Re: [PATCH] Bluetooth: hci_event: Add support for handling LE BIG Sync Lost event
From: Yang Li
Date: Wed Jun 25 2025 - 02:02:20 EST
在 2025/6/25 1:17, Luiz Augusto von Dentz 写道:
[ EXTERNAL EMAIL ]
Hi,
On Tue, Jun 24, 2025 at 12:56 PM Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
Hi,
On Tue, Jun 24, 2025 at 1:20 AM Yang Li via B4 Relay
<devnull+yang.li.amlogic.com@xxxxxxxxxx> wrote:
From: Yang Li <yang.li@xxxxxxxxxxx>
When the BIS source stops, the controller sends an LE BIG Sync Lost
event (subevent 0x1E). Currently, this event is not handled, causing
the BIS stream to remain active in BlueZ and preventing recovery.
Signed-off-by: Yang Li <yang.li@xxxxxxxxxxx>
---
include/net/bluetooth/hci.h | 6 ++++++
net/bluetooth/hci_event.c | 23 +++++++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 82cbd54443ac..48389a64accb 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -2849,6 +2849,12 @@ struct hci_evt_le_big_sync_estabilished {
__le16 bis[];
} __packed;
+#define HCI_EVT_LE_BIG_SYNC_LOST 0x1e
+struct hci_evt_le_big_sync_lost {
+ __u8 handle;
+ __u8 reason;
+} __packed;
+
#define HCI_EVT_LE_BIG_INFO_ADV_REPORT 0x22
struct hci_evt_le_big_info_adv_report {
__le16 sync_handle;
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 66052d6aaa1d..730deaf1851f 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -7026,6 +7026,24 @@ static void hci_le_big_sync_established_evt(struct hci_dev *hdev, void *data,
hci_dev_unlock(hdev);
}
+static void hci_le_big_sync_lost_evt(struct hci_dev *hdev, void *data,
+ struct sk_buff *skb)
+{
+ struct hci_evt_le_big_sync_lost *ev = data;
+ struct hci_conn *conn;
+
+ bt_dev_dbg(hdev, "BIG Sync Lost: big_handle 0x%2.2x", ev->handle);
+
+ hci_dev_lock(hdev);
+
+ list_for_each_entry(conn, &hdev->conn_hash.list, list) {
+ if (test_bit(HCI_CONN_BIG_SYNC, &conn->flags))
+ hci_disconn_cfm(conn, HCI_ERROR_REMOTE_USER_TERM);
+ }
Let's start with the obvious problems:
1. This does not use the handle, instead it disconnects all the
connections with HCI_CONN_BIG_SYNC
2. It doesn't use the reason either
3. hci_disconnect_cfm should be followed with hci_conn_del to free the hci_conn
So this does tell me you don't fully understand what you are doing, I
hope I am not dealing with some AI generated code otherwise I would
just do it myself.
Thank you for pointing that out. I overlooked these three issues, and
they will be fixed in the next revision.
Btw, the spec does says the controller shall cleanup the connection
handle and data path:
When the HCI_LE_BIG_Sync_Lost event occurs, the Controller shall
remove the connection handle(s) and data paths of all BIS(s) in the
BIG with which the Controller was synchronized.
I wonder if that shall be interpreted as no HCI_Disconnection_Complete
shall be generated or what, also we might need to implement this into
BlueZ emulator in order to replicate this in our CI tests.
It seems we are not sending anything to the remote devices when
receiving BT_HCI_CMD_LE_BIG_TERM_SYNC:
https://github.com/bluez/bluez/blob/master/emulator/btdev.c#L6661
When the HCI_LE_BIG_Sync_Lost event occurs, there is no accompanying
HCI_Disconnection_Complete event.
However, in the patch submitted to BlueZ, it is described that the
HCI_Disconnection_Complete event will be reported when the CIS link is
disconnected.
https://lore.kernel.org/all/20250624-bap_for_big_sync_lost-v1-1-0df90a0f55d0@xxxxxxxxxxx/
I believe that the HCI_LE_BIG_Sync_Lost event is triggered passively by
the controller when it is unable to synchronize with the BIS stream.
This may occur for various reasons — such as the BIS source pausing
transmission, the device moving out of range, or interference.
This behavior is different from the host actively issuing the
LE_BIG_Terminate_Sync command.
In actual products, this condition can be communicated back to the phone
(Assistant) via the Broadcast Receive State characteristic defined in BASS.
However, in a simulator or test environment, there's often not much that
needs to be done when sending LE_BIG_Terminate_Sync command.
+ hci_dev_unlock(hdev);
+}
+
static void hci_le_big_info_adv_report_evt(struct hci_dev *hdev, void *data,
struct sk_buff *skb)
{
@@ -7149,6 +7167,11 @@ static const struct hci_le_ev {
hci_le_big_sync_established_evt,
sizeof(struct hci_evt_le_big_sync_estabilished),
HCI_MAX_EVENT_SIZE),
+ /* [0x1e = HCI_EVT_LE_BIG_SYNC_LOST] */
+ HCI_LE_EV_VL(HCI_EVT_LE_BIG_SYNC_LOST,
+ hci_le_big_sync_lost_evt,
+ sizeof(struct hci_evt_le_big_sync_lost),
+ HCI_MAX_EVENT_SIZE),
/* [0x22 = HCI_EVT_LE_BIG_INFO_ADV_REPORT] */
HCI_LE_EV_VL(HCI_EVT_LE_BIG_INFO_ADV_REPORT,
hci_le_big_info_adv_report_evt,
---
base-commit: bd35cd12d915bc410c721ba28afcada16f0ebd16
change-id: 20250612-handle_big_sync_lost_event-4c7dc64390a2
Best regards,
--
Yang Li <yang.li@xxxxxxxxxxx>
--
Luiz Augusto von Dentz
--
Luiz Augusto von Dentz