NG_H4(4)               FreeBSD Kernel Interfaces Manual               NG_H4(4)

NAME
     ng_h4 - Netgraph node type that is also an H4 line discipline

SYNOPSIS
     #include <sys/types.h>
     #include <netgraph/bluetooth/include/ng_h4.h>

DEPRECATION NOTICE
     The ng_h4 Netgraph node is not present in FreeBSD 14.0.

DESCRIPTION
     The h4 node type is both a persistent Netgraph node type and a H4 line
     discipline.  It implements a Bluetooth HCI UART transport layer as per
     chapter H4 of the Bluetooth Specification Book v1.1.  A new node is
     created when the corresponding line discipline, H4DISC, is registered on
     a tty device (see tty(4)).

     The node has a single hook called hook.  Incoming bytes received on the
     tty device are re-assembled into HCI frames (according to the length).
     Full HCI frames are sent out on the hook.  HCI frames received on hook
     are transmitted out on the tty device.  No modification to the data is
     performed in either direction.  While the line discipline is installed on
     a tty, the normal read and write operations are unavailable, returning
     EIO.

     Information about the node is available via the netgraph ioctl(2) command
     NGIOCGINFO.  This command returns a struct nodeinfo similar to the
     NGM_NODEINFO netgraph(4) control message.

HOOKS
     This node type supports the following hooks:

     hook      single HCI frame contained in single mbuf structure.

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

     NGM_H4_NODE_RESET
          Reset the node.

     NGM_H4_NODE_GET_STATE
          Returns current receiving state for the node.

     NGM_H4_NODE_GET_DEBUG
          Returns an integer containing the current debug level for the node.

     NGM_H4_NODE_SET_DEBUG
          This command takes an integer argument and sets current debug level
          for the node.

     NGM_H4_NODE_GET_QLEN
          Returns current length of outgoing queue for the node.

     NGM_H4_NODE_SET_QLEN
          This command takes an integer argument and sets maximum length of
          outgoing queue for the node.

     NGM_H4_NODE_GET_STAT
          Returns various statistic information for the node, such as: number
          of bytes (frames) sent, number of bytes (frames) received and number
          of input (output) errors.

     NGM_H4_NODE_RESET_STAT
          Reset all statistic counters to zero.

SHUTDOWN
     This node shuts down when the corresponding device is closed (or the line
     discipline is uninstalled on the device).

SEE ALSO
     ioctl(2), netgraph(4), tty(4), ngctl(8)

HISTORY
     The h4 node type was implemented in FreeBSD 5.0.

AUTHORS
     Maksim Yevmenkin <m_evmenkin@yahoo.com>

BUGS
     This node still uses spltty(9) to lock tty layer.  This is wrong.

FreeBSD 13.1-RELEASE-p6        November 27, 2021       FreeBSD 13.1-RELEASE-p6