Implement Bluetooth Passthrough with libusbK support

[BParks21]

Would be nice to be able to use the libusbK driver so we can get native wiimote support bypassing the windows bluetooth stack like upstream dolphin.

[flyinghead]

Bluetooth passthrough is already available. See #82. Real wiimotes are fully supported.

USB passthrough, however, is not.

[BParks21]

The adapter I have which has libusbK installed to it is not detected in libretro dolphin. Works fine in upstream. Can be paired and all pairings are remembered. Upstream dolphin requires a sync button press like on real hardware to put it into sync mode. For passthrough you cannot sync a wiimote the same way the emulated bluetooth works with simply leaving continuous scanning on. You either need to assign a hotkey or press the sync button option in dolphins gui. So it's either implemented and theres no way to actually use it or it's not implemented. The adapter i use is listed on the dolphin bluetooth wiki and confirmed to be compatible. It's the Sena UD100 http://www.senanetworks.com/ud100-g03.html?sc=14&category=3968
https://wiki.dolphin-emu.org/index.php?title=Bluetooth_Passthrough

I'm not talking about usb passthrough. Real Wiimote and bluetooth passthrough are 2 completely different things. The "Real Wiimote" option is using the Windows bluetooth stack. Bluetooth passthrough does not and this is why the two are separated within dolphin. If you sync a real physical wiimote in retroach it will remain on when closing the game. This is the behavior of the emulated bluetooth feature in dolphin which allows the real physical wiimote to sync. However this is using Windows bluetooth stack. Bluetooth passthrough is not emulating the wii bluetooth dongle it is bypassing the windows bluetooth stack. The behavior of bluetooth passthrough is requiring the real wii sync process by replicating pressing the wii systems sync button on the console. If passthrough is actually being used by the dolphin core the wiimotes would shut down when the emulated game is being closed. Replicating turning off the console, hence wiimotes shutdown.

Note: For any future readers on this issue please read these pages before commenting
https://dolphin-emu.org/blog/2016/10/24/bluetooth-passthrough/
https://wiki.dolphin-emu.org/index.php?title=Bluetooth_Passthrough

[BParks21]

Closing as it is now implemented.

[BParks21]

Ok so this has been implemented but how do you pair a Wiimote when using Bluetooth passthrough in RA? There needs to be a way in the core options to enter the sync/pairing mode. The only way I could get it to work was to pair it in standalone Dolphin then copy the LinkKeys: from the Dolphin.ini file into the RA Dolphin.ini file. Also this is an outdated implementation/revision of the Bluetooth passthrough. The feature has been greatly improved in the latest Dolphin builds becoming more reliable and accurate. You can read here. https://dolphin-emu.org/blog/2025/09/16/dolphin-progress-report-release-2509/

[cscd98]

Added in #405 (don't know what libusbK is though..)