ACPI: dock driver

Create a driver which lives in the acpi subsystem to handle dock events.
This driver is not an "ACPI" driver, because acpi drivers require that the
object be present when the driver is loaded.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

4 files changed, 770 insertions, 0 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 94b8d820c512..ce15aed1df3f 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 5984b4f6715a..f0a68ecf1e57 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 000000000000..510a94524298
--- /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 a7b1fda572cf..401e723e6c66 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;