[PATCH] Bluetooth: MGMT: Send Connection Subrate on LE connection and update

[Kevin Dewald <kevin@simpleble.org>]

Userspace is not told the parameters of LE connections: the Connection
Subrate event is only sent for LE Connection Rate Change, which needs
the Shorter Connection Interval feature, and nothing is sent when a
connection is established or updated with LE Connection Update
Complete. Applications that need the connection interval, e.g. to
estimate throughput or latency, have to read it from HCI traffic
instead.

Send the Connection Subrate event when an LE connection is established
and after each LE Connection Update, with the interval converted to
units of 0.125 ms. As these do not report subrating, keep the subrate
factor and continuation number of the last connection rate change, or
1 and 0 if there was none.

Assisted-by: Claude:claude-opus-5.5
Signed-off-by: Kevin Dewald <kevin@simpleble.org>
---
bluetoothd already registers the Connection Subrate event, and only logs
it for now. Once this is merged, I'll send the BlueZ side: it exposes
the parameters as properties of org.bluez.Bearer.LE1 (Interval, Latency,
SupervisionTimeout and Subrate), and documents the new cases of the
event in doc/mgmt-protocol.rst.

I reused the Connection Subrate event since it already carries the
interval, latency and supervision timeout. If you would rather keep it
for the connection rate procedure, I can add a separate event instead.

Tested in test-runner with the functional tests of those BlueZ changes:
with this patch both hosts report the parameters once connected and
after a connection update, and without it neither does. The kernel
testers and the HoG tests, which also watch this event, pass as before.
Only tested with the emulator.

The PHY in use could be reported the same way, but the kernel does not
know which PHY a connection starts on, so that would also need LE Read
PHY after connecting. I left it out for now.

 include/net/bluetooth/hci_core.h |  1 +
 net/bluetooth/hci_event.c        |  2 ++
 net/bluetooth/mgmt.c             | 20 ++++++++++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 9d5d3ab4a0..89aaae4be5 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -2589,6 +2589,7 @@ void mgmt_adv_monitor_device_lost(struct hci_dev *hdev, u16 handle,
 				  bdaddr_t *bdaddr, u8 addr_type);
 void mgmt_conn_subrate_notify(struct hci_dev *hdev, struct hci_conn *conn,
 			      u8 status);
+void mgmt_conn_update_notify(struct hci_dev *hdev, struct hci_conn *conn);
 
 int hci_abort_conn(struct hci_conn *conn, u8 reason);
 void hci_le_conn_update(struct hci_conn *conn, u16 min, u16 max, u16 latency,
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index d05934fef4..13a8adccb3 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -6032,6 +6032,7 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
 	conn->le_conn_interval = interval;
 	conn->le_conn_latency = latency;
 	conn->le_supv_timeout = supervision_timeout;
+	mgmt_conn_update_notify(hdev, conn);
 
 	hci_debugfs_create_conn(conn);
 	hci_conn_add_sysfs(conn);
@@ -6296,6 +6297,7 @@ static void hci_le_conn_update_complete_evt(struct hci_dev *hdev, void *data,
 		conn->le_conn_interval = le16_to_cpu(ev->interval);
 		conn->le_conn_latency = le16_to_cpu(ev->latency);
 		conn->le_supv_timeout = le16_to_cpu(ev->supervision_timeout);
+		mgmt_conn_update_notify(hdev, conn);
 	}
 
 	hci_dev_unlock(hdev);
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 3cb4f9ece8..385c4c543f 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -11071,6 +11071,26 @@ void mgmt_conn_subrate_notify(struct hci_dev *hdev, struct hci_conn *conn,
 	mgmt_event(MGMT_EV_CONN_SUBRATE, hdev, &ev, sizeof(ev), NULL);
 }
 
+void mgmt_conn_update_notify(struct hci_dev *hdev, struct hci_conn *conn)
+{
+	struct mgmt_ev_conn_subrate ev;
+
+	bacpy(&ev.addr.bdaddr, &conn->dst);
+	ev.addr.type = link_to_bdaddr(conn->type, conn->dst_type);
+	ev.status = MGMT_STATUS_SUCCESS;
+	/* The connection interval is in units of 1.25 ms and the event uses
+	 * units of 0.125 ms. Connection updates don't report subrating, so
+	 * keep the values of the last connection rate change, if any.
+	 */
+	ev.interval = cpu_to_le16(conn->le_conn_interval * 10);
+	ev.subrate = cpu_to_le16(conn->le_subrate ? : 1);
+	ev.latency = cpu_to_le16(conn->le_conn_latency);
+	ev.cont_num = cpu_to_le16(conn->le_cont_num);
+	ev.supv_timeout = cpu_to_le16(conn->le_supv_timeout);
+
+	mgmt_event(MGMT_EV_CONN_SUBRATE, hdev, &ev, sizeof(ev), NULL);
+}
+
 void mgmt_exit(void)
 {
 	hci_mgmt_chan_unregister(&chan);

base-commit: 1081a6ef8f1e0661fd52eb3f878691b0b96cdff9
-- 
2.53.0