Revert "Revert "ACPI: dock driver""

This reverts 953969ddf5b049361ed1e8471cc43dc4134d2a6f commit.

4 files changed, 770 insertions, 0 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 290c767..fef7bab 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -133,6 +133,13 @@ config ACPI_FAN
 	  This driver adds support for ACPI fan devices, allowing user-mode 
 	  applications to perform basic fan control (on, off, status).
 
+config ACPI_DOCK
+	tristate "Dock"
+	depends on !ACPI_IBM_DOCK
+	default y
+	help
+	  This driver adds support for ACPI controlled docking stations
+
 config ACPI_PROCESSOR
 	tristate "Processor"
 	default y
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index bb5b80a..bce7ca2 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_ACPI_BATTERY)	+= battery.o
 obj-$(CONFIG_ACPI_BUTTON)	+= button.o
 obj-$(CONFIG_ACPI_EC)		+= ec.o
 obj-$(CONFIG_ACPI_FAN)		+= fan.o
+obj-$(CONFIG_ACPI_DOCK)		+= dock.o
 obj-$(CONFIG_ACPI_VIDEO)	+= video.o 
 obj-$(CONFIG_ACPI_HOTKEY)	+= hotkey.o
 obj-y				+= pci_root.o pci_link.o pci_irq.o pci_bind.o
diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
new file mode 100644
index 0000000..510a945
--- /dev/null
+++ b/drivers/acpi/dock.c
@@ -0,0 +1,739 @@
+/*
+ *  dock.c - ACPI dock station driver
+ *
+ *  Copyright (C) 2006 Kristen Carlson Accardi <kristen.c.accardi@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; either version 2 of the License, or (at
+ *  your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/notifier.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_drivers.h>
+
+#define ACPI_DOCK_DRIVER_NAME "ACPI Dock Station Driver"
+
+ACPI_MODULE_NAME("dock")
+MODULE_AUTHOR("Kristen Carlson Accardi");
+MODULE_DESCRIPTION(ACPI_DOCK_DRIVER_NAME);
+MODULE_LICENSE("GPL");
+
+static struct atomic_notifier_head dock_notifier_list;
+
+struct dock_station {
+	acpi_handle handle;
+	unsigned long last_dock_time;
+	u32 flags;
+	spinlock_t dd_lock;
+	spinlock_t hp_lock;
+	struct list_head dependent_devices;
+	struct list_head hotplug_devices;
+};
+
+struct dock_dependent_device {
+	struct list_head list;
+	struct list_head hotplug_list;
+	acpi_handle handle;
+	acpi_notify_handler handler;
+	void *context;
+};
+
+#define DOCK_DOCKING	0x00000001
+#define DOCK_EVENT	KOBJ_DOCK
+#define UNDOCK_EVENT	KOBJ_UNDOCK
+
+static struct dock_station *dock_station;
+
+/*****************************************************************************
+ *                         Dock Dependent device functions                   *
+ *****************************************************************************/
+/**
+ *  alloc_dock_dependent_device - allocate and init a dependent device
+ *  @handle: the acpi_handle of the dependent device
+ *
+ *  Allocate memory for a dependent device structure for a device referenced
+ *  by the acpi handle
+ */
+static struct dock_dependent_device *
+alloc_dock_dependent_device(acpi_handle handle)
+{
+	struct dock_dependent_device *dd;
+
+	dd = kzalloc(sizeof(*dd), GFP_KERNEL);
+	if (dd) {
+		dd->handle = handle;
+		INIT_LIST_HEAD(&dd->list);
+		INIT_LIST_HEAD(&dd->hotplug_list);
+	}
+	return dd;
+}
+
+/**
+ * add_dock_dependent_device - associate a device with the dock station
+ * @ds: The dock station
+ * @dd: The dependent device
+ *
+ * Add the dependent device to the dock's dependent device list.
+ */
+static void
+add_dock_dependent_device(struct dock_station *ds,
+			  struct dock_dependent_device *dd)
+{
+	spin_lock(&ds->dd_lock);
+	list_add_tail(&dd->list, &ds->dependent_devices);
+	spin_unlock(&ds->dd_lock);
+}
+
+/**
+ * dock_add_hotplug_device - associate a hotplug handler with the dock station
+ * @ds: The dock station
+ * @dd: The dependent device struct
+ *
+ * Add the dependent device to the dock's hotplug device list
+ */
+static void
+dock_add_hotplug_device(struct dock_station *ds,
+			struct dock_dependent_device *dd)
+{
+	spin_lock(&ds->hp_lock);
+	list_add_tail(&dd->hotplug_list, &ds->hotplug_devices);
+	spin_unlock(&ds->hp_lock);
+}
+
+/**
+ * dock_del_hotplug_device - remove a hotplug handler from the dock station
+ * @ds: The dock station
+ * @dd: the dependent device struct
+ *
+ * Delete the dependent device from the dock's hotplug device list
+ */
+static void
+dock_del_hotplug_device(struct dock_station *ds,
+			struct dock_dependent_device *dd)
+{
+	spin_lock(&ds->hp_lock);
+	list_del(&dd->hotplug_list);
+	spin_unlock(&ds->hp_lock);
+}
+
+/**
+ * find_dock_dependent_device - get a device dependent on this dock
+ * @ds: the dock station
+ * @handle: the acpi_handle of the device we want
+ *
+ * iterate over the dependent device list for this dock.  If the
+ * dependent device matches the handle, return.
+ */
+static struct dock_dependent_device *
+find_dock_dependent_device(struct dock_station *ds, acpi_handle handle)
+{
+	struct dock_dependent_device *dd;
+
+	spin_lock(&ds->dd_lock);
+	list_for_each_entry(dd, &ds->dependent_devices, list) {
+		if (handle == dd->handle) {
+			spin_unlock(&ds->dd_lock);
+			return dd;
+		}
+	}
+	spin_unlock(&ds->dd_lock);
+	return NULL;
+}
+
+/*****************************************************************************
+ *                         Dock functions                                    *
+ *****************************************************************************/
+/**
+ * is_dock - see if a device is a dock station
+ * @handle: acpi handle of the device
+ *
+ * If an acpi object has a _DCK method, then it is by definition a dock
+ * station, so return true.
+ */
+static int is_dock(acpi_handle handle)
+{
+	acpi_status status;
+	acpi_handle tmp;
+
+	status = acpi_get_handle(handle, "_DCK", &tmp);
+	if (ACPI_FAILURE(status))
+		return 0;
+	return 1;
+}
+
+/**
+ * is_dock_device - see if a device is on a dock station
+ * @handle: acpi handle of the device
+ *
+ * If this device is either the dock station itself,
+ * or is a device dependent on the dock station, then it
+ * is a dock device
+ */
+int is_dock_device(acpi_handle handle)
+{
+	if (!dock_station)
+		return 0;
+
+	if (is_dock(handle) || find_dock_dependent_device(dock_station, handle))
+		return 1;
+
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(is_dock_device);
+
+/**
+ * dock_present - see if the dock station is present.
+ * @ds: the dock station
+ *
+ * execute the _STA method.  note that present does not
+ * imply that we are docked.
+ */
+static int dock_present(struct dock_station *ds)
+{
+	unsigned long sta;
+	acpi_status status;
+
+	if (ds) {
+		status = acpi_evaluate_integer(ds->handle, "_STA", NULL, &sta);
+		if (ACPI_SUCCESS(status) && sta)
+			return 1;
+	}
+	return 0;
+}
+
+
+
+/**
+ * dock_create_acpi_device - add new devices to acpi
+ * @handle - handle of the device to add
+ *
+ *  This function will create a new acpi_device for the given
+ *  handle if one does not exist already.  This should cause
+ *  acpi to scan for drivers for the given devices, and call
+ *  matching driver's add routine.
+ *
+ *  Returns a pointer to the acpi_device corresponding to the handle.
+ */
+static struct acpi_device * dock_create_acpi_device(acpi_handle handle)
+{
+	struct acpi_device *device = NULL;
+	struct acpi_device *parent_device;
+	acpi_handle parent;
+	int ret;
+
+	if (acpi_bus_get_device(handle, &device)) {
+		/*
+		 * no device created for this object,
+		 * so we should create one.
+		 */
+		acpi_get_parent(handle, &parent);
+		if (acpi_bus_get_device(parent, &parent_device))
+			parent_device = NULL;
+
+		ret = acpi_bus_add(&device, parent_device, handle,
+			ACPI_BUS_TYPE_DEVICE);
+		if (ret) {
+			pr_debug("error adding bus, %x\n",
+				-ret);
+			return NULL;
+		}
+	}
+	return device;
+}
+
+/**
+ * dock_remove_acpi_device - remove the acpi_device struct from acpi
+ * @handle - the handle of the device to remove
+ *
+ *  Tell acpi to remove the acpi_device.  This should cause any loaded
+ *  driver to have it's remove routine called.
+ */
+static void dock_remove_acpi_device(acpi_handle handle)
+{
+	struct acpi_device *device;
+	int ret;
+
+	if (!acpi_bus_get_device(handle, &device)) {
+		ret = acpi_bus_trim(device, 1);
+		if (ret)
+			pr_debug("error removing bus, %x\n", -ret);
+	}
+}
+
+
+/**
+ * hotplug_dock_devices - insert or remove devices on the dock station
+ * @ds: the dock station
+ * @event: either bus check or eject request
+ *
+ * Some devices on the dock station need to have drivers called
+ * to perform hotplug operations after a dock event has occurred.
+ * Traverse the list of dock devices that have registered a
+ * hotplug handler, and call the handler.
+ */
+static void hotplug_dock_devices(struct dock_station *ds, u32 event)
+{
+	struct dock_dependent_device *dd;
+
+	spin_lock(&ds->hp_lock);
+
+	/*
+	 * First call driver specific hotplug functions
+	 */
+	list_for_each_entry(dd, &ds->hotplug_devices, hotplug_list) {
+		if (dd->handler)
+			dd->handler(dd->handle, event, dd->context);
+	}
+
+	/*
+	 * Now make sure that an acpi_device is created for each
+	 * dependent device, or removed if this is an eject request.
+	 * This will cause acpi_drivers to be stopped/started if they
+	 * exist
+	 */
+	list_for_each_entry(dd, &ds->dependent_devices, list) {
+		if (event == ACPI_NOTIFY_EJECT_REQUEST)
+			dock_remove_acpi_device(dd->handle);
+		else
+			dock_create_acpi_device(dd->handle);
+	}
+	spin_unlock(&ds->hp_lock);
+}
+
+static void dock_event(struct dock_station *ds, u32 event, int num)
+{
+	struct acpi_device *device;
+
+	device = dock_create_acpi_device(ds->handle);
+	if (device)
+		kobject_uevent(&device->kobj, num);
+}
+
+/**
+ * eject_dock - respond to a dock eject request
+ * @ds: the dock station
+ *
+ * This is called after _DCK is called, to execute the dock station's
+ * _EJ0 method.
+ */
+static void eject_dock(struct dock_station *ds)
+{
+	struct acpi_object_list arg_list;
+	union acpi_object arg;
+	acpi_status status;
+	acpi_handle tmp;
+
+	/* all dock devices should have _EJ0, but check anyway */
+	status = acpi_get_handle(ds->handle, "_EJ0", &tmp);
+	if (ACPI_FAILURE(status)) {
+		pr_debug("No _EJ0 support for dock device\n");
+		return;
+	}
+
+	arg_list.count = 1;
+	arg_list.pointer = &arg;
+	arg.type = ACPI_TYPE_INTEGER;
+	arg.integer.value = 1;
+
+	if (ACPI_FAILURE(acpi_evaluate_object(ds->handle, "_EJ0",
+					      &arg_list, NULL)))
+		pr_debug("Failed to evaluate _EJ0!\n");
+}
+
+/**
+ * handle_dock - handle a dock event
+ * @ds: the dock station
+ * @dock: to dock, or undock - that is the question
+ *
+ * Execute the _DCK method in response to an acpi event
+ */
+static void handle_dock(struct dock_station *ds, int dock)
+{
+	acpi_status status;
+	struct acpi_object_list arg_list;
+	union acpi_object arg;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	struct acpi_buffer name_buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+
+	acpi_get_name(ds->handle, ACPI_FULL_PATHNAME, &name_buffer);
+	obj = name_buffer.pointer;
+
+	printk(KERN_INFO PREFIX "%s\n", dock ? "docking" : "undocking");
+
+	/* _DCK method has one argument */
+	arg_list.count = 1;
+	arg_list.pointer = &arg;
+	arg.type = ACPI_TYPE_INTEGER;
+	arg.integer.value = dock;
+	status = acpi_evaluate_object(ds->handle, "_DCK", &arg_list, &buffer);
+	if (ACPI_FAILURE(status))
+		pr_debug("%s: failed to execute _DCK\n", obj->string.pointer);
+	kfree(buffer.pointer);
+	kfree(name_buffer.pointer);
+}
+
+static inline void dock(struct dock_station *ds)
+{
+	handle_dock(ds, 1);
+}
+
+static inline void undock(struct dock_station *ds)
+{
+	handle_dock(ds, 0);
+}
+
+static inline void begin_dock(struct dock_station *ds)
+{
+	ds->flags |= DOCK_DOCKING;
+}
+
+static inline void complete_dock(struct dock_station *ds)
+{
+	ds->flags &= ~(DOCK_DOCKING);
+	ds->last_dock_time = jiffies;
+}
+
+/**
+ * dock_in_progress - see if we are in the middle of handling a dock event
+ * @ds: the dock station
+ *
+ * Sometimes while docking, false dock events can be sent to the driver
+ * because good connections aren't made or some other reason.  Ignore these
+ * if we are in the middle of doing something.
+ */
+static int dock_in_progress(struct dock_station *ds)
+{
+	if ((ds->flags & DOCK_DOCKING) ||
+	    time_before(jiffies, (ds->last_dock_time + HZ)))
+		return 1;
+	return 0;
+}
+
+/**
+ * register_dock_notifier - add yourself to the dock notifier list
+ * @nb: the callers notifier block
+ *
+ * If a driver wishes to be notified about dock events, they can
+ * use this function to put a notifier block on the dock notifier list.
+ * this notifier call chain will be called after a dock event, but
+ * before hotplugging any new devices.
+ */
+int register_dock_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&dock_notifier_list, nb);
+}
+
+EXPORT_SYMBOL_GPL(register_dock_notifier);
+
+/**
+ * unregister_dock_notifier - remove yourself from the dock notifier list
+ * @nb: the callers notifier block
+ */
+void unregister_dock_notifier(struct notifier_block *nb)
+{
+	atomic_notifier_chain_unregister(&dock_notifier_list, nb);
+}
+
+EXPORT_SYMBOL_GPL(unregister_dock_notifier);
+
+/**
+ * register_hotplug_dock_device - register a hotplug function
+ * @handle: the handle of the device
+ * @handler: the acpi_notifier_handler to call after docking
+ * @context: device specific data
+ *
+ * If a driver would like to perform a hotplug operation after a dock
+ * event, they can register an acpi_notifiy_handler to be called by
+ * the dock driver after _DCK is executed.
+ */
+int
+register_hotplug_dock_device(acpi_handle handle, acpi_notify_handler handler,
+			     void *context)
+{
+	struct dock_dependent_device *dd;
+
+	if (!dock_station)
+		return -ENODEV;
+
+	/*
+	 * make sure this handle is for a device dependent on the dock,
+	 * this would include the dock station itself
+	 */
+	dd = find_dock_dependent_device(dock_station, handle);
+	if (dd) {
+		dd->handler = handler;
+		dd->context = context;
+		dock_add_hotplug_device(dock_station, dd);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+EXPORT_SYMBOL_GPL(register_hotplug_dock_device);
+
+/**
+ * unregister_hotplug_dock_device - remove yourself from the hotplug list
+ * @handle: the acpi handle of the device
+ */
+void unregister_hotplug_dock_device(acpi_handle handle)
+{
+	struct dock_dependent_device *dd;
+
+	if (!dock_station)
+		return;
+
+	dd = find_dock_dependent_device(dock_station, handle);
+	if (dd)
+		dock_del_hotplug_device(dock_station, dd);
+}
+
+EXPORT_SYMBOL_GPL(unregister_hotplug_dock_device);
+
+/**
+ * dock_notify - act upon an acpi dock notification
+ * @handle: the dock station handle
+ * @event: the acpi event
+ * @data: our driver data struct
+ *
+ * If we are notified to dock, then check to see if the dock is
+ * present and then dock.  Notify all drivers of the dock event,
+ * and then hotplug and devices that may need hotplugging.  For undock
+ * check to make sure the dock device is still present, then undock
+ * and hotremove all the devices that may need removing.
+ */
+static void dock_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct dock_station *ds = (struct dock_station *)data;
+
+	switch (event) {
+	case ACPI_NOTIFY_BUS_CHECK:
+		if (!dock_in_progress(ds) && dock_present(ds)) {
+			begin_dock(ds);
+			dock(ds);
+			if (!dock_present(ds)) {
+				printk(KERN_ERR PREFIX "Unable to dock!\n");
+				break;
+			}
+			atomic_notifier_call_chain(&dock_notifier_list,
+						   event, NULL);
+			hotplug_dock_devices(ds, event);
+			complete_dock(ds);
+			dock_event(ds, event, DOCK_EVENT);
+		}
+		break;
+	case ACPI_NOTIFY_DEVICE_CHECK:
+	/*
+         * According to acpi spec 3.0a, if a DEVICE_CHECK notification
+         * is sent and _DCK is present, it is assumed to mean an
+         * undock request.  This notify routine will only be called
+         * for objects defining _DCK, so we will fall through to eject
+         * request here.  However, we will pass an eject request through
+	 * to the driver who wish to hotplug.
+         */
+	case ACPI_NOTIFY_EJECT_REQUEST:
+		if (!dock_in_progress(ds) && dock_present(ds)) {
+			/*
+			 * here we need to generate the undock
+			 * event prior to actually doing the undock
+			 * so that the device struct still exists.
+			 */
+			dock_event(ds, event, UNDOCK_EVENT);
+			hotplug_dock_devices(ds, ACPI_NOTIFY_EJECT_REQUEST);
+			undock(ds);
+			eject_dock(ds);
+			if (dock_present(ds))
+				printk(KERN_ERR PREFIX "Unable to undock!\n");
+		}
+		break;
+	default:
+		printk(KERN_ERR PREFIX "Unknown dock event %d\n", event);
+	}
+}
+
+/**
+ * find_dock_devices - find devices on the dock station
+ * @handle: the handle of the device we are examining
+ * @lvl: unused
+ * @context: the dock station private data
+ * @rv: unused
+ *
+ * This function is called by acpi_walk_namespace.  It will
+ * check to see if an object has an _EJD method.  If it does, then it
+ * will see if it is dependent on the dock station.
+ */
+static acpi_status
+find_dock_devices(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	acpi_status status;
+	acpi_handle tmp;
+	struct dock_station *ds = (struct dock_station *)context;
+	struct dock_dependent_device *dd;
+
+	status = acpi_bus_get_ejd(handle, &tmp);
+	if (ACPI_FAILURE(status))
+		return AE_OK;
+
+	if (tmp == ds->handle) {
+		dd = alloc_dock_dependent_device(handle);
+		if (dd)
+			add_dock_dependent_device(ds, dd);
+	}
+
+	return AE_OK;
+}
+
+/**
+ * dock_add - add a new dock station
+ * @handle: the dock station handle
+ *
+ * allocated and initialize a new dock station device.  Find all devices
+ * that are on the dock station, and register for dock event notifications.
+ */
+static int dock_add(acpi_handle handle)
+{
+	int ret;
+	acpi_status status;
+	struct dock_dependent_device *dd;
+
+	/* allocate & initialize the dock_station private data */
+	dock_station = kzalloc(sizeof(*dock_station), GFP_KERNEL);
+	if (!dock_station)
+		return -ENOMEM;
+	dock_station->handle = handle;
+	dock_station->last_dock_time = jiffies - HZ;
+	INIT_LIST_HEAD(&dock_station->dependent_devices);
+	INIT_LIST_HEAD(&dock_station->hotplug_devices);
+	spin_lock_init(&dock_station->dd_lock);
+	spin_lock_init(&dock_station->hp_lock);
+
+	/* Find dependent devices */
+	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+			    ACPI_UINT32_MAX, find_dock_devices, dock_station,
+			    NULL);
+
+	/* add the dock station as a device dependent on itself */
+	dd = alloc_dock_dependent_device(handle);
+	if (!dd) {
+		kfree(dock_station);
+		return -ENOMEM;
+	}
+	add_dock_dependent_device(dock_station, dd);
+
+	/* register for dock events */
+	status = acpi_install_notify_handler(dock_station->handle,
+					     ACPI_SYSTEM_NOTIFY,
+					     dock_notify, dock_station);
+
+	if (ACPI_FAILURE(status)) {
+		printk(KERN_ERR PREFIX "Error installing notify handler\n");
+		ret = -ENODEV;
+		goto dock_add_err;
+	}
+
+	printk(KERN_INFO PREFIX "%s \n", ACPI_DOCK_DRIVER_NAME);
+
+	return 0;
+
+dock_add_err:
+	kfree(dock_station);
+	kfree(dd);
+	return ret;
+}
+
+/**
+ * dock_remove - free up resources related to the dock station
+ */
+static int dock_remove(void)
+{
+	struct dock_dependent_device *dd, *tmp;
+	acpi_status status;
+
+	if (!dock_station)
+		return 0;
+
+	/* remove dependent devices */
+	list_for_each_entry_safe(dd, tmp, &dock_station->dependent_devices,
+				 list)
+	    kfree(dd);
+
+	/* remove dock notify handler */
+	status = acpi_remove_notify_handler(dock_station->handle,
+					    ACPI_SYSTEM_NOTIFY,
+					    dock_notify);
+	if (ACPI_FAILURE(status))
+		printk(KERN_ERR "Error removing notify handler\n");
+
+	/* free dock station memory */
+	kfree(dock_station);
+	return 0;
+}
+
+/**
+ * find_dock - look for a dock station
+ * @handle: acpi handle of a device
+ * @lvl: unused
+ * @context: counter of dock stations found
+ * @rv: unused
+ *
+ * This is called by acpi_walk_namespace to look for dock stations.
+ */
+static acpi_status
+find_dock(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	int *count = (int *)context;
+	acpi_status status = AE_OK;
+
+	if (is_dock(handle)) {
+		if (dock_add(handle) >= 0) {
+			(*count)++;
+			status = AE_CTRL_TERMINATE;
+		}
+	}
+	return status;
+}
+
+static int __init dock_init(void)
+{
+	int num = 0;
+
+	dock_station = NULL;
+
+	/* look for a dock station */
+	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+			    ACPI_UINT32_MAX, find_dock, &num, NULL);
+
+	if (!num)
+		return -ENODEV;
+
+	return 0;
+}
+
+static void __exit dock_exit(void)
+{
+	dock_remove();
+}
+
+postcore_initcall(dock_init);
+module_exit(dock_exit);
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index cac4fcd..5fcb50c 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -663,6 +663,29 @@ static int acpi_bus_find_driver(struct acpi_device *device)
                                  Device Enumeration
    -------------------------------------------------------------------------- */
 
+acpi_status
+acpi_bus_get_ejd(acpi_handle handle, acpi_handle *ejd)
+{
+	acpi_status status;
+	acpi_handle tmp;
+	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
+	union acpi_object *obj;
+
+	status = acpi_get_handle(handle, "_EJD", &tmp);
+	if (ACPI_FAILURE(status))
+		return status;
+
+	status = acpi_evaluate_object(handle, "_EJD", NULL, &buffer);
+	if (ACPI_SUCCESS(status)) {
+		obj = buffer.pointer;
+		status = acpi_get_handle(NULL, obj->string.pointer, ejd);
+		kfree(buffer.pointer);
+	}
+	return status;
+}
+EXPORT_SYMBOL_GPL(acpi_bus_get_ejd);
+
+
 static int acpi_bus_get_flags(struct acpi_device *device)
 {
 	acpi_status status = AE_OK;