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We left the power management on for our USB hub. This has the effect of switching itself off and then switching itself on again when accessed. I don't know when the access happens or when the hub is switched off.

One of the devices connected to this hub has the strange behaviour where it updates the UI number whenever it is reconnected. I thought these UI numbers only went as far as 256 but yesterday, the number was up to 932.

I've been searching for this on the internet but I can't find the answer. The question is - how high does the UI number go? It is a ULONG so does it go to MAXINT?

Edit

It is basically a unique number given to the device. For instance, on PCIE devices, the UI number would be the slot number. The device I am using has a serial number but it is the same for every single device. The UI number, location path and location info are one of the few ways I have of uniquely identifying the device.

I can get the UI number by using SetupDiGetDeviceInterfaceProperty and setting the third parameter to SRDP_UI_NUMBER. It is a ULONG value

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    could you please help us understand what "UI Numbers" means? I don't believe that that is a standard term.
    – Frank Thomas
    Commented Mar 6 at 6:29
  • I have a hunch that the max would be 255 x the number of ports you have, but that is just a guess. do you ever see the same UI number applied to devices on different ports, or are they all globally unique?
    – Frank Thomas
    Commented Mar 6 at 19:42
  • For this particular device, they are always unique. The devices sometimes have the same friendly names but the UI number and Location Info are always unique. The location path is sometimes missing - especially when the device is on a long port-chain.
    – cup
    Commented Mar 6 at 22:07

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