38. Miscellaneous Protocols¶
38.1. EFI Timestamp Protocol¶
38.1.1. EFI_TIMESTAMP_PROTOCOL¶
Summary
The Timestamp protocol provides a platform independent interface for retrieving a high resolution timestamp counter.
GUID
#define EFI_TIMESTAMP_PROTOCOL_GUID \
{ 0xafbfde41, 0x2e6e, 0x4262,\
{ 0xba, 0x65, 0x62, 0xb9, 0x23, 0x6e, 0x54, 0x95 }}
Protocol Interface Structure
typedef struct _ EFI_TIMESTAMP_PROTOCOL {
TIMESTAMP_GET GetTimestamp;
TIMESTAMP_GET_PROPERTIES GetProperties;
} EFI_TIMESTAMP_PROTOCOL;
38.1.2. EFI_TIMESTAMP_PROTOCOL.GetTimestamp()¶
Summary
Retrieves the current timestamp counter value.
Prototype
typedef
UINT64
(EFIAPI *TIMESTAMP_GET) (
VOID
);
Description
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.
Return Value
The current value of the free running timestamp counter.
38.1.3. EFI_TIMESTAMP_PROTOCOL.GetProperties()¶
Summary
Obtains timestamp counter properties including frequency and value limits.
Prototype
typedef
EFI_STATUS
(EFIAPI *TIMESTAMP_GET_PROPERTIES) (
OUT EFI_TIMESTAMP_PROPERTIES *Properties
);
Parameters
- Properties
The properties of the timestamp counter. See”Related Definitions” below.
Description
Retrieves the timestamp counter properties structure.
Related Definitions
typedef struct {
UINT64 Frequency;
UINT64 EndValue;
} EFI_TIMESTAMP_PROPERTIES;
- Frequency
The frequency of the timestamp counter in Hz.
- EndValue
The value that the timestamp counter ends with immediately before it rolls over. For example, a 64-bit free running counter would have an EndValue of 0xFFFFFFFFFFFFFFFF. A 24-bit free running counter would have an EndValue of 0xFFFFFF.
Status Codes Returned
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 updated. |
EFI_INVALID_PARAMETER |
Properties is NULL. |
38.2. Reset Notification Protocol¶
38.2.1. EFI_RESET_NOTIFICATION_PROTOCOL¶
Summary
This protocol provides services to register for a notification when ResetSystem is called.
GUID
#define EFI_RESET_NOTIFICATION_PROTOCOL_GUID \
{ 0x9da34ae0, 0xeaf9, 0x4bbf, \
{ 0x8e, 0xc3, 0xfd, 0x60, 0x22, 0x6c, 0x44, 0xbe } }
Protocol Interface Structure
typedef struct _EFI_RESET_NOTIFICATION_PROTOCOL {
EFI_REGISTER_RESET_NOTIFY RegisterResetNotify;
EFI_UNREGISTER_RESET_NOTIFY UnRegisterResetNotify;
} EFI_RESET_NOTIFICATION_PROTOCOL;
Parameters
- RegisterResetNotify
Register a notification function to be called when ResetSystem() is called.
- UnRegisterResetNotify
Removes a reset notification function that has been previously registered with RegisterResetNotify().
38.2.2. EFI_RESET_NOTIFICATION_PROTOCOL.RegisterResetNotify()¶
Summary
Register a notification function to be called when ResetSystem() is called.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_REGISTER_RESET_NOTIFY) (
IN EFI_RESET_NOTIFICATION_PROTOCOL *This,
IN EFI_RESET_SYSTEM *ResetFunction,
);
Parameters
- This
A pointer to the EFI_RESET_NOTIFICATION_PROTOCOL instance.
- ResetFunction
Points to the function to be called when a ResetSystem() is executed.
Description
The RegisterResetNotify() function registers a notification function that is called when ResetSystem() is called and prior to completing the reset of the platform.
The registered functions must not perform a platform reset themselves. These notifications are intended only for the notification of components which may need some special-purpose maintenance prior to the platform resetting.
The list of registered reset notification functions are processed if ResetSystem() is called before ExitBootServices() . The list of registered reset notification functions is ignored if ResetSystem() is called after ExitBootServices() .
Status Codes Returned
EFI_SUCCESS |
The reset notification function was successfully registered. |
EFI_INVALID_PARAMETER |
ResetFunction is NULL. |
EFI_OUT_OF_RESOURCES |
There are not enough resources available to register the reset notification function. |
EFI_ALREADY_STARTED |
The reset notification function specified by ResetFunction has already been registered. |
38.2.3. EFI_RESET_NOTIFICATION_PROTOCOL.UnregisterResetNotify()¶
Summary
Unregister a notification function.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_UNREGISTER_RESET_NOTIFY) (
IN EFI_RESET_NOTIFICATION_PROTOCOL *This,
IN EFI_RESET_SYSTEM *ResetFunction
);
Parameters
- This
A pointer to the EFI_RESET_NOTIFICATION_PROTOCOL instance.
- ResetFunction
The pointer to the ResetFunction being unregistered.
Description
The UnregisterResetNotify() function removes the previously registered notification using RegisterResetNotify().
Status Codes Returned
EFI_SUCCESS |
The reset notification function was unregistered. |
EFI_INVALID_PARAMETER |
ResetFunction is NULL. |
EFI_INVALID_PARAMETER |
The reset notification function specified by ResetFunction was not previously registered using RegisterResetNotify(). |