USBMS will *always* suspend whatever else the Kindle is doing, because it *has* to, as @knc1 explained. That's not limited to KUAL

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If you're plugging the device to a computer for charging purposes only, you can either eject it straight away, it'll go back to what it was doing and keep charging; or switch to USBNet mode, because that obviously won't even trigger the USBMS mode in the first place

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