PORTS Forum

Ports and Interfaces => USB => Topic started by: sudheerg_ on October 23, 2019, 10:10:09 am

Title: WinUSB Device Power States [D0, D2, D3 and etc...]
Post by: sudheerg_ on October 23, 2019, 10:10:09 am

Hi Jan and All,

We have a USB Device which presents two interfaces.

• Interface 1 is Billboard Interface. It doesn't have any Endpoints and binds winusb driver using MS OS Descriptor
• Interface 2 is Vendor Interface, it binds to WinUSB Device and it has 1 Bulk and 1 Interrupt Endpoint
• After sometime I see that Billboard Interface shows its power state as D2 but WinUSB Device shows as D0
• I have seen following URL:https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/winusb-power-management, but how this reg keys are mapped to the descriptors.

Regards,
Sudheer

Title: Re: WinUSB Device Power States [D0, D2, D3 and etc...]
Post by: Jan Axelson on October 23, 2019, 03:45:37 pm

The registry keys are configuration values, such as whether the device is capable of being powered down when idle.

The power state is the current state of the device or interface.

Title: Re: WinUSB Device Power States [D0, D2, D3 and etc...]
Post by: sudheerg_ on October 24, 2019, 12:25:06 am

Hi Jan,

What am I looking is how / depending on what these registry keys are populated. Are they populated based on USB Descriptors.

If so, how can I map registry key to USB Descriptor field.

Regards,
Sudheer

Title: Re: WinUSB Device Power States [D0, D2, D3 and etc...]
Post by: Jan Axelson on October 25, 2019, 10:44:24 am

These might help

https://docs.microsoft.com/en-us/windows/win32/api/winusb/nf-winusb-winusb_setpowerpolicy

https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/selective-suspend-in-umdf-drivers

https://blogs.msdn.microsoft.com/peterwie/2007/03/28/how-to-enable-usb-selective-suspend-and-system-wake-in-the-umdf-driver-for-a-usb-device/