The value of
SERIAL_POLICY should be settable through a boot configuration option. However traditionally there was no non-volatile storage available on the PC platform. This requires console auto-selection methods which can be inconvenient and/or unstable in some situations. The selection policy should be adapted to the local hardware configuration, which might require code changes. (Some BIOS versions, particularly those used on large servers and in embedded and single-board industrial computers, have integrated support for serial consoles. The boot loader should query for these settings if possible.)
The serial communication parameters (byte-size, parity, stop-bits) are not settable (either at compile time or run time). The default parameters are “8 N 1”.
The baud rate is not settable when using BIOS I/O. It should be settable at compile time with “
CONSPEED” just as it is when using “
DIRECT_SERIAL”. The default speed is 9600 baud (the maximum for BIOS I/O).