Intel Extensible Firmware Interface, Specification

Page: 53 / 494

Services
Version 1.02 12/12/00 35
3.1.4 WaitForEvent()
Summary
Stops execution until an event is signaled.
Prototype
EFI_STATUS
WaitForEvent (
IN UINTN NumberOfEvents,
IN EFI_EVENT *Event,
OUT UINTN *Index
);
Parameters
NumberOfEvents
The number of events in the
Event
array.
Event
An array of
EFI_EVENT
. Type
EFI_EVENT
is defined in
Section 3.1.1.
Index
Pointer to the index of the event which satisfied the wait condition.
Description
The
WaitForEvent()
function waits for any event in the
Event
array to be signaled. On
success, the signaled state of the event is cleared and execution is returned with
Index
indicating
which event caused the return. It is possible for an event to be signaled before being waited on. In
this case, the next wait operation for that event would immediately return with the signaled event.
Waiting on an event of type
EVT_NOTIFY_SIGNAL
is not permitted. If any event in
Event
is of
type
EVT_NOTIFY_SIGNAL
,
WaitForEvent()
returns
EFI_INVALID_PARAMETER
and
sets
Index
to indicate which event caused the failure. This function must be called at priority
level
TPL_APPLICATION
. If an attempt is made to call it at any other priority level,
EFI_UNSUPPORTED
is returned.
To wait for a specified time, a timer event must be included in the
Event
array.
WaitForEvent()
will always check for signaled events in order, with the first event in the array
being checked first. To check if an event is signaled without waiting, an already signaled event can
be used as the last event in the list being checked, or the
CheckEvent()
interface may be used.
Status Codes Returned
EFI_SUCCESS
The event indicated by Index was signaled.
EFI_INVALID_PARAMETER
The event indicated by Index has a notification function or
Event
was not a valid type.
EFI_UNSUPPORTED
The current TPL is not TPL_APPLICATION .