Bluetooth disconnect event / Link layer monitoring

[Guy Morand <g.morand@scewo.ch>]

Hello bluetooth developers,

We are developing a wheelchair that we can controle with a bluetooth
gamepad, the XBOX 360 controller to be more precise. It basically works
fine but when I remove the battery, I get the disconnect event in the
user space around 10 seconds later. That is not acceptable since the
wheelchair will keep rolling to potentially dangerous places!

I tried to implement a ping mechanism on the bluetooth layer, inspired
from bluez sources somewhere:
  int _socket_fd = socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_L2CAP);
  // bind on AF_BLUETOOTH
  // connect with AF_BLUETOOTH

  send_cmd->ident = PING_IDENT;
  send_cmd->len = htobs(PING_DATA_SIZE);
  send_cmd->code = L2CAP_ECHO_REQ;
  if (send(_socket_fd, send_buffer, PING_PACKET_SIZE, 0) <= 0) {
    // ...
  }

It basically works fine except when the signal gets bad. This will get
printed by the kernel:
[  859.629431] Bluetooth: hci0 link tx timeout
[  859.635482] Bluetooth: hci0 killing stalled connection 9c:aa:1b:6b:51:c9

In that case, I don't get event from the /dev/jsX device but the gamepad
seems to still answer to pings??!!

Since I haven't found any acceptable workaround and always find the same
pages again and again, I'm asking here:
* Is it possible to achieve what I want?
* Does it make sense that the ping work but the HID layer seems dead?
* Any recommendation, pointers?

Best regards,

Guy

-- 
Guy Morand
Software Engineer
Scewo AG, Technoparkstrasse 2, 8406 Winterthur

www.scewo.ch
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