@daltz333 said in Bluetooth Filter Driver for DS3-compatibility - research notes: Quite interesting research. So putting this into simple terms, the filter driver will pickup the DS4 and will interpret it's requests instead? Which is bad because the DS4 has bluetooth support already. The filter is stupid and has no idea what kind of device is connecting, it looks for Protocol/Service Multiplexer values 0x11 (HID Control) and 0x13 (HID Interrupt) and patches them to artificial values the profile driver listens on. So now the profile driver is in charge of handling the connection requests. The profile driver needs to know what kind of device connects because anything else than the PS3 peripherals could in theory use those PSMs as well. Now we also know that the DS4 tries them as well for whatever reason. It doesn't need to because it has a valid SDP record but I guess it does it to "poke" the Bluetooth host and switches to native PS4 mode if the PSMs get accepted. Who knows what would happen then.