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.\" $Id: ng_h4.4,v 1.2 2003/05/21 19:37:35 max Exp $
.\"
.Dd November 27, 2021
.Dt NG_H4 4
.Os
.Sh NAME
.Nm ng_h4
.Nd Netgraph node type that is also an H4 line discipline
.Sh SYNOPSIS
.In sys/types.h
.In netgraph/bluetooth/include/ng_h4.h
.Sh DEPRECATION NOTICE
The
.Nm
Netgraph node is not present in
.Fx 14.0 .
.Sh DESCRIPTION
The
.Nm 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,
.Dv H4DISC ,
is registered on a tty device (see
.Xr tty 4 ) .
.Pp
The node has a single hook called
.Dv 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
.Dv 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
.Er EIO .
.Pp
Information about the node is available via the netgraph
.Xr ioctl 2
command
.Dv NGIOCGINFO .
This command returns a
.Vt "struct nodeinfo"
similar to the
.Dv NGM_NODEINFO
.Xr netgraph 4
control message.
.Sh HOOKS
This node type supports the following hooks:
.Bl -tag -width ".Va hook"
.It Va hook
single HCI frame contained in single
.Vt mbuf
structure.
.El
.Sh CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
.Bl -tag -width foo
.It Dv NGM_H4_NODE_RESET
Reset the node.
.It Dv NGM_H4_NODE_GET_STATE
Returns current receiving state for the node.
.It Dv NGM_H4_NODE_GET_DEBUG
Returns an integer containing the current debug level for the node.
.It Dv NGM_H4_NODE_SET_DEBUG
This command takes an integer argument and sets current debug level
for the node.
.It Dv NGM_H4_NODE_GET_QLEN
Returns current length of outgoing queue for the node.
.It Dv NGM_H4_NODE_SET_QLEN
This command takes an integer argument and sets maximum length of
outgoing queue for the node.
.It Dv 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.
.It Dv NGM_H4_NODE_RESET_STAT
Reset all statistic counters to zero.
.El
.Sh SHUTDOWN
This node shuts down when the corresponding device is closed
(or the line discipline is uninstalled on the device).
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr netgraph 4 ,
.Xr tty 4 ,
.Xr ngctl 8
.Sh HISTORY
The
.Nm h4
node type was implemented in
.Fx 5.0 .
.Sh AUTHORS
.An Maksim Yevmenkin Aq Mt m_evmenkin@yahoo.com
.Sh BUGS
This node still uses
.Xr spltty 9
to lock tty layer.
This is wrong.