Re: [PATCH] Bluetooth: hci_h5: avoid sending two SYNC messages

[Javier Nieto <jgnieto@cs.stanford.edu>]

Dear Paul,

> Great commit message, thank you. I´d appreciate it if you documented your
> test environment, and maybe paste the logs (for the timestamps) before and
> after, so others could easily reproduce the issue.

Appologies for that. My test environment is a MangoPi MQ-Pro board
(with a Realtek RTL8723DS Bluetooth chip) running the tip of
bluetooth-next, although I also observed this issue on 6.8 kernel.
Originally, I spotted it using a logic analyzer on the UART PCB traces.
I added a temporary log message to h5_link_control(), which prints the
first byte and the length of the packet being sent. Here is the relevant
part before the patch:

[   67.328445] Bluetooth: h5_link_control sending 1 with len 2
[   67.432393] Bluetooth: h5_link_control sending 1 with len 2
[   67.436424] Bluetooth: h5_link_control sending 3 with len 3
[   67.436592] Bluetooth: h5_link_control sending 2 with len 2
[   67.436693] Bluetooth: h5_link_control sending 3 with len 3
[   67.439510] Bluetooth: h5_link_control sending 2 with len 2
[   67.440004] Bluetooth: h5_link_control sending 4 with len 2
[   67.440030] Bluetooth: h5_link_control sending 3 with len 3

And here after the patch:

[   67.498228] Bluetooth: h5_link_control sending 1 with len 2
[   67.501444] Bluetooth: h5_link_control sending 3 with len 3
[   67.501615] Bluetooth: h5_link_control sending 2 with len 2
[   67.504976] Bluetooth: h5_link_control sending 2 with len 2
[   67.505141] Bluetooth: h5_link_control sending 4 with len 2
[   67.505168] Bluetooth: h5_link_control sending 3 with len 3

Notice that in the first case, two SYNC packets (type 1) are sent, one 100ms
after the other, while in the second case only one is sent. In both
cases, using bluetoothctl to connect to a device later on works fine.

Thanks for the feedback,

Javier