* [RFC PATCH] Bluetooth: hci_event: negotiate LE Data Length after features
@ 2026-10-13 3:35 Kyle Pepper
2026-10-13 14:30 ` Luiz Augusto von Dentz
0 siblings, 1 reply; 2+ messages in thread
From: Kyle Pepper @ 2026-10-13 3:35 UTC (permalink / raw)
To: linux-bluetooth; +Cc: Marcel Holtmann, Luiz Augusto von Dentz, linux-kernel
Request the controller transmit limits once both peers support DLE.
Queue the connection with a reference so pending requests coalesce and
connection deletion cancels them. Check the connection under the device
lock before constructing the command.
Assisted-by: OpenCode:gpt-6.1-sol
Signed-off-by: Kyle Pepper <cochcoder@proton.me>
---
Submission review notes (not part of the commit message):
The user reports that retaining the explicit DLE request enables the N8
to disconnect automatically after audio stops, whereas removing it
leaves the device connected. This idle-transition behavior is the
reported reason for retaining the topic, not an in-stream timeout.
October 9 no-DLE trials already negotiate TX 251 octets / 2120 us and
stream successfully; startup throughput alone does not test idle behavior.
The supplied captures do not establish a controlled post-STOP comparison
or the causal mechanism. This patch requests data length during setup;
it does not itself implement STOP or issue a disconnect command.
The claimed ASHA idle-disconnect requirement needs a protocol citation.
The corrected ownership implementation is included in the working kernel.
Native disconnect/handle reuse, LL ordering and post-snapshot races remain
unproved. Submit as an independent RFC with these limitations disclosed.
include/net/bluetooth/hci_sync.h | 1 +
net/bluetooth/hci_event.c | 10 +++++++
net/bluetooth/hci_sync.c | 47 ++++++++++++++++++++++++++++++++
3 files changed, 58 insertions(+)
diff --git a/include/net/bluetooth/hci_sync.h b/include/net/bluetooth/hci_sync.h
index 59cb918d1..5a37d3e50 100644
--- a/include/net/bluetooth/hci_sync.h
+++ b/include/net/bluetooth/hci_sync.h
@@ -194,3 +194,4 @@ int hci_le_read_remote_features(struct hci_conn *conn);
int hci_acl_change_pkt_type(struct hci_conn *conn, u16 pkt_type);
int hci_le_set_phy(struct hci_conn *conn, u8 tx_phys, u8 rx_phys);
+int hci_le_set_data_len(struct hci_conn *conn);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index c055d16cf..4035f2659 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -6846,6 +6846,16 @@ static void hci_le_remote_feat_complete_evt(struct hci_dev *hdev, void *data,
conn->le_tx_def_phys &= ~HCI_LE_SET_PHY_CODED;
conn->le_rx_def_phys &= ~HCI_LE_SET_PHY_CODED;
}
+
+ /* Request the controller maximum when both sides support
+ * LL Data Length Extension. The Link Layer negotiates
+ * the remote limits (Core v5.4, Vol 6, Part B,
+ * Sec. 4.5.10).
+ */
+ if ((hdev->le_features[0] & HCI_LE_DATA_LEN_EXT) &&
+ (conn->le_features[0] & HCI_LE_DATA_LEN_EXT) &&
+ hdev->le_max_tx_len > 0x001b)
+ hci_le_set_data_len(conn);
}
if (conn->state == BT_CONFIG) {
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index efbd2e538..20c690007 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -8123,3 +8123,50 @@ int hci_le_set_phy(struct hci_conn *conn, u8 tx_phys, u8 rx_phys)
return (err == -EEXIST) ? 0 : err;
}
+
+static void le_set_data_len_complete(struct hci_dev *hdev, void *data,
+ int err)
+{
+ struct hci_conn *conn = data;
+
+ bt_dev_dbg(hdev, "err %d", err);
+
+ hci_conn_put(conn);
+}
+
+static int hci_le_set_data_len_sync(struct hci_dev *hdev, void *data)
+{
+ struct hci_conn *conn = data;
+ struct hci_cp_le_set_data_len cp;
+
+ hci_dev_lock(hdev);
+
+ if (!hci_conn_valid(hdev, conn) || conn->type != LE_LINK ||
+ (conn->state != BT_CONNECTED && conn->state != BT_CONFIG)) {
+ hci_dev_unlock(hdev);
+ return -ECANCELED;
+ }
+
+ cp.handle = cpu_to_le16(conn->handle);
+ cp.tx_len = cpu_to_le16(hdev->le_max_tx_len);
+ cp.tx_time = cpu_to_le16(hdev->le_max_tx_time);
+
+ hci_dev_unlock(hdev);
+
+ return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_DATA_LEN,
+ sizeof(cp), &cp, HCI_CMD_TIMEOUT);
+}
+
+int hci_le_set_data_len(struct hci_conn *conn)
+{
+ struct hci_dev *hdev = conn->hdev;
+ int err;
+
+ err = hci_cmd_sync_queue_once(hdev, hci_le_set_data_len_sync,
+ hci_conn_get(conn),
+ le_set_data_len_complete);
+ if (err)
+ hci_conn_put(conn);
+
+ return (err == -EEXIST) ? 0 : err;
+}
base-commit: 964430c038967fd06643e866f68115664e1a1bd1
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [RFC PATCH] Bluetooth: hci_event: negotiate LE Data Length after features
2026-10-13 3:35 [RFC PATCH] Bluetooth: hci_event: negotiate LE Data Length after features Kyle Pepper
@ 2026-10-13 14:30 ` Luiz Augusto von Dentz
0 siblings, 0 replies; 2+ messages in thread
From: Luiz Augusto von Dentz @ 2026-10-13 14:30 UTC (permalink / raw)
To: Kyle Pepper; +Cc: linux-bluetooth, Marcel Holtmann, linux-kernel
Hi Kyle,
On Mon, Oct 12, 2026 at 11:35 PM Kyle Pepper <cochcoder@proton.me> wrote:
>
> Request the controller transmit limits once both peers support DLE.
> Queue the connection with a reference so pending requests coalesce and
> connection deletion cancels them. Check the connection under the device
> lock before constructing the command.
>
> Assisted-by: OpenCode:gpt-6.1-sol
> Signed-off-by: Kyle Pepper <cochcoder@proton.me>
> ---
> Submission review notes (not part of the commit message):
> The user reports that retaining the explicit DLE request enables the N8
> to disconnect automatically after audio stops, whereas removing it
> leaves the device connected. This idle-transition behavior is the
> reported reason for retaining the topic, not an in-stream timeout.
> October 9 no-DLE trials already negotiate TX 251 octets / 2120 us and
> stream successfully; startup throughput alone does not test idle behavior.
> The supplied captures do not establish a controlled post-STOP comparison
> or the causal mechanism. This patch requests data length during setup;
> it does not itself implement STOP or issue a disconnect command.
> The claimed ASHA idle-disconnect requirement needs a protocol citation.
> The corrected ownership implementation is included in the working kernel.
> Native disconnect/handle reuse, LL ordering and post-snapshot races remain
> unproved. Submit as an independent RFC with these limitations disclosed.
>
> include/net/bluetooth/hci_sync.h | 1 +
> net/bluetooth/hci_event.c | 10 +++++++
> net/bluetooth/hci_sync.c | 47 ++++++++++++++++++++++++++++++++
> 3 files changed, 58 insertions(+)
>
> diff --git a/include/net/bluetooth/hci_sync.h b/include/net/bluetooth/hci_sync.h
> index 59cb918d1..5a37d3e50 100644
> --- a/include/net/bluetooth/hci_sync.h
> +++ b/include/net/bluetooth/hci_sync.h
> @@ -194,3 +194,4 @@ int hci_le_read_remote_features(struct hci_conn *conn);
>
> int hci_acl_change_pkt_type(struct hci_conn *conn, u16 pkt_type);
> int hci_le_set_phy(struct hci_conn *conn, u8 tx_phys, u8 rx_phys);
> +int hci_le_set_data_len(struct hci_conn *conn);
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index c055d16cf..4035f2659 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -6846,6 +6846,16 @@ static void hci_le_remote_feat_complete_evt(struct hci_dev *hdev, void *data,
> conn->le_tx_def_phys &= ~HCI_LE_SET_PHY_CODED;
> conn->le_rx_def_phys &= ~HCI_LE_SET_PHY_CODED;
> }
> +
> + /* Request the controller maximum when both sides support
> + * LL Data Length Extension. The Link Layer negotiates
> + * the remote limits (Core v5.4, Vol 6, Part B,
> + * Sec. 4.5.10).
> + */
> + if ((hdev->le_features[0] & HCI_LE_DATA_LEN_EXT) &&
> + (conn->le_features[0] & HCI_LE_DATA_LEN_EXT) &&
> + hdev->le_max_tx_len > 0x001b)
> + hci_le_set_data_len(conn);
We use HCI_OP_LE_WRITE_DEF_DATA_LEN to setup this for every
connection, so either the controller has a bug and doesn't trigger
trigger DLE or something else is off here. In case it is really a
specific controller then we might need a quirk which once set by the
driver indicates the host has to perform the DLE procedure manually
like above.
> }
>
> if (conn->state == BT_CONFIG) {
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index efbd2e538..20c690007 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -8123,3 +8123,50 @@ int hci_le_set_phy(struct hci_conn *conn, u8 tx_phys, u8 rx_phys)
>
> return (err == -EEXIST) ? 0 : err;
> }
> +
> +static void le_set_data_len_complete(struct hci_dev *hdev, void *data,
> + int err)
> +{
> + struct hci_conn *conn = data;
> +
> + bt_dev_dbg(hdev, "err %d", err);
> +
> + hci_conn_put(conn);
> +}
> +
> +static int hci_le_set_data_len_sync(struct hci_dev *hdev, void *data)
> +{
> + struct hci_conn *conn = data;
> + struct hci_cp_le_set_data_len cp;
> +
> + hci_dev_lock(hdev);
> +
> + if (!hci_conn_valid(hdev, conn) || conn->type != LE_LINK ||
> + (conn->state != BT_CONNECTED && conn->state != BT_CONFIG)) {
> + hci_dev_unlock(hdev);
> + return -ECANCELED;
> + }
> +
> + cp.handle = cpu_to_le16(conn->handle);
> + cp.tx_len = cpu_to_le16(hdev->le_max_tx_len);
> + cp.tx_time = cpu_to_le16(hdev->le_max_tx_time);
> +
> + hci_dev_unlock(hdev);
> +
> + return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_DATA_LEN,
> + sizeof(cp), &cp, HCI_CMD_TIMEOUT);
> +}
> +
> +int hci_le_set_data_len(struct hci_conn *conn)
> +{
> + struct hci_dev *hdev = conn->hdev;
> + int err;
> +
> + err = hci_cmd_sync_queue_once(hdev, hci_le_set_data_len_sync,
> + hci_conn_get(conn),
> + le_set_data_len_complete);
> + if (err)
> + hci_conn_put(conn);
> +
> + return (err == -EEXIST) ? 0 : err;
> +}
>
> base-commit: 964430c038967fd06643e866f68115664e1a1bd1
>
--
Luiz Augusto von Dentz
^ permalink raw reply [flat|nested] 2+ messages in thread
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