Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit
Driver Power States
Driver Power States
Applications and device drivers are able to use the DevicePowerNotify function to control the power state of peripheral devices. For instance, you can call DevicePowerNotify to inform Power Manager that you want to change the power level of a backlight driver, such as BLK1:. Power Manager expects you to specify the desired power state at the one of the following five different power levels, according to the hardware device capabilities:
? D0 Full On; the device is fully functional.
? D1 Low On; the device is functional, but the performance is reduced.
? D2 Standby; the device is partially powered and will wake up on requests.
? D3 Sleep; the device is partially powered. In this state the device still has power and can raise interrupts that will wake up the CPU (device-initiated wakeup).
? D4 Off; device has no power. The device should not consume any significant power in this state.
NOTE
CE device power state levels
The device power states (D0 through D4) are guidelines to help OEMs implement power management functions on their platforms. Power Manager does not impose restrictions on device power consumption, responsiveness, or capabilities in any of the states. As a general rule, higher-numbered states should consume less power than lower numbered states and power states D0 and D1 should be for devices perceived as operational from the perspective of the user. Device drivers that manage the power level of a physical device with fewer granularities can implement a subset of the power states. DO is the only required power state.
Оглавление книги
- Lesson 5: Implementing Power Management
- Power Manager Overview
- System Power States
- Lesson 5: Implementing Power Management for a Device Driver
- IClass Power Management Interfaces
- System Power Policies
- Handling Set Power IRPs
- JDBC Туре 4 DRIVER
- User-land states
- За пределами PowerPoint
- Testing Wdm2 Power Capabilities
- Глава 1. POWERPOINT – ЗЛО?