* [PATCH v1] Bluetooth: hci_sync: Fix invalid Supervision_Timeout in LE Set Default Rate
@ 2026-10-15 15:39 Luiz Augusto von Dentz
2026-10-15 16:43 ` [v1] " bluez.test.bot
2026-10-15 19:40 ` [PATCH v1] " patchwork-bot+bluetooth
0 siblings, 2 replies; 3+ messages in thread
From: Luiz Augusto von Dentz @ 2026-10-15 15:39 UTC (permalink / raw)
To: linux-bluetooth
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
The LE Set Default Rate Parameters command is rejected with Invalid HCI
Command Parameters (0x12) because the Supervision_Timeout of 120 ms is
exactly the minimum recommended by HOGP v1.2:
Greater than or equal to (1 + Peripheral Latency) x Subrate max x
Connection Interval max x 2
But the Core spec treats the equality as invalid:
BLUETOOTH CORE SPECIFICATION Version 6.3 | Vol 4, Part E
7.8.158. LE Set Default Rate Parameters command
If Connection_Interval_Max x Subrate_Max x (Max_Latency + 1) is
greater than or equal to Supervision_Timeout x 40, the Controller
shall return the error code Invalid HCI Command Parameters (0x12).
With the current values 0x78 x 4 x 1 = 480 >= 0x0c x 40 = 480.
Fix this by using 2 s as the default Supervision_Timeout, which is 10x
lower than the 20 s used for non-SCI connections while still well above
the minimum required, and make sure it remains above the minimum in
case interval_max is raised to match the controller's minimum supported
connection interval.
Fixes: 2f8784cfe8a9 ("Bluetooth: Add support for Shorter Connection Interval (SCI) feature")
Assisted-by: OpenCode:claude-opus-5.5
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
net/bluetooth/hci_sync.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 03f706c1f815..7ac26daba966 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -4828,6 +4828,9 @@ static int hci_le_set_def_rate_sync(struct hci_dev *hdev)
struct hci_cp_le_set_def_rate cp;
u16 interval_min = 0x000a; /* 1.25 ms */
u16 interval_max = 0x0078; /* 15 ms */
+ u16 subrate_max = 0x0004;
+ u16 max_latency = 0x0000;
+ u32 supv_timeout;
if (!le_sci_capable(hdev))
return 0;
@@ -4852,10 +4855,31 @@ static int hci_le_set_def_rate_sync(struct hci_dev *hdev)
cp.interval_min = cpu_to_le16(interval_min);
cp.interval_max = cpu_to_le16(interval_max);
cp.subrate_min = cpu_to_le16(0x0001);
- cp.subrate_max = cpu_to_le16(0x0004);
- cp.max_latency = cpu_to_le16(0x0000);
+ cp.subrate_max = cpu_to_le16(subrate_max);
+ cp.max_latency = cpu_to_le16(max_latency);
cp.cont_num = cpu_to_le16(0x0001);
- cp.supv_timeout = cpu_to_le16(0x000c); /* 120 ms */
+
+ /* HOGP v1.2 recommends a Supervision_Timeout greater than or equal to
+ * (1 + Max_Latency) x Subrate_Max x Connection_Interval_Max x 2, but
+ * the Core spec treats the equality as invalid:
+ *
+ * BLUETOOTH CORE SPECIFICATION Version 6.3 | Vol 4, Part E
+ * 7.8.158. LE Set Default Rate Parameters command
+ *
+ * If Connection_Interval_Max x Subrate_Max x (Max_Latency + 1) is
+ * greater than or equal to Supervision_Timeout x 40, the Controller
+ * shall return the error code Invalid HCI Command Parameters (0x12).
+ *
+ * So default to 2 s, 10x lower than the 20 s used for non-SCI
+ * connections while still well above the minimum required, but make
+ * sure it stays strictly above the minimum in case interval_max has
+ * been raised.
+ */
+ supv_timeout = (u32)interval_max * subrate_max * (max_latency + 1);
+ supv_timeout = supv_timeout / 40 + 1;
+ supv_timeout = clamp_t(u32, max_t(u32, supv_timeout, 0x00c8),
+ 0x000a, 0x0c80);
+ cp.supv_timeout = cpu_to_le16(supv_timeout);
/* The connection event length recommended in requests by a Peripheral
* uses units of 125 us with a valid range of 0x0001 to 0x7CFF
--
2.56.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2026-10-15 15:39 [PATCH v1] Bluetooth: hci_sync: Fix invalid Supervision_Timeout in LE Set Default Rate Luiz Augusto von Dentz
2026-10-15 16:43 ` [v1] " bluez.test.bot
2026-10-15 19:40 ` [PATCH v1] " patchwork-bot+bluetooth
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