FunctionFS配置3个端点（2个中断IN、1个批量OUT）启动失败，错误码-524排查求助

各位好，我现在在Linux上用FunctionFS实现一个USB Gadget，配置了3个端点：EP1 IN（中断传输）、EP2 IN（中断传输）、EP3 OUT（批量传输）。但执行绑定UDC的命令时失败了：

echo <udc> > /sys/kernel/config/usb_gadget/mygadget/UDC

对应的内核报错如下：

configfs-gadget 5100000.udc-controller: failed to start mygadget: -524
sh: write error: No error information

下面是我C代码里相关的描述符定义：

.intf = {
    .bLength = sizeof(vendor_descs.hs_descs.intf),
    .bDescriptorType = USB_DT_INTERFACE,
    .bNumEndpoints = 3,
    .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
    .iInterface = 1,
    .bInterfaceNumber = 0,
    .bAlternateSetting = 0,
    .bInterfaceSubClass = 0x00,
    .bInterfaceProtocol = 0x00,
},
.ep_in_cmd = {
    .bLength = sizeof(vendor_descs.hs_descs.ep_in_cmd),
    .bDescriptorType = USB_DT_ENDPOINT,
    .bmAttributes = USB_ENDPOINT_XFER_INT,
    .bEndpointAddress = 1 | USB_DIR_IN,
    .wMaxPacketSize = __cpu_to_le16(64),
    .bInterval = 0x04,
},
.ep_in_video = {
    .bLength = sizeof(vendor_descs.hs_descs.ep_in_video),
    .bDescriptorType = USB_DT_ENDPOINT,
    .bmAttributes = USB_ENDPOINT_XFER_INT,
    .bEndpointAddress = 2 | USB_DIR_IN,
    .wMaxPacketSize = __cpu_to_le16(64),
    .bInterval = 0x04,
},
.ep_out_cmd = {
    .bLength = sizeof(vendor_descs.hs_descs.ep_out_cmd),
    .bDescriptorType = USB_DT_ENDPOINT,
    .bmAttributes = USB_ENDPOINT_XFER_BULK,
    .bEndpointAddress = 3 | USB_DIR_OUT,
    .wMaxPacketSize = __cpu_to_le16(512),
    .bInterval = 0x00,
},

我已经仔细检查过这些点：

• 接口描述符里的.bNumEndpoints = 3确实正确设置了
• 描述符总长度用了.length = __cpu_to_le32(sizeof(vendor_descs))，格式没问题
• 绑定UDC前已经把描述符和字符串写入了ep0
• /sys/class/udc/里能看到有效的UDC设备5100000.udc-controller
• /dev/ffs_vendor/下已经成功创建了ep0、ep1、ep2、ep3这几个端点

想请教各位大佬，这个错误码-524对应的根本原因可能是什么？

我的环境信息：

• Linux内核：5.x（自定义编译版本）
• 使用FunctionFS descriptor v2
• USB工作在高速模式
• Allwinner SoC，UDC控制器为5100000.udc-controller

感谢各位的指导！

内容来源于stack exchange