.\"-
.\" Copyright (c) 2012 Robert N. M. Watson
.\" All rights reserved.
.\"
.\" This software was developed by SRI International and the University of
.\" Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
.\" ("CTSRD"), as part of the DARPA CRASH research programme.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 18, 2012
.Dt ALTERA_JTAG_UART 4
.Os
.Sh NAME
.Nm altera_jtag_uart
.Nd driver for the Altera JTAG UART Core
.Sh SYNOPSIS
.Cd "device altera_jtag_uart"
.Pp
In
.Pa /boot/device.hints :
.Cd hint.altera_jtag_uart.0.at="nexus0"
.Cd hint.altera_jtag_uart.0.maddr=0x7f000000
.Cd hint.altera_jtag_uart.0.msize=0x40
.Cd hint.altera_jtag_uart.0.irq=0
.Cd hint.altera_jtag_uart.1.at="nexus0"
.Cd hint.altera_jtag_uart.1.maddr=0x7f001000
.Cd hint.altera_jtag_uart.1.msize=0x40
.Sh DESCRIPTION
The
.Nm
device driver provides support for the Altera JTAG UART core, which allows
multiple UART-like streams to be carried over JTAG.
.Nm
allows JTAG UART streams to be attached to both the low-level console
interface, used for direct kernel input and output, and the
.Xr tty 4
layer, to be used with
.Xr ttys 5
and
.Xr login 1 .
Sequential Altera JTAG UART devices will appear as
.Li ttyu0 ,
.Li ttyu1 ,
etc.
.Sh HARDWARE
Altera JTAG UART devices can be connected to using Altera's
.Pa nios2-terminal
program, with the instance selected using the
.Li --instance
argument on the management host.
.Nm
supports JTAG UART cores with or without interrupt lines connected; if the
.Li irq
portion of the
.Pa device.hints
entry is omitted, the driver will poll rather than configure interrupts.
.Sh SEE ALSO
.Xr login 1 ,
.Xr tty 4 ,
.Xr ttys 5
.Rs
.%T Altera Embedded Peripherals IP User Guide
.%D June 2011
.%I Altera Corporation
.%U http://www.altera.com/literature/ug/ug_embedded_ip.pdf
.Re
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 10.0 .
.Sh AUTHORS
The
.Nm
device driver and this manual page were
developed by SRI International and the University of Cambridge Computer
Laboratory under DARPA/AFRL contract
.Pq FA8750-10-C-0237
.Pq Do CTSRD Dc ,
as part of the DARPA CRASH research programme.
This device driver was written by
.An Robert N. M. Watson .
.Sh BUGS
.Nm
must dynamically poll to detect when JTAG is present, in order to disable flow
control in the event that there is no receiving endpoint.
Otherwise, the boot may hang waiting for the JTAG client to be attached, and
user processes attached to JTAG UART devices might block indefinitely.
However, there is no way to flush the output buffer once JTAG is detected to
have disappeared; this means that a small amount of stale output data will
remain in the output buffer, being displayed by
.Li nios2-terminal
when it is connected.
Loss of JTAG will not generate a hang-up event, as that is rarely the desired
behaviour.
.Pp
.Li nios2-terminal
does not place the client-side TTY in raw mode, and so by default will not
pass all control characters through to the UART.