Intel Extensible Firmware Interface, Specification

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Extensible Firmware Interface Specification
98 12/12/00 Version 1.02
3.8.2 SetWatchdogTimer()
Summary
Sets the system’s watchdog timer.
Prototype
EFI_STATUS
SetWatchdogTimer (
IN UINTN Timeout,
IN UINT64 WatchdogCode,
IN UINTN DataSize,
IN CHAR16 *WatchdogData OPTIONAL
);
Parameters
Timeout
The number of seconds to set the watchdog timer to. A value of zero
disables the timer.
WatchdogCode
The numeric code to log on a watchdog timer timeout event. The
firmware reserves codes 0x0000 to 0xFFFF. Loaders and operating
systems may use other timeout codes.
DataSize
The size, in bytes, of
WatchdogData
.
WatchdogData
A data buffer that includes a Null-terminated Unicode string, optionally
followed by additional binary data. The string is a description that the
call may use to further indicate the reason to be logged with a watchdog
event.
Description
The
SetWatchdogTimer()
function sets the system’s watchdog timer.
If the watchdog timer expires, a system reset is generated and the event is logged by the firmware.
The watchdog timer is armed before the firmware's boot manager invokes an EFI boot option. The
watchdog must be set to a period of 5 minutes. The EFI Image may reset or disable the watchdog
timer as needed. If control is returned to the firmware's boot manager, the watchdog timer must be
disabled.
The watchdog timer is only used during boot services. On successful completion of
ExitBootServices()
the watchdog timer is disabled.
The accuracy of the watchdog timer is +/- 1 second from the requested
Timeout
.