IOCTL_SERIAL_GET_COMMSTATUS control code
The IOCTL_SERIAL_GET_COMMSTATUS request returns information about the communication status of a serial device. For more information about the status information that is retrieved by this request, see SERIAL_STATUS.
The Parameters.DeviceIoControl.OutputBufferLength member is set to the size in bytes of a SERIAL_STATUS structure.
The AssociatedIrp.SystemBuffer member points to a client-allocated SERIAL_STATUS structure that the serial controller driver uses to output communication status information.
If the request is successful, the Information member is set to the size in bytes of a SERIAL_STATUS structure. Otherwise, the Information member is set to zero.
The Status member is set to one of the Generic Status Values for Serial Device Control Requests.