PATH ADC Home > Documentation > Hardware > Device Managers and Drivers > PCI Card Services > Designing PCI Cards and Drivers for Power Macintosh Computers

  

---

SetPowerState (csCode = 25)

The optional SetPowerState routine lets the display hardware be placed in various power states.

--> powerState

Switch display hardware to this state

<-- powerFlags

Describes the status of the new state

The powerState constants correlate with the VESA Device Power Management Standards. The system pairs SetPowerState and SetSync calls. The display hardware should only be placed in a low power state if the graphics controller can also place the connected display in a low power state. In other words, never place the display hardware in a low power state that visibly disrupts video if the connected display would remain active after a corresponding SetSync call. The driver is responsible for restoring its state when full power is restored.

Set the kPowerStateNeedsRefreshBit bit in powerFlags if VRAM decays in the new powerState condition. When the driver transitions from a powerState condition in which VRAM decays to one in which VRAM is stable, the system will refresh the VRAM.