@@ -36,6 +36,7 @@ static const char *dummy_hid = "device";
 static const struct acpi_device_id acpi_platform_device_ids[] = {
 
 	{ "PNP0D40" },
+	{ "INTF000" },
 
 	{ }
 };

@@ -35,6 +35,7 @@
 #include <linux/serial_core.h>
 #include <linux/serial.h>
 #include <linux/serial_8250.h>
+#include <linux/serial_bus.h>
 #include <linux/nmi.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>

@@ -2986,6 +2987,8 @@ void serial8250_resume_port(int line)
 	uart_resume_port(&serial8250_reg, port);
 }
 
+struct uart_device *uart_dummy;
+
 /*
  * Register a set of serial devices attached to a platform device.  The
  * list is terminated with a zero flags entry, which means we expect

@@ -2996,6 +2999,7 @@ static int __devinit serial8250_probe(struct platform_device *dev)
 	struct plat_serial8250_port *p = dev->dev.platform_data;
 	struct uart_8250_port uart;
 	int ret, i, irqflag = 0;
+	unsigned int dummy_line;
 
 	memset(&uart, 0, sizeof(uart));
 

@@ -3031,6 +3035,13 @@ static int __devinit serial8250_probe(struct platform_device *dev)
 				p->irq, ret);
 		}
 	}
+
+	dummy_line = serial8250_ports[nr_uarts-1].port.line;
+	pr_info("registering DUMMY at line %d.\n", dummy_line);
+	uart_dummy = uart_register_dummy(&dev->dev,
+					 serial8250_reg.tty_driver,
+					 dummy_line);
+
 	return 0;
 }
 

@@ -3041,6 +3052,7 @@ static int __devexit serial8250_remove(struct platform_device *dev)
 {
 	int i;
 
+	uart_unregister_device(uart_dummy);
 	for (i = 0; i < nr_uarts; i++) {
 		struct uart_8250_port *up = &serial8250_ports[i];
 

@@ -0,0 +1,129 @@
+/*
+ * 8250_dummy.c: Dummy 8250 UART target device enumerator
+ *
+ * Copyright (c) 2012, Intel Corporation
+ * Author: Lv Zheng <lv.zheng@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_bus.h>
+#include <linux/acpi.h>
+#include <linux/acpi_uart.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct dummy8250_data {
+	int	last_lcr;
+	int	line;
+};
+
+static void dummy8250_serial_out(struct uart_port *p, int offset, int value)
+{
+}
+
+static unsigned int dummy8250_serial_in(struct uart_port *p, int offset)
+{
+	return 0;
+}
+
+struct klist *dummy8250_mgr;
+int dummy8250_num;
+
+static int __devinit dummy8250_probe(struct platform_device *pdev)
+{
+	struct uart_8250_port uart = {};
+	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	struct dummy8250_data *data;
+#ifdef CONFIG_ACPI_UART
+	struct klist *mgr;
+#endif
+
+	dev_info(&pdev->dev, "1\n");
+	if (!regs) {
+		dev_err(&pdev->dev, "no registers defined\n");
+		return -EINVAL;
+	}
+
+	dev_info(&pdev->dev, "2\n");
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	uart.port.private_data = data;
+
+	spin_lock_init(&uart.port.lock);
+	uart.port.mapbase = regs->start;
+	uart.port.type = PORT_8250;
+	uart.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP |
+		UPF_FIXED_PORT | UPF_FIXED_TYPE;
+	uart.port.dev = &pdev->dev;
+
+	uart.port.iotype = UPIO_MEM;
+	uart.port.serial_in = dummy8250_serial_in;
+	uart.port.serial_out = dummy8250_serial_out;
+	uart.port.uartclk = 40000000;
+
+	dev_info(&pdev->dev, "3\n");
+	data->line = serial8250_register_8250_port(&uart);
+	if (data->line < 0)
+		return data->line;
+
+#ifdef CONFIG_ACPI_UART
+	dev_info(&pdev->dev, "4\n");
+	mgr = acpi_uart_register_devices(dummy8250_mgr,
+					 &pdev->dev,
+					 serial8250_reg.tty_driver,
+					 data->line);
+	if (mgr) {
+		dummy8250_mgr = mgr;
+		dummy8250_num++;
+	}
+#endif
+	dev_info(&pdev->dev, "5\n");
+	platform_set_drvdata(pdev, data);
+
+	return 0;
+}
+
+static int __devexit dummy8250_remove(struct platform_device *pdev)
+{
+	struct dummy8250_data *data = platform_get_drvdata(pdev);
+
+#ifdef CONFIG_ACPI_UART
+	dummy8250_num--;
+	if (!dummy8250_num)
+		acpi_uart_unregister_devices(dummy8250_mgr);
+#endif
+	serial8250_unregister_port(data->line);
+
+	return 0;
+}
+
+static const struct acpi_device_id dummy8250_match[] = {
+	{ .id = "INTF000" },
+	{ /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(acpi, dummy8250_match);
+
+static struct platform_driver dummy8250_platform_driver = {
+	.driver = {
+		.name			= "dummy-uart",
+		.owner			= THIS_MODULE,
+		.acpi_match_table	= dummy8250_match,
+	},
+	.probe				= dummy8250_probe,
+	.remove				= __devexit_p(dummy8250_remove),
+};
+
+module_platform_driver(dummy8250_platform_driver);
+
+MODULE_AUTHOR("Lv Zheng");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Dummy 8250 serial port driver");

@@ -270,6 +270,16 @@ config SERIAL_8250_DW
 	  Selecting this option will enable handling of the extra features
 	  present in the Synopsys DesignWare APB UART.
 
+config SERIAL_8250_DUMMY
+	tristate "Support for dummy ACPI 8250"
+	depends on SERIAL_8250 && ACPI
+	help
+	  Selecting this option will enable a test UART target device DUMMY
+	  under the ISA serial8250 and a test UART host adapter INTF000
+	  as an platform device for the purpose of testing the ACPI UART
+	  enumeration support.
+	  If unsure, say "N" here.
+
 config SERIAL_8250_EM
 	tristate "Support for Emma Mobile intergrated serial port"
 	depends on SERIAL_8250 && ARM && HAVE_CLK

@@ -19,3 +19,4 @@ obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
 obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
 obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
 obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
+obj-$(CONFIG_SERIAL_8250_DUMMY)		+= 8250_dummy.o

@@ -393,6 +393,23 @@ void uart_del_adapter(struct klist *adap)
 }
 EXPORT_SYMBOL_GPL(uart_del_adapter);
 
+static struct uart_board_info dummy_target = {
+	.type = "DUMMY",
+	.baud = 115200,
+	.cflag = CS8 | CSTOPB | CRTSCTS,
+	.iflag = (IXON | IXOFF),
+	.mctrl = TIOCM_LE | TIOCM_RTS,
+};
+
+struct uart_device *uart_register_dummy(struct device *dev,
+					struct tty_driver *drv,
+					unsigned int line)
+{
+	dummy_target.line = line;
+	return uart_register_device(NULL, dev, drv, &dummy_target);
+}
+EXPORT_SYMBOL_GPL(uart_register_dummy);
+
 struct bus_type uart_bus_type = {
 	.name		= "uart",
 };

@@ -118,4 +118,9 @@ struct device *uart_tty_find(struct tty_driver *drv, unsigned int line,
 			     struct device *dev);
 void uart_tty_name(struct tty_driver *driver, unsigned int line, char *p);
 
+/* Test dummy device registration */
+struct uart_device *uart_register_dummy(struct device *dev,
+					struct tty_driver *drv,
+					unsigned int line);
+
 #endif /* LINUX_SERIAL_BUS_H */