usb-descriptor - 谁有关于gadgetfs的文档或博客？

Question

我在http://www.linux-usb.org/gadget/usb.c中找到了一个示例，但对我来说它较少。我想给gadgetfs写一个描述符，但是总是错的。我意识到我对描述符或gadgetfs的错误想法。我需要更多文档或示例！真的真的谢谢！！

生成描述符的代码。参数“dev”来自 USB 设备。

int gen_gadget_descriptor(char* descriptor,struct libusb_device* dev){
    char* ptr = descriptor;
    //前四字节为0
    ptr[0] = ptr[1] = ptr[2] = ptr[3] = 0;
    ptr += 4;

    struct libusb_device_descriptor devDesc;
    libusb_get_device_descriptor(dev, &devDesc);

    struct libusb_config_descriptor* confDesc;
    libusb_get_config_descriptor(dev,0,&confDesc);

    for (int l = 0; l < devDesc.bNumConfigurations; l++) {
        //加入配置描述符
        memcpy(ptr, &confDesc[l], confDesc->bLength);
        ptr += confDesc[l].bLength;
        //遍历配置描述符中的接口结构体的数量
        int nbIfaces = confDesc->bNumInterfaces;
        for (int i = 0; i<nbIfaces; i++) {
            //遍历该接口结构体下的接口描述符
            for (int j = 0; j<confDesc->interface[i].num_altsetting; j++) {
                //加入接口描述符
                memcpy(ptr, &confDesc->interface[i].altsetting[j], confDesc->interface[i].altsetting[j].bLength);
                ptr += confDesc->interface[i].altsetting->bLength;
                //遍历接口描述符下的端点描述符
                for (int k = 0; k<confDesc->interface[i].altsetting[j].bNumEndpoints; k++) {
                    memcpy(ptr, &confDesc->interface[i].altsetting[j].endpoint[k], 
                        confDesc->interface[i].altsetting[j].endpoint[k].bLength);
                    ptr += confDesc->interface[i].altsetting[j].endpoint[k].bLength;
                }
            }
        }
        libusb_free_config_descriptor(confDesc);
    }


    //加入设备描述符

    printf("devDesc.length=%d\n",devDesc.bLength);
    memcpy(ptr, (char*)&devDesc,sizeof(struct usb_device_descriptor));
    ptr += sizeof(struct usb_device_descriptor);
    int descriptorLen = ptr - descriptor;

    return descriptorLen;
}