GIMX is now able to talk to a PS4
I worked on adding bluetooth proxy capabilities to GIMX. Before connecting to the PS4, GIMX waits for a Dualshock 4 to connect. Then it forwards HID control transfers, and it directly handles SDP and HID interrupt transfers.
I had to solve an issue with the SDP: the DS4 sends a 708-byte service attribute search response, which is larger than the 672-byte outgoing L2CAP MTU. As the Linux kernel rightly refuses to send L2CAP packets larger than the outgoing L2CAP MTU, I had to go to a lower level in the bluetooth stack so as to directly send ACL packets.
I now have to see how to achieve a high packet rate (800 packets per second). It seems a single bluetooth dongle will not be enough to handle twice this packet rate (from the DS4 + to the PS4).