#ifndef LIBUSB_CALL
#define LIBUSB_CALL
#endif
 
#define DEBUG_PRINT_BUF(buf, len) \
    do { \
        if (LOG_LEVEL_IS(LOG_LVL_DEBUG_IO)) { \
            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_IO("%s", buf_string); \
                    buf_string_pos = 0; \
                } \
            } \
            if (buf_string_pos > 0) \
                LOG_DEBUG_IO("%s", buf_string);\
        } \
    } while (0)
 
#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 {
    struct libusb_context *usb_ctx;
    struct 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 int write_size;
    unsigned int write_count;
    uint8_t *read_buffer;
    unsigned int read_size;
    unsigned int read_count;
    uint8_t *read_chunk;
    unsigned int read_chunk_size;
    struct bit_copy_queue read_queue;
    int retval;
};
 
/* Returns true if the string descriptor indexed by str_index in device matches string */
static bool string_descriptor_equal(struct 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 %s", libusb_error_name(retval));
        return false;
    }
    return strncmp(string, desc_string, sizeof(desc_string)) == 0;
}
 
static bool device_location_equal(struct libusb_device *device, const char *location)
{
    bool result = false;
#ifdef HAVE_LIBUSB_GET_PORT_NUMBERS
    char *loc = strdup(location);
    uint8_t port_path[7];
    int path_step, path_len;
    uint8_t dev_bus = libusb_get_bus_number(device);
    char *ptr;
 
    path_len = libusb_get_port_numbers(device, port_path, 7);
    if (path_len == LIBUSB_ERROR_OVERFLOW) {
        LOG_ERROR("cannot determine path to usb device! (more than 7 ports in path)");
        goto done;
    }
 
    LOG_DEBUG("device path has %i steps", path_len);
 
    ptr = strtok(loc, "-:");
    if (!ptr) {
        LOG_DEBUG("no ':' in path");
        goto done;
    }
    if (atoi(ptr) != dev_bus) {
        LOG_DEBUG("bus mismatch");
        goto done;
    }
 
    path_step = 0;
    while (path_step < 7) {
        ptr = strtok(NULL, ".,");
        if (!ptr) {
            LOG_DEBUG("no more tokens in path at step %i", path_step);
            break;
        }
 
        if (path_step < path_len
            && atoi(ptr) != port_path[path_step]) {
            LOG_DEBUG("path mismatch at step %i", path_step);
            break;
        }
 
        path_step++;
    };
 
    /* walked the full path, all elements match */
    if (path_step == path_len)
        result = true;
 
 done:
    free(loc);
#endif
    return result;
}
 
/* 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 vids[], const uint16_t pids[],
    const char *product, const char *serial, const char *location)
{
    struct 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 %s", libusb_error_name(cnt));
 
    for (ssize_t i = 0; i < cnt; i++) {
        struct libusb_device *device = list[i];
 
        err = libusb_get_device_descriptor(device, &desc);
        if (err != LIBUSB_SUCCESS) {
            LOG_ERROR("libusb_get_device_descriptor() failed with %s", libusb_error_name(err));
            continue;
        }
 
        if (!jtag_libusb_match_ids(&desc, vids, pids))
            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 (location && !device_location_equal(device, location)) {
            libusb_close(ctx->usb_dev);
            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) {
        /* The caller reports detailed error desc */
        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 %s", libusb_error_name(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 %s", libusb_error_name(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 %s", libusb_error_name(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_WARNING("libusb_detach_kernel_driver() failed with %s, trying to continue anyway",
            libusb_error_name(err));
    }
 
    err = libusb_claim_interface(ctx->usb_dev, ctx->interface);
    if (err != LIBUSB_SUCCESS) {
        LOG_ERROR("libusb_claim_interface() failed with %s", libusb_error_name(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: %s", libusb_error_name(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;
    case 0x2800:
        ctx->type = TYPE_FT2233HP;
        break;
    case 0x2900:
        ctx->type = TYPE_FT4233HP;
        break;
    case 0x3000:
        ctx->type = TYPE_FT2232HP;
        break;
    case 0x3100:
        ctx->type = TYPE_FT4232HP;
        break;
    case 0x3200:
        ctx->type = TYPE_FT233HP;
        break;
    case 0x3300:
        ctx->type = TYPE_FT232HP;
        break;
    case 0x3600:
        ctx->type = TYPE_FT4232HA;
        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 vids[], const uint16_t pids[], const char *description,
    const char *serial, const char *location, int channel)
{
    struct mpsse_ctx *ctx = calloc(1, sizeof(*ctx));
    int err;
 
    if (!ctx)
        return NULL;
 
    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);
 
    /* Use calloc to make valgrind happy: buffer_write() sets payload
     * on bit basis, so some bits can be left uninitialized in write_buffer.
     * Although this is perfectly ok with MPSSE, valgrind reports
     * Syscall param ioctl(USBDEVFS_SUBMITURB).buffer points to uninitialised byte(s) */
    ctx->write_buffer = calloc(1, 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 %s", libusb_error_name(err));
        goto error;
    }
 
    if (!open_matching_device(ctx, vids, pids, description, serial, location)) {
        LOG_ERROR("unable to open ftdi device with description '%s', "
                "serial '%s' at bus location '%s'",
                description ? description : "*",
                serial ? serial : "*",
                location ? location : "*");
        ctx->usb_dev = NULL;
        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: %s", libusb_error_name(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: %s", libusb_error_name(err));
        goto error;
    }
 
    mpsse_purge(ctx);
 
    return ctx;
error:
    mpsse_close(ctx);
    return NULL;
}
 
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);
 
    free(ctx->write_buffer);
    free(ctx->read_buffer);
    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;
    ctx->retval = ERROR_OK;
    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: %s", libusb_error_name(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: %s", libusb_error_name(err));
        return;
    }
}
 
static unsigned int buffer_write_space(struct mpsse_ctx *ctx)
{
    /* Reserve one byte for SEND_IMMEDIATE */
    return ctx->write_size - ctx->write_count - 1;
}
 
static unsigned int 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)
{
    LOG_DEBUG_IO("%02x", data);
    assert(ctx->write_count < ctx->write_size);
    ctx->write_buffer[ctx->write_count++] = data;
}
 
static unsigned int buffer_write(struct mpsse_ctx *ctx, const uint8_t *out, unsigned int out_offset,
    unsigned int bit_count)
{
    LOG_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 int buffer_add_read(struct mpsse_ctx *ctx, uint8_t *in, unsigned int in_offset,
    unsigned int bit_count, unsigned int offset)
{
    LOG_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;
}
 
void mpsse_clock_data_out(struct mpsse_ctx *ctx, const uint8_t *out, unsigned int out_offset,
    unsigned int length, uint8_t mode)
{
    mpsse_clock_data(ctx, out, out_offset, NULL, 0, length, mode);
}
 
void mpsse_clock_data_in(struct mpsse_ctx *ctx, uint8_t *in, unsigned int in_offset, unsigned int length,
    uint8_t mode)
{
    mpsse_clock_data(ctx, NULL, 0, in, in_offset, length, mode);
}
 
void mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, unsigned int out_offset, uint8_t *in,
    unsigned int in_offset, unsigned int length, uint8_t mode)
{
    /* TODO: Fix MSB first modes */
    LOG_DEBUG_IO("%s%s %d bits", in ? "in" : "", out ? "out" : "", length);
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    /* 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))
            ctx->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 int 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 int n = 0; n < this_bytes; n++)
                        buffer_write_byte(ctx, 0x00);
                length -= this_bytes * 8;
            }
        }
    }
}
 
void mpsse_clock_tms_cs_out(struct mpsse_ctx *ctx, const uint8_t *out, unsigned int out_offset,
    unsigned int length, bool tdi, uint8_t mode)
{
    mpsse_clock_tms_cs(ctx, out, out_offset, NULL, 0, length, tdi, mode);
}
 
void mpsse_clock_tms_cs(struct mpsse_ctx *ctx, const uint8_t *out, unsigned int out_offset, uint8_t *in,
    unsigned int in_offset, unsigned int length, bool tdi, uint8_t mode)
{
    LOG_DEBUG_IO("%sout %d bits, tdi=%d", in ? "in" : "", length, tdi);
    assert(out);
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    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))
            ctx->retval = mpsse_flush(ctx);
 
        /* Byte transfer */
        unsigned int 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;
        }
    }
}
 
void mpsse_set_data_bits_low_byte(struct mpsse_ctx *ctx, uint8_t data, uint8_t dir)
{
    LOG_DEBUG_IO("-");
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 3)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, 0x80);
    buffer_write_byte(ctx, data);
    buffer_write_byte(ctx, dir);
}
 
void mpsse_set_data_bits_high_byte(struct mpsse_ctx *ctx, uint8_t data, uint8_t dir)
{
    LOG_DEBUG_IO("-");
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 3)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, 0x82);
    buffer_write_byte(ctx, data);
    buffer_write_byte(ctx, dir);
}
 
void mpsse_read_data_bits_low_byte(struct mpsse_ctx *ctx, uint8_t *data)
{
    LOG_DEBUG_IO("-");
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 1 || buffer_read_space(ctx) < 1)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, 0x81);
    buffer_add_read(ctx, data, 0, 8, 0);
}
 
void mpsse_read_data_bits_high_byte(struct mpsse_ctx *ctx, uint8_t *data)
{
    LOG_DEBUG_IO("-");
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 1 || buffer_read_space(ctx) < 1)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, 0x83);
    buffer_add_read(ctx, data, 0, 8, 0);
}
 
static void single_byte_boolean_helper(struct mpsse_ctx *ctx, bool var, uint8_t val_if_true,
    uint8_t val_if_false)
{
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 1)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, var ? val_if_true : val_if_false);
}
 
void mpsse_loopback_config(struct mpsse_ctx *ctx, bool enable)
{
    LOG_DEBUG("%s", enable ? "on" : "off");
    single_byte_boolean_helper(ctx, enable, 0x84, 0x85);
}
 
void mpsse_set_divisor(struct mpsse_ctx *ctx, uint16_t divisor)
{
    LOG_DEBUG("%d", divisor);
 
    if (ctx->retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring command due to previous error");
        return;
    }
 
    if (buffer_write_space(ctx) < 3)
        ctx->retval = mpsse_flush(ctx);
 
    buffer_write_byte(ctx, 0x86);
    buffer_write_byte(ctx, divisor & 0xff);
    buffer_write_byte(ctx, divisor >> 8);
}
 
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");
    single_byte_boolean_helper(ctx, enable, 0x8b, 0x8a);
 
    return ERROR_OK;
}
 
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");
    single_byte_boolean_helper(ctx, enable, 0x96, 0x97);
 
    return ERROR_OK;
}
 
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_divide_by_5_config(ctx, false) == ERROR_OK) {
        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);
 
    mpsse_set_divisor(ctx, divisor);
 
    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 int transferred;
};
 
static LIBUSB_CALL void read_cb(struct libusb_transfer *transfer)
{
    struct transfer_result *res = transfer->user_data;
    struct mpsse_ctx *ctx = res->ctx;
 
    unsigned int 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 int num_packets = DIV_ROUND_UP(transfer->actual_length, packet_size);
    unsigned int chunk_remains = transfer->actual_length;
    for (unsigned int i = 0; i < num_packets && chunk_remains > 2; i++) {
        unsigned int 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;
        }
    }
 
    LOG_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 = transfer->user_data;
    struct mpsse_ctx *ctx = res->ctx;
 
    res->transferred += transfer->actual_length;
 
    LOG_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)
{
    int retval = ctx->retval;
 
    if (retval != ERROR_OK) {
        LOG_DEBUG_IO("Ignoring flush due to previous error");
        assert(ctx->write_count == 0 && ctx->read_count == 0);
        ctx->retval = ERROR_OK;
        return retval;
    }
 
    LOG_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 */
 
    if (ctx->write_count == 0)
        return retval;
 
    struct libusb_transfer *read_transfer = NULL;
    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 (retval != LIBUSB_SUCCESS)
        goto error_check;
 
    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);
        if (retval != LIBUSB_SUCCESS)
            goto error_check;
    }
 
    /* Polling loop, more or less taken from libftdi */
    int64_t start = timeval_ms();
    int64_t warn_after = 2000;
    while (!write_result.done || !read_result.done) {
        struct timeval timeout_usb;
 
        timeout_usb.tv_sec = 1;
        timeout_usb.tv_usec = 0;
 
        retval = libusb_handle_events_timeout_completed(ctx->usb_ctx, &timeout_usb, NULL);
        keep_alive();
 
        int64_t now = timeval_ms();
        if (now - start > warn_after) {
            LOG_WARNING("Haven't made progress in mpsse_flush() for %" PRId64
                    "ms.", now - start);
            warn_after *= 2;
        }
 
        if (retval == LIBUSB_ERROR_INTERRUPTED)
            continue;
 
        if (retval != LIBUSB_SUCCESS) {
            libusb_cancel_transfer(write_transfer);
            if (read_transfer)
                libusb_cancel_transfer(read_transfer);
        }
    }
 
error_check:
    if (retval != LIBUSB_SUCCESS) {
        LOG_ERROR("libusb_handle_events() failed with %s", libusb_error_name(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;
    }
 
    if (retval != ERROR_OK)
        mpsse_purge(ctx);
 
    libusb_free_transfer(write_transfer);
    if (read_transfer)
        libusb_free_transfer(read_transfer);
 
    return retval;
}