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Bluetooth device class cannot be retrieved if Bluetooth is not activated
The Bluetooth device class can be retrieved using the Publish and Subscribe(PS) keys KUidSystemCategory and KPropertyKeyBluetoothGetDeviceClass. However, when the device is rebooted, the initial value of the PS key is set to NULL and any attempt to read the Bluetooth device class using this key will return an empty value.
Thus, after the phone reboot, the Bluetooth device class can be retrieved only after Bluetooth has been powered on at least once.
How to reproduce
Reboot the phone. Without starting Bluetooth, try to retrieve the Bluetooth device class using the (slightly modified) code snippet from the Wiki page How to get local Bluetooth Device Address, i.e. replace the code concerning the Bluetooth device address by code concerning the Bluetooth device class.
No known solution.