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Questions on connected standby RRS feed

  • Question

  • Hello,

    I have a few questions about drivers and connected standby that would help me see what i need to change in my driver to support connected standby. I have done my due diligence(i think) in going through forums posts msdn articles and documents about connected standby and am still left with questions(including anything that says CS or connected standby or PEP or PoFx etc on msdn forums,seen the build video by Pat): 

    I am working on a monolithic driver for a device on an SOC which depends on processor state(i cannot give you more details unfortunately). If the processor is shut off completely like in S3/S4 state, some data i hold in the driver related to the device becomes invalid. I am trying to understand the the impact of connected standby on the processor state and the current driver architecture dealing with system going into S3 and S4. 

    1) I have a device that does not support any state other than D0. So on a system that conforms to the Windows connected standby requirements and can go into connected standby, Is there a callback that the driver can register for that will inform me of the system going into connected standby ? I read in this OSR article that i can register for a power event on the display in my driver to know when the system is going into connected standby.(http://www.osronline.com/showthread.cfm?link=226744_). I assume there is a cleaner and MSFT approved way for a driver to know that the system is going into connected standby. Any inputs ?

    2) I read that the system sends WM_POWERBROADCAST on conencted standby to all applications and drivers in one of the articles(lost the link). I assume the drivers referred to in this article only meant UMDF drivers and not KMDF drivers ?

    3)Am i correct in assuming any and all ACPI device needs to be ACPI5.0 compliant and set the appropriate bit (LOW_POWER_XXX) for the system to be able to go into windows connected standby ? I read in the article about DAM that we can find if a system has windows connected standby by checking the AOAC field in the SYSTEM_POWER_CAPABILITIES? (http://msdn.microsoft.com/en-us/library/windows/desktop/hh848040(v=vs.85).aspx). Is this proof enough that windows connected standby is enabled ? Can i just have one device which supports ACPI5.0 which sets the LOW_POWER_XXX flag in the ACPI table and have the SYSTEM_POWER_CAPABILITIES set the AOAC field to true ? 

    4) Do we require a separate driver for an ACPI device for a system with and without connected standby ? 

    5) I have read all over the place that the driver can talk to the windows power management framework using the PoFxXXX API's to provide component level states(F0,F1...). I have also read that PoFramework talks to this driver called the power engine plug in(PEP). I dont see a driver sample for power engine plugin or any example on how a device driver can talk to the power engine plugin driver or how to even get one loaded on a system?

    6) THere is no information on what state the CPU will be in. I know on windows 7 during S3/S4, the processor is shut of completely. What is the state of the processor in connected standby. Can this and will this be controlled by PEP drivers provided by SOC or processor manufacturers such as NVIDIA qualcomm etc? 

    7) what are the requirements for an ACPI device driver to support AOAC/Windows COnnected standby ?

    Any help appreciated.


    Wednesday, April 17, 2013 9:15 PM

All replies

  • please contact me in email, doron.holan (at) Microsoft.com and we will get this answered since this appears to be an NDA type of thing

    d -- This posting is provided "AS IS" with no warranties, and confers no rights.

    • Marked as answer by Doron Holan [MSFT] Thursday, April 18, 2013 2:28 AM
    • Unmarked as answer by R__K Thursday, April 18, 2013 10:02 PM
    Thursday, April 18, 2013 2:28 AM
  • Doron, Email sent. Have another general question: 

    Do we get the EvtDeviceD0Exit call back every time the system enter connected standby ? I saw a post on the forum that seems to suggest so. 


    Thursday, April 18, 2013 9:28 PM