Re: [Libusb-win32-devel] Fix for coming out of standby

[Stephan M. <ste...@we...>]

Thanks for the patch, Dan. I'll apply it by adding a third parameter
to power_set_device_state():


void power_set_device_state(libusb_device_t *dev, 
                            DEVICE_POWER_STATE device_state, bool_t block)
{
  NTSTATUS status;
  KEVENT event;
  POWER_STATE power_state;

  power_state.DeviceState = device_state;

  if(block) /* wait for IRP to complete */
    {
      KeInitializeEvent(&event, NotificationEvent, FALSE);
      
      /* set the device power state and wait for completion */
      status = PoRequestPowerIrp(dev->physical_device_object, 
                                 IRP_MN_SET_POWER, 
                                 power_state,
                                 on_power_set_device_state_complete, 
                                 &event, NULL);
      
      if(status == STATUS_PENDING)
        {
          KeWaitForSingleObject(&event, Executive, KernelMode, FALSE, NULL);
        }
    }
  else
    {
      PoRequestPowerIrp(dev->physical_device_object, IRP_MN_SET_POWER,
                        power_state, NULL, NULL, NULL);
    }
}			


 

> After much exploration I've discovered the cause of the inability for
> some laptops to coming out of standby is.
>  
> The power irp for changing device state is being issued in the
> completion routine for the system power irp, and then the thread is
> blocked waiting for the device power irp to complete.
>  
> Before the blocking takes place, the power manager attempts to send the
> irp all the way, the power dispatcher sees the device power irp, and
> tries to send it down the stack, but the usbhub below returns status
> pending so the completion handler isn't called at that point.
>  
> The libusb thread then blocks waiting for the irp to complete, but it
> never does because the thread which would go on to call the completion
> routing is being blocked!
>  
> Replacing the call to on_power_set_device_state_complete with :
>  
> power_state.DeviceState =
> dev->device_power_states[power_state.SystemState];
> 
> /* set the device power state and don't wait for completion */
> 
> (void) PoRequestPowerIrp(dev->physical_device_object, 
>                          IRP_MN_SET_POWER, 
>                          power_state,
>                          NULL,
>                          NULL, NULL);
> 
> Seems to resolve the problem.
> 
> I've attached this as a patch.
> 
> Comments?
> 
> Cheers,
>  
> -- 
> Dan Ellis
> Newnham Research
> 
> 
> <hr>
> 
> <hr>
> _______________________________________________
> Libusb-win32-devel mailing list
> Lib...@li...
> https://lists.sourceforge.net/lists/listinfo/libusb-win32-devel
> 


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