/*
 *  pci_root.c - ACPI PCI Root Bridge Driver ($Revision: 40 $)
 *
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@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/mutex.h>
#include <linux/pm.h>
#include <linux/pm_runtime.h>
#include <linux/pci.h>
#include <linux/pci-acpi.h>
#include <linux/pci-aspm.h>
#include <linux/acpi.h>
#include <linux/slab.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include <acpi/apei.h>

#define PREFIX "ACPI: "

#define _COMPONENT              ACPI_PCI_COMPONENT
ACPI_MODULE_NAME("pci_root");
#define ACPI_PCI_ROOT_CLASS             "pci_bridge"
#define ACPI_PCI_ROOT_DEVICE_NAME       "PCI Root Bridge"
static int acpi_pci_root_add(struct acpi_device *device,
                             const struct acpi_device_id *not_used);
static void acpi_pci_root_remove(struct acpi_device *device);

#define ACPI_PCIE_REQ_SUPPORT (OSC_EXT_PCI_CONFIG_SUPPORT \
                                | OSC_ACTIVE_STATE_PWR_SUPPORT \
                                | OSC_CLOCK_PWR_CAPABILITY_SUPPORT \
                                | OSC_MSI_SUPPORT)

static const struct acpi_device_id root_device_ids[] = {
        {"PNP0A03", 0},
        {"", 0},
};

static struct acpi_scan_handler pci_root_handler = {
        .ids = root_device_ids,
        .attach = acpi_pci_root_add,
        .detach = acpi_pci_root_remove,
};

/* Lock to protect both acpi_pci_roots and acpi_pci_drivers lists */
static DEFINE_MUTEX(acpi_pci_root_lock);
static LIST_HEAD(acpi_pci_roots);
static LIST_HEAD(acpi_pci_drivers);

static DEFINE_MUTEX(osc_lock);

int acpi_pci_register_driver(struct acpi_pci_driver *driver)
{
        int n = 0;
        struct acpi_pci_root *root;

        mutex_lock(&acpi_pci_root_lock);
        list_add_tail(&driver->node, &acpi_pci_drivers);
        if (driver->add)
                list_for_each_entry(root, &acpi_pci_roots, node) {
                        driver->add(root);
                        n++;
                }
        mutex_unlock(&acpi_pci_root_lock);

        return n;
}
EXPORT_SYMBOL(acpi_pci_register_driver);

void acpi_pci_unregister_driver(struct acpi_pci_driver *driver)
{
        struct acpi_pci_root *root;

        mutex_lock(&acpi_pci_root_lock);
        list_del(&driver->node);
        if (driver->remove)
                list_for_each_entry(root, &acpi_pci_roots, node)
                        driver->remove(root);
        mutex_unlock(&acpi_pci_root_lock);
}
EXPORT_SYMBOL(acpi_pci_unregister_driver);

/**
 * acpi_is_root_bridge - determine whether an ACPI CA node is a PCI root bridge
 * @handle - the ACPI CA node in question.
 *
 * Note: we could make this API take a struct acpi_device * instead, but
 * for now, it's more convenient to operate on an acpi_handle.
 */
int acpi_is_root_bridge(acpi_handle handle)
{
        int ret;
        struct acpi_device *device;

        ret = acpi_bus_get_device(handle, &device);
        if (ret)
                return 0;

        ret = acpi_match_device_ids(device, root_device_ids);
        if (ret)
                return 0;
        else
                return 1;
}
EXPORT_SYMBOL_GPL(acpi_is_root_bridge);

static acpi_status
get_root_bridge_busnr_callback(struct acpi_resource *resource, void *data)
{
        struct resource *res = data;
        struct acpi_resource_address64 address;

        if (resource->type != ACPI_RESOURCE_TYPE_ADDRESS16 &&
            resource->type != ACPI_RESOURCE_TYPE_ADDRESS32 &&
            resource->type != ACPI_RESOURCE_TYPE_ADDRESS64)
                return AE_OK;

        acpi_resource_to_address64(resource, &address);
        if ((address.address_length > 0) &&
            (address.resource_type == ACPI_BUS_NUMBER_RANGE)) {
                res->start = address.minimum;
                res->end = address.minimum + address.address_length - 1;
        }

        return AE_OK;
}

static acpi_status try_get_root_bridge_busnr(acpi_handle handle,
                                             struct resource *res)
{
        acpi_status status;

        res->start = -1;
        status =
            acpi_walk_resources(handle, METHOD_NAME__CRS,
                                get_root_bridge_busnr_callback, res);
        if (ACPI_FAILURE(status))
                return status;
        if (res->start == -1)
                return AE_ERROR;
        return AE_OK;
}

static u8 pci_osc_uuid_str[] = "33DB4D5B-1FF7-401C-9657-7441C03DD766";

static acpi_status acpi_pci_run_osc(acpi_handle handle,
                                    const u32 *capbuf, u32 *retval)
{
        struct acpi_osc_context context = {
                .uuid_str = pci_osc_uuid_str,
                .rev = 1,
                .cap.length = 12,
                .cap.pointer = (void *)capbuf,
        };
        acpi_status status;

        status = acpi_run_osc(handle, &context);
        if (ACPI_SUCCESS(status)) {
                *retval = *((u32 *)(context.ret.pointer + 8));
                kfree(context.ret.pointer);
        }
        return status;
}

static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
                                        u32 support,
                                        u32 *control)
{
        acpi_status status;
        u32 result, capbuf[3];

        support &= OSC_PCI_SUPPORT_MASKS;
        support |= root->osc_support_set;

        capbuf[OSC_QUERY_TYPE] = OSC_QUERY_ENABLE;
        capbuf[OSC_SUPPORT_TYPE] = support;
        if (control) {
                *control &= OSC_PCI_CONTROL_MASKS;
                capbuf[OSC_CONTROL_TYPE] = *control | root->osc_control_set;
        } else {
                /* Run _OSC query only with existing controls. */
                capbuf[OSC_CONTROL_TYPE] = root->osc_control_set;
        }

        status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
        if (ACPI_SUCCESS(status)) {
                root->osc_support_set = support;
                if (control)
                        *control = result;
        }
        return status;
}

static acpi_status acpi_pci_osc_support(struct acpi_pci_root *root, u32 flags)
{
        acpi_status status;
        acpi_handle tmp;

        status = acpi_get_handle(root->device->handle, "_OSC", &tmp);
        if (ACPI_FAILURE(status))
                return status;
        mutex_lock(&osc_lock);
        status = acpi_pci_query_osc(root, flags, NULL);
        mutex_unlock(&osc_lock);
        return status;
}

struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
{
        struct acpi_pci_root *root;
        struct acpi_device *device;

        if (acpi_bus_get_device(handle, &device) ||
            acpi_match_device_ids(device, root_device_ids))
                return NULL;

        root = acpi_driver_data(device);

        return root;
}
EXPORT_SYMBOL_GPL(acpi_pci_find_root);

struct acpi_handle_node {
        struct list_head node;
        acpi_handle handle;
};

/**
 * acpi_get_pci_dev - convert ACPI CA handle to struct pci_dev
 * @handle: the handle in question
 *
 * Given an ACPI CA handle, the desired PCI device is located in the
 * list of PCI devices.
 *
 * If the device is found, its reference count is increased and this
 * function returns a pointer to its data structure.  The caller must
 * decrement the reference count by calling pci_dev_put().
 * If no device is found, %NULL is returned.
 */
struct pci_dev *acpi_get_pci_dev(acpi_handle handle)
{
        int dev, fn;
        unsigned long long adr;
        acpi_status status;
        acpi_handle phandle;
        struct pci_bus *pbus;
        struct pci_dev *pdev = NULL;
        struct acpi_handle_node *node, *tmp;
        struct acpi_pci_root *root;
        LIST_HEAD(device_list);

        /*
         * Walk up the ACPI CA namespace until we reach a PCI root bridge.
         */
        phandle = handle;
        while (!acpi_is_root_bridge(phandle)) {
                node = kzalloc(sizeof(struct acpi_handle_node), GFP_KERNEL);
                if (!node)
                        goto out;

                INIT_LIST_HEAD(&node->node);
                node->handle = phandle;
                list_add(&node->node, &device_list);

                status = acpi_get_parent(phandle, &phandle);
                if (ACPI_FAILURE(status))
                        goto out;
        }

        root = acpi_pci_find_root(phandle);
        if (!root)
                goto out;

        pbus = root->bus;

        /*
         * Now, walk back down the PCI device tree until we return to our
         * original handle. Assumes that everything between the PCI root
         * bridge and the device we're looking for must be a P2P bridge.
         */
        list_for_each_entry(node, &device_list, node) {
                acpi_handle hnd = node->handle;
                status = acpi_evaluate_integer(hnd, "_ADR", NULL, &adr);
                if (ACPI_FAILURE(status))
                        goto out;
                dev = (adr >> 16) & 0xffff;
                fn  = adr & 0xffff;

                pdev = pci_get_slot(pbus, PCI_DEVFN(dev, fn));
                if (!pdev || hnd == handle)
                        break;

                pbus = pdev->subordinate;
                pci_dev_put(pdev);

                /*
                 * This function may be called for a non-PCI device that has a
                 * PCI parent (eg. a disk under a PCI SATA controller).  In that
                 * case pdev->subordinate will be NULL for the parent.
                 */
                if (!pbus) {
                        dev_dbg(&pdev->dev, "Not a PCI-to-PCI bridge\n");
                        pdev = NULL;
                        break;
                }
        }
out:
        list_for_each_entry_safe(node, tmp, &device_list, node)
                kfree(node);

        return pdev;
}
EXPORT_SYMBOL_GPL(acpi_get_pci_dev);

/**
 * acpi_pci_osc_control_set - Request control of PCI root _OSC features.
 * @handle: ACPI handle of a PCI root bridge (or PCIe Root Complex).
 * @mask: Mask of _OSC bits to request control of, place to store control mask.
 * @req: Mask of _OSC bits the control of is essential to the caller.
 *
 * Run _OSC query for @mask and if that is successful, compare the returned
 * mask of control bits with @req.  If all of the @req bits are set in the
 * returned mask, run _OSC request for it.
 *
 * The variable at the @mask address may be modified regardless of whether or
 * not the function returns success.  On success it will contain the mask of
 * _OSC bits the BIOS has granted control of, but its contents are meaningless
 * on failure.
 **/
acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
{
        struct acpi_pci_root *root;
        acpi_status status;
        u32 ctrl, capbuf[3];
        acpi_handle tmp;

        if (!mask)
                return AE_BAD_PARAMETER;

        ctrl = *mask & OSC_PCI_CONTROL_MASKS;
        if ((ctrl & req) != req)
                return AE_TYPE;

        root = acpi_pci_find_root(handle);
        if (!root)
                return AE_NOT_EXIST;

        status = acpi_get_handle(handle, "_OSC", &tmp);
        if (ACPI_FAILURE(status))
                return status;

        mutex_lock(&osc_lock);

        *mask = ctrl | root->osc_control_set;
        /* No need to evaluate _OSC if the control was already granted. */
        if ((root->osc_control_set & ctrl) == ctrl)
                goto out;

        /* Need to check the available controls bits before requesting them. */
        while (*mask) {
                status = acpi_pci_query_osc(root, root->osc_support_set, mask);
                if (ACPI_FAILURE(status))
                        goto out;
                if (ctrl == *mask)
                        break;
                ctrl = *mask;
        }

        if ((ctrl & req) != req) {
                status = AE_SUPPORT;
                goto out;
        }

        capbuf[OSC_QUERY_TYPE] = 0;
        capbuf[OSC_SUPPORT_TYPE] = root->osc_support_set;
        capbuf[OSC_CONTROL_TYPE] = ctrl;
        status = acpi_pci_run_osc(handle, capbuf, mask);
        if (ACPI_SUCCESS(status))
                root->osc_control_set = *mask;
out:
        mutex_unlock(&osc_lock);
        return status;
}
EXPORT_SYMBOL(acpi_pci_osc_control_set);

static int acpi_pci_root_add(struct acpi_device *device,
                             const struct acpi_device_id *not_used)
{
        unsigned long long segment, bus;
        acpi_status status;
        int result;
        struct acpi_pci_root *root;
        struct acpi_pci_driver *driver;
        u32 flags, base_flags;

        root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
        if (!root)
                return -ENOMEM;

        segment = 0;
        status = acpi_evaluate_integer(device->handle, METHOD_NAME__SEG, NULL,
                                       &segment);
        if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
                printk(KERN_ERR PREFIX "can't evaluate _SEG\n");
                result = -ENODEV;
                goto end;
        }

        /* Check _CRS first, then _BBN.  If no _BBN, default to zero. */
        root->secondary.flags = IORESOURCE_BUS;
        status = try_get_root_bridge_busnr(device->handle, &root->secondary);
        if (ACPI_FAILURE(status)) {
                /*
                 * We need both the start and end of the downstream bus range
                 * to interpret _CBA (MMCONFIG base address), so it really is
                 * supposed to be in _CRS.  If we don't find it there, all we
                 * can do is assume [_BBN-0xFF] or [0-0xFF].
                 */
                root->secondary.end = 0xFF;
                printk(KERN_WARNING FW_BUG PREFIX
                       "no secondary bus range in _CRS\n");
                status = acpi_evaluate_integer(device->handle, METHOD_NAME__BBN,
                                               NULL, &bus);
                if (ACPI_SUCCESS(status))
                        root->secondary.start = bus;
                else if (status == AE_NOT_FOUND)
                        root->secondary.start = 0;
                else {
                        printk(KERN_ERR PREFIX "can't evaluate _BBN\n");
                        result = -ENODEV;
                        goto end;
                }
        }

        INIT_LIST_HEAD(&root->node);
        root->device = device;
        root->segment = segment & 0xFFFF;
        strcpy(acpi_device_name(device), ACPI_PCI_ROOT_DEVICE_NAME);
        strcpy(acpi_device_class(device), ACPI_PCI_ROOT_CLASS);
        device->driver_data = root;

        printk(KERN_INFO PREFIX "%s [%s] (domain %04x %pR)\n",
               acpi_device_name(device), acpi_device_bid(device),
               root->segment, &root->secondary);

        root->mcfg_addr = acpi_pci_root_get_mcfg_addr(device->handle);

        /*
         * All supported architectures that use ACPI have support for
         * PCI domains, so we indicate this in _OSC support capabilities.
         */
        flags = base_flags = OSC_PCI_SEGMENT_GROUPS_SUPPORT;
        acpi_pci_osc_support(root, flags);

        /*
         * TBD: Need PCI interface for enumeration/configuration of roots.
         */

        mutex_lock(&acpi_pci_root_lock);
        list_add_tail(&root->node, &acpi_pci_roots);
        mutex_unlock(&acpi_pci_root_lock);

        /*
         * Scan the Root Bridge
         * --------------------
         * Must do this prior to any attempt to bind the root device, as the
         * PCI namespace does not get created until this call is made (and
         * thus the root bridge's pci_dev does not exist).
         */
        root->bus = pci_acpi_scan_root(root);
        if (!root->bus) {
                printk(KERN_ERR PREFIX
                            "Bus %04x:%02x not present in PCI namespace\n",
                            root->segment, (unsigned int)root->secondary.start);
                result = -ENODEV;
                goto out_del_root;
        }

        /* Indicate support for various _OSC capabilities. */
        if (pci_ext_cfg_avail())
                flags |= OSC_EXT_PCI_CONFIG_SUPPORT;
        if (pcie_aspm_support_enabled()) {
                flags |= OSC_ACTIVE_STATE_PWR_SUPPORT |
                OSC_CLOCK_PWR_CAPABILITY_SUPPORT;
        }
        if (pci_msi_enabled())
                flags |= OSC_MSI_SUPPORT;
        if (flags != base_flags) {
                status = acpi_pci_osc_support(root, flags);
                if (ACPI_FAILURE(status)) {
                        dev_info(&device->dev, "ACPI _OSC support "
                                "notification failed, disabling PCIe ASPM\n");
                        pcie_no_aspm();
                        flags = base_flags;
                }
        }

        if (!pcie_ports_disabled
            && (flags & ACPI_PCIE_REQ_SUPPORT) == ACPI_PCIE_REQ_SUPPORT) {
                flags = OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL
                        | OSC_PCI_EXPRESS_NATIVE_HP_CONTROL
                        | OSC_PCI_EXPRESS_PME_CONTROL;

                if (pci_aer_available()) {
                        if (aer_acpi_firmware_first())
                                dev_dbg(&device->dev,
                                        "PCIe errors handled by BIOS.\n");
                        else
                                flags |= OSC_PCI_EXPRESS_AER_CONTROL;
                }

                dev_info(&device->dev,
                        "Requesting ACPI _OSC control (0x%02x)\n", flags);

                status = acpi_pci_osc_control_set(device->handle, &flags,
                                       OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL);
                if (ACPI_SUCCESS(status)) {
                        dev_info(&device->dev,
                                "ACPI _OSC control (0x%02x) granted\n", flags);
                        if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
                                /*
                                 * We have ASPM control, but the FADT indicates
                                 * that it's unsupported. Clear it.
                                 */
                                pcie_clear_aspm(root->bus);
                        }
                } else {
                        dev_info(&device->dev,
                                "ACPI _OSC request failed (%s), "
                                "returned control mask: 0x%02x\n",
                                acpi_format_exception(status), flags);
                        pr_info("ACPI _OSC control for PCIe not granted, "
                                "disabling ASPM\n");
                        pcie_no_aspm();
                }
        } else {
                dev_info(&device->dev,
                         "Unable to request _OSC control "
                         "(_OSC support mask: 0x%02x)\n", flags);
        }

        pci_acpi_add_bus_pm_notifier(device, root->bus);
        if (device->wakeup.flags.run_wake)
                device_set_run_wake(root->bus->bridge, true);

        if (system_state != SYSTEM_BOOTING) {
                pcibios_resource_survey_bus(root->bus);
                pci_assign_unassigned_bus_resources(root->bus);
        }

        mutex_lock(&acpi_pci_root_lock);
        list_for_each_entry(driver, &acpi_pci_drivers, node)
                if (driver->add)
                        driver->add(root);
        mutex_unlock(&acpi_pci_root_lock);

        /* need to after hot-added ioapic is registered */
        if (system_state != SYSTEM_BOOTING)
                pci_enable_bridges(root->bus);

        pci_bus_add_devices(root->bus);
        return 1;

out_del_root:
        mutex_lock(&acpi_pci_root_lock);
        list_del(&root->node);
        mutex_unlock(&acpi_pci_root_lock);

end:
        kfree(root);
        return result;
}

static void acpi_pci_root_remove(struct acpi_device *device)
{
        struct acpi_pci_root *root = acpi_driver_data(device);
        struct acpi_pci_driver *driver;

        pci_stop_root_bus(root->bus);

        mutex_lock(&acpi_pci_root_lock);
        list_for_each_entry_reverse(driver, &acpi_pci_drivers, node)
                if (driver->remove)
                        driver->remove(root);
        mutex_unlock(&acpi_pci_root_lock);

        device_set_run_wake(root->bus->bridge, false);
        pci_acpi_remove_bus_pm_notifier(device);

        pci_remove_root_bus(root->bus);

        mutex_lock(&acpi_pci_root_lock);
        list_del(&root->node);
        mutex_unlock(&acpi_pci_root_lock);
        kfree(root);
}

void __init acpi_pci_root_init(void)
{
        acpi_hest_init();

        if (!acpi_pci_disabled) {
                pci_acpi_crs_quirks();
                acpi_scan_add_handler(&pci_root_handler);
        }
}
/* Support root bridge hotplug */

static void handle_root_bridge_insertion(acpi_handle handle)
{
        struct acpi_device *device;

        if (!acpi_bus_get_device(handle, &device)) {
                printk(KERN_DEBUG "acpi device exists...\n");
                return;
        }

        if (acpi_bus_scan(handle))
                printk(KERN_ERR "cannot add bridge to acpi list\n");
}

static void handle_root_bridge_removal(struct acpi_device *device)
{
        acpi_status status;
        struct acpi_eject_event *ej_event;

        ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
        if (!ej_event) {
                /* Inform firmware the hot-remove operation has error */
                (void) acpi_evaluate_hotplug_ost(device->handle,
                                        ACPI_NOTIFY_EJECT_REQUEST,
                                        ACPI_OST_SC_NON_SPECIFIC_FAILURE,
                                        NULL);
                return;
        }

        ej_event->device = device;
        ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;

        status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
        if (ACPI_FAILURE(status))
                kfree(ej_event);
}

static void _handle_hotplug_event_root(struct work_struct *work)
{
        struct acpi_pci_root *root;
        struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER };
        struct acpi_hp_work *hp_work;
        acpi_handle handle;
        u32 type;

        hp_work = container_of(work, struct acpi_hp_work, work);
        handle = hp_work->handle;
        type = hp_work->type;

        acpi_scan_lock_acquire();

        root = acpi_pci_find_root(handle);
        acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);

        switch (type) {
        case ACPI_NOTIFY_BUS_CHECK:
                /* bus enumerate */
                printk(KERN_DEBUG "%s: Bus check notify on %s\n", __func__,
                                 (char *)buffer.pointer);
                if (!root)
                        handle_root_bridge_insertion(handle);

                break;

        case ACPI_NOTIFY_DEVICE_CHECK:
                /* device check */
                printk(KERN_DEBUG "%s: Device check notify on %s\n", __func__,
                                 (char *)buffer.pointer);
                if (!root)
                        handle_root_bridge_insertion(handle);
                break;

        case ACPI_NOTIFY_EJECT_REQUEST:
                /* request device eject */
                printk(KERN_DEBUG "%s: Device eject notify on %s\n", __func__,
                                 (char *)buffer.pointer);
                if (root)
                        handle_root_bridge_removal(root->device);
                break;
        default:
                printk(KERN_WARNING "notify_handler: unknown event type 0x%x for %s\n",
                                 type, (char *)buffer.pointer);
                break;
        }

        acpi_scan_lock_release();
        kfree(hp_work); /* allocated in handle_hotplug_event_bridge */
        kfree(buffer.pointer);
}

static void handle_hotplug_event_root(acpi_handle handle, u32 type,
                                        void *context)
{
        alloc_acpi_hp_work(handle, type, context,
                                _handle_hotplug_event_root);
}

static acpi_status __init
find_root_bridges(acpi_handle handle, u32 lvl, void *context, void **rv)
{
        acpi_status status;
        char objname[64];
        struct acpi_buffer buffer = { .length = sizeof(objname),
                                      .pointer = objname };
        int *count = (int *)context;

        if (!acpi_is_root_bridge(handle))
                return AE_OK;

        (*count)++;

        acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);

        status = acpi_install_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
                                        handle_hotplug_event_root, NULL);
        if (ACPI_FAILURE(status))
                printk(KERN_DEBUG "acpi root: %s notify handler is not installed, exit status: %u\n",
                                  objname, (unsigned int)status);
        else
                printk(KERN_DEBUG "acpi root: %s notify handler is installed\n",
                                 objname);

        return AE_OK;
}

void __init acpi_pci_root_hp_init(void)
{
        int num = 0;

        acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
                ACPI_UINT32_MAX, find_root_bridges, NULL, &num, NULL);

        printk(KERN_DEBUG "Found %d acpi root devices\n", num);
}