When initiating a transparent eSCO connection, make use of T2 settings at
first try. T2 is the recommended settings from HFP 1.6 WideBand Speech. Upon
connection failure, try T1 settings.
T2 failure is detected if Synchronous Connection Complete event fails with
error 0x0d. This error code has been found experimentally by sending a T2
request to a T1 only SCO listener. It means "Connection Rejected due to
Limited resource".
To know which of T2 or T1 should be used, conn->fallback is used. Bluez only
attempt to reconnect twice. In the future, we will need more than 2 fallback
possibilities. Thus, test conn->fallback as an alternative measure. We want to
fallback only if conn->fallback is positive. Calling hci_setup_sync with
conn->fallback == 0 is an initial connection attempt.
Signed-off-by: Frédéric Dalleau <frederic.dalleau@xxxxxxxxxxxxxxx>
---
include/net/bluetooth/hci_core.h | 1 +
net/bluetooth/hci_conn.c | 20 +++++++++++++++++---
net/bluetooth/hci_event.c | 3 ++-
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index b5996b3..c8b91d2 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -321,6 +321,7 @@ struct hci_conn {
__u8 passkey_entered;
__u16 disc_timeout;
__u16 setting;
+ __u8 fallback;
unsigned long flags;
__u8 remote_cap;
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index cd7452e..8d71d73 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -31,6 +31,17 @@
#include <net/bluetooth/a2mp.h>
#include <net/bluetooth/smp.h>
+struct sco_param {
+ u16 pkt_type;
+ u16 max_latency;
+ u8 next;
+};
+
+static const struct sco_param sco_param_wideband[] = {
+ { EDR_ESCO_MASK & ~ESCO_2EV3, 0x000d, 1 },
+ { EDR_ESCO_MASK | ESCO_EV3, 0x0008, 0 },
+};
+
static void hci_le_create_connection(struct hci_conn *conn)
{
struct hci_dev *hdev = conn->hdev;
@@ -176,6 +187,7 @@ void hci_setup_sync(struct hci_conn *conn, __u16 handle)
{
struct hci_dev *hdev = conn->hdev;
struct hci_cp_setup_sync_conn cp;
+ const struct sco_param *param;
BT_DBG("hcon %p", conn);
@@ -191,11 +203,13 @@ void hci_setup_sync(struct hci_conn *conn, __u16 handle)
switch (hci_sco_airmode(conn->setting)) {
case SCO_AIRMODE_TRANSP:
- cp.pkt_type = __constant_cpu_to_le16(EDR_ESCO_MASK &
- ~ESCO_2EV3);
- cp.max_latency = __constant_cpu_to_le16(0x000d);
+ param = &sco_param_wideband[conn->fallback];
+ cp.pkt_type = __constant_cpu_to_le16(param->pkt_type);
+ cp.max_latency = __constant_cpu_to_le16(param->max_latency);
cp.voice_setting = __constant_cpu_to_le16(SCO_AIRMODE_TRANSP);
cp.retrans_effort = 0x02;
+
+ conn->fallback = param->next;
break;
case SCO_AIRMODE_CVSD:
cp.pkt_type = cpu_to_le16(conn->pkt_type);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index db58e72..9be10be 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -2904,11 +2904,12 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
hci_conn_add_sysfs(conn);
break;
+ case 0x0d: /* No resource available */
case 0x11: /* Unsupported Feature or Parameter Value */
case 0x1c: /* SCO interval rejected */
case 0x1a: /* Unsupported Remote Feature */
case 0x1f: /* Unspecified error */
- if (conn->out && conn->attempt < 2) {
+ if (conn->out && (conn->attempt < 2 || conn->fallback > 0)) {
conn->pkt_type = (hdev->esco_type & SCO_ESCO_MASK) |
(hdev->esco_type & EDR_ESCO_MASK);
hci_setup_sync(conn, conn->link->handle);
--
1.7.9.5
--
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