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

Columbarium

Re: "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..." What is the problem you're trying to solve, exactly? The exact device name format is an operating system implementation detail. You're not supposed to parse or extract information out from the device name. – Shipentine

I am trying to uniquely identify devices and their interfaces/outputs on a per-OS basis. You're right, I shouldn't extract information from the device name, so I won't. – Columbarium

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.

Dereism

Very useful, thanks!! The important thing here is "that means it can be used for string comparison, but not for interpretation." That definitely answers my question. – Columbarium

Answer 2

This string with GUID on the end - is actually device interface instance id (symbolic link name). And yes, its unique and persists across system restart. Some details also here.

You can use CM_Get_Device_Interface_Property or SetupDiGetDeviceInterfaceProperty on interface instance id with DEVPKEY_Device_InstanceId to get device instance id (one device can have multiple interfaces).

In your example - you have a HID device. Its device id format is described here.

Info on general USB devices id format is here.

After you have device instance id you can use CM_Get_DevNode_Property or SetupDiGetDeviceProperty with DEVPKEY_NAME to get localized friendly name of a device (which is shown in Device Manager).

To sum up:

• \\?\HID#VID_203A&PID_FFFC&MI_01#7&2de99099&0&0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd} - is device interface id (also referred as "device interface path" or "device interface symbolic name" in docs). This is path in virtual device file system.
• {378de44c-56ef-11d1-bc8c-00a0c91405dd} - device interface class guid (GUID_DEVINTERFACE_MOUSE in this case. It determines which IOCTLs can be called on this device. IOCTL_MOUSE_QUERY_ATTRIBUTES in this case)
• HID\VID_203A&PID_FFFC&MI_01\7&2de99099&0&0000 - is device instance id

NOTE: exact device interface id format is not documented, each device interface can generate file name it want. I don't recommend you to parse it - it could be changed in later Windows version, better aquire device instance id - its format is documented.

You can browse these device interfaces in the Sysinternals WinObj tool. They are usually under GLOBAL?? namespace:

Afterburning