Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 14 Feb 2008 12:10:26 +0000 | From | Alan Cox <> | Subject | Re: Handshaking on USB serial devices |
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> To make it clear: Even aside from the buffer in 2.6's pl2303.c, there's > a race: An in-flight write URB can fill all hardware buffers, making > unsafe what previously appeared to be a safe write. I think it's > essential to delay submission of the URB on a stop-transmit condition.
Hardware flow control *is* a race, and always will be. The remote end has a delay in signalling 'stop' there is a propogation delay and a response delay. This is why most implementations assert stop a bit *before* they run out.
Given the size of transfers and the internal buffering one would hope the USB devices do their own flow control if told to properly.
Alan
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