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SYSTEM_POWER_STATE_CONTEXT structure

The SYSTEM_POWER_STATE_CONTEXT structure is a partially opaque system structure that contains information about the previous system power states of a computer.

Syntax


typedef struct _SYSTEM_POWER_STATE_CONTEXT {
  union {
    struct {
      ULONG Reserved1  :8;
      ULONG TargetSystemState  :4;
      ULONG EffectiveSystemState  :4;
      ULONG CurrentSystemState  :4;
      ULONG IgnoreHibernationPath  :1;
      ULONG PseudoTransition  :1;
      ULONG Reserved2  :10;
    } DUMMYSTRUCTNAME;
    ULONG  ContextAsUlong;
  } DUMMYUNIONNAME;
} SYSTEM_POWER_STATE_CONTEXT, *PSYSTEM_POWER_STATE_CONTEXT;

Members

DUMMYUNIONNAME

Unnamed union.

DUMMYSTRUCTNAME

Unnamed structure.

Reserved1

Opaque member. Reserved for system use.

TargetSystemState

The target system power state of the previous system power IRP that the driver received. This member is set to a SYSTEM_POWER_STATE enumeration value. Drivers should treat this member as read-only.

EffectiveSystemState

The effective previous system power state, as perceived by the user. This member is set to a SYSTEM_POWER_STATE enumeration value. Drivers should treat this member as read-only. This member value might not match the TargetSystemState member if, for example, the previous system power IRP indicated that the computer was about to enter hibernation, but a hybrid shutdown instead occurred to prepare the computer for a fast startup. For more information, see Remarks.

CurrentSystemState

Opaque member. Reserved for system use.

IgnoreHibernationPath

Opaque member. Reserved for system use.

PseudoTransition

Opaque member. Reserved for system use.

Reserved2

Opaque member. Reserved for system use.

ContextAsUlong

Opaque member. Reserved for system use.

Remarks

Starting with Windows Vista, the I/O stack location in a system power IRP contains a SYSTEM_POWER_STATE_CONTEXT structure. The Power member of the IO_STACK_LOCATION structure contains a SystemPowerStateContext member, which is a SYSTEM_POWER_STATE_CONTEXT structure. For more information, see IO_STACK_LOCATION.

The size of the SYSTEM_POWER_STATE_CONTEXT structure is four bytes. This structure is divided into bit fields, most of which are opaque to drivers and reserved exclusively for use by the operating system. However, two of these bit fields, TargetSystemState and EffectiveSystemState, can be read by kernel-mode drivers to distinguish a fast startup from a wake-from-hibernation startup. For more information, see Distinguishing Fast Startup from Wake-from-Hibernation.

Requirements

Version

Available starting with Windows Vista.

Header

Wdm.h

See also

IO_STACK_LOCATION
SYSTEM_POWER_STATE

 

 

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