Bluetooth: Use non-flushable by default L2CAP data packets

Modification of Nick Pelly <npelly@google.com> patch.

With Bluetooth 2.1 ACL packets can be flushable or non-flushable. This commit
makes ACL data packets non-flushable by default on compatible chipsets, and
adds the BT_FLUSHABLE socket option to explicitly request flushable ACL
data packets for a given L2CAP socket. This is useful for A2DP data which can
be safely discarded if it can not be delivered within a short time (while
other ACL data should not be discarded).

Note that making ACL data flushable has no effect unless the automatic flush
timeout for that ACL link is changed from its default of 0 (infinite).

Default packet types (for compatible chipsets):
Frame 34: 13 bytes on wire (104 bits), 13 bytes captured (104 bits)
Bluetooth HCI H4
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x0002
    ..00 .... .... .... = PB Flag: First Non-automatically Flushable Packet (0)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 8
Bluetooth L2CAP Packet

After setting BT_FLUSHABLE
(sock.setsockopt(274 /*SOL_BLUETOOTH*/, 8 /* BT_FLUSHABLE */, 1 /* flush */))
Frame 34: 13 bytes on wire (104 bits), 13 bytes captured (104 bits)
Bluetooth HCI H4
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x0002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 8
Bluetooth L2CAP Packet

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@nokia.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

4 files changed, 9 insertions, 0 deletions

diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 0c5e72503b77..ed7d775337e0 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -64,6 +64,11 @@ struct bt_security {
 
 #define BT_DEFER_SETUP  7
 
+#define BT_FLUSHABLE    8
+
+#define BT_FLUSHABLE_OFF        0
+#define BT_FLUSHABLE_ON         1
+
 #define BT_INFO(fmt, arg...) printk(KERN_INFO "Bluetooth: " fmt "\n" , ## arg)
 #define BT_ERR(fmt, arg...)  printk(KERN_ERR "%s: " fmt "\n" , __func__ , ## arg)
 #define BT_DBG(fmt, arg...)  pr_debug("%s: " fmt "\n" , __func__ , ## arg)
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 29a7a8ca0438..5d033dc9d43b 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -150,6 +150,7 @@ enum {
 #define EDR_ESCO_MASK  (ESCO_2EV3 | ESCO_3EV3 | ESCO_2EV5 | ESCO_3EV5)
 
 /* ACL flags */
+#define ACL_START_NO_FLUSH      0x00
 #define ACL_CONT                0x01
 #define ACL_START               0x02
 #define ACL_ACTIVE_BCAST        0x04
@@ -194,6 +195,7 @@ enum {
 #define LMP_EDR_3S_ESCO 0x80
 
 #define LMP_SIMPLE_PAIR 0x08
+#define LMP_NO_FLUSH    0x40
 
 /* Connection modes */
 #define HCI_CM_ACTIVE   0x0000
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index d2cf88407690..4e14610baece 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -458,6 +458,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn);
 #define lmp_sniffsubr_capable(dev) ((dev)->features[5] & LMP_SNIFF_SUBR)
 #define lmp_esco_capable(dev)      ((dev)->features[3] & LMP_ESCO)
 #define lmp_ssp_capable(dev)       ((dev)->features[6] & LMP_SIMPLE_PAIR)
+#define lmp_no_flush_capable(dev)  ((dev)->features[6] & LMP_NO_FLUSH)
 
 /* ----- HCI protocols ----- */
 struct hci_proto {
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 7ad25ca60ec0..7f88a87d7a46 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -327,6 +327,7 @@ struct l2cap_pinfo {
         __u8            sec_level;
         __u8            role_switch;
         __u8            force_reliable;
+        __u8            flushable;
 
         __u8            conf_req[64];
         __u8            conf_len;