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Power Services

For those devices that can change their power usage, the STREAMS module must export the entry point OTSetPowerLevel. This lets the system set the device's power level before its driver is installed into a stream.



 
void OTSetPowerLevel(UInt32 powerSelector);

In addition, devices that can change their power usage should support the I_OTSetPowerLevel IOCTL call. However, I_OTSetPowerLevel is used only if the driver is already installed into a stream.

Following are the four-byte selectors that can be passed to I_OTSetPowerLevel, with their return values:

`'pmn3'`	Returns the card's maximum power consumption in microwatts from the 3.3 V supply while in low power mode.
`'pmn5'`	Returns the card's maximum power consumption in microwatts from the 5 V supply while in low power mode.
`'pmx3'`	Returns the card's maximum power consumption in microwatts from the 3.3 V supply while in high power mode.
`'pmx5'`	Returns the card's maximum power consumption in microwatts from the 5 V supply while in high power mode.
`'psta'`	Returns a value of 1 if the card is in high power mode.
`'psup'`	Returns a value of 1 if the card supports power control, 0 if it does not.
`'ptog'`	Returns a value of 1 if the card supports switch between high and low power after initialization, 0 if it does not.
`'sphi'`	Sets the card to high power mode. Returns a value of 0 if completed successfully, `OSErr` if not.
`'splo'`	Sets the card to low power mode. Returns a value of 0 if completed successfully, `OSErr` if not.