How to get Device Instance Path from Windows kerne

Question

Take a look at this example: a USB device in Windows 7 is reported to have Device instance path(DevinstPath) USB\VID_1EAB&PID_0501\7&25C389C1&0&1 and I know exactly that it corresponds to the so-called hardware-key(hwkey) in registry.

Now my question is: When my KMDF driver code has WDFDEVICE handle for that USB device, how can I know its DevinstPath?

I know I can

• send a BusQueryDeviceID to achieve the so-called device-id USB\VID_1EAB&PID_0501;
• send a BusQueryInstanceID to achieve the so-called instance-id 1 .

But I don't know how to get the so-called "instance-path". Could some kernel guru kindly tell me how I can get that?

MSDN doc seems really vague on this!

BTW: I also realize that user-layer function SetupDiGetDeviceInstanceId actually returns the DevinstPath -- although it is named "InstanceId".

Answer 1

Device instance path can be queried using DEVPKEY_Device_InstanceId, using either WdfDeviceAllocAndQueryPropertyEx or IoGetDevicePropertyData (passing the WDM physical device object)

Answer 2

Device Instance id is autoincrement sequence. You can find HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum in registry; Rules:NextPareneID.XXXXXXXX.N XXXXXX use UUID Calculation crc32 values(test ok) N is 1~9 Device Instance id format is N&PareneID&random's number&index

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