Timestamp.h File Reference

Data Structures
struct	EFI_TIMESTAMP_PROPERTIES
struct	_EFI_TIMESTAMP_PROTOCOL

Macros
#define	EFI_TIMESTAMP_PROTOCOL_GUID   { 0xafbfde41, 0x2e6e, 0x4262, {0xba, 0x65, 0x62, 0xb9, 0x23, 0x6e, 0x54, 0x95 } }

Typedefs
typedef struct _EFI_TIMESTAMP_PROTOCOL	EFI_TIMESTAMP_PROTOCOL
typedef UINT64(EFIAPI *	TIMESTAMP_GET )(VOID)
typedef EFI_STATUS(EFIAPI *	TIMESTAMP_GET_PROPERTIES )(OUT EFI_TIMESTAMP_PROPERTIES *Properties)

Variables
EFI_GUID	gEfiTimestampProtocolGuid

Detailed Description

EFI Timestamp Protocol as defined in UEFI2.4 Specification. Used to provide a platform independent interface for retrieving a high resolution timestamp counter.

Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.
SPDX-License-Identifier: BSD-2-Clause-Patent

Revision Reference:

This Protocol is introduced in UEFI Specification 2.4

Macro Definition Documentation

#define EFI_TIMESTAMP_PROTOCOL_GUID   { 0xafbfde41, 0x2e6e, 0x4262, {0xba, 0x65, 0x62, 0xb9, 0x23, 0x6e, 0x54, 0x95 } }

Typedef Documentation

typedef struct _EFI_TIMESTAMP_PROTOCOL EFI_TIMESTAMP_PROTOCOL

Declare forward reference for the Time Stamp Protocol

typedef UINT64(EFIAPI * TIMESTAMP_GET)(VOID)

Retrieves the current value of a 64-bit free running timestamp counter.

The counter shall count up in proportion to the amount of time that has passed. The counter value will always roll over to zero. The properties of the counter can be retrieved from GetProperties(). The caller should be prepared for the function to return the same value twice across successive calls. The counter value will not go backwards other than when wrapping, as defined by EndValue in GetProperties(). The frequency of the returned timestamp counter value must remain constant. Power management operations that affect clocking must not change the returned counter frequency. The quantization of counter value updates may vary as long as the value reflecting time passed remains consistent.

Parameters

None.

Return values

The	current value of the free running timestamp counter.

typedef EFI_STATUS(EFIAPI * TIMESTAMP_GET_PROPERTIES)(OUT EFI_TIMESTAMP_PROPERTIES *Properties)

Obtains timestamp counter properties including frequency and value limits.

Parameters

[out]

Properties

The properties of the timestamp counter.

Return values

EFI_SUCCESS	The properties were successfully retrieved.
EFI_DEVICE_ERROR	An error occurred trying to retrieve the properties of the timestamp counter subsystem. Properties is not pedated.
EFI_INVALID_PARAMETER	Properties is NULL.

Variable Documentation

EFI_GUID gEfiTimestampProtocolGuid