Manual Reference Pages - NG_TTY (4)
- netgraph node type that is also a TTY hook
node type is both a netgraph node type and a TTY hook.
The node has a single hook called
Incoming bytes received on the tty device are sent out on this hook,
and frames received on
are transmitted out on the tty device.
No modification to the data is performed in either direction.
While the hook is installed on a tty, the normal read and write
operations are unavailable, returning
Incoming data is delivered directly to ng_tty via the tty bypass hook as a
buffer pointer and length, this is converted to a mbuf and passed to the peer.
The node supports an optional
If the driver can not deliver data directly to the tty bypass hook then each
character is input one at a time.
If set to non-zero and bypass mode is unavailable, incoming
data from the tty device is queued until this character is seen.
This avoids sending lots of mbufs containing a small number of bytes,
but introduces potentially infinite latency.
The default hot character is 0x7e, consistent with
being connected to a
The hot character has no effect on the transmission of data.
This node type supports the following hooks:
serial data contained in
structures, with arbitrary inter-frame boundaries.
This node type supports the generic control messages, plus the following:
This command takes an integer argument and sets the hot character
from the lower 8 bits.
A hot character of zero disables queueing,
so that all received data is forwarded immediately.
Returns an integer containing the current hot character in the lower
This command takes integer process ID and file descriptor of open tty
and registers the tty hooks.
This node shuts down when the corresponding device is closed.
node type was implemented in
.Fx 4.0 .
.An Archie Cobbs Aq archie@FreeBSD.org
.An Andrew Thompson Aq thompsa@FreeBSD.org
The serial driver code also has a notion of a
Unfortunately, this value is statically defined in terms of the
line discipline and cannot be changed.
Therefore, if a hot character other than 0x7e (the default) is set for the
node, the node has no way to convey this information to the
serial driver, and sub-optimal performance may result.
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.