Windows HID Device Name Format

Question

There are various ways to retrieve the Windows "Device Name" of a HID device, GetRawInputDeviceInfo with RIDI_DEVICENAME being one way to do it.

Given the example name:

\?\HID#VID_FEED&PID_DEAD#6&3559c8ea&0&0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}

I'm wondering if there is any documentation whatsoever on what is what in this string?

\?\HID#VID_AAAA&PID_BBBB#C&DDDDDD&E&FFFF#{GUID}

So the obvious ones are A(VID), B(PID) and the GUID on the end. What I'm wondering is what EXACTLY are C, D, E and F?

It seems that C and D are unique even if you plug in two of the exact same HID devices which is great for my problem, but I'd feel more comfortable if I could know exactly how this is determined on a per OS basis, or at least that it follows some known format.

I have been googling like a madman trying to figure this out, am I missing something obvious?

Thanks in advance

Answer 1

According to a similar MSDN post, the value represents a unique device instance ID:

the device instance ID is unique and constant for the physical location the device is plugged into, but it is also opaque and should not be parsed. that means it can be used for string comparison, but not for interpretation.