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ng_hci(4)

NAME

     ng_hci -- Netgraph node type that is also a Bluetooth Host Controller
     Interface (HCI) layer

SYNOPSIS

     #include <sys/types.h>
     #include <netgraph/bluetooth/include/ng_hci.h>

DESCRIPTION

     The hci node type is a Netgraph node type that implements Bluetooth Host
     Controller Interface (HCI) layer as per chapter H1 of the Bluetooth Spec-
     ification Book v1.1.

INTRODUCTION TO BLUETOOTH

     Bluetooth is a short-range radio link intended to replace the cable(s)
     connecting portable and/or fixed electronic devices.  Bluetooth operates
     in the unlicensed ISM band at 2.4 GHz.  The Bluetooth protocol uses a
     combination of circuit and packet switching.  Bluetooth can support an
     asynchronous data channel, up to three simultaneous synchronous voice
     channels, or a channel which simultaneously supports asynchronous data
     and synchronous voice.  Each voice channel supports a 64 kb/s synchronous
     (voice) channel in each direction.  The asynchronous channel can support
     maximal 723.2 kb/s asymmetric (and still up to 57.6 kb/s in the return
     direction), or 433.9 kb/s symmetric.

     The Bluetooth system provides a point-to-point connection (only two Blue-
     tooth units involved), or a point-to-multipoint connection.  In the
     point-to-multipoint connection, the channel is shared among several Blue-
     tooth units.  Two or more units sharing the same channel form a
     ``piconet''.  One Bluetooth unit acts as the master of the piconet,
     whereas the other unit(s) acts as slave(s).  Up to seven slaves can be
     active in the piconet.  In addition, many more slaves can remain locked
     to the master in a so-called parked state.  These parked slaves cannot be
     active on the channel, but remain synchronized to the master.  Both for
     active and parked slaves, the channel access is controlled by the master.

     Multiple piconets with overlapping coverage areas form a ``scatternet''.
     Each piconet can only have a single master.  However, slaves can partici-
     pate in different piconets on a time-division multiplex basis.  In addi-
     tion, a master in one piconet can be a slave in another piconet.  The
     piconets shall not be frequency-synchronized.  Each piconet has its own
     hopping channel.

   Time Slots
     The channel is divided into time slots, each 625 usec in length.  The
     time slots are numbered according to the Bluetooth clock of the piconet
     master.  The slot numbering ranges from 0 to 2^27 -1 and is cyclic with a
     cycle length of 2^27.  In the time slots, master and slave can transmit
     packets.

   SCO Link
     The SCO link is a symmetric, point-to-point link between the master and a
     specific slave.  The SCO link reserves slots and can therefore be consid-
     ered as a circuit-switched connection between the master and the slave.
     The SCO link typically supports time-bounded information like voice.  The
     master can support up to three SCO links to the same slave or to differ-
     ent slaves.  A slave can support up to three SCO links from the same mas-
     ported.  Between a master and a slave only a single ACL link can exist.
     For most ACL packets, packet retransmission is applied to assure data
     integrity.

HOST CONTROLLER INTERFACE (HCI)

     The HCI provides a command interface to the baseband controller and link
     manager, and access to hardware status and control registers.  This
     interface provides a uniform method of accessing the Bluetooth baseband
     capabilities.

     The HCI layer on the Host exchanges data and commands with the HCI
     firmware on the Bluetooth hardware.  The Host Controller Transport Layer
     (i.e., physical bus) driver provides both HCI layers with the ability to
     exchange information with each other.

     The Host will receive asynchronous notifications of HCI events indepen-
     dent of which Host Controller Transport Layer is used.  HCI events are
     used for notifying the Host when something occurs.  When the Host discov-
     ers that an event has occurred it will then parse the received event
     packet to determine which event occurred.	The next sections specify the
     HCI packet formats.

   HCI Command Packet
	   #define NG_HCI_CMD_PKT 0x01
	   typedef struct {
		   u_int8_t  type;   /* MUST be 0x1 */
		   u_int16_t opcode; /* OpCode */
		   u_int8_t  length; /* parameter(s) length in bytes */
	   } __attribute__ ((packed)) ng_hci_cmd_pkt_t;

     The HCI command packet is used to send commands to the Host Controller
     from the Host.  When the Host Controller completes most of the commands,
     a Command Complete event is sent to the Host.  Some commands do not
     receive a Command Complete event when they have been completed.  Instead,
     when the Host Controller receives one of these commands the Host Con-
     troller sends a Command Status event back to the Host when it has begun
     to execute the command.  Later on, when the actions associated with the
     command have finished, an event that is associated with the sent command
     will be sent by the Host Controller to the Host.

   HCI Event Packet
	   #define NG_HCI_EVENT_PKT 0x04
	   typedef struct {
		   u_int8_t type;   /* MUST be 0x4 */
		   u_int8_t event;  /* event */
		   u_int8_t length; /* parameter(s) length in bytes */
	   } __attribute__ ((packed)) ng_hci_event_pkt_t;

     The HCI event packet is used by the Host Controller to notify the Host
     when events occur.

   HCI ACL Data Packet
	   #define NG_HCI_ACL_DATA_PKT 0x02
	   typedef struct {
		   u_int8_t  type;	 /* MUST be 0x2 */
		   u_int16_t con_handle; /* connection handle + PB + BC flags */
		   u_int16_t length;	 /* payload length in bytes */
	   } __attribute__ ((packed)) ng_hci_acldata_pkt_t;
		   u_int16_t con_handle; /* connection handle + reserved bits */
		   u_int8_t  length;	 /* payload length in bytes */
	   } __attribute__ ((packed)) ng_hci_scodata_pkt_t;

     HCI SCO data packets are used to exchange SCO data between the Host and
     Host Controller.

HCI INITIALIZATION

     On initialization, HCI control application must issue the following HCI
     commands (in any order).

     Read_BD_ADDR
	     To obtain BD_ADDR of the Bluetooth unit.

     Read_Local_Supported_Features
	     To obtain the list of features supported by Bluetooth unit.

     Read_Buffer_Size
	     To determine the maximum size of HCI ACL and SCO HCI data packets
	     (excluding header) that can be sent from the Host to the Host
	     Controller.  There are also two additional return parameters that
	     specify the total number of HCI ACL and SCO data packets that the
	     Host Controller can have waiting for transmission in its buffers.

     As soon as HCI initialization has been successfully performed, HCI con-
     trol application must turn on ``inited'' bit for the node.  Once HCI node
     has been initialized all upsteam hooks will receive a NGM_HCI_NODE_UP
     Netgraph message defined as follows.

	   #define NGM_HCI_NODE_UP 112 /* HCI -> Upper */
	   typedef struct {
		   u_int16_t pkt_size; /* max. ACL/SCO packet size (w/o hdr) */
		   u_int16_t num_pkts; /* ACL/SCO packet queue size */
		   u_int16_t reserved; /* place holder */
		   bdaddr_t  bdaddr;   /* bdaddr */
	   } ng_hci_node_up_ep;

HCI FLOW CONTROL

     HCI layer performs flow control on baseband connection basis (i.e., ACL
     and SCO link).  Each baseband connection has ``connection handle'' and
     queue of outgoing data packets.  Upper layers protocols are allowed to
     send up to (num_pkts - pending) packets at one time.  HCI layer will send
     NGM_HCI_SYNC_CON_QUEUE Netgraph messages to inform upper layers about
     current queue state for each connection handle.  The
     NGM_HCI_SYNC_CON_QUEUE Netgraph message is defined as follows.

	   #define NGM_HCI_SYNC_CON_QUEUE 113 /* HCI -> Upper */
	   typedef struct {
		   u_int16_t con_handle; /* connection handle */
		   u_int16_t completed;  /* number of completed packets */
	   } ng_hci_sync_con_queue_ep;

HOOKS

     This node type supports the following hooks:

     drv     Bluetooth Host Controller Transport Layer hook.  Single HCI
	     packet contained in single mbuf structure.

	     tooth raw HCI socket layer is connected to the hook.  Single HCI
	     frame contained in single mbuf structure.

BLUETOOTH UPPER LAYER PROTOCOLS INTERFACE (LP CONTROL MESSAGES)

     NGM_HCI_LP_CON_REQ
	     Requests the lower protocol to create a connection.  If a physi-
	     cal link to the remote device does not exist, this message must
	     be sent to the lower protocol (baseband) to establish the physi-
	     cal connection.

     NGM_HCI_LP_DISCON_REQ
	     Requests the lower protocol (baseband) to terminate a connection.

     NGM_HCI_LP_CON_CFM
	     Confirms success or failure of the NGM_HCI_LP_CON_REQ request to
	     establish a lower layer (baseband) connection.  This includes
	     passing the authentication challenge if authentication is
	     required to establish the physical link.

     NGM_HCI_LP_CON_IND
	     Indicates the lower protocol (baseband) has successfully estab-
	     lished incoming connection.

     NGM_HCI_LP_CON_RSP
	     A response accepting or rejecting the previous connection indica-
	     tion request.

     NGM_HCI_LP_DISCON_IND
	     Indicates the lower protocol (baseband) has terminated connec-
	     tion.  This could be a response to NGM_HCI_LP_DISCON_REQ or a
	     timeout event.

     NGM_HCI_LP_QOS_REQ
	     Requests the lower protocol (baseband) to accommodate a particu-
	     lar QoS parameter set.

     NGM_HCI_LP_QOS_CFM
	     Confirms success or failure of the request for a given quality of
	     service.

     NGM_HCI_LP_QOS_IND
	     Indicates the lower protocol (baseband) has detected a violation
	     of the QoS agreement.

NETGRAPH CONTROL MESSAGES

     This node type supports the generic control messages, plus the following:

     NGM_HCI_NODE_GET_STATE
	     Returns current state for the node.

     NGM_HCI_NODE_INIT
	     Turn on ``inited'' bit for the node.

     NGM_HCI_NODE_GET_DEBUG
	     Returns an integer containing the current debug level for the
	     node.

     NGM_HCI_NODE_SET_DEBUG

     NGM_HCI_NODE_GET_FEATURES
	     Returns the list of features supported by hardware (as cached by
	     the node).

     NGM_HCI_NODE_GET_NEIGHBOR_CACHE
	     Returns content of the neighbor cache.

     NGM_HCI_NODE_FLUSH_NEIGHBOR_CACHE
	     Remove all neighbor cache entries.

     NGM_HCI_NODE_GET_CON_LIST
	     Returns list of active baseband connections (i.e., ACL and SCO
	     links).

     NGM_HCI_NODE_GET_STAT
	     Returns various statistic counters.

     NGM_HCI_NODE_RESET_STAT
	     Resets all statistic counters to zero.

     NGM_HCI_NODE_SET_LINK_POLICY_SETTINGS_MASK
	     Sets current link policy settings mask.  After the new ACL con-
	     nection is created the HCI node will try set link policy for the
	     ACL connection.  By default, every supported Link Manager (LM)
	     mode will be enabled.  User can override this by setting link
	     policy settings mask which specifies LM modes to be enabled.

     NGM_HCI_NODE_GET_LINK_POLICY_SETTINGS_MASK
	     Returns current link policy settings mask.

     NGM_HCI_NODE_SET_PACKET_MASK
	     Sets current packet mask.	When new baseband (ACL or SCO) connec-
	     tion is created the HCI node will specify every packet type sup-
	     ported by the device.  User can override this by setting packet
	     mask which specifies packet types to be used for new baseband
	     connections.

     NGM_HCI_NODE_GET_PACKET_MASK
	     Returns current packet mask.

     NGM_HCI_NODE_SET_ROLE_SWITCH
	     Sets the value of the role switch.  Role switch is enabled when
	     this value is not zero.  This is the default state.  Note that
	     actual role switch at Bluetooth link level will only be performed
	     if hardware supports role switch and it was enabled.

     NGM_HCI_NODE_GET_ROLE_SWITCH
	     Returns the value of the role switch for the node.

SHUTDOWN

     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
     when all hooks have been disconnected.

BUGS

     Most likely.  Please report if found.

SEE ALSO

FreeBSD 5.4			 June 25, 2002			   FreeBSD 5.4

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