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authorMat Martineau <mathewm@codeaurora.org>2010-08-05 15:54:27 -0700
committerMarcel Holtmann <marcel@holtmann.org>2010-08-10 07:59:11 -0400
commitdb12d647ccc971ed120199dc7ea5be2b5887d328 (patch)
tree6720ef2cbcd408fcca4c94b855970ca1e9908f3e
parentcff70fae111efba80c27023772ce5265797fb514 (diff)
Bluetooth: Use 3-DH5 payload size for default ERTM max PDU size
The previous value of 672 for L2CAP_DEFAULT_MAX_PDU_SIZE is based on the default L2CAP MTU. That default MTU is calculated from the size of two DH5 packets, minus ACL and L2CAP b-frame header overhead. ERTM is used with newer basebands that typically support larger 3-DH5 packets, and i-frames and s-frames have more header overhead. With clean RF conditions, basebands will typically attempt to use 1021-byte 3-DH5 packets for maximum throughput. Adjusting for 2 bytes of ACL headers plus 10 bytes of worst-case L2CAP headers yields 1009 bytes of payload. This PDU size imposes less overhead for header bytes and gives the baseband the option to choose 3-DH5 packets, but is small enough for ERTM traffic to interleave well with other L2CAP or SCO data. 672-byte payloads do not allow the most efficient over-the-air packet choice, and cannot achieve maximum throughput over BR/EDR. Signed-off-by: Mat Martineau <mathewm@codeaurora.org> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
-rw-r--r--include/net/bluetooth/l2cap.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 16e412f3722..6c241444f90 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -35,7 +35,7 @@
#define L2CAP_DEFAULT_MAX_TX 3
#define L2CAP_DEFAULT_RETRANS_TO 2000 /* 2 seconds */
#define L2CAP_DEFAULT_MONITOR_TO 12000 /* 12 seconds */
-#define L2CAP_DEFAULT_MAX_PDU_SIZE 672
+#define L2CAP_DEFAULT_MAX_PDU_SIZE 1009 /* Sized for 3-DH5 packet */
#define L2CAP_DEFAULT_ACK_TO 200
#define L2CAP_LOCAL_BUSY_TRIES 12