dock.c

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/*
 *  dock.c - ACPI dock station driver
 *
 *  Copyright (C) 2006 Kristen Carlson Accardi <[email protected]>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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/slab.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/notifier.h>
#include <linux/platform_device.h>
#include <linux/jiffies.h>
#include <linux/stddef.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>

#define PREFIX "ACPI: "

#define ACPI_DOCK_DRIVER_DESCRIPTION "ACPI Dock Station Driver"

ACPI_MODULE_NAME("dock");
MODULE_AUTHOR("Kristen Carlson Accardi");
MODULE_DESCRIPTION(ACPI_DOCK_DRIVER_DESCRIPTION);
MODULE_LICENSE("GPL");

static bool immediate_undock = 1;
module_param(immediate_undock, bool, 0644);
MODULE_PARM_DESC(immediate_undock, "1 (default) will cause the driver to "
    "undock immediately when the undock button is pressed, 0 will cause"
    " the driver to wait for userspace to write the undock sysfs file "
    " before undocking");

static struct atomic_notifier_head dock_notifier_list;

static const struct acpi_device_id dock_device_ids[] = {
    {"LNXDOCK", 0},
    {"", 0},
};
MODULE_DEVICE_TABLE(acpi, dock_device_ids);

struct dock_station {
    acpi_handle handle;
    unsigned long last_dock_time;
    u32 flags;
    spinlock_t dd_lock;
    struct mutex hp_lock;
    struct list_head dependent_devices;
    struct list_head hotplug_devices;

    struct list_head sibling;
    struct platform_device *dock_device;
};
static LIST_HEAD(dock_stations);
static int dock_station_count;

struct dock_dependent_device {
    struct list_head list;
    struct list_head hotplug_list;
    acpi_handle handle;
    const struct acpi_dock_ops *ops;
    void *context;
};

#define DOCK_DOCKING    0x00000001
#define DOCK_UNDOCKING  0x00000002
#define DOCK_IS_DOCK    0x00000010
#define DOCK_IS_ATA 0x00000020
#define DOCK_IS_BAT 0x00000040
#define DOCK_EVENT  3
#define UNDOCK_EVENT    2

/*****************************************************************************
 *                         Dock Dependent device functions                   *
 *****************************************************************************/
static int
add_dock_dependent_device(struct dock_station *ds, acpi_handle handle)
{
    struct dock_dependent_device *dd;

    dd = kzalloc(sizeof(*dd), GFP_KERNEL);
    if (!dd)
        return -ENOMEM;

    dd->handle = handle;
    INIT_LIST_HEAD(&dd->list);
    INIT_LIST_HEAD(&dd->hotplug_list);

    spin_lock(&ds->dd_lock);
    list_add_tail(&dd->list, &ds->dependent_devices);
    spin_unlock(&ds->dd_lock);

    return 0;
}

static void
dock_add_hotplug_device(struct dock_station *ds,
            struct dock_dependent_device *dd)
{
    mutex_lock(&ds->hp_lock);
    list_add_tail(&dd->hotplug_list, &ds->hotplug_devices);
    mutex_unlock(&ds->hp_lock);
}

static void
dock_del_hotplug_device(struct dock_station *ds,
            struct dock_dependent_device *dd)
{
    mutex_lock(&ds->hp_lock);
    list_del(&dd->hotplug_list);
    mutex_unlock(&ds->hp_lock);
}

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                                    *
 *****************************************************************************/
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;
}

static int is_ejectable(acpi_handle handle)
{
    acpi_status status;
    acpi_handle tmp;

    status = acpi_get_handle(handle, "_EJ0", &tmp);
    if (ACPI_FAILURE(status))
        return 0;
    return 1;
}

static int is_ata(acpi_handle handle)
{
    acpi_handle tmp;

    if ((ACPI_SUCCESS(acpi_get_handle(handle, "_GTF", &tmp))) ||
       (ACPI_SUCCESS(acpi_get_handle(handle, "_GTM", &tmp))) ||
       (ACPI_SUCCESS(acpi_get_handle(handle, "_STM", &tmp))) ||
       (ACPI_SUCCESS(acpi_get_handle(handle, "_SDD", &tmp))))
        return 1;

    return 0;
}

static int is_battery(acpi_handle handle)
{
    struct acpi_device_info *info;
    int ret = 1;

    if (!ACPI_SUCCESS(acpi_get_object_info(handle, &info)))
        return 0;
    if (!(info->valid & ACPI_VALID_HID))
        ret = 0;
    else
        ret = !strcmp("PNP0C0A", info->hardware_id.string);

    kfree(info);
    return ret;
}

static int is_ejectable_bay(acpi_handle handle)
{
    acpi_handle phandle;

    if (!is_ejectable(handle))
        return 0;
    if (is_battery(handle) || is_ata(handle))
        return 1;
    if (!acpi_get_parent(handle, &phandle) && is_ata(phandle))
        return 1;
    return 0;
}

int is_dock_device(acpi_handle handle)
{
    struct dock_station *dock_station;

    if (!dock_station_count)
        return 0;

    if (is_dock(handle))
        return 1;

    list_for_each_entry(dock_station, &dock_stations, sibling)
        if (find_dock_dependent_device(dock_station, handle))
            return 1;

    return 0;
}
EXPORT_SYMBOL_GPL(is_dock_device);

static int dock_present(struct dock_station *ds)
{
    unsigned long 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;
}

static struct acpi_device * dock_create_acpi_device(acpi_handle handle)
{
    struct acpi_device *device;
    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;
}

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);
    }
}

static void hotplug_dock_devices(struct dock_station *ds, u32 event)
{
    struct dock_dependent_device *dd;

    mutex_lock(&ds->hp_lock);

    /*
     * First call driver specific hotplug functions
     */
    list_for_each_entry(dd, &ds->hotplug_devices, hotplug_list)
        if (dd->ops && dd->ops->handler)
            dd->ops->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);
    }
    mutex_unlock(&ds->hp_lock);
}

static void dock_event(struct dock_station *ds, u32 event, int num)
{
    struct device *dev = &ds->dock_device->dev;
    char event_string[13];
    char *envp[] = { event_string, NULL };
    struct dock_dependent_device *dd;

    if (num == UNDOCK_EVENT)
        sprintf(event_string, "EVENT=undock");
    else
        sprintf(event_string, "EVENT=dock");

    /*
     * Indicate that the status of the dock station has
     * changed.
     */
    if (num == DOCK_EVENT)
        kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);

    list_for_each_entry(dd, &ds->hotplug_devices, hotplug_list)
        if (dd->ops && dd->ops->uevent)
            dd->ops->uevent(dd->handle, event, dd->context);

    if (num != DOCK_EVENT)
        kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
}

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;

    status = acpi_evaluate_object(ds->handle, "_EJ0", &arg_list, NULL);
    if (ACPI_FAILURE(status))
        pr_debug("Failed to evaluate _EJ0!\n");
}

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 };

    acpi_get_name(ds->handle, ACPI_FULL_PATHNAME, &name_buffer);

    printk(KERN_INFO PREFIX "%s - %s\n",
        (char *)name_buffer.pointer, 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) && status != AE_NOT_FOUND)
        ACPI_EXCEPTION((AE_INFO, status, "%s - failed to execute"
            " _DCK\n", (char *)name_buffer.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;
}

static inline void begin_undock(struct dock_station *ds)
{
    ds->flags |= DOCK_UNDOCKING;
}

static inline void complete_undock(struct dock_station *ds)
{
    ds->flags &= ~(DOCK_UNDOCKING);
}

static void dock_lock(struct dock_station *ds, int lock)
{
    struct acpi_object_list arg_list;
    union acpi_object arg;
    acpi_status status;

    arg_list.count = 1;
    arg_list.pointer = &arg;
    arg.type = ACPI_TYPE_INTEGER;
    arg.integer.value = !!lock;
    status = acpi_evaluate_object(ds->handle, "_LCK", &arg_list, NULL);
    if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
        if (lock)
            printk(KERN_WARNING PREFIX "Locking device failed\n");
        else
            printk(KERN_WARNING PREFIX "Unlocking device failed\n");
    }
}

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;
}

int register_dock_notifier(struct notifier_block *nb)
{
    if (!dock_station_count)
        return -ENODEV;

    return atomic_notifier_chain_register(&dock_notifier_list, nb);
}
EXPORT_SYMBOL_GPL(register_dock_notifier);

void unregister_dock_notifier(struct notifier_block *nb)
{
    if (!dock_station_count)
        return;

    atomic_notifier_chain_unregister(&dock_notifier_list, nb);
}
EXPORT_SYMBOL_GPL(unregister_dock_notifier);

int
register_hotplug_dock_device(acpi_handle handle, const struct acpi_dock_ops *ops,
                 void *context)
{
    struct dock_dependent_device *dd;
    struct dock_station *dock_station;
    int ret = -EINVAL;

    if (!dock_station_count)
        return -ENODEV;

    /*
     * make sure this handle is for a device dependent on the dock,
     * this would include the dock station itself
     */
    list_for_each_entry(dock_station, &dock_stations, sibling) {
        /*
         * An ATA bay can be in a dock and itself can be ejected
         * separately, so there are two 'dock stations' which need the
         * ops
         */
        dd = find_dock_dependent_device(dock_station, handle);
        if (dd) {
            dd->ops = ops;
            dd->context = context;
            dock_add_hotplug_device(dock_station, dd);
            ret = 0;
        }
    }

    return ret;
}
EXPORT_SYMBOL_GPL(register_hotplug_dock_device);

void unregister_hotplug_dock_device(acpi_handle handle)
{
    struct dock_dependent_device *dd;
    struct dock_station *dock_station;

    if (!dock_station_count)
        return;

    list_for_each_entry(dock_station, &dock_stations, sibling) {
        dd = find_dock_dependent_device(dock_station, handle);
        if (dd)
            dock_del_hotplug_device(dock_station, dd);
    }
}
EXPORT_SYMBOL_GPL(unregister_hotplug_dock_device);

static int handle_eject_request(struct dock_station *ds, u32 event)
{
    if (dock_in_progress(ds))
        return -EBUSY;

    /*
     * here we need to generate the undock
     * event prior to actually doing the undock
     * so that the device struct still exists.
     * Also, even send the dock event if the
     * device is not present anymore
     */
    dock_event(ds, event, UNDOCK_EVENT);

    hotplug_dock_devices(ds, ACPI_NOTIFY_EJECT_REQUEST);
    undock(ds);
    dock_lock(ds, 0);
    eject_dock(ds);
    if (dock_present(ds)) {
        printk(KERN_ERR PREFIX "Unable to undock!\n");
        return -EBUSY;
    }
    complete_undock(ds);
    return 0;
}

static void dock_notify(acpi_handle handle, u32 event, void *data)
{
    struct dock_station *ds = data;
    struct acpi_device *tmp;
    int surprise_removal = 0;

    /*
     * 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.
     */
    if ((ds->flags & DOCK_IS_DOCK) && event == ACPI_NOTIFY_DEVICE_CHECK)
        event = ACPI_NOTIFY_EJECT_REQUEST;

    /*
     * dock station: BUS_CHECK - docked or surprise removal
     *       DEVICE_CHECK - undocked
     * other device: BUS_CHECK/DEVICE_CHECK - added or surprise removal
     *
     * To simplify event handling, dock dependent device handler always
     * get ACPI_NOTIFY_BUS_CHECK/ACPI_NOTIFY_DEVICE_CHECK for add and
     * ACPI_NOTIFY_EJECT_REQUEST for removal
     */
    switch (event) {
    case ACPI_NOTIFY_BUS_CHECK:
    case ACPI_NOTIFY_DEVICE_CHECK:
        if (!dock_in_progress(ds) && acpi_bus_get_device(ds->handle,
           &tmp)) {
            begin_dock(ds);
            dock(ds);
            if (!dock_present(ds)) {
                printk(KERN_ERR PREFIX "Unable to dock!\n");
                complete_dock(ds);
                break;
            }
            atomic_notifier_call_chain(&dock_notifier_list,
                           event, NULL);
            hotplug_dock_devices(ds, event);
            complete_dock(ds);
            dock_event(ds, event, DOCK_EVENT);
            dock_lock(ds, 1);
            acpi_update_all_gpes();
            break;
        }
        if (dock_present(ds) || dock_in_progress(ds))
            break;
        /* This is a surprise removal */
        surprise_removal = 1;
        event = ACPI_NOTIFY_EJECT_REQUEST;
        /* Fall back */
    case ACPI_NOTIFY_EJECT_REQUEST:
        begin_undock(ds);
        if ((immediate_undock && !(ds->flags & DOCK_IS_ATA))
           || surprise_removal)
            handle_eject_request(ds, event);
        else
            dock_event(ds, event, UNDOCK_EVENT);
        break;
    default:
        printk(KERN_ERR PREFIX "Unknown dock event %d\n", event);
    }
}

struct dock_data {
    acpi_handle handle;
    unsigned long event;
    struct dock_station *ds;
};

static void acpi_dock_deferred_cb(void *context)
{
    struct dock_data *data = context;

    dock_notify(data->handle, data->event, data->ds);
    kfree(data);
}

static int acpi_dock_notifier_call(struct notifier_block *this,
    unsigned long event, void *data)
{
    struct dock_station *dock_station;
    acpi_handle handle = data;

    if (event != ACPI_NOTIFY_BUS_CHECK && event != ACPI_NOTIFY_DEVICE_CHECK
       && event != ACPI_NOTIFY_EJECT_REQUEST)
        return 0;
    list_for_each_entry(dock_station, &dock_stations, sibling) {
        if (dock_station->handle == handle) {
            struct dock_data *dd;

            dd = kmalloc(sizeof(*dd), GFP_KERNEL);
            if (!dd)
                return 0;
            dd->handle = handle;
            dd->event = event;
            dd->ds = dock_station;
            acpi_os_hotplug_execute(acpi_dock_deferred_cb, dd);
            return 0 ;
        }
    }
    return 0;
}

static struct notifier_block dock_acpi_notifier = {
    .notifier_call = acpi_dock_notifier_call,
};

static acpi_status
find_dock_devices(acpi_handle handle, u32 lvl, void *context, void **rv)
{
    acpi_status status;
    acpi_handle tmp, parent;
    struct dock_station *ds = context;

    status = acpi_bus_get_ejd(handle, &tmp);
    if (ACPI_FAILURE(status)) {
        /* try the parent device as well */
        status = acpi_get_parent(handle, &parent);
        if (ACPI_FAILURE(status))
            goto fdd_out;
        /* see if parent is dependent on dock */
        status = acpi_bus_get_ejd(parent, &tmp);
        if (ACPI_FAILURE(status))
            goto fdd_out;
    }

    if (tmp == ds->handle)
        add_dock_dependent_device(ds, handle);

fdd_out:
    return AE_OK;
}

/*
 * show_docked - read method for "docked" file in sysfs
 */
static ssize_t show_docked(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    struct acpi_device *tmp;

    struct dock_station *dock_station = dev->platform_data;

    if (ACPI_SUCCESS(acpi_bus_get_device(dock_station->handle, &tmp)))
        return snprintf(buf, PAGE_SIZE, "1\n");
    return snprintf(buf, PAGE_SIZE, "0\n");
}
static DEVICE_ATTR(docked, S_IRUGO, show_docked, NULL);

/*
 * show_flags - read method for flags file in sysfs
 */
static ssize_t show_flags(struct device *dev,
              struct device_attribute *attr, char *buf)
{
    struct dock_station *dock_station = dev->platform_data;
    return snprintf(buf, PAGE_SIZE, "%d\n", dock_station->flags);

}
static DEVICE_ATTR(flags, S_IRUGO, show_flags, NULL);

/*
 * write_undock - write method for "undock" file in sysfs
 */
static ssize_t write_undock(struct device *dev, struct device_attribute *attr,
               const char *buf, size_t count)
{
    int ret;
    struct dock_station *dock_station = dev->platform_data;

    if (!count)
        return -EINVAL;

    begin_undock(dock_station);
    ret = handle_eject_request(dock_station, ACPI_NOTIFY_EJECT_REQUEST);
    return ret ? ret: count;
}
static DEVICE_ATTR(undock, S_IWUSR, NULL, write_undock);

/*
 * show_dock_uid - read method for "uid" file in sysfs
 */
static ssize_t show_dock_uid(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    unsigned long long lbuf;
    struct dock_station *dock_station = dev->platform_data;
    acpi_status status = acpi_evaluate_integer(dock_station->handle,
                    "_UID", NULL, &lbuf);
    if (ACPI_FAILURE(status))
        return 0;

    return snprintf(buf, PAGE_SIZE, "%llx\n", lbuf);
}
static DEVICE_ATTR(uid, S_IRUGO, show_dock_uid, NULL);

static ssize_t show_dock_type(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct dock_station *dock_station = dev->platform_data;
    char *type;

    if (dock_station->flags & DOCK_IS_DOCK)
        type = "dock_station";
    else if (dock_station->flags & DOCK_IS_ATA)
        type = "ata_bay";
    else if (dock_station->flags & DOCK_IS_BAT)
        type = "battery_bay";
    else
        type = "unknown";

    return snprintf(buf, PAGE_SIZE, "%s\n", type);
}
static DEVICE_ATTR(type, S_IRUGO, show_dock_type, NULL);

static struct attribute *dock_attributes[] = {
    &dev_attr_docked.attr,
    &dev_attr_flags.attr,
    &dev_attr_undock.attr,
    &dev_attr_uid.attr,
    &dev_attr_type.attr,
    NULL
};

static struct attribute_group dock_attribute_group = {
    .attrs = dock_attributes
};

static int __init dock_add(acpi_handle handle)
{
    int ret, id;
    struct dock_station ds, *dock_station;
    struct platform_device *dd;

    id = dock_station_count;
    memset(&ds, 0, sizeof(ds));
    dd = platform_device_register_data(NULL, "dock", id, &ds, sizeof(ds));
    if (IS_ERR(dd))
        return PTR_ERR(dd);

    dock_station = dd->dev.platform_data;

    dock_station->handle = handle;
    dock_station->dock_device = dd;
    dock_station->last_dock_time = jiffies - HZ;

    mutex_init(&dock_station->hp_lock);
    spin_lock_init(&dock_station->dd_lock);
    INIT_LIST_HEAD(&dock_station->sibling);
    INIT_LIST_HEAD(&dock_station->hotplug_devices);
    ATOMIC_INIT_NOTIFIER_HEAD(&dock_notifier_list);
    INIT_LIST_HEAD(&dock_station->dependent_devices);

    /* we want the dock device to send uevents */
    dev_set_uevent_suppress(&dd->dev, 0);

    if (is_dock(handle))
        dock_station->flags |= DOCK_IS_DOCK;
    if (is_ata(handle))
        dock_station->flags |= DOCK_IS_ATA;
    if (is_battery(handle))
        dock_station->flags |= DOCK_IS_BAT;

    ret = sysfs_create_group(&dd->dev.kobj, &dock_attribute_group);
    if (ret)
        goto err_unregister;

    /* Find dependent devices */
    acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
                ACPI_UINT32_MAX, find_dock_devices, NULL,
                dock_station, NULL);

    /* add the dock station as a device dependent on itself */
    ret = add_dock_dependent_device(dock_station, handle);
    if (ret)
        goto err_rmgroup;

    dock_station_count++;
    list_add(&dock_station->sibling, &dock_stations);
    return 0;

err_rmgroup:
    sysfs_remove_group(&dd->dev.kobj, &dock_attribute_group);
err_unregister:
    platform_device_unregister(dd);
    printk(KERN_ERR "%s encountered error %d\n", __func__, ret);
    return ret;
}

static int dock_remove(struct dock_station *ds)
{
    struct dock_dependent_device *dd, *tmp;
    struct platform_device *dock_device = ds->dock_device;

    if (!dock_station_count)
        return 0;

    /* remove dependent devices */
    list_for_each_entry_safe(dd, tmp, &ds->dependent_devices, list)
        kfree(dd);

    list_del(&ds->sibling);

    /* cleanup sysfs */
    sysfs_remove_group(&dock_device->dev.kobj, &dock_attribute_group);
    platform_device_unregister(dock_device);

    return 0;
}

static __init acpi_status
find_dock(acpi_handle handle, u32 lvl, void *context, void **rv)
{
    if (is_dock(handle))
        dock_add(handle);

    return AE_OK;
}

static __init acpi_status
find_bay(acpi_handle handle, u32 lvl, void *context, void **rv)
{
    /* If bay is a dock, it's already handled */
    if (is_ejectable_bay(handle) && !is_dock(handle))
        dock_add(handle);
    return AE_OK;
}

static int __init dock_init(void)
{
    if (acpi_disabled)
        return 0;

    /* look for a dock station */
    acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
                ACPI_UINT32_MAX, find_dock, NULL, NULL, NULL);

    /* look for bay */
    acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
            ACPI_UINT32_MAX, find_bay, NULL, NULL, NULL);
    if (!dock_station_count) {
        printk(KERN_INFO PREFIX "No dock devices found.\n");
        return 0;
    }

    register_acpi_bus_notifier(&dock_acpi_notifier);
    printk(KERN_INFO PREFIX "%s: %d docks/bays found\n",
        ACPI_DOCK_DRIVER_DESCRIPTION, dock_station_count);
    return 0;
}

static void __exit dock_exit(void)
{
    struct dock_station *tmp, *dock_station;

    unregister_acpi_bus_notifier(&dock_acpi_notifier);
    list_for_each_entry_safe(dock_station, tmp, &dock_stations, sibling)
        dock_remove(dock_station);
}

/*
 * Must be called before drivers of devices in dock, otherwise we can't know
 * which devices are in a dock
 */
subsys_initcall(dock_init);
module_exit(dock_exit);