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    SubjectRe: Handshaking on USB serial devices
    > 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.


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