The uart(4) driver is an universal driver for various UART hardware.

It improves on sio(4) in the following areas:
o  Fully newbusified to allow for memory mapped I/O. This is a must
   for ia64 and sparc64,
o  Machine dependent code to take full advantage of machine and firm-
   ware specific ways to define serial consoles and/or debug ports.
o  Hardware abstraction layer to allow the driver to be used with
   various UARTs, such as the well-known ns8250 family of UARTs, the
   Siemens sab82532 or the Zilog Z8530. This is especially important
   for pc98 and sparc64 where it's common to have different UARTs,
o  The notion of system devices to unkludge low-level consoles and
   remote gdb ports and provides the mechanics necessary to support
   the keyboard on sparc64 (which is UART based).
o  The notion of a kernel interface so that a UART can be tied to
   something other than the well-known TTY interface. This is needed
   on sparc64 to present the user with a device and ioctl handling
   suitable for a keyboard, but also allows us to cleanly hide an
   UART when used as a debug port.

Following is a list of features and bugs/flaws specific to the ns8250
family of UARTs as compared to their support in sio(4):
o  The uart(4) driver determines the FIFO size and automaticly takes
   advantages of larger FIFOs and/or additional features. Note that
   since I don't have sufficient access to 16[679]5x UARTs, hardware
   flow control has not been enabled. This is almost trivial to do,
   provided one can test. The downside of this is that broken UARTs
   are more likely to not work correctly with uart(4). The need for
   tunables or knobs may be large enough to warrant their creation.
o  The uart(4) driver does not share the same bumpy history as sio(4)
   and will therefore not provide the necessary hooks, tweaks, quirks
   or work-arounds to deal with once common hardware. To that extend,
   uart(4) supports a subset of the UARTs that sio(4) supports. The
   question before us is whether the subset is sufficient for current
   hardware.
o  There is no support for multiport UARTs in uart(4). The decision
   behind this is that uart(4) deals with one EIA RS232-C interface.
   Packaging of multiple interfaces in a single chip or on a single
   expansion board is beyond the scope of uart(4) and is now mostly
   left for puc(4) to deal with. Lack of hardware made it impossible
   to actually implement such a dependency other than is present for
   the dual channel SAB82532 and Z8350 SCCs.

The current list of missing features is:
o  No configuration capabilities. A set of tunables and sysctls is
   being worked out. There are likely not going to be any or much
   compile-time knobs. Such configuration does not fit well with
   current hardware.
o  No support for the PPS API. This is partly dependent on the
   ability to configure uart(4) and partly dependent on having
   sufficient information to implement it properly.

As usual, the manpage is present but lacks the attention the
software has gotten.

1 files changed, 138 insertions, 0 deletions

diff --git a/sys/dev/uart/uart_if.m b/sys/dev/uart/uart_if.m
new file mode 100644
index 0000000..772883d
--- /dev/null
+++ b/sys/dev/uart/uart_if.m
@@ -0,0 +1,138 @@
+# Copyright (c) 2003 Marcel Moolenaar
+# All rights reserved.
+#
+# 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 ``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 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.
+#
+# $FreeBSD$
+
+#include <sys/bus.h>
+#include <machine/bus.h>
+#include <dev/uart/uart.h>
+#include <dev/uart/uart_bus.h>
+
+# The UART hardware interface. The core UART code is hardware independent.
+# The details of the hardware are abstracted by the UART hardware interface.
+
+INTERFACE uart;
+
+# attach() - attach hardware.
+# This method is called when the device is being attached. All resources
+# have been allocated. The transmit and receive buffers exist, but no
+# high-level (ie tty) initialization has been done yet.
+# The intend of this method is to setup the hardware for normal operation.
+METHOD int attach {
+	struct uart_softc *this;
+};
+
+# detach() - detach hardware.
+# This method is called when a device is being detached from its bus. It
+# is the first action performed, so even the high-level (ie tty) interface
+# is still operational.
+# The intend of this method is to disable the hardware.
+METHOD int detach {
+	struct uart_softc *this;
+};
+
+# flush() - flush FIFOs.
+# This method is called to flush the transmitter and/or the receiver as
+# specified by the what argument. Characters are expected to be lost.
+METHOD int flush {
+	struct uart_softc *this;
+	int	what;
+};
+
+# getsig() - get line and modem signals.
+# This method retrieves the DTE and DCE signals and their corresponding
+# delta bits. The delta bits include those corresponding to DTE signals
+# when they were changed by a call to setsig. The delta bits maintained
+# by the hardware driver are cleared as a side-effect. A second call to
+# this function will not have any delta bits set, unless there was a
+# change in the signals in the mean time.
+METHOD int getsig {
+	struct uart_softc *this;
+};
+
+# ioctl() - get or set miscellaneous parameters.
+# This method is the bitbucket method. It can (and will) be used when there's
+# something we need to set or get for which a new method is overkill. It's
+# used for example to set HW or SW flow-control.
+METHOD int ioctl {
+	struct uart_softc *this;
+	int request;
+	intptr_t data;
+};
+
+# ipend() - query UART for pending interrupts.
+# When an interrupt is signalled, the handler will call this method to find
+# out which of the interrupt sources needs attention. The handler will use
+# this information to dispatch service routines that deal with each of the
+# interrupt sources. An advantage of this approach is that it allows multi-
+# port drivers (like puc(4)) to query multiple devices concurrently and
+# service them on an interrupt priority basis. If the hardware cannot provide
+# the information reliably, it is free to service the interrupt and return 0,
+# meaning that no attention is required.
+METHOD int ipend {
+	struct uart_softc *this;
+}
+
+# param() - set communication parameters.
+# This method is called to change the communication parameters.
+METHOD int param {
+	struct uart_softc *this;
+	int	baudrate;
+	int	databits;
+	int	stopbits;
+	int	parity;
+};
+
+# probe() - detect hardware.
+# This method is called as part of the bus probe to make sure the
+# hardware exists. This function should also set the device description
+# to something that represents the hardware.
+METHOD int probe {
+	struct uart_softc *this;
+};
+
+# receive() - move data from the receive FIFO to the receive buffer.
+# This method is called to move received data to the receive buffer and
+# additionally should make sure the receive interrupt should be cleared.
+METHOD int receive {
+	struct uart_softc *this;
+};
+
+# setsig() - set line and modem signals.
+# This method allows changing DTE signals. The DTE delta bits indicate which
+# signals are to be changed and the DTE bits themselves indicate whether to
+# set or clear the signals. A subsequent call to getsig will return with the
+# DTE delta bits set of those DTE signals that did change by this method.
+METHOD int setsig {
+	struct uart_softc *this;
+	int	sig;
+};
+
+# transmit() - move data from the transmit buffer to the transmit FIFO.
+# This method is responsible for writing the Tx buffer to the UART and
+# additionally should make sure that a transmit interrupt is generated
+# when transmission is complete.
+METHOD int transmit {
+	struct uart_softc *this;
+};