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Listing 12-2 shows sample code that retrieves power consumption information from a PCI device.
Listing 12-2 Determining power consumption
/*
* IEEE 1275 defines the "power-consumption" property.
*/
#define kDevicePowerProperty "power-consumption"
/*
* Power values are encoded in a vector of "maximum in microwatts." Unspecified
* values shall be zero if other values are provided. Power consumption is 0 for
* missing values. If the property is missing, the default value will be used.
*/
enum{
kUnspecifiedStandby,
kUnspecifiedFullPower,
kFiveVoltStandby,
kFiveVoltFullPower,
kThreeVoltStandby,
kThreeVoltFullPower,
kIOPowerStandby,
kIOPowerFullPower,
kReservedStandby,
kReservedFullPower
};
/*
* The function uses this structure to equate registry entry values with
* DriverGestalt selectors.
*/
typedef structPowerInfo{
OSType driverGestaltSelector;
short correctIndex;
short fallbackIndex;
}PowerInfo;
static constPowerInfogPowerInfo[] ={
{ kDriverGestalt5MaxHighPower, kFiveVoltFullPower, kUnspecifiedFullPower },
{ kDriverGestalt5MaxLowPower, kFiveVoltStandby, kUnspecifiedStandby },
{ kDriverGestalt3MaxHighPower, kThreeVoltFullPower, kUnspecifiedFullPower },
{ kDriverGestalt3MaxLowPower, kThreeVoltStandby, kUnspecifiedStandby },
{ 0, 0, 0 }
};
/******************************************
* Retrieve the driver power consumption vector and search it for the desired power
* consumption value. Return the desired value, or a default value if the desired
* value is unavailable. This function does not allocate memory or return any errors.
*/
UInt32
GetDevicePowerConsumption(
RegEntryIDPtr regEntryIDPtr, /* driver's NameRegistryID */
OSType driverGestaltSelector, /* PBStatus parameter */
UInt32 defaultPowerConsumption /* default return value */
)
{
OSErr status;
UInt32 result;
short i;
short index;
ItemCount nValues;
RegPropertyValueSize size;
UInt32 microWatts[kReservedFullPower];
result = defaultPowerConsumption;
status = RegistryPropertyGetSize(
regEntryIDPtr,
kDevicePowerProperty,
&size
);
if (status == noErr && size <= sizeofmicroWatts){
status = RegistryPropertyGet(
regEntryIDPtr,
kDevicePowerProperty,
(RegPropertyValue *) microWatts,
&size
);
}
if (status == noErr){
nValues = size/sizeofmicroWatts[0];
for (i = 0; gPowerInfo[i].driverGestaltSelector != 0; i++){
if (gPowerInfo[i].driverGestaltSelector == driverGestaltSelector){
index = gPowerInfo[i].correctIndex;
if (index >= nValues)
index = gPowerInfo[i].fallbackIndex;
if (index < nValues)
result = microWatts[index];
break;
}
}
}
return (result);
}