Plug and Play BIOS Specification

Plug and Play BIOS Specification 1.0A Page 39
Response Messages 00h through 3Fh:
Message Identifier Value Description
OK 00h Instructs the system to continue with the sequence which
initiated the event. This message is only valid when the Get
Event function has returned one of the ABOUT_TO_XXXXX
events. When the system software is notified with an
ABOUT_TO_XXXXX message, the appropriate actions will not
take place until the Send Message BIOS Function is called with
OK.
ABORT 01h Abort the action which initiated the ABOUT_TO_XXXXX
event. This message instructs the system BIOS to prevent the
event from occurring. For instance, if the event is an undocking
sequence, then the system will not be allowed to undock. It is
assumed that it is the responsibility of the system software to
communicate to the user the reason for not allowing the system
to carry out the action for the event. This message is only valid
when Get Event has returned one of the ABOUT_TO_XXXXX
messages.
Control Messages 40h through 7Fh:
Message Identifier Value Description
UNDOCK_DEFAULT_ACTION 40h This message provides a mechanism for system software to soft
eject the system and instructs the system BIOS to take the
default action when ejecting the system.
POWER_OFF 41h This message instructs the system BIOS to power off the system.
It is assumed that the system software will perform the necessary
actions to shut the system down before sending this message.
PNP_OS_ACTIVE 42h This message allows the PnP BIOS to track whether a PnP OS is
active and defines event timing. The PnP BIOS may default to
either a PnP-OS-Inactive or PnP-OS-Active state as needed.
However, upon initial OS load, a PnP OS will register with the
PnP BIOS by sending the PNP_OS_ACTIVE message to the PnP
BIOS. When the PNP_OS_ACTIVE message is received, the
PnP BIOS will operate in the PnP-OS-Active state. In this state,
the PnP BIOS will wait forever after signaling a system event.
This will allow the PnP OS to execute a Plug and Play BIOS
Function Get Event call and handle the event (See Section 4.6).
Although a PnP BIOS is not required to support the
PNP_OS_ACTIVE message, support is recommended in systems
that generate events. If this message is unsupported, then
MESSAGE_NOT _SUPPORTED should be returned.
PNP_OS_INACTIVE 43h This message complements the PNP_OS_ACTIVE message. A
PnP OS will send the PNP_OS_INACTIVE message to the PnP
BIOS upon OS termination. When the PNP_OS_INACTIVE
message is received, the PnP BIOS will operate in the PnP-OS-
Inactive state. In this state, no PnP event timing constraints
exist. The PnP BIOS does not have to wait for the PnP OS to
execute a Plug and Play BIOS Function Get Event call (See
Section 4.6) and can handle event timing in the manner it best
determines. Although a PnP BIOS is not required to support the
PNP_OS_INACTIVE message, support is recommended in
systems that generate events. If this message is unsupported,
then MESSAGE_NOT _SUPPORTED should be returned.
OEM Defined Messages 8000h through FFFFh:
Message Identifier Value Description