hid_libusb.c

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/*
 HIDAPI - Multi-Platform library for communication with HID devices.
 
 Copyright (c) 2009 by Alan Ott, Signal 11 Software (8/22/2009)
 All Rights Reserved.
 
 Linux Version - 6/2/2010
 Libusb Version - 8/13/2010
 FreeBSD Version - 11/1/2011
 
 Changes for use with SX Filter Wheel INDI Driver by CloudMakers - 11/6/2012
 
 This program is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the Free
 Software Foundation; either version 2 of the License, or (at your option)
 any later version.
 
 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 more details.
 
 You should have received a copy of the GNU General Public License along with
 this program; if not, write to the Free Software Foundation, Inc., 59
 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
 The full GNU General Public License is included in this distribution in the
 file called LICENSE.
 
 These files may also be found in the public source code repository located:
 http://github.com/signal11/hidapi
*/
 
#define _GNU_SOURCE // needed for wcsdup() before glibc 2.10
 
#include "indi_hidapi.h"
#include "locale_compat.h"
 
/* GNU / LibUSB */
#include <libusb.h>
#include "iconv.h"
 
/* C */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
 
/* Unix */
#include <pthread.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
#define DEBUG_PRINTF
 
#ifdef DEBUG_PRINTF
#define LOG(...) fprintf(stderr, __VA_ARGS__)
#else
#define LOG(...) \
    do           \
    {            \
    } while (0)
#endif
 
#if !defined(__FreeBSD__) && !defined(__OpenBSD__)
#define DETACH_KERNEL_DRIVER
#endif
 
/* Uncomment to enable the retrieval of Usage and Usage Page in
hid_enumerate(). Warning, on platforms different from FreeBSD
this is very invasive as it requires the detach
and re-attach of the kernel driver. See comments inside hid_enumerate().
libusb HIDAPI programs are encouraged to use the interface number
instead to differentiate between interfaces on a composite HID device. */
 
// 2018-01-13 JM: It seems that on ARM systems, we need to detach and reattach the kernel driver otherwise we get LIBUSB_ERROR_BUSY
// So for now we use INVASIVE_GET_USAGE
#ifdef __arm__
#define INVASIVE_GET_USAGE
#endif
 
/* Linked List of input reports received from the device. */
struct input_report
{
    uint8_t *data;
    size_t len;
    struct input_report *next;
};
 
struct hid_device_
{
    /* Handle to the actual device. */
    libusb_device_handle *device_handle;
 
    /* Endpoint information */
    int input_endpoint;
    int output_endpoint;
    int input_ep_max_packet_size;
 
    /* The interface number of the HID */
    int interface;
 
    /* Indexes of Strings */
    int manufacturer_index;
    int product_index;
    int serial_index;
 
    /* Whether blocking reads are used */
    int blocking; /* boolean */
 
    /* Read thread objects */
    pthread_t thread;
    pthread_mutex_t mutex; /* Protects input_reports */
    pthread_cond_t condition;
    pthread_barrier_t barrier; /* Ensures correct startup sequence */
    int shutdown_thread;
    struct libusb_transfer *transfer;
 
    /* List of received input reports. */
    struct input_report *input_reports;
};
 
static libusb_context *usb_context = NULL;
 
uint16_t get_usb_code_for_current_locale(void);
static int return_data(hid_device *dev, unsigned char *data, size_t length);
 
static hid_device *new_hid_device(void)
{
    hid_device *dev = calloc(1, sizeof(hid_device));
    dev->blocking   = 1;
 
    pthread_mutex_init(&dev->mutex, NULL);
    pthread_cond_init(&dev->condition, NULL);
    pthread_barrier_init(&dev->barrier, NULL, 2);
 
    return dev;
}
 
static void free_hid_device(hid_device *dev)
{
    /* Clean up the thread objects */
    pthread_barrier_destroy(&dev->barrier);
    pthread_cond_destroy(&dev->condition);
    pthread_mutex_destroy(&dev->mutex);
 
    /* Free the device itself */
    free(dev);
}
 
#if 0
//TODO: Implement this function on hidapi/libusb..
static void register_error(hid_device * device, const char * op)
{
 
}
#endif
 
#ifdef INVASIVE_GET_USAGE
/* Get bytes from a HID Report Descriptor.
   Only call with a num_bytes of 0, 1, 2, or 4. */
static uint32_t get_bytes(uint8_t *rpt, size_t len, size_t num_bytes, size_t cur)
{
    /* Return if there aren't enough bytes. */
    if (cur + num_bytes >= len)
        return 0;
 
    if (num_bytes == 0)
        return 0;
    else if (num_bytes == 1)
    {
        return rpt[cur + 1];
    }
    else if (num_bytes == 2)
    {
        return (rpt[cur + 2] * 256 + rpt[cur + 1]);
    }
    else if (num_bytes == 4)
    {
        return (rpt[cur + 4] * 0x01000000 + rpt[cur + 3] * 0x00010000 + rpt[cur + 2] * 0x00000100 +
                rpt[cur + 1] * 0x00000001);
    }
    else
        return 0;
}
 
/* Retrieves the device's Usage Page and Usage from the report
   descriptor. The algorithm is simple, as it just returns the first
   Usage and Usage Page that it finds in the descriptor.
   The return value is 0 on success and -1 on failure. */
static int get_usage(uint8_t *report_descriptor, size_t size, unsigned short *usage_page, unsigned short *usage)
{
    size_t i = 0;
    int size_code;
    int data_len, key_size;
    int usage_found = 0, usage_page_found = 0;
 
    while (i < size)
    {
        int key     = report_descriptor[i];
        int key_cmd = key & 0xfc;
 
        //printf("key: %02hhx\n", key);
 
        if ((key & 0xf0) == 0xf0)
        {
            /* This is a Long Item. The next byte contains the
               length of the data section (value) for this key.
               See the HID specification, version 1.11, section
               6.2.2.3, titled "Long Items." */
            if (i + 1 < size)
                data_len = report_descriptor[i + 1];
            else
                data_len = 0; /* malformed report */
            key_size = 3;
        }
        else
        {
            /* This is a Short Item. The bottom two bits of the
               key contain the size code for the data section
               (value) for this key.  Refer to the HID
               specification, version 1.11, section 6.2.2.2,
               titled "Short Items." */
            size_code = key & 0x3;
            switch (size_code)
            {
                case 0:
                case 1:
                case 2:
                    data_len = size_code;
                    break;
                case 3:
                    data_len = 4;
                    break;
                default:
                    /* Can't ever happen since size_code is & 0x3 */
                    data_len = 0;
                    break;
            };
            key_size = 1;
        }
 
        if (key_cmd == 0x4)
        {
            *usage_page      = get_bytes(report_descriptor, size, data_len, i);
            usage_page_found = 1;
            //printf("Usage Page: %x\n", (uint32_t)*usage_page);
        }
        if (key_cmd == 0x8)
        {
            *usage      = get_bytes(report_descriptor, size, data_len, i);
            usage_found = 1;
            //printf("Usage: %x\n", (uint32_t)*usage);
        }
 
        if (usage_page_found && usage_found)
            return 0; /* success */
 
        /* Skip over this key and it's associated data */
        i += data_len + key_size;
    }
 
    return -1; /* failure */
}
#endif // INVASIVE_GET_USAGE
 
/* Get the first language the device says it reports. This comes from
   USB string #0. */
static uint16_t get_first_language(libusb_device_handle *dev)
{
    uint16_t buf[32];
    int len;
 
    /* Get the string from libusb. */
    len = libusb_get_string_descriptor(dev, 0x0, /* String ID */
                                       0x0,      /* Language */
                                       (unsigned char *)buf, sizeof(buf));
    if (len < 4)
        return 0x0;
 
    return buf[1]; // First two bytes are len and descriptor type.
}
 
static int is_language_supported(libusb_device_handle *dev, uint16_t lang)
{
    uint16_t buf[32];
    int len;
    int i;
 
    /* Get the string from libusb. */
    len = libusb_get_string_descriptor(dev, 0x0, /* String ID */
                                       0x0,      /* Language */
                                       (unsigned char *)buf, sizeof(buf));
    if (len < 4)
        return 0x0;
 
    len /= 2; /* language IDs are two-bytes each. */
    /* Start at index 1 because there are two bytes of protocol data. */
    for (i = 1; i < len; i++)
    {
        if (buf[i] == lang)
            return 1;
    }
 
    return 0;
}
 
/* This function returns a newly allocated wide string containing the USB
   device string numbered by the index. The returned string must be freed
   by using free(). */
static wchar_t *get_usb_string(libusb_device_handle *dev, uint8_t idx)
{
    char buf[512];
    int len;
    wchar_t *str = NULL;
    wchar_t wbuf[256];
 
    /* iconv variables */
    iconv_t ic;
    size_t inbytes;
    size_t outbytes;
    size_t res;
    char *inptr;
    char *outptr;
 
    /* Determine which language to use. */
    uint16_t lang;
    lang = get_usb_code_for_current_locale();
    if (!is_language_supported(dev, lang))
        lang = get_first_language(dev);
 
    /* Get the string from libusb. */
    len = libusb_get_string_descriptor(dev, idx, lang, (unsigned char *)buf, sizeof(buf));
    if (len < 0)
        return NULL;
 
    /* buf does not need to be explicitly NULL-terminated because
       it is only passed into iconv() which does not need it. */
 
    /* Initialize iconv. */
    ic = iconv_open("WCHAR_T", "UTF-16LE");
    if (ic == (iconv_t)-1)
    {
        LOG("iconv_open() failed\n");
        return NULL;
    }
 
    /* Convert to native wchar_t (UTF-32 on glibc/BSD systems).
       Skip the first character (2-bytes). */
    inptr    = buf + 2;
    inbytes  = len - 2;
    outptr   = (char *)wbuf;
    outbytes = sizeof(wbuf);
    res      = iconv(ic, &inptr, &inbytes, &outptr, &outbytes);
    if (res == (size_t)-1)
    {
        LOG("iconv() failed\n");
        goto err;
    }
 
    /* Write the terminating NULL. */
    wbuf[sizeof(wbuf) / sizeof(wbuf[0]) - 1] = 0x00000000;
    if (outbytes >= sizeof(wbuf[0]))
        *((wchar_t *)outptr) = 0x00000000;
 
    /* Allocate and copy the string. */
    str = wcsdup(wbuf);
 
err:
    iconv_close(ic);
 
    return str;
}
 
static char *make_path(libusb_device *dev, int interface_number)
{
    char str[64];
    snprintf(str, sizeof(str), "%04x:%04x:%02x", libusb_get_bus_number(dev), libusb_get_device_address(dev),
             interface_number);
    str[sizeof(str) - 1] = '\0';
 
    return strdup(str);
}
 
int HID_API_EXPORT hid_init(void)
{
    if (!usb_context)
    {
        locale_char_t *locale;
 
        /* Init Libusb */
        if (libusb_init(&usb_context))
            return -1;
 
        /* Set the locale if it's not set. */
        locale = indi_setlocale(LC_CTYPE, NULL);
        if (!locale)
            indi_setlocale(LC_CTYPE, INDI_LOCALE(""));
    }
 
    return 0;
}
 
int HID_API_EXPORT hid_exit(void)
{
    if (usb_context)
    {
        libusb_exit(usb_context);
        usb_context = NULL;
    }
 
    return 0;
}
 
struct hid_device_info HID_API_EXPORT *hid_enumerate(unsigned short vendor_id, unsigned short product_id)
{
    libusb_device **devs;
    libusb_device *dev;
    libusb_device_handle *handle;
    ssize_t num_devs;
    int i = 0;
 
    LOG("Searching for HID Device VID: %#04x PID: %#04x\n", vendor_id, product_id);
 
    struct hid_device_info *root    = NULL; // return object
    struct hid_device_info *cur_dev = NULL;
 
    hid_init();
 
    num_devs = libusb_get_device_list(usb_context, &devs);
    if (num_devs < 0)
        return NULL;
 
    while ((dev = devs[i++]) != NULL)
    {
        struct libusb_device_descriptor desc;
        struct libusb_config_descriptor *conf_desc = NULL;
        int j, k;
        int interface_num = 0;
 
        int res                = libusb_get_device_descriptor(dev, &desc);
        unsigned short dev_vid = desc.idVendor;
        unsigned short dev_pid = desc.idProduct;
 
        /* HID's are defined at the interface level. */
        if (desc.bDeviceClass != LIBUSB_CLASS_PER_INTERFACE)
            continue;
 
        res = libusb_get_active_config_descriptor(dev, &conf_desc);
        if (res < 0)
            libusb_get_config_descriptor(dev, 0, &conf_desc);
        if (conf_desc)
        {
            for (j = 0; j < conf_desc->bNumInterfaces; j++)
            {
                const struct libusb_interface *intf = &conf_desc->interface[j];
                for (k = 0; k < intf->num_altsetting; k++)
                {
                    const struct libusb_interface_descriptor *intf_desc;
                    intf_desc = &intf->altsetting[k];
                    if (intf_desc->bInterfaceClass == LIBUSB_CLASS_HID)
                    {
                        interface_num = intf_desc->bInterfaceNumber;
 
                        /* Check the VID/PID against the arguments */
                        if ((vendor_id == 0x0 && product_id == 0x0) || (vendor_id == dev_vid && product_id == dev_pid))
                        {
                            struct hid_device_info *tmp;
 
                            /* VID/PID match. Create the record. */
                            tmp = calloc(1, sizeof(struct hid_device_info));
                            if (cur_dev)
                            {
                                cur_dev->next = tmp;
                            }
                            else
                            {
                                root = tmp;
                            }
                            cur_dev = tmp;
 
                            /* Fill out the record */
                            cur_dev->next = NULL;
                            cur_dev->path = make_path(dev, interface_num);
 
                            res = libusb_open(dev, &handle);
 
                            if (res >= 0)
                            {
                                /* Serial Number */
                                if (desc.iSerialNumber > 0)
                                    cur_dev->serial_number = get_usb_string(handle, desc.iSerialNumber);
 
                                /* Manufacturer and Product strings */
                                if (desc.iManufacturer > 0)
                                    cur_dev->manufacturer_string = get_usb_string(handle, desc.iManufacturer);
                                if (desc.iProduct > 0)
                                    cur_dev->product_string = get_usb_string(handle, desc.iProduct);
 
#ifdef INVASIVE_GET_USAGE
                                /*
                                This section is removed because it is too
                                invasive on the system. Getting a Usage Page
                                and Usage requires parsing the HID Report
                                descriptor. Getting a HID Report descriptor
                                involves claiming the interface. Claiming the
                                interface involves detaching the kernel driver.
                                Detaching the kernel driver is hard on the system
                                because it will unclaim interfaces (if another
                                app has them claimed) and the re-attachment of
                                the driver will sometimes change /dev entry names.
                                It is for these reasons that this section is
                                #if 0. For composite devices, use the interface
                                field in the hid_device_info struct to distinguish
                                between interfaces. */
                                unsigned char data[256];
#ifdef DETACH_KERNEL_DRIVER
                                int detached = 0;
                                /* Usage Page and Usage */
                                res = libusb_kernel_driver_active(handle, interface_num);
                                if (res == 1)
                                {
                                    res = libusb_detach_kernel_driver(handle, interface_num);
                                    if (res < 0)
                                        LOG("Couldn't detach kernel driver, even though a kernel driver was attached.");
                                    else
                                        detached = 1;
                                }
#endif
                                res = libusb_claim_interface(handle, interface_num);
                                if (res >= 0)
                                {
                                    /* Get the HID Report Descriptor. */
                                    res = libusb_control_transfer(
                                        handle, LIBUSB_ENDPOINT_IN | LIBUSB_RECIPIENT_INTERFACE,
                                        LIBUSB_REQUEST_GET_DESCRIPTOR, (LIBUSB_DT_REPORT << 8) | interface_num, 0, data,
                                        sizeof(data), 5000);
                                    if (res >= 0)
                                    {
                                        unsigned short page = 0, usage = 0;
                                        /* Parse the usage and usage page
                                           out of the report descriptor. */
                                        get_usage(data, res, &page, &usage);
                                        cur_dev->usage_page = page;
                                        cur_dev->usage      = usage;
                                    }
                                    else
                                        LOG("libusb_control_transfer() for getting the HID report failed with %d\n",
                                            res);
 
                                    /* Release the interface */
                                    res = libusb_release_interface(handle, interface_num);
                                    if (res < 0)
                                        LOG("Can't release the interface.\n");
                                }
                                else
                                    LOG("Can't claim interface %d\n", res);
#ifdef DETACH_KERNEL_DRIVER
                                /* Re-attach kernel driver if necessary. */
                                if (detached)
                                {
                                    res = libusb_attach_kernel_driver(handle, interface_num);
                                    if (res < 0)
                                        LOG("Couldn't re-attach kernel driver.\n");
                                }
#endif
 
#endif // INVASIVE_GET_USAGE
 
                                libusb_close(handle);
                            }
                            /* VID/PID */
                            cur_dev->vendor_id  = dev_vid;
                            cur_dev->product_id = dev_pid;
 
                            /* Release Number */
                            cur_dev->release_number = desc.bcdDevice;
 
                            /* Interface Number */
                            cur_dev->interface_number = interface_num;
                        }
                    }
                } /* altsettings */
            }     /* interfaces */
            libusb_free_config_descriptor(conf_desc);
        }
    }
 
    libusb_free_device_list(devs, 1);
 
    return root;
}
 
void HID_API_EXPORT hid_free_enumeration(struct hid_device_info *devs)
{
    struct hid_device_info *d = devs;
    while (d)
    {
        struct hid_device_info *next = d->next;
        free(d->path);
        free(d->serial_number);
        free(d->manufacturer_string);
        free(d->product_string);
        free(d);
        d = next;
    }
}
 
hid_device *hid_open(unsigned short vendor_id, unsigned short product_id, const wchar_t *serial_number)
{
    struct hid_device_info *devs, *cur_dev;
    const char *path_to_open = NULL;
    hid_device *handle       = NULL;
 
    devs    = hid_enumerate(vendor_id, product_id);
    cur_dev = devs;
    while (cur_dev)
    {
        if (cur_dev->vendor_id == vendor_id && cur_dev->product_id == product_id)
        {
            if (serial_number)
            {
                if (wcscmp(serial_number, cur_dev->serial_number) == 0)
                {
                    path_to_open = cur_dev->path;
                    break;
                }
            }
            else
            {
                path_to_open = cur_dev->path;
                break;
            }
        }
        cur_dev = cur_dev->next;
    }
 
    if (path_to_open)
    {
        /* Open the device */
        handle = hid_open_path(path_to_open);
    }
 
    hid_free_enumeration(devs);
 
    return handle;
}
 
static void read_callback(struct libusb_transfer *transfer)
{
    hid_device *dev = transfer->user_data;
    int res=0;
 
    if (transfer->status == LIBUSB_TRANSFER_COMPLETED)
    {
        struct input_report *rpt = malloc(sizeof(*rpt));
        rpt->data                = malloc(transfer->actual_length);
        memcpy(rpt->data, transfer->buffer, transfer->actual_length);
        rpt->len  = transfer->actual_length;
        rpt->next = NULL;
 
        pthread_mutex_lock(&dev->mutex);
 
        /* Attach the new report object to the end of the list. */
        if (dev->input_reports == NULL)
        {
            /* The list is empty. Put it at the root. */
            dev->input_reports = rpt;
            pthread_cond_signal(&dev->condition);
        }
        else
        {
            /* Find the end of the list and attach. */
            struct input_report *cur = dev->input_reports;
            int num_queued           = 0;
            while (cur->next != NULL)
            {
                cur = cur->next;
                num_queued++;
            }
            cur->next = rpt;
 
            /* Pop one off if we've reached 30 in the queue. This
               way we don't grow forever if the user never reads
               anything from the device. */
            if (num_queued > 30)
            {
                return_data(dev, NULL, 0);
            }
        }
        pthread_mutex_unlock(&dev->mutex);
    }
    else if (transfer->status == LIBUSB_TRANSFER_CANCELLED)
    {
        dev->shutdown_thread = 1;
        return;
    }
    else if (transfer->status == LIBUSB_TRANSFER_NO_DEVICE)
    {
        dev->shutdown_thread = 1;
        return;
    }
    else if (transfer->status == LIBUSB_TRANSFER_TIMED_OUT)
    {
        //LOG("Timeout (normal)\n");
    }
    else
    {
        LOG("Unknown transfer code: #%d %s\n", transfer->status, libusb_error_name(res));
    }
 
    /* Re-submit the transfer object. */
    res = libusb_submit_transfer(transfer);
    if (res != 0)
    {
        LOG("Unable to submit URB. libusb error code: #%d %s\n", res, libusb_error_name(res));
        dev->shutdown_thread = 1;
    }
}
 
static void *read_thread(void *param)
{
    hid_device *dev = param;
    unsigned char *buf;
    const size_t length = dev->input_ep_max_packet_size;
 
    /* Set up the transfer object. */
    buf           = malloc(length);
    dev->transfer = libusb_alloc_transfer(0);
    libusb_fill_interrupt_transfer(dev->transfer, dev->device_handle, dev->input_endpoint, buf, length, read_callback,
                                   dev, 5000 /*timeout*/);
 
    /* Make the first submission. Further submissions are made
       from inside read_callback() */
    libusb_submit_transfer(dev->transfer);
 
    // Notify the main thread that the read thread is up and running.
    pthread_barrier_wait(&dev->barrier);
 
    /* Handle all the events. */
    while (!dev->shutdown_thread)
    {
        int res;
        res = libusb_handle_events(usb_context);
        if (res < 0)
        {
            /* There was an error. */
            LOG("read_thread(): libusb reports error #%d %s\n", res, libusb_error_name(res));
 
            /* Break out of this loop only on fatal error.*/
            if (res != LIBUSB_ERROR_BUSY && res != LIBUSB_ERROR_TIMEOUT && res != LIBUSB_ERROR_OVERFLOW &&
                res != LIBUSB_ERROR_INTERRUPTED)
            {
                break;
            }
        }
    }
 
    /* Cancel any transfer that may be pending. This call will fail
       if no transfers are pending, but that's OK. */
    if (libusb_cancel_transfer(dev->transfer) == 0)
    {
        /* The transfer was cancelled, so wait for its completion. */
        libusb_handle_events(usb_context);
    }
 
    /* Now that the read thread is stopping, Wake any threads which are
       waiting on data (in hid_read_timeout()). Do this under a mutex to
       make sure that a thread which is about to go to sleep waiting on
       the condition actually will go to sleep before the condition is
       signaled. */
    pthread_mutex_lock(&dev->mutex);
    pthread_cond_broadcast(&dev->condition);
    pthread_mutex_unlock(&dev->mutex);
 
    /* The dev->transfer->buffer and dev->transfer objects are cleaned up
       in hid_close(). They are not cleaned up here because this thread
       could end either due to a disconnect or due to a user
       call to hid_close(). In both cases the objects can be safely
       cleaned up after the call to pthread_join() (in hid_close()), but
       since hid_close() calls libusb_cancel_transfer(), on these objects,
       they can not be cleaned up here. */
 
    return NULL;
}
 
hid_device *HID_API_EXPORT hid_open_path(const char *path)
{
    hid_device *dev = NULL;
 
    dev = new_hid_device();
 
    libusb_device **devs;
    libusb_device *usb_dev;
    ssize_t num_devs;
    int res;
    int d         = 0;
    int good_open = 0;
 
    hid_init();
 
    num_devs = libusb_get_device_list(usb_context, &devs);
    if (num_devs < 0)
        return NULL;
 
    while ((usb_dev = devs[d++]) != NULL)
    {
        struct libusb_device_descriptor desc;
        struct libusb_config_descriptor *conf_desc = NULL;
        int i, j, k;
        libusb_get_device_descriptor(usb_dev, &desc);
 
        if (libusb_get_active_config_descriptor(usb_dev, &conf_desc) < 0)
            continue;
        for (j = 0; j < conf_desc->bNumInterfaces; j++)
        {
            const struct libusb_interface *intf = &conf_desc->interface[j];
            for (k = 0; k < intf->num_altsetting; k++)
            {
                const struct libusb_interface_descriptor *intf_desc;
                intf_desc = &intf->altsetting[k];
                if (intf_desc->bInterfaceClass == LIBUSB_CLASS_HID)
                {
                    char *dev_path = make_path(usb_dev, intf_desc->bInterfaceNumber);
                    if (!strcmp(dev_path, path))
                    {
                        /* Matched Paths. Open this device */
 
                        // OPEN HERE //
                        res = libusb_open(usb_dev, &dev->device_handle);
                        if (res < 0)
                        {
                            LOG("can't open device: %s\n", libusb_error_name(res));
                            free(dev_path);
                            break;
                        }
                        good_open = 1;
#ifdef DETACH_KERNEL_DRIVER
                        /* Detach the kernel driver, but only if the
                           device is managed by the kernel */
                        if (libusb_kernel_driver_active(dev->device_handle, intf_desc->bInterfaceNumber) == 1)
                        {
                            res = libusb_detach_kernel_driver(dev->device_handle, intf_desc->bInterfaceNumber);
                            if (res < 0)
                            {
                                libusb_close(dev->device_handle);
                                LOG("Unable to detach Kernel Driver: %s\n", libusb_error_name(res));
                                free(dev_path);
                                good_open = 0;
                                break;
                            }
                        }
#endif
                        res = libusb_claim_interface(dev->device_handle, intf_desc->bInterfaceNumber);
                        if (res < 0)
                        {
                            LOG("can't claim interface %d: %d %s\n", intf_desc->bInterfaceNumber, res, libusb_error_name(res));
                            free(dev_path);
                            libusb_close(dev->device_handle);
                            good_open = 0;
                            break;
                        }
 
                        /* Store off the string descriptor indexes */
                        dev->manufacturer_index = desc.iManufacturer;
                        dev->product_index      = desc.iProduct;
                        dev->serial_index       = desc.iSerialNumber;
 
                        /* Store off the interface number */
                        dev->interface = intf_desc->bInterfaceNumber;
 
                        /* Find the INPUT and OUTPUT endpoints. An
                           OUTPUT endpoint is not required. */
                        for (i = 0; i < intf_desc->bNumEndpoints; i++)
                        {
                            const struct libusb_endpoint_descriptor *ep = &intf_desc->endpoint[i];
 
                            /* Determine the type and direction of this
                               endpoint. */
                            int is_interrupt =
                                (ep->bmAttributes & LIBUSB_TRANSFER_TYPE_MASK) == LIBUSB_TRANSFER_TYPE_INTERRUPT;
                            int is_output = (ep->bEndpointAddress & LIBUSB_ENDPOINT_DIR_MASK) == LIBUSB_ENDPOINT_OUT;
                            int is_input  = (ep->bEndpointAddress & LIBUSB_ENDPOINT_DIR_MASK) == LIBUSB_ENDPOINT_IN;
 
                            /* Decide whether to use it for input or output. */
                            if (dev->input_endpoint == 0 && is_interrupt && is_input)
                            {
                                /* Use this endpoint for INPUT */
                                dev->input_endpoint           = ep->bEndpointAddress;
                                dev->input_ep_max_packet_size = ep->wMaxPacketSize;
                            }
                            if (dev->output_endpoint == 0 && is_interrupt && is_output)
                            {
                                /* Use this endpoint for OUTPUT */
                                dev->output_endpoint = ep->bEndpointAddress;
                            }
                        }
 
                        pthread_create(&dev->thread, NULL, read_thread, dev);
 
                        // Wait here for the read thread to be initialized.
                        pthread_barrier_wait(&dev->barrier);
                    }
                    free(dev_path);
                }
            }
        }
        libusb_free_config_descriptor(conf_desc);
    }
 
    libusb_free_device_list(devs, 1);
 
    // If we have a good handle, return it.
    if (good_open)
    {
        return dev;
    }
    else
    {
        // Unable to open any devices.
        free_hid_device(dev);
        return NULL;
    }
}
 
int HID_API_EXPORT hid_write(hid_device *dev, const unsigned char *data, size_t length)
{
    int res;
    int report_number     = data[0];
    int skipped_report_id = 0;
 
    if (report_number == 0x0)
    {
        data++;
        length--;
        skipped_report_id = 1;
    }
 
    if (dev->output_endpoint <= 0)
    {
        /* No interrupt out endpoint. Use the Control Endpoint */
        res = libusb_control_transfer(dev->device_handle,
                                      LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE | LIBUSB_ENDPOINT_OUT,
                                      0x09 /*HID Set_Report*/, (2 /*HID output*/ << 8) | report_number, dev->interface,
                                      (unsigned char *)data, length, 1000 /*timeout millis*/);
 
        if (res < 0)
            return -1;
 
        if (skipped_report_id)
            length++;
 
        return length;
    }
    else
    {
        /* Use the interrupt out endpoint */
        int actual_length;
        res = libusb_interrupt_transfer(dev->device_handle, dev->output_endpoint, (unsigned char *)data, length,
                                        &actual_length, 1000);
 
        if (res < 0)
            return -1;
 
        if (skipped_report_id)
            actual_length++;
 
        return actual_length;
    }
}
 
/* Helper function, to simplify hid_read().
   This should be called with dev->mutex locked. */
static int return_data(hid_device *dev, unsigned char *data, size_t length)
{
    /* Copy the data out of the linked list item (rpt) into the
       return buffer (data), and delete the liked list item. */
    struct input_report *rpt = dev->input_reports;
    size_t len               = (length < rpt->len) ? length : rpt->len;
    if (len > 0)
        memcpy(data, rpt->data, len);
    dev->input_reports = rpt->next;
    free(rpt->data);
    free(rpt);
    return len;
}
 
static void cleanup_mutex(void *param)
{
    hid_device *dev = param;
    pthread_mutex_unlock(&dev->mutex);
}
 
int HID_API_EXPORT hid_read_timeout(hid_device *dev, unsigned char *data, size_t length, int milliseconds)
{
    volatile int bytes_read = 0;
 
#if 0
    int transferred;
    int res = libusb_interrupt_transfer(dev->device_handle, dev->input_endpoint, data, length, &transferred, 5000);
    LOG("transferred: %d\n", transferred);
    return transferred;
#endif
 
    pthread_mutex_lock(&dev->mutex);
    pthread_cleanup_push(&cleanup_mutex, dev);
 
    /* There's an input report queued up. Return it. */
    if (dev->input_reports)
    {
        /* Return the first one */
        bytes_read = return_data(dev, data, length);
        goto ret;
    }
 
    if (dev->shutdown_thread)
    {
        /* This means the device has been disconnected.
           An error code of -1 should be returned. */
        bytes_read = -1;
        goto ret;
    }
 
    if (milliseconds == -1)
    {
        /* Blocking */
        while (!dev->input_reports && !dev->shutdown_thread)
        {
            pthread_cond_wait(&dev->condition, &dev->mutex);
        }
        if (dev->input_reports)
        {
            bytes_read = return_data(dev, data, length);
        }
    }
    else if (milliseconds > 0)
    {
        /* Non-blocking, but called with timeout. */
        int res;
        struct timespec ts;
        clock_gettime(CLOCK_REALTIME, &ts);
        ts.tv_sec += milliseconds / 1000;
        ts.tv_nsec += (milliseconds % 1000) * 1000000;
        if (ts.tv_nsec >= 1000000000L)
        {
            ts.tv_sec++;
            ts.tv_nsec -= 1000000000L;
        }
 
        while (!dev->input_reports && !dev->shutdown_thread)
        {
            res = pthread_cond_timedwait(&dev->condition, &dev->mutex, &ts);
            if (res == 0)
            {
                if (dev->input_reports)
                {
                    bytes_read = return_data(dev, data, length);
                    break;
                }
 
                /* If we're here, there was a spurious wake up
                   or the read thread was shutdown. Run the
                   loop again (ie: don't break). */
            }
            else if (res == ETIMEDOUT)
            {
                /* Timed out. */
                bytes_read = 0;
                break;
            }
            else
            {
                /* Error. */
                bytes_read = -1;
                break;
            }
        }
    }
    else
    {
        /* Purely non-blocking */
        bytes_read = 0;
    }
 
ret:
    pthread_mutex_unlock(&dev->mutex);
    pthread_cleanup_pop(0);
 
    return bytes_read;
}
 
int HID_API_EXPORT hid_read(hid_device *dev, unsigned char *data, size_t length)
{
    return hid_read_timeout(dev, data, length, dev->blocking ? -1 : 0);
}
 
int HID_API_EXPORT hid_set_nonblocking(hid_device *dev, int nonblock)
{
    dev->blocking = !nonblock;
 
    return 0;
}
 
int HID_API_EXPORT hid_send_feature_report(hid_device *dev, const unsigned char *data, size_t length)
{
    int res               = -1;
    int skipped_report_id = 0;
    int report_number     = data[0];
 
    if (report_number == 0x0)
    {
        data++;
        length--;
        skipped_report_id = 1;
    }
 
    res = libusb_control_transfer(dev->device_handle,
                                  LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE | LIBUSB_ENDPOINT_OUT,
                                  0x09 /*HID set_report*/, (3 /*HID feature*/ << 8) | report_number, dev->interface,
                                  (unsigned char *)data, length, 1000 /*timeout millis*/);
 
    if (res < 0)
        return -1;
 
    /* Account for the report ID */
    if (skipped_report_id)
        length++;
 
    return length;
}
 
int HID_API_EXPORT hid_get_feature_report(hid_device *dev, unsigned char *data, size_t length)
{
    int res               = -1;
    int skipped_report_id = 0;
    int report_number     = data[0];
 
    if (report_number == 0x0)
    {
        /* Offset the return buffer by 1, so that the report ID
           will remain in byte 0. */
        data++;
        length--;
        skipped_report_id = 1;
    }
    res = libusb_control_transfer(dev->device_handle,
                                  LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE | LIBUSB_ENDPOINT_IN,
                                  0x01 /*HID get_report*/, (3 /*HID feature*/ << 8) | report_number, dev->interface,
                                  (unsigned char *)data, length, 1000 /*timeout millis*/);
 
    if (res < 0)
        return -1;
 
    if (skipped_report_id)
        res++;
 
    return res;
}
 
void HID_API_EXPORT hid_close(hid_device *dev)
{
    if (!dev)
        return;
 
    /* Cause read_thread() to stop. */
    dev->shutdown_thread = 1;
    libusb_cancel_transfer(dev->transfer);
 
    /* Wait for read_thread() to end. */
    pthread_join(dev->thread, NULL);
 
    /* Clean up the Transfer objects allocated in read_thread(). */
    free(dev->transfer->buffer);
    libusb_free_transfer(dev->transfer);
 
    /* release the interface */
    libusb_release_interface(dev->device_handle, dev->interface);
 
    /* Close the handle */
    libusb_close(dev->device_handle);
 
    /* Clear out the queue of received reports. */
    pthread_mutex_lock(&dev->mutex);
    while (dev->input_reports)
    {
        return_data(dev, NULL, 0);
    }
    pthread_mutex_unlock(&dev->mutex);
 
    free_hid_device(dev);
}
 
int HID_API_EXPORT_CALL hid_get_manufacturer_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
    return hid_get_indexed_string(dev, dev->manufacturer_index, string, maxlen);
}
 
int HID_API_EXPORT_CALL hid_get_product_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
    return hid_get_indexed_string(dev, dev->product_index, string, maxlen);
}
 
int HID_API_EXPORT_CALL hid_get_serial_number_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
    return hid_get_indexed_string(dev, dev->serial_index, string, maxlen);
}
 
int HID_API_EXPORT_CALL hid_get_indexed_string(hid_device *dev, int string_index, wchar_t *string, size_t maxlen)
{
    wchar_t *str;
 
    str = get_usb_string(dev->device_handle, string_index);
    if (str)
    {
        wcsncpy(string, str, maxlen);
        string[maxlen - 1] = L'\0';
        free(str);
        return 0;
    }
    else
        return -1;
}
 
HID_API_EXPORT const wchar_t *HID_API_CALL hid_error(hid_device *dev)
{
    (void)dev;
    return NULL;
}
 
struct lang_map_entry
{
    const char *name;
    const char *string_code;
    uint16_t usb_code;
};
 
#define LANG(name, code, usb_code) \
    {                              \
        name, code, usb_code       \
    }
static struct lang_map_entry lang_map[] = {
    LANG("Afrikaans", "af", 0x0436),
    LANG("Albanian", "sq", 0x041C),
    LANG("Arabic - United Arab Emirates", "ar_ae", 0x3801),
    LANG("Arabic - Bahrain", "ar_bh", 0x3C01),
    LANG("Arabic - Algeria", "ar_dz", 0x1401),
    LANG("Arabic - Egypt", "ar_eg", 0x0C01),
    LANG("Arabic - Iraq", "ar_iq", 0x0801),
    LANG("Arabic - Jordan", "ar_jo", 0x2C01),
    LANG("Arabic - Kuwait", "ar_kw", 0x3401),
    LANG("Arabic - Lebanon", "ar_lb", 0x3001),
    LANG("Arabic - Libya", "ar_ly", 0x1001),
    LANG("Arabic - Morocco", "ar_ma", 0x1801),
    LANG("Arabic - Oman", "ar_om", 0x2001),
    LANG("Arabic - Qatar", "ar_qa", 0x4001),
    LANG("Arabic - Saudi Arabia", "ar_sa", 0x0401),
    LANG("Arabic - Syria", "ar_sy", 0x2801),
    LANG("Arabic - Tunisia", "ar_tn", 0x1C01),
    LANG("Arabic - Yemen", "ar_ye", 0x2401),
    LANG("Armenian", "hy", 0x042B),
    LANG("Azeri - Latin", "az_az", 0x042C),
    LANG("Azeri - Cyrillic", "az_az", 0x082C),
    LANG("Basque", "eu", 0x042D),
    LANG("Belarusian", "be", 0x0423),
    LANG("Bulgarian", "bg", 0x0402),
    LANG("Catalan", "ca", 0x0403),
    LANG("Chinese - China", "zh_cn", 0x0804),
    LANG("Chinese - Hong Kong SAR", "zh_hk", 0x0C04),
    LANG("Chinese - Macau SAR", "zh_mo", 0x1404),
    LANG("Chinese - Singapore", "zh_sg", 0x1004),
    LANG("Chinese - Taiwan", "zh_tw", 0x0404),
    LANG("Croatian", "hr", 0x041A),
    LANG("Czech", "cs", 0x0405),
    LANG("Danish", "da", 0x0406),
    LANG("Dutch - Netherlands", "nl_nl", 0x0413),
    LANG("Dutch - Belgium", "nl_be", 0x0813),
    LANG("English - Australia", "en_au", 0x0C09),
    LANG("English - Belize", "en_bz", 0x2809),
    LANG("English - Canada", "en_ca", 0x1009),
    LANG("English - Caribbean", "en_cb", 0x2409),
    LANG("English - Ireland", "en_ie", 0x1809),
    LANG("English - Jamaica", "en_jm", 0x2009),
    LANG("English - New Zealand", "en_nz", 0x1409),
    LANG("English - Phillippines", "en_ph", 0x3409),
    LANG("English - Southern Africa", "en_za", 0x1C09),
    LANG("English - Trinidad", "en_tt", 0x2C09),
    LANG("English - Great Britain", "en_gb", 0x0809),
    LANG("English - United States", "en_us", 0x0409),
    LANG("Estonian", "et", 0x0425),
    LANG("Farsi", "fa", 0x0429),
    LANG("Finnish", "fi", 0x040B),
    LANG("Faroese", "fo", 0x0438),
    LANG("French - France", "fr_fr", 0x040C),
    LANG("French - Belgium", "fr_be", 0x080C),
    LANG("French - Canada", "fr_ca", 0x0C0C),
    LANG("French - Luxembourg", "fr_lu", 0x140C),
    LANG("French - Switzerland", "fr_ch", 0x100C),
    LANG("Gaelic - Ireland", "gd_ie", 0x083C),
    LANG("Gaelic - Scotland", "gd", 0x043C),
    LANG("German - Germany", "de_de", 0x0407),
    LANG("German - Austria", "de_at", 0x0C07),
    LANG("German - Liechtenstein", "de_li", 0x1407),
    LANG("German - Luxembourg", "de_lu", 0x1007),
    LANG("German - Switzerland", "de_ch", 0x0807),
    LANG("Greek", "el", 0x0408),
    LANG("Hebrew", "he", 0x040D),
    LANG("Hindi", "hi", 0x0439),
    LANG("Hungarian", "hu", 0x040E),
    LANG("Icelandic", "is", 0x040F),
    LANG("Indonesian", "id", 0x0421),
    LANG("Italian - Italy", "it_it", 0x0410),
    LANG("Italian - Switzerland", "it_ch", 0x0810),
    LANG("Japanese", "ja", 0x0411),
    LANG("Korean", "ko", 0x0412),
    LANG("Latvian", "lv", 0x0426),
    LANG("Lithuanian", "lt", 0x0427),
    LANG("F.Y.R.O. Macedonia", "mk", 0x042F),
    LANG("Malay - Malaysia", "ms_my", 0x043E),
    LANG("Malay - Brunei", "ms_bn", 0x083E),
    LANG("Maltese", "mt", 0x043A),
    LANG("Marathi", "mr", 0x044E),
    LANG("Norwegian - Bokml", "no_no", 0x0414),
    LANG("Norwegian - Nynorsk", "no_no", 0x0814),
    LANG("Polish", "pl", 0x0415),
    LANG("Portuguese - Portugal", "pt_pt", 0x0816),
    LANG("Portuguese - Brazil", "pt_br", 0x0416),
    LANG("Raeto-Romance", "rm", 0x0417),
    LANG("Romanian - Romania", "ro", 0x0418),
    LANG("Romanian - Republic of Moldova", "ro_mo", 0x0818),
    LANG("Russian", "ru", 0x0419),
    LANG("Russian - Republic of Moldova", "ru_mo", 0x0819),
    LANG("Sanskrit", "sa", 0x044F),
    LANG("Serbian - Cyrillic", "sr_sp", 0x0C1A),
    LANG("Serbian - Latin", "sr_sp", 0x081A),
    LANG("Setsuana", "tn", 0x0432),
    LANG("Slovenian", "sl", 0x0424),
    LANG("Slovak", "sk", 0x041B),
    LANG("Sorbian", "sb", 0x042E),
    LANG("Spanish - Spain (Traditional)", "es_es", 0x040A),
    LANG("Spanish - Argentina", "es_ar", 0x2C0A),
    LANG("Spanish - Bolivia", "es_bo", 0x400A),
    LANG("Spanish - Chile", "es_cl", 0x340A),
    LANG("Spanish - Colombia", "es_co", 0x240A),
    LANG("Spanish - Costa Rica", "es_cr", 0x140A),
    LANG("Spanish - Dominican Republic", "es_do", 0x1C0A),
    LANG("Spanish - Ecuador", "es_ec", 0x300A),
    LANG("Spanish - Guatemala", "es_gt", 0x100A),
    LANG("Spanish - Honduras", "es_hn", 0x480A),
    LANG("Spanish - Mexico", "es_mx", 0x080A),
    LANG("Spanish - Nicaragua", "es_ni", 0x4C0A),
    LANG("Spanish - Panama", "es_pa", 0x180A),
    LANG("Spanish - Peru", "es_pe", 0x280A),
    LANG("Spanish - Puerto Rico", "es_pr", 0x500A),
    LANG("Spanish - Paraguay", "es_py", 0x3C0A),
    LANG("Spanish - El Salvador", "es_sv", 0x440A),
    LANG("Spanish - Uruguay", "es_uy", 0x380A),
    LANG("Spanish - Venezuela", "es_ve", 0x200A),
    LANG("Southern Sotho", "st", 0x0430),
    LANG("Swahili", "sw", 0x0441),
    LANG("Swedish - Sweden", "sv_se", 0x041D),
    LANG("Swedish - Finland", "sv_fi", 0x081D),
    LANG("Tamil", "ta", 0x0449),
    LANG("Tatar", "tt", 0X0444),
    LANG("Thai", "th", 0x041E),
    LANG("Turkish", "tr", 0x041F),
    LANG("Tsonga", "ts", 0x0431),
    LANG("Ukrainian", "uk", 0x0422),
    LANG("Urdu", "ur", 0x0420),
    LANG("Uzbek - Cyrillic", "uz_uz", 0x0843),
    LANG("Uzbek - Latin", "uz_uz", 0x0443),
    LANG("Vietnamese", "vi", 0x042A),
    LANG("Xhosa", "xh", 0x0434),
    LANG("Yiddish", "yi", 0x043D),
    LANG("Zulu", "zu", 0x0435),
    LANG(NULL, NULL, 0x0),
};
 
uint16_t get_usb_code_for_current_locale(void)
{
    locale_char_t *locale;
    char search_string[64];
    char *ptr;
 
    /* Get the current locale. */
    locale = indi_setlocale(0, NULL);
    if (!locale)
        return 0x0;
 
    /* Make a copy of the current locale string. */
    strncpy(search_string, locale, sizeof(search_string));
    search_string[sizeof(search_string) - 1] = '\0';
 
    /* Chop off the encoding part, and make it lower case. */
    ptr = search_string;
    while (*ptr)
    {
        *ptr = tolower(*ptr);
        if (*ptr == '.')
        {
            *ptr = '\0';
            break;
        }
        ptr++;
    }
 
    /* Find the entry which matches the string code of our locale. */
    struct lang_map_entry *lang = lang_map;
    while (lang->string_code)
    {
        if (!strcmp(lang->string_code, search_string))
        {
            return lang->usb_code;
        }
        lang++;
    }
 
    /* There was no match. Find with just the language only. */
    /* Chop off the variant. Chop it off at the '_'. */
    ptr = search_string;
    while (*ptr)
    {
        *ptr = tolower(*ptr);
        if (*ptr == '_')
        {
            *ptr = '\0';
            break;
        }
        ptr++;
    }
 
#if 0 // TODO: Do we need this?
    /* Find the entry which matches the string code of our language. */
    lang = lang_map;
    while (lang->string_code)
    {
        if (!strcmp(lang->string_code, search_string))
        {
            return lang->usb_code;
        }
        lang++;
    }
#endif
 
    /* Found nothing. */
    return 0x0;
}
 
#ifdef __cplusplus
}
#endif