Connect to the USB stack (usbd_connect()) and provide two callbacks: one for insertion and one for removal. In the insertion callback: Connect to the USB device (usbd_attach()). Get descriptors (usbd_descriptor()). Select the configuration (usbd_select_config()) and interface (usbd_select_interface()). Set up communications pipes to the appropriate endpoint (usbd_open_pipe()). In the removal callback, detach from the USB device (usbd_detach()). Set up all data communications (e.g. reading and writing data, sending and receiving control information, etc.) via the usbd_setup_*() functions (usbd_setup_bulk(), usbd_setup_interrupt(), etc.). Initiate data transfer using the usbd_io() function (with completion callbacks if required). 这是官方的示例流程

感谢提供官方示例流程。根据你提供的流程，以下是使用 QNX 的 USB 库进行 USB 读卡器数据访问的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/iofunc.h>
#include <devctl.h>
#include <hw/usbdi.h>

int insertion_callback(usbd_device_t *dev, usbd_device_handle_t dev_handle, int iface_idx, int alt_idx)
{
    // 连接到 USB 设备
    if (usbd_attach(dev_handle, iface_idx, alt_idx) != EOK) {
        fprintf(stderr, "Failed to attach USB device\n");
        return -1;
    }

    // 获取设备描述符
    if (usbd_descriptor(dev_handle) != EOK) {
        fprintf(stderr, "Failed to get USB device descriptors\n");
        usbd_detach(dev_handle);
        return -1;
    }

    // 选择配置和接口
    if (usbd_select_config(dev_handle, 0) != EOK) {
        fprintf(stderr, "Failed to select USB device configuration\n");
        usbd_detach(dev_handle);
        return -1;
    }

    if (usbd_select_interface(dev_handle, iface_idx) != EOK) {
        fprintf(stderr, "Failed to select USB device interface\n");
        usbd_detach(dev_handle);
        return -1;
    }

    // 设置通信管道
    unsigned int ep_num = 1; // 假设使用端点1进行数据传输
    usbd_pipe_handle_t pipe = usbd_open_pipe(dev_handle, ep_num);
    if (pipe == NULL) {
        fprintf(stderr, "Failed to open USB pipe\n");
        usbd_detach(dev_handle);
        return -1;
    }

    // 在此处可以进行数据传输等操作

    return 0;
}

void removal_callback(usbd_device_t *dev, usbd_device_handle_t dev_handle)
{
    // 从 USB 设备中断开连接
    usbd_detach(dev_handle);
}

int main()
{
    // 连接到 USB 栈
    if (usbd_connect() != EOK) {
        fprintf(stderr, "Failed to connect to USB stack\n");
        return -1;
    }

    // 注册插入和移除回调函数
    if (usbd_register_device_insertion_callback(insertion_callback) != EOK) {
        fprintf(stderr, "Failed to register insertion callback\n");
        return -1;
    }

    if (usbd_register_device_removal_callback(removal_callback) != EOK) {
        fprintf(stderr, "Failed to register removal callback\n");
        return -1;
    }

    // 在此处可以进行其他操作

    // 等待 USB 设备插入和移除事件
    while (1) {
        sleep(1);
    }

    // 断开与 USB 栈的连接
    usbd_disconnect();

    return 0;
}

请注意，以上代码仅为示例，实际应用中可能需要根据具体的 USB 读卡器设备和要求进行相应的修改和调整。同时，还需要根据实际需求添加数据传输、读写等相关操作。建议参考 QNX 官方文档和示例代码以获取更详细和准确的信息。