SerialDriverkit - Flowcontol setup… | Apple Developer Forums

SerialDriverkit - Flowcontol setup with customized high baudrate

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

Code Block 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;
}

Code Block
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.

Code Block HwProgramFlowControl_Impl, arg:0x0, On:0x11, Off:0x13
HwProgramBaudRate_Impl, baudrate:3000000

Code Block
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.