linux_kernel/drivers/pci/hotplug/acpiphp_glue.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * ACPI PCI HotPlug glue functions to ACPI CA subsystem
 *
 * Copyright (C) 2002,2003 Takayoshi Kochi (t-kochi@bq.jp.nec.com)
 * Copyright (C) 2002 Hiroshi Aono (h-aono@ap.jp.nec.com)
 * Copyright (C) 2002,2003 NEC Corporation
 * Copyright (C) 2003-2005 Matthew Wilcox (matthew.wilcox@hp.com)
 * Copyright (C) 2003-2005 Hewlett Packard
 * Copyright (C) 2005 Rajesh Shah (rajesh.shah@intel.com)
 * Copyright (C) 2005 Intel Corporation
 *
 * All rights reserved.
 *
 * Send feedback to <kristen.c.accardi@intel.com>
 *
 */

/*
 * Lifetime rules for pci_dev:
 *  - The one in acpiphp_bridge has its refcount elevated by pci_get_slot()
 *    when the bridge is scanned and it loses a refcount when the bridge
 *    is removed.
 *  - When a P2P bridge is present, we elevate the refcount on the subordinate
 *    bus. It loses the refcount when the the driver unloads.
 */

#define pr_fmt(fmt) "acpiphp_glue: " fmt

#include <linux/module.h>

#include <linux/kernel.h>
#include <linux/pci.h>
#include <linux/pci_hotplug.h>
#include <linux/pci-acpi.h>
#include <linux/pm_runtime.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/acpi.h>

#include "../pci.h"
#include "acpiphp.h"

static LIST_HEAD(bridge_list);
static DEFINE_MUTEX(bridge_mutex);

static int acpiphp_hotplug_notify(struct acpi_device *adev, u32 type);
static void acpiphp_post_dock_fixup(struct acpi_device *adev);
static void acpiphp_sanitize_bus(struct pci_bus *bus);
static void hotplug_event(u32 type, struct acpiphp_context *context);
static void free_bridge(struct kref *kref);

/**
 * acpiphp_init_context - Create hotplug context and grab a reference to it.
 * @adev: ACPI device object to create the context for.
 *
 * Call under acpi_hp_context_lock.
 */
static struct acpiphp_context *acpiphp_init_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

	context = kzalloc(sizeof(*context), GFP_KERNEL);
	if (!context)
		return NULL;

	context->refcount = 1;
	context->hp.notify = acpiphp_hotplug_notify;
	context->hp.fixup = acpiphp_post_dock_fixup;
	acpi_set_hp_context(adev, &context->hp);
	return context;
}

/**
 * acpiphp_get_context - Get hotplug context and grab a reference to it.
 * @adev: ACPI device object to get the context for.
 *
 * Call under acpi_hp_context_lock.
 */
static struct acpiphp_context *acpiphp_get_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

	if (!adev->hp)
		return NULL;

	context = to_acpiphp_context(adev->hp);
	context->refcount++;
	return context;
}

/**
 * acpiphp_put_context - Drop a reference to ACPI hotplug context.
 * @context: ACPI hotplug context to drop a reference to.
 *
 * The context object is removed if there are no more references to it.
 *
 * Call under acpi_hp_context_lock.
 */
static void acpiphp_put_context(struct acpiphp_context *context)
{
	if (--context->refcount)
		return;

	WARN_ON(context->bridge);
	context->hp.self->hp = NULL;
	kfree(context);
}

static inline void get_bridge(struct acpiphp_bridge *bridge)
{
	kref_get(&bridge->ref);
}

static inline void put_bridge(struct acpiphp_bridge *bridge)
{
	kref_put(&bridge->ref, free_bridge);
}

static struct acpiphp_context *acpiphp_grab_context(struct acpi_device *adev)
{
	struct acpiphp_context *context;

	acpi_lock_hp_context();
	context = acpiphp_get_context(adev);
	if (!context || context->func.parent->is_going_away) {
		acpi_unlock_hp_context();
		return NULL;
	}
	get_bridge(context->func.parent);
	acpiphp_put_context(context);
	acpi_unlock_hp_context();
	return context;
}

static void acpiphp_let_context_go(struct acpiphp_context *context)
{
	put_bridge(context->func.parent);
}

static void free_bridge(struct kref *kref)
{
	struct acpiphp_context *context;
	struct acpiphp_bridge *bridge;
	struct acpiphp_slot *slot, *next;
	struct acpiphp_func *func, *tmp;

	acpi_lock_hp_context();

	bridge = container_of(kref, struct acpiphp_bridge, ref);

	list_for_each_entry_safe(slot, next, &bridge->slots, node) {
		list_for_each_entry_safe(func, tmp, &slot->funcs, sibling)
			acpiphp_put_context(func_to_context(func));

		kfree(slot);
	}

	context = bridge->context;
	/* Root bridges will not have hotplug context. */
	if (context) {
		/* Release the reference taken by acpiphp_enumerate_slots(). */
		put_bridge(context->func.parent);
		context->bridge = NULL;
		acpiphp_put_context(context);
	}

	put_device(&bridge->pci_bus->dev);
	pci_dev_put(bridge->pci_dev);
	kfree(bridge);

	acpi_unlock_hp_context();
}

/**
 * acpiphp_post_dock_fixup - Post-dock fixups for PCI devices.
 * @adev: ACPI device object corresponding to a PCI device.
 *
 * TBD - figure out a way to only call fixups for systems that require them.
 */
static void acpiphp_post_dock_fixup(struct acpi_device *adev)
{
	struct acpiphp_context *context = acpiphp_grab_context(adev);
	struct pci_bus *bus;
	u32 buses;

	if (!context)
		return;

	bus = context->func.slot->bus;
	if (!bus->self)
		goto out;

	/* fixup bad _DCK function that rewrites
	 * secondary bridge on slot
	 */
	pci_read_config_dword(bus->self, PCI_PRIMARY_BUS, &buses);

	if (((buses >> 8) & 0xff) != bus->busn_res.start) {
		buses = (buses & 0xff000000)
			| ((unsigned int)(bus->primary)     <<  0)
			| ((unsigned int)(bus->busn_res.start)   <<  8)
			| ((unsigned int)(bus->busn_res.end) << 16);
		pci_write_config_dword(bus->self, PCI_PRIMARY_BUS, buses);
	}

 out:
	acpiphp_let_context_go(context);
}

/**
 * acpiphp_add_context - Add ACPIPHP context to an ACPI device object.
 * @handle: ACPI handle of the object to add a context to.
 * @lvl: Not used.
 * @data: The object's parent ACPIPHP bridge.
 * @rv: Not used.
 */
static acpi_status acpiphp_add_context(acpi_handle handle, u32 lvl, void *data,
				       void **rv)
{
	struct acpiphp_bridge *bridge = data;
	struct acpiphp_context *context;
	struct acpi_device *adev;
	struct acpiphp_slot *slot;
	struct acpiphp_func *newfunc;
	acpi_status status = AE_OK;
	unsigned long long adr;
	int device, function;
	struct pci_bus *pbus = bridge->pci_bus;
	struct pci_dev *pdev = bridge->pci_dev;
	u32 val;

	status = acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
	if (ACPI_FAILURE(status)) {
		if (status != AE_NOT_FOUND)
			acpi_handle_warn(handle,
				"can't evaluate _ADR (%#x)\n", status);
		return AE_OK;
	}
	if (acpi_bus_get_device(handle, &adev))
		return AE_OK;

	device = (adr >> 16) & 0xffff;
	function = adr & 0xffff;

	acpi_lock_hp_context();
	context = acpiphp_init_context(adev);
	if (!context) {
		acpi_unlock_hp_context();
		acpi_handle_err(handle, "No hotplug context\n");
		return AE_NOT_EXIST;
	}
	newfunc = &context->func;
	newfunc->function = function;
	newfunc->parent = bridge;
	acpi_unlock_hp_context();

	/*
	 * If this is a dock device, its _EJ0 should be executed by the dock
	 * notify handler after calling _DCK.
	 */
	if (!is_dock_device(adev) && acpi_has_method(handle, "_EJ0"))
		newfunc->flags = FUNC_HAS_EJ0;

	if (acpi_has_method(handle, "_STA"))
		newfunc->flags |= FUNC_HAS_STA;

	/* search for objects that share the same slot */
	list_for_each_entry(slot, &bridge->slots, node)
		if (slot->device == device)
			goto slot_found;

	slot = kzalloc(sizeof(struct acpiphp_slot), GFP_KERNEL);
	if (!slot) {
		acpi_lock_hp_context();
		acpiphp_put_context(context);
		acpi_unlock_hp_context();
		return AE_NO_MEMORY;
	}

	slot->bus = bridge->pci_bus;
	slot->device = device;
	INIT_LIST_HEAD(&slot->funcs);

	list_add_tail(&slot->node, &bridge->slots);

	/*
	 * Expose slots to user space for functions that have _EJ0 or _RMV or
	 * are located in dock stations.  Do not expose them for devices handled
	 * by the native PCIe hotplug (PCIeHP), becuase that code is supposed to
	 * expose slots to user space in those cases.
	 */
	if ((acpi_pci_check_ejectable(pbus, handle) || is_dock_device(adev))
	    && !(pdev && pdev->is_hotplug_bridge && pciehp_is_native(pdev))) {
		unsigned long long sun;
		int retval;

		bridge->nr_slots++;
		status = acpi_evaluate_integer(handle, "_SUN", NULL, &sun);
		if (ACPI_FAILURE(status))
			sun = bridge->nr_slots;

		pr_debug("found ACPI PCI Hotplug slot %llu at PCI %04x:%02x:%02x\n",
		    sun, pci_domain_nr(pbus), pbus->number, device);

		retval = acpiphp_register_hotplug_slot(slot, sun);
		if (retval) {
			slot->slot = NULL;
			bridge->nr_slots--;
			if (retval == -EBUSY)
				pr_warn("Slot %llu already registered by another hotplug driver\n", sun);
			else
				pr_warn("acpiphp_register_hotplug_slot failed (err code = 0x%x)\n", retval);
		}
		/* Even if the slot registration fails, we can still use it. */
	}

 slot_found:
	newfunc->slot = slot;
	list_add_tail(&newfunc->sibling, &slot->funcs);

	if (pci_bus_read_dev_vendor_id(pbus, PCI_DEVFN(device, function),
				       &val, 60*1000))
		slot->flags |= SLOT_ENABLED;

	return AE_OK;
}

static void cleanup_bridge(struct acpiphp_bridge *bridge)
{
	struct acpiphp_slot *slot;
	struct acpiphp_func *func;

	list_for_each_entry(slot, &bridge->slots, node) {
		list_for_each_entry(func, &slot->funcs, sibling) {
			struct acpi_device *adev = func_to_acpi_device(func);

			acpi_lock_hp_context();
			adev->hp->notify = NULL;
			adev->hp->fixup = NULL;
			acpi_unlock_hp_context();
		}
		slot->flags |= SLOT_IS_GOING_AWAY;
		if (slot->slot)
			acpiphp_unregister_hotplug_slot(slot);
	}

	mutex_lock(&bridge_mutex);
	list_del(&bridge->list);
	mutex_unlock(&bridge_mutex);

	acpi_lock_hp_context();
	bridge->is_going_away = true;
	acpi_unlock_hp_context();
}

/**
 * acpiphp_max_busnr - return the highest reserved bus number under the given bus.
 * @bus: bus to start search with
 */
static unsigned char acpiphp_max_busnr(struct pci_bus *bus)
{
	struct pci_bus *tmp;
	unsigned char max, n;

	/*
	 * pci_bus_max_busnr will return the highest
	 * reserved busnr for all these children.
	 * that is equivalent to the bus->subordinate
	 * value.  We don't want to use the parent's
	 * bus->subordinate value because it could have
	 * padding in it.
	 */
	max = bus->busn_res.start;

	list_for_each_entry(tmp, &bus->children, node) {
		n = pci_bus_max_busnr(tmp);
		if (n > max)
			max = n;
	}
	return max;
}

static void acpiphp_set_acpi_region(struct acpiphp_slot *slot)
{
	struct acpiphp_func *func;
	union acpi_object params[2];
	struct acpi_object_list arg_list;

	list_for_each_entry(func, &slot->funcs, sibling) {
		arg_list.count = 2;
		arg_list.pointer = params;
		params[0].type = ACPI_TYPE_INTEGER;
		params[0].integer.value = ACPI_ADR_SPACE_PCI_CONFIG;
		params[1].type = ACPI_TYPE_INTEGER;
		params[1].integer.value = 1;
		/* _REG is optional, we don't care about if there is failure */
		acpi_evaluate_object(func_to_handle(func), "_REG", &arg_list,
				     NULL);
	}
}

static void check_hotplug_bridge(struct acpiphp_slot *slot, struct pci_dev *dev)
{
	struct acpiphp_func *func;

	/* quirk, or pcie could set it already */
	if (dev->is_hotplug_bridge)
		return;

	list_for_each_entry(func, &slot->funcs, sibling) {
		if (PCI_FUNC(dev->devfn) == func->function) {
			dev->is_hotplug_bridge = 1;
			break;
		}
	}
}

static int acpiphp_rescan_slot(struct acpiphp_slot *slot)
{
	struct acpiphp_func *func;

	list_for_each_entry(func, &slot->funcs, sibling) {
		struct acpi_device *adev = func_to_acpi_device(func);

		acpi_bus_scan(adev->handle);
		if (acpi_device_enumerated(adev))
			acpi_device_set_power(adev, ACPI_STATE_D0);
	}
	return pci_scan_slot(slot->bus, PCI_DEVFN(slot->device, 0));
}

/**
 * enable_slot - enable, configure a slot
 * @slot: slot to be enabled
 *
 * This function should be called per *physical slot*,
 * not per each slot object in ACPI namespace.
 */
static void enable_slot(struct acpiphp_slot *slot)
{
	struct pci_dev *dev;
	struct pci_bus *bus = slot->bus;
	struct acpiphp_func *func;
	int max, pass;
	LIST_HEAD(add_list);

	acpiphp_rescan_slot(slot);
	max = acpiphp_max_busnr(bus);
	for (pass = 0; pass < 2; pass++) {
		for_each_pci_bridge(dev, bus) {
			if (PCI_SLOT(dev->devfn) != slot->device)
				continue;

			max = pci_scan_bridge(bus, dev, max, pass);
			if (pass && dev->subordinate) {
				check_hotplug_bridge(slot, dev);
				pcibios_resource_survey_bus(dev->subordinate);
				__pci_bus_size_bridges(dev->subordinate, &add_list);
			}
		}
	}
	__pci_bus_assign_resources(bus, &add_list, NULL);

	acpiphp_sanitize_bus(bus);
	pcie_bus_configure_settings(bus);
	acpiphp_set_acpi_region(slot);

	list_for_each_entry(dev, &bus->devices, bus_list) {
		/* Assume that newly added devices are powered on already. */
		if (!dev->is_added)
			dev->current_state = PCI_D0;
	}

	pci_bus_add_devices(bus);

	slot->flags |= SLOT_ENABLED;
	list_for_each_entry(func, &slot->funcs, sibling) {
		dev = pci_get_slot(bus, PCI_DEVFN(slot->device,
						  func->function));
		if (!dev) {
			/* Do not set SLOT_ENABLED flag if some funcs
			   are not added. */
			slot->flags &= (~SLOT_ENABLED);
			continue;
		}
	}
}

/**
 * disable_slot - disable a slot
 * @slot: ACPI PHP slot
 */
static void disable_slot(struct acpiphp_slot *slot)
{
	struct pci_bus *bus = slot->bus;
	struct pci_dev *dev, *prev;
	struct acpiphp_func *func;

	/*
	 * enable_slot() enumerates all functions in this device via
	 * pci_scan_slot(), whether they have associated ACPI hotplug
	 * methods (_EJ0, etc.) or not.  Therefore, we remove all functions
	 * here.
	 */
	list_for_each_entry_safe_reverse(dev, prev, &bus->devices, bus_list)
		if (PCI_SLOT(dev->devfn) == slot->device)
			pci_stop_and_remove_bus_device(dev);

	list_for_each_entry(func, &slot->funcs, sibling)
		acpi_bus_trim(func_to_acpi_device(func));

	slot->flags &= (~SLOT_ENABLED);
}

static bool slot_no_hotplug(struct acpiphp_slot *slot)
{
	struct pci_bus *bus = slot->bus;
	struct pci_dev *dev;

	list_for_each_entry(dev, &bus->devices, bus_list) {
		if (PCI_SLOT(dev->devfn) == slot->device && dev->ignore_hotplug)
			return true;
	}
	return false;
}

/**
 * get_slot_status - get ACPI slot status
 * @slot: ACPI PHP slot
 *
 * If a slot has _STA for each function and if any one of them
 * returned non-zero status, return it.
 *
 * If a slot doesn't have _STA and if any one of its functions'
 * configuration space is configured, return 0x0f as a _STA.
 *
 * Otherwise return 0.
 */
static unsigned int get_slot_status(struct acpiphp_slot *slot)
{
	unsigned long long sta = 0;
	struct acpiphp_func *func;
	u32 dvid;

	list_for_each_entry(func, &slot->funcs, sibling) {
		if (func->flags & FUNC_HAS_STA) {
			acpi_status status;

			status = acpi_evaluate_integer(func_to_handle(func),
						       "_STA", NULL, &sta);
			if (ACPI_SUCCESS(status) && sta)
				break;
		} else {
			if (pci_bus_read_dev_vendor_id(slot->bus,
					PCI_DEVFN(slot->device, func->function),
					&dvid, 0)) {
				sta = ACPI_STA_ALL;
				break;
			}
		}
	}

	if (!sta) {
		/*
		 * Check for the slot itself since it may be that the
		 * ACPI slot is a device below PCIe upstream port so in
		 * that case it may not even be reachable yet.
		 */
		if (pci_bus_read_dev_vendor_id(slot->bus,
				PCI_DEVFN(slot->device, 0), &dvid, 0)) {
			sta = ACPI_STA_ALL;
		}
	}

	return (unsigned int)sta;
}

static inline bool device_status_valid(unsigned int sta)
{
	/*
	 * ACPI spec says that _STA may return bit 0 clear with bit 3 set
	 * if the device is valid but does not require a device driver to be
	 * loaded (Section 6.3.7 of ACPI 5.0A).
	 */
	unsigned int mask = ACPI_STA_DEVICE_ENABLED | ACPI_STA_DEVICE_FUNCTIONING;
	return (sta & mask) == mask;
}

/**
 * trim_stale_devices - remove PCI devices that are not responding.
 * @dev: PCI device to start walking the hierarchy from.
 */
static void trim_stale_devices(struct pci_dev *dev)
{
	struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
	struct pci_bus *bus = dev->subordinate;
	bool alive = dev->ignore_hotplug;

	if (adev) {
		acpi_status status;
		unsigned long long sta;

		status = acpi_evaluate_integer(adev->handle, "_STA", NULL, &sta);
		alive = alive || (ACPI_SUCCESS(status) && device_status_valid(sta));
	}
	if (!alive)
		alive = pci_device_is_present(dev);

	if (!alive) {
		pci_stop_and_remove_bus_device(dev);
		if (adev)
			acpi_bus_trim(adev);
	} else if (bus) {
		struct pci_dev *child, *tmp;

		/* The device is a bridge. so check the bus below it. */
		pm_runtime_get_sync(&dev->dev);
		list_for_each_entry_safe_reverse(child, tmp, &bus->devices, bus_list)
			trim_stale_devices(child);

		pm_runtime_put(&dev->dev);
	}
}

/**
 * acpiphp_check_bridge - re-enumerate devices
 * @bridge: where to begin re-enumeration
 *
 * Iterate over all slots under this bridge and make sure that if a
 * card is present they are enabled, and if not they are disabled.
 */
static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
{
	struct acpiphp_slot *slot;

	/* Bail out if the bridge is going away. */
	if (bridge->is_going_away)
		return;

	if (bridge->pci_dev)
		pm_runtime_get_sync(&bridge->pci_dev->dev);

	list_for_each_entry(slot, &bridge->slots, node) {
		struct pci_bus *bus = slot->bus;
		struct pci_dev *dev, *tmp;

		if (slot_no_hotplug(slot)) {
			; /* do nothing */
		} else if (device_status_valid(get_slot_status(slot))) {
			/* remove stale devices if any */
			list_for_each_entry_safe_reverse(dev, tmp,
							 &bus->devices, bus_list)
				if (PCI_SLOT(dev->devfn) == slot->device)
					trim_stale_devices(dev);

			/* configure all functions */
			enable_slot(slot);
		} else {
			disable_slot(slot);
		}
	}

	if (bridge->pci_dev)
		pm_runtime_put(&bridge->pci_dev->dev);
}

/*
 * Remove devices for which we could not assign resources, call
 * arch specific code to fix-up the bus
 */
static void acpiphp_sanitize_bus(struct pci_bus *bus)
{
	struct pci_dev *dev, *tmp;
	int i;
	unsigned long type_mask = IORESOURCE_IO | IORESOURCE_MEM;

	list_for_each_entry_safe_reverse(dev, tmp, &bus->devices, bus_list) {
		for (i = 0; i < PCI_BRIDGE_RESOURCES; i++) {
			struct resource *res = &dev->resource[i];
			if ((res->flags & type_mask) && !res->start &&
					res->end) {
				/* Could not assign a required resources
				 * for this device, remove it */
				pci_stop_and_remove_bus_device(dev);
				break;
			}
		}
	}
}

/*
 * ACPI event handlers
 */

void acpiphp_check_host_bridge(struct acpi_device *adev)
{
	struct acpiphp_bridge *bridge = NULL;

	acpi_lock_hp_context();
	if (adev->hp) {
		bridge = to_acpiphp_root_context(adev->hp)->root_bridge;
		if (bridge)
			get_bridge(bridge);
	}
	acpi_unlock_hp_context();
	if (bridge) {
		pci_lock_rescan_remove();

		acpiphp_check_bridge(bridge);

		pci_unlock_rescan_remove();
		put_bridge(bridge);
	}
}

static int acpiphp_disable_and_eject_slot(struct acpiphp_slot *slot);

static void hotplug_event(u32 type, struct acpiphp_context *context)
{
	acpi_handle handle = context->hp.self->handle;
	struct acpiphp_func *func = &context->func;
	struct acpiphp_slot *slot = func->slot;
	struct acpiphp_bridge *bridge;

	acpi_lock_hp_context();
	bridge = context->bridge;
	if (bridge)
		get_bridge(bridge);

	acpi_unlock_hp_context();

	pci_lock_rescan_remove();

	switch (type) {
	case ACPI_NOTIFY_BUS_CHECK:
		/* bus re-enumerate */
		acpi_handle_debug(handle, "Bus check in %s()\n", __func__);
		if (bridge)
			acpiphp_check_bridge(bridge);
		else if (!(slot->flags & SLOT_IS_GOING_AWAY))
			enable_slot(slot);

		break;

	case ACPI_NOTIFY_DEVICE_CHECK:
		/* device check */
		acpi_handle_debug(handle, "Device check in %s()\n", __func__);
		if (bridge) {
			acpiphp_check_bridge(bridge);
		} else if (!(slot->flags & SLOT_IS_GOING_AWAY)) {
			/*
			 * Check if anything has changed in the slot and rescan
			 * from the parent if that's the case.
			 */
			if (acpiphp_rescan_slot(slot))
				acpiphp_check_bridge(func->parent);
		}
		break;

	case ACPI_NOTIFY_EJECT_REQUEST:
		/* request device eject */
		acpi_handle_debug(handle, "Eject request in %s()\n", __func__);
		acpiphp_disable_and_eject_slot(slot);
		break;
	}

	pci_unlock_rescan_remove();
	if (bridge)
		put_bridge(bridge);
}

static int acpiphp_hotplug_notify(struct acpi_device *adev, u32 type)
{
	struct acpiphp_context *context;

	context = acpiphp_grab_context(adev);
	if (!context)
		return -ENODATA;

	hotplug_event(type, context);
	acpiphp_let_context_go(context);
	return 0;
}

/**
 * acpiphp_enumerate_slots - Enumerate PCI slots for a given bus.
 * @bus: PCI bus to enumerate the slots for.
 *
 * A "slot" is an object associated with a PCI device number.  All functions
 * (PCI devices) with the same bus and device number belong to the same slot.
 */
void acpiphp_enumerate_slots(struct pci_bus *bus)
{
	struct acpiphp_bridge *bridge;
	struct acpi_device *adev;
	acpi_handle handle;
	acpi_status status;

	if (acpiphp_disabled)
		return;

	adev = ACPI_COMPANION(bus->bridge);
	if (!adev)
		return;

	handle = adev->handle;
	bridge = kzalloc(sizeof(struct acpiphp_bridge), GFP_KERNEL);
	if (!bridge)
		return;

	INIT_LIST_HEAD(&bridge->slots);
	kref_init(&bridge->ref);
	bridge->pci_dev = pci_dev_get(bus->self);
	bridge->pci_bus = bus;

	/*
	 * Grab a ref to the subordinate PCI bus in case the bus is
	 * removed via PCI core logical hotplug. The ref pins the bus
	 * (which we access during module unload).
	 */
	get_device(&bus->dev);

	acpi_lock_hp_context();
	if (pci_is_root_bus(bridge->pci_bus)) {
		struct acpiphp_root_context *root_context;

		root_context = kzalloc(sizeof(*root_context), GFP_KERNEL);
		if (!root_context)
			goto err;

		root_context->root_bridge = bridge;
		acpi_set_hp_context(adev, &root_context->hp);
	} else {
		struct acpiphp_context *context;

		/*
		 * This bridge should have been registered as a hotplug function
		 * under its parent, so the context should be there, unless the
		 * parent is going to be handled by pciehp, in which case this
		 * bridge is not interesting to us either.
		 */
		context = acpiphp_get_context(adev);
		if (!context)
			goto err;

		bridge->context = context;
		context->bridge = bridge;
		/* Get a reference to the parent bridge. */
		get_bridge(context->func.parent);
	}
	acpi_unlock_hp_context();

	/* Must be added to the list prior to calling acpiphp_add_context(). */
	mutex_lock(&bridge_mutex);
	list_add(&bridge->list, &bridge_list);
	mutex_unlock(&bridge_mutex);

	/* register all slot objects under this bridge */
	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
				     acpiphp_add_context, NULL, bridge, NULL);
	if (ACPI_FAILURE(status)) {
		acpi_handle_err(handle, "failed to register slots\n");
		cleanup_bridge(bridge);
		put_bridge(bridge);
	}
	return;

 err:
	acpi_unlock_hp_context();
	put_device(&bus->dev);
	pci_dev_put(bridge->pci_dev);
	kfree(bridge);
}

static void acpiphp_drop_bridge(struct acpiphp_bridge *bridge)
{
	if (pci_is_root_bus(bridge->pci_bus)) {
		struct acpiphp_root_context *root_context;
		struct acpi_device *adev;

		acpi_lock_hp_context();
		adev = ACPI_COMPANION(bridge->pci_bus->bridge);
		root_context = to_acpiphp_root_context(adev->hp);
		adev->hp = NULL;
		acpi_unlock_hp_context();
		kfree(root_context);
	}
	cleanup_bridge(bridge);
	put_bridge(bridge);
}

/**
 * acpiphp_remove_slots - Remove slot objects associated with a given bus.
 * @bus: PCI bus to remove the slot objects for.
 */
void acpiphp_remove_slots(struct pci_bus *bus)
{
	struct acpiphp_bridge *bridge;

	if (acpiphp_disabled)
		return;

	mutex_lock(&bridge_mutex);
	list_for_each_entry(bridge, &bridge_list, list)
		if (bridge->pci_bus == bus) {
			mutex_unlock(&bridge_mutex);
			acpiphp_drop_bridge(bridge);
			return;
		}

	mutex_unlock(&bridge_mutex);
}

/**
 * acpiphp_enable_slot - power on slot
 * @slot: ACPI PHP slot
 */
int acpiphp_enable_slot(struct acpiphp_slot *slot)
{
	pci_lock_rescan_remove();

	if (slot->flags & SLOT_IS_GOING_AWAY) {
		pci_unlock_rescan_remove();
		return -ENODEV;
	}

	/* configure all functions */
	if (!(slot->flags & SLOT_ENABLED))
		enable_slot(slot);

	pci_unlock_rescan_remove();
	return 0;
}

/**
 * acpiphp_disable_and_eject_slot - power off and eject slot
 * @slot: ACPI PHP slot
 */
static int acpiphp_disable_and_eject_slot(struct acpiphp_slot *slot)
{
	struct acpiphp_func *func;

	if (slot->flags & SLOT_IS_GOING_AWAY)
		return -ENODEV;

	/* unconfigure all functions */
	disable_slot(slot);

	list_for_each_entry(func, &slot->funcs, sibling)
		if (func->flags & FUNC_HAS_EJ0) {
			acpi_handle handle = func_to_handle(func);

			if (ACPI_FAILURE(acpi_evaluate_ej0(handle)))
				acpi_handle_err(handle, "_EJ0 failed\n");

			break;
		}

	return 0;
}

int acpiphp_disable_slot(struct acpiphp_slot *slot)
{
	int ret;

	/*
	 * Acquire acpi_scan_lock to ensure that the execution of _EJ0 in
	 * acpiphp_disable_and_eject_slot() will be synchronized properly.
	 */
	acpi_scan_lock_acquire();
	pci_lock_rescan_remove();
	ret = acpiphp_disable_and_eject_slot(slot);
	pci_unlock_rescan_remove();
	acpi_scan_lock_release();
	return ret;
}

/*
 * slot enabled:  1
 * slot disabled: 0
 */
u8 acpiphp_get_power_status(struct acpiphp_slot *slot)
{
	return (slot->flags & SLOT_ENABLED);
}

/*
 * latch   open:  1
 * latch closed:  0
 */
u8 acpiphp_get_latch_status(struct acpiphp_slot *slot)
{
	return !(get_slot_status(slot) & ACPI_STA_DEVICE_UI);
}

/*
 * adapter presence : 1
 *          absence : 0
 */
u8 acpiphp_get_adapter_status(struct acpiphp_slot *slot)
{
	return !!get_slot_status(slot);
}