libusb在libusb_bulk_transfer（）上抛出LIBUSB_ERROR_NOT_FOUND

Question

我的问题是libusb不会传输批量来读取键盘输入。这是代码：

#include <stdio.h>
#include <libusb-1.0/libusb.h>

int main(void)
{

    libusb_init(NULL);

    libusb_device **list;
    libusb_device *found = NULL;
    ssize_t cnt = libusb_get_device_list(NULL, &list);
    ssize_t i = 0;

    struct libusb_device_descriptor desc;
    libusb_device_handle *h;

    unsigned char strDesc[128];

    for (i = 0; i < cnt; i++) {
        libusb_device *device = list[i];
        libusb_get_device_descriptor(device, &desc);
        if (desc.idProduct == 0x203) {
            libusb_open(device, &h);
            libusb_get_string_descriptor_ascii(h, desc.iProduct, strDesc, 128);
            printf("=== %s found in host ===\n", strDesc);

            found = device;

            break;
        }
    }

    libusb_device_handle *handle;
    libusb_open(found, &handle);

    unsigned char data[16];
    int act_len;

    libusb_get_device_descriptor(found, &desc);

    int r = libusb_bulk_transfer(handle, LIBUSB_ENDPOINT_IN, data, sizeof(data), &act_len, 0);
    const char *err = libusb_error_name(r);
    printf("%s\n", err);

    libusb_free_device_list(list, 1);
    libusb_close(handle);

    return 0;
}

基本上它遍历所有列出的设备，直到找到我的键盘，pId为0x203。然后它尝试启动libusb_bulk_transfer()，但在执行时它会抛出LIBUSB_ERROR_NOT_FOUND。 有人可以帮我解决这个问题吗？我搜索过，但似乎没有人有解决方案。谢谢！

我正在运行OS X 10.10.1。