Netgraph node type that is also an H4 line discipline
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
The node has a single hook called
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
Information about the node is available via the netgraph
command returns a struct nodeinfo similar to the
NGM_NODEINFO netgraph(4) control
This node type supports the following hooks:
- single HCI frame contained in single mbuf
This node type supports the generic control messages, plus the following:
- Reset the node.
- Returns current receiving state for the node.
- Returns an integer containing the current debug level for the node.
- This command takes an integer argument and sets current debug level for
- Returns current length of outgoing queue for the node.
- This command takes an integer argument and sets maximum length of outgoing
queue for the node.
- Returns various statistic information for the node, such as: number of
bytes (frames) sent, number of bytes (frames) received and number of input
- Reset all statistic counters to zero.
This node shuts down when the corresponding device is closed (or the line
discipline is uninstalled on the device).
h4 node type was implemented in
This node still uses spltty(9) to lock tty layer. This is