usb - USB 控制传输是否保证交付？

Question

USB 2.0 specifies 4 种传输类型(在第 5.4 节传输类型中):

控制转移

同步传输

中断传输

批量转账

第 5.8 节说批量传输提供:

• Access to the USB on a bandwidth-available basis
• Retry of transfers, in the case of occasional delivery failure due to errors on the bus
• Guaranteed delivery of data but no guarantee of bandwidth or latency

(强调我的。)

我没有看到类似的控制转移声明。他们也保证交货吗？如果没有，用户如何处理故障？

请提供引文以支持您的回答。

Answer 1

USB 规范为控制传输提供了强大的错误检测和恢复。控制传输要么完成，要么 USB 主机知道它失败了，我认为这就是“保证交付”的意思。这很重要，因为控制传输用于在您将设备插入计算机时设置设备，并且它们还被各种 USB 设备类用于许多重要目的(例如，它们用于设置串行端口的波特率) USB CDC ACM 设备)。

来自 USB 2.0 规范的第 5.5.5 节:

The USB provides robust error detection and recovery/retransmission for errors that occur during control transfers. Transmitters and receivers can remain synchronized with regard to where they are in a control transfer and recover with minimum effort. Retransmission of Data and Status packets can be detected by a receiver via data retry indicators in the packet. A transmitter can reliably determine that its corresponding receiver has successfully accepted a transmitted packet by information returned in a handshake to the packet. The protocol allows for distinguishing a retransmitted packet from its original packet except for a control Setup packet. Setup packets may be retransmitted due to a transmission error; however, Setup packets cannot indicate that a packet is an original or a retried transmission.

唯一没有保证交付的传输类型是等时传输。此外，帧开始 (SOF) 数据包无法保证交付。