And then it has to wait for the read request to finish.

然后它必须等待读取请求完成。

So what it does is it queues a read request from this endpoint with a length of 0x4000 bytes, because that's how big the DMA buffer in memory is.

所以它所做的是将来自该端点的读取请求排队，长度为 0x4000 字节，因为这是内存中 DMA 缓冲区的大小。

And then there is a length that describes the length of optional data that might be written or read from the device, depending on if this is a read request or a write request to the device.

然后是一个长度，它描述了可能写入或从设备读取的可选数据的长度，具体取决于这是对设备的读取请求还是写入请求。