IOCTL_SERIAL_GET_CHARS control code
The IOCTL_SERIAL_GET_CHARS request retrieves the special characters that the serial controller driver uses with handshake flow control. The special characters are described by a SERIAL_CHARS structure.
To set special characters, a client can use an IOCTL_SERIAL_SET_CHARS request.
The Parameters.DeviceIoControl.OutputBufferLength member is set to the size in bytes of a SERIAL_CHARS structure.
The AssociatedIrp.SystemBuffer member points to a client-allocated SERIAL_CHARS structure that the serial controller driver uses to output the special characters.
If the request is successful, the Information member is set to the size in bytes of SERIAL_CHARS. 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.