Intel Extensible Firmware Interface, Specification

Page: 119 / 494

Services
Version 1.02 12/12/00 101
3.8.4 GetNextMonotonicCount()
Summary
Returns a monotonically increasing count for the platform.
Prototype
EFI_STATUS
GetNextMonotonicCount (
OUT UINT64 *Count
);
Parameters
Count
Pointer to returned value.
Description
The
GetNextMonotonicCount()
function returns a 64 bit value that is numerically larger
then the last time the function was called.
The platform’s monotonic counter is comprised of two parts: the high 32 bits and the low 32 bits.
The low 32 bit value is volatile and is reset to zero on every system reset. It is increased by 1 on
every call to
GetNextMonotonicCount()
. The high 32 bit value is non-volatile and is
increased by 1 on whenever the system resets or the low 32 bit counter overflows.
Status Codes Returned
EFI_SUCCESS The next monotonic count was returned.
EFI_DEVICE_ERROR The device is not functioning properly.
EFI_INVALID_PARAMETER One of the parameters has an invalid value.