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TECHNOTE: Inside Macintosh: Devices, Power Manager Addenda


Technote 1046 MAY 1996


Vinnie Moscaritolo
Apple Developer Technical Support (DTS)

This Technote discusses addenda to the Inside Macintosh: Devices, Power Manager Chapter.

This Note is intended for Macintosh developers who are using the Power Manager Dispatch routines.

Contents


Addenda to the Power Manager Dispatch Routines

PMFeatures

One additional bit field: hasStartupTimer has been added to the possible PMFeature return values:


Bit Name          Bit Number      Description                      
hasStartupTimer      10                 The startup timer is supported.

Startup Time Structure

The startup time structure used by the GetStartupTimer and SetStartupTimer functions is defined by the StartupTime data type. 

 typedef struct StartupTime {
 	unsigned long	startTime;    	/* startup time as number of 
 					seconds since midnight, January 1, 1904*/
	Boolean	startEnabled;	/* 1=enable startup timer, 0=disable timer*/
	SInt8	filler;

} StartupTime;

GetStartupTimer

You can use the GetStartupTimer function to find out when the computer will start up from power off mode. 

void GetStartupTimer(StartupTime *theTime);

theTime	A pointer to a StartupTime structure, which specifies whether 
	the timer is enabled or disabled and the time at which the 
	startup timer is set to start up the computer.
DESCRIPTION
The GetStartupTimer function returns the time when the computer will start up from a power off mode.

If the computer doesn't support the startup timer, GetStartupTimer returns a value of 0.

ASSEMBLY-LANGUAGE INFORMATION

The trap is _PowerManagerDispatch ($A09E). The selector value is for GetStartupTimer is 38 ($26) in the low word of register D0. The pointer to StartupTime is passed in register A0.

SEE ALSO

The StartupTime structure is described in Startup Time Structure.

SetStartupTimer

You can use the SetStartupTimer function to set the time when the computer will start up from power off mode. 

void SetStartupTimer(StartupTime *theTime);

theTime	A pointer to a StartupTime structure, which specifies whether 
	to enable or disable the timer, and the time at which the 
	startup timer is set to start up the computer.
DESCRIPTION

The SetStartupTimer function sets the time when the computer will start up from a power off mode and enables or disables the timer. On a computer that doesn't support the startup timer, SetStartupTimer does nothing.

ASSEMBLY-LANGUAGE INFORMATION

The trap is _PowerManagerDispatch ($A09E). The selector value is for SetStartupTimer is 39 ($27) in the low word of register D0. The pointer to StartupTime is passed in register A0.

SEE ALSO

The StartupTime structure is described in Startup Time Structure.

State Change Notification Queue Structure

The state change notification queue structure used by the PMgrStateQInstall and PMgrStateQInstall functions is defined by the PMgrQueueElement data type. 

#define PMgrStateQType	'PM'

struct PMgrQueueElement {
	Ptr		*pmQLink;	/* pointer to next queue element*/
	short		pmQType;	/* queue type (must be
					  PMgrStateQType)*/
	short		pmFlags;	/* as defined below			*/
	long		pmNotifyBits;	/* bitmap of desired notifications*/
	StateNotifyProc	pmProc;		/*pointer to routine to call*/
	long		pmUser;		/* user-defined private storage,*/
} PMgrQueueElement;
The values of the bits in the pmFlags field are as follows: 
Bit Name           Bit Number     Description                               
sleepTimeout       0              The sleep timer value has changed.        
sleepEnable        1              Sleep control has been enabled/disabled   
hardDiskTimeout    2              The hard disk timer has changed.          
hardDiskSpindown   3              The hard disk spindown state has          
                                  changed.                                  
dimmingTimeout     4              The screen dimming timer has changed.     
dimmingEnable      5              Screen dimming has been enabled or        
                                  disabled                                  
diskModeAddress    6              The SCSI disk mode address has changed    
processorCycling   7              Processor cycling has been enabled or     
                                  disabled                                  
processorSpeed     8              The processor speed has changed           
wakeupTimer        9              The wakeup timer has changed.             
startupTimer       10             The startup timer has changed.            
hdPowerRemoved     11             The hard disk power has been removed by   
                                  the user.

PMgrStateQInstall

 You can use the PMgrStateQInstall function to notify your software when Power Manager state configuration parameters have changed. 

OSErr PMgrStateQInstall(PMgrStateQElement *theElement);

theElement	A pointer to an element for the state change 
		notification queue.
DESCRIPTION
The PMgrStateQInstall function installs an element into the state configuration change queue to provide notification to your software when certain Power Manager state configuration parameters have changed.

When a requested configuration parameter has changed, the software calls the routine pointed to by the pmProc field so that it can do any special processing. The routine is passed a pointer to its queue element so that, for example, the routine can reference its variables.

Before calling PMgrStateQInstall, the calling program must set the pmQType field to PmgrStateQtype or the queue element won't be added to the queue and PMgrStateQInstall will return an error.

SPECIAL CONSIDERATIONS
The pmNotifyBits field may be modified by the PMgrStateQInstall if it requests notification for a feature that this computer does not support. In this case your software may remove the element.

ASSEMBLY-LANGUAGE INFORMATION
The trap is _PowerManagerDispatch ($A09E). The selector value for PMgrStateQInstall is 34 ($22) in the low word of register D0. The pointer to PMgrStateQElement is passed in register A0. The result code is returned in the low word of register D0.

RESULT CODE
noErr	0	No error
SEE ALSO
The PMgrStateQElement structure is described in State Change Notification Queue Structure.

The application-defined state change notification function is described in State Change Notification Function.

PMgrStateQRemove

You can use the PMgrStateQRemove function to discontinue notification of your software when Power Manager state configuration parameters have changed. 

OSErr PMgrStateQRemove(PMgrStateQElement *theElement);

theElement	A pointer to the element for the state change 
		notification queue that you wish to remove.
DESCRIPTION
The PMgrStateQRemove function removes a queue element installed by PMgrStateQInstall. If the pmQType field of the queue element is not set to PmgrStateQtype, PMgrStateQInstall will return an error.

ASSEMBLY-LANGUAGE INFORMATION
The trap is _PowerManagerDispatch ($A09E). The selector value is for PMgrStateQRemove is 35 ($23) in the low word of register D0. The pointer to PMgrStateQElement is passed in register A0. The result code is returned in the low word of register D0.

RESULT CODE
noErr	0	No error
SEE ALSO
The PMgrStateQElement structure is described in State Change Notification Queue Structure.

The application-defined state change notification function is described in State Change Notification Function.

State Change Notification Function

A state change notification function can perform any operation that you require when certain Power Manager state configuration parameters have changed . 

pascal void MyStateNotificationProc (PMgrStateQElement *theElement);

theElement	A pointer to the element in the configuration 
		change queue that was used to install 
		this function.
DESCRIPTION
Your state change notification function is called by the Power Manager when certain configuration parameters have changed. It is called, for instance, when the sleep timer value or processor speed have changed. You can determine which of the configuration parameters have changed by examining the bit map in the pmNotifyBits field of the PMgrStateQElement that was passed to your function.

SEE ALSO
The PMgrStateQElement structure is described in State Change Notification Queue Structure.

The PMgrStateQInstall function and the PMgrStateQRemove function.

UpdateSystemActivity

You can use the UpdateSystemActivity function to notify the Power Manager that activity has taken place . 

void UpdateSystemActivity(short activityType);

activityType	A value indicating the type of activity that has 
		        occurred. See the description below for the meaning 
		        of this field.
DESCRIPTION
The UpdateSystemActivity function is used to notify the Power Manager that activity has taken place and the timers used to measure idle time should be updated to the time of this call. This function can be used by device drivers to prevent the computer from entering a low power mode while critical activity is taking place on a particular device. The function is passed a parameter indicating the type of activity that has occurred.

This function is slightly different from DelaySystemIdle, which should be used to prevent sleep or idle during a critical section. UpdateSystemActivity simply updates the tick count for the activity type selected. Conversely, DelaySystemIdle actually moves the counter to some number of ticks into the future, which allows the caller to go off and do somethingwithout fear of idling.

The valid types of activity are: 

Value Name       Value        Description                      
OverallAct       0            general type of activity          
UsrActivity      1            user activity (i.e.keyboard or    
                              mouse)                            
NetActivity      2            interaction with network(s)       
HDActivity       3            hard disk or storage device in    
                              use
SPECIAL CONSIDERATIONS
In general, device drivers should make this call to notify the Power Manager of system activity on their particular device. For example, input device drivers would call UpdateSystemActivity(UsrActivity) while a storage device driver would call UpdateSystemActivity(HDActivity).

If a device driver registers with the power manager state change queue and implements its own power management timing facilities, it does not need to call UpdateSystemActivity. For example, a media bay hard disk on a PowerBook should register for sleeptimeout, sleepenabled, spindownenabled, and hdtimeout change notificiations. It then can maintain its own timer. This allows the internal hard disk and the media bay hard disk to spin down independently. By not calling UpdateSystemActivity, it won't unnecessarily keep the internal drive powered. It should also be installed in the sleep queue so it can refuse sleep requests if activity is occurring on its associated device.

IMPORTANT:
Calling UpdateSystemActivity more than necessary will cause delays in the invocation of power saving features which will reduce battery life and overall power efficiency.
ASSEMBLY-LANGUAGE INFORMATION
The trap is _PowerManagerDispatch ($A09E). The selector value for UpdateSystemActivity is 36 ($24) in the low word of register D0. The activityType is passed in the high word of D0.

SEE ALSO
The GetLastActivity function.

GetLastActivity

You can use the GetLastActivity function to find out when the last time a particular activity took place. 

OSErr GetLastActivity(ActivityInfo *theActivity();

theActivity	    A pointer to an ActivityInfo structure, which 
		        specifies the  type of activity and when that 
		        activity last occurred.
DESCRIPTION
The GetLastActivity function returns the time in ticks of the last occurrence of the specified activity type. This function can be used by software that needs to track power management activity. The activity type and time are specified in the following structure:

struct ActivityInfo {
	short		activityType;	/* same selectors as
					   UpdateSystemActivity */
	unsigned long	activityTime;	/*time of last event of selected
					   type as number of 
					   seconds since midnight, 
					   January 1, 1904 */
} ActivityInfo;
ASSEMBLY-LANGUAGE INFORMATION
The trap is _PowerManagerDispatch ($A09E). The selector value for GetLastActivity is 40 ($28) in the low word of register D0. The pointer to the ActivityInfo structure is passed in register A0.

SEE ALSO
The UpdateSystemActivity function.

DelaySystemIdle

You can use the DelaySystemIdle function to control power cycling.

void DelaySystemIdle();
DESCRIPTION
The DelaySystemIdle function delays power cycling and/or sleep to a time in the near future. This call should only be used when timing-sensitive I/O operations (e.g. Read/Write) need to occur without interruption from the Power Manager and the power cycling wait time or sleep timeout may not be long enough to ensure that this occurs.

SPECIAL CONSIDERATIONS
Care should be taken to make this call only when absolutely necessary since it can affect power efficiency.

ASSEMBLY-LANGUAGE INFORMATION
The trap is _PowerManagerDispatch ($A09E). The selector value is for DelaySystemIdle is 37 ($25) in the low word of register D0.

Acknowledgments

Thanks to Cameron Birse, Paul Black, Russ Emmons, Mike Hanlon, and Mark Pontarelli.


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