Re: [RFC PATCH] Bluetooth: l2cap: honor local LE connection interval range

[Luiz Augusto von Dentz]

Hi Kyle,

On Mon, Oct 12, 2026 at 11:31 PM Kyle Pepper <cochcoder@xxxxxxxxx> wrote:
>
> Intersect a valid peer request with the locally configured interval
> range. Reject disjoint ranges and preserve validation of the original
> request before applying local policy.
>
> Assisted-by: OpenCode:gpt-6.1-sol
> Signed-off-by: Kyle Pepper <cochcoder@xxxxxxxxx>
> ---
> Submission review notes (not part of the commit message):
> October 12 no-intersection trial accepts [16,24] and completes 30 ms
> with STATUS 03 02 18 and normal host TX; the user hears silence. Volume
> and multi-day acoustic comparison controls are incomplete. The working
> intersection yields 20 ms. Maximum-only rejection failed in kernel 5
> and is not this proposal. Generic minimum/range policy and LL-path
> consistency remain RFC questions, not established by one renderer.

I need to check the git history but I believe we tried something
similar not long ago that created interoperability problems if we use
strict range matching like this.

>  net/bluetooth/l2cap_core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 49a998804..49e201d3e 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -4968,6 +4968,13 @@ static inline int l2cap_conn_param_update_req(struct l2cap_conn *conn,
>         memset(&rsp, 0, sizeof(rsp));
>
>         err = hci_check_conn_params(min, max, latency, to_multiplier);
> +       if (!err) {
> +               /* Apply local policy only after validating the peer's request. */
> +               min = max_t(u16, min, hcon->le_conn_min_interval);
> +               max = min_t(u16, max, hcon->le_conn_max_interval);
> +               err = hci_check_conn_params(min, max, latency, to_multiplier);
> +       }
> +
>         if (err)
>                 rsp.result = cpu_to_le16(L2CAP_CONN_PARAM_REJECTED);
>         else
>
> base-commit: 964430c038967fd06643e866f68115664e1a1bd1
>


-- 
Luiz Augusto von Dentz