Hi I am developing a driver of usb to serial device. Hence, I overwrite those related functions from SerialDriverKit, for example HwProgramFlowControl, like as under code kern_return_t IMPL(MyUserUSBInterfaceDriver, HwProgramFlowControl) {     os_log(OS_LOG_DEFAULT,"-- %{PUBLIC}s, arg:0x%x, On:0x%x, Off:0x%x",            __FUNCTION__, arg, xon, xoff);     return 0; } And use coolTerm be my verification tool. As normal, I receive arg value 0x18 if software flowcontrol is enabled, and 0x24 if CTS is enabled However, if I use customized high baudrate, for example 3M, the value of arg will be 0. HwProgramFlowControl_Impl, arg:0x0, On:0x11, Off:0x13 HwProgramBaudRate_Impl, baudrate:3000000 Does it exist any way to know the flowcontrol has been enabled or not when customized high baudrate ? Thanks.