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, 83 insertions, 0 deletions

diff --git a/sys/dev/uart/uart_bus_acpi.c b/sys/dev/uart/uart_bus_acpi.c
new file mode 100644
index 0000000..ac75f0c
--- /dev/null
+++ b/sys/dev/uart/uart_bus_acpi.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2001 M. Warner Losh.  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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/conf.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+#include <machine/bus.h>
+#include <sys/rman.h>
+#include <machine/resource.h>
+
+#include <isa/isavar.h>
+
+#include <dev/uart/uart.h>
+#include <dev/uart/uart_bus.h>
+
+static int uart_acpi_probe(device_t dev);
+
+static device_method_t uart_acpi_methods[] = {
+	/* Device interface */
+	DEVMETHOD(device_probe,		uart_acpi_probe),
+	DEVMETHOD(device_attach,	uart_bus_attach),
+	DEVMETHOD(device_detach,	uart_bus_detach),
+	{ 0, 0 }
+};
+
+static driver_t uart_acpi_driver = {
+	uart_driver_name,
+	uart_acpi_methods,
+	sizeof(struct uart_softc),
+};
+
+static struct isa_pnp_id acpi_ns8250_ids[] = {
+	{0x0005d041, "Standard PC COM port"},		/* PNP0500 */
+	{0x0105d041, "16550A-compatible COM port"},	/* PNP0501 */
+	{0}
+};
+
+static int
+uart_acpi_probe(device_t dev)
+{
+	struct uart_softc *sc;
+	device_t parent;
+
+	parent = device_get_parent(dev);
+	sc = device_get_softc(dev);
+
+	if (!ISA_PNP_PROBE(parent, dev, acpi_ns8250_ids)) {
+		sc->sc_class = &uart_ns8250_class;
+		return (uart_bus_probe(dev, 0, 0, 0));
+	}
+
+	/* Add checks for non-ns8250 IDs here. */
+	return (ENXIO);
+}
+
+DRIVER_MODULE(uart, acpi, uart_acpi_driver, uart_devclass, 0, 0);