/*
 *  pci_link.c - ACPI PCI Interrupt Link Device Driver ($Revision: 34 $)
 *
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2002       Dominik Brodowski <devel@brodo.de>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * TBD: 
 *      1. Support more than one IRQ resource entry per link device (index).
 *	2. Implement start/stop mechanism and use ACPI Bus Driver facilities
 *	   for IRQ management (e.g. start()->_SRS).
 */

#include <linux/sysdev.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/proc_fs.h>
#include <linux/spinlock.h>
#include <linux/pm.h>
#include <linux/pci.h>
#include <linux/mutex.h>

#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>

#define _COMPONENT		ACPI_PCI_COMPONENT
ACPI_MODULE_NAME("pci_link")
#define ACPI_PCI_LINK_CLASS		"pci_irq_routing"
#define ACPI_PCI_LINK_HID		"PNP0C0F"
#define ACPI_PCI_LINK_DRIVER_NAME	"ACPI PCI Interrupt Link Driver"
#define ACPI_PCI_LINK_DEVICE_NAME	"PCI Interrupt Link"
#define ACPI_PCI_LINK_FILE_INFO		"info"
#define ACPI_PCI_LINK_FILE_STATUS	"state"
#define ACPI_PCI_LINK_MAX_POSSIBLE 16
static int acpi_pci_link_add(struct acpi_device *device);
static int acpi_pci_link_remove(struct acpi_device *device, int type);

static struct acpi_driver acpi_pci_link_driver = {
	.name = ACPI_PCI_LINK_DRIVER_NAME,
	.class = ACPI_PCI_LINK_CLASS,
	.ids = ACPI_PCI_LINK_HID,
	.ops = {
		.add = acpi_pci_link_add,
		.remove = acpi_pci_link_remove,
		},
};

/*
 * If a link is initialized, we never change its active and initialized
 * later even the link is disable. Instead, we just repick the active irq
 */
struct acpi_pci_link_irq {
	u8 active;		/* Current IRQ */
	u8 triggering;		/* All IRQs */
	u8 polarity;	/* All IRQs */
	u8 resource_type;
	u8 possible_count;
	u8 possible[ACPI_PCI_LINK_MAX_POSSIBLE];
	u8 initialized:1;
	u8 reserved:7;
};

struct acpi_pci_link {
	struct list_head node;
	struct acpi_device *device;
	acpi_handle handle;
	struct acpi_pci_link_irq irq;
	int refcnt;
};

static struct {
	int count;
	struct list_head entries;
} acpi_link;
DEFINE_MUTEX(acpi_link_lock);

/* --------------------------------------------------------------------------
                            PCI Link Device Management
   -------------------------------------------------------------------------- */

/*
 * set context (link) possible list from resource list
 */
static acpi_status
acpi_pci_link_check_possible(struct acpi_resource *resource, void *context)
{
	struct acpi_pci_link *link = (struct acpi_pci_link *)context;
	u32 i = 0;

	ACPI_FUNCTION_TRACE("acpi_pci_link_check_possible");

	switch (resource->type) {
	case ACPI_RESOURCE_TYPE_START_DEPENDENT:
		return_ACPI_STATUS(AE_OK);
	case ACPI_RESOURCE_TYPE_IRQ:
		{
			struct acpi_resource_irq *p = &resource->data.irq;
			if (!p || !p->interrupt_count) {
				ACPI_DEBUG_PRINT((ACPI_DB_WARN,
						  "Blank IRQ resource\n"));
				return_ACPI_STATUS(AE_OK);
			}
			for (i = 0;
			     (i < p->interrupt_count
			      && i < ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
				if (!p->interrupts[i]) {
					ACPI_DEBUG_PRINT((ACPI_DB_WARN,
							  "Invalid IRQ %d\n",
							  p->interrupts[i]));
					continue;
				}
				link->irq.possible[i] = p->interrupts[i];
				link->irq.possible_count++;
			}
			link->irq.triggering = p->triggering;
			link->irq.polarity = p->polarity;
			link->irq.resource_type = ACPI_RESOURCE_TYPE_IRQ;
			break;
		}
	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
		{
			struct acpi_resource_extended_irq *p =
			    &resource->data.extended_irq;
			if (!p || !p->interrupt_count) {
				ACPI_DEBUG_PRINT((ACPI_DB_WARN,
						  "Blank EXT IRQ resource\n"));
				return_ACPI_STATUS(AE_OK);
			}
			for (i = 0;
			     (i < p->interrupt_count
			      && i < ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
				if (!p->interrupts[i]) {
					ACPI_DEBUG_PRINT((ACPI_DB_WARN,
							  "Invalid IRQ %d\n",
							  p->interrupts[i]));
					continue;
				}
				link->irq.possible[i] = p->interrupts[i];
				link->irq.possible_count++;
			}
			link->irq.triggering = p->triggering;
			link->irq.polarity = p->polarity;
			link->irq.resource_type = ACPI_RESOURCE_TYPE_EXTENDED_IRQ;
			break;
		}
	default:
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
				  "Resource is not an IRQ entry\n"));
		return_ACPI_STATUS(AE_OK);
	}

	return_ACPI_STATUS(AE_CTRL_TERMINATE);
}

static int acpi_pci_link_get_possible(struct acpi_pci_link *link)
{
	acpi_status status;

	ACPI_FUNCTION_TRACE("acpi_pci_link_get_possible");

	if (!link)
		return_VALUE(-EINVAL);

	status = acpi_walk_resources(link->handle, METHOD_NAME__PRS,
				     acpi_pci_link_check_possible, link);
	if (ACPI_FAILURE(status)) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _PRS\n"));
		return_VALUE(-ENODEV);
	}

	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
			  "Found %d possible IRQs\n",
			  link->irq.possible_count));

	return_VALUE(0);
}

static acpi_status
acpi_pci_link_check_current(struct acpi_resource *resource, void *context)
{
	int *irq = (int *)context;

	ACPI_FUNCTION_TRACE("acpi_pci_link_check_current");

	switch (resource->type) {
	case ACPI_RESOURCE_TYPE_IRQ:
		{
			struct acpi_resource_irq *p = &resource->data.irq;
			if (!p || !p->interrupt_count) {
				/*
				 * IRQ descriptors may have no IRQ# bits set,
				 * particularly those those w/ _STA disabled
				 */
				ACPI_DEBUG_PRINT((ACPI_DB_INFO,
						  "Blank IRQ resource\n"));
				return_ACPI_STATUS(AE_OK);
			}
			*irq = p->interrupts[0];
			break;
		}
	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
		{
			struct acpi_resource_extended_irq *p =
			    &resource->data.extended_irq;
			if (!p || !p->interrupt_count) {
				/*
				 * extended IRQ descriptors must
				 * return at least 1 IRQ
				 */
				ACPI_DEBUG_PRINT((ACPI_DB_WARN,
						  "Blank EXT IRQ resource\n"));
				return_ACPI_STATUS(AE_OK);
			}
			*irq = p->interrupts[0];
			break;
		}
		break;
	default:
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Resource %d isn't an IRQ\n", resource->type));
	case ACPI_RESOURCE_TYPE_END_TAG:
		return_ACPI_STATUS(AE_OK);
	}
	return_ACPI_STATUS(AE_CTRL_TERMINATE);
}

/*
 * Run _CRS and set link->irq.active
 *
 * return value:
 * 0 - success
 * !0 - failure
 */
static int acpi_pci_link_get_current(struct acpi_pci_link *link)
{
	int result = 0;
	acpi_status status = AE_OK;
	int irq = 0;

	ACPI_FUNCTION_TRACE("acpi_pci_link_get_current");

	if (!link || !link->handle)
		return_VALUE(-EINVAL);

	link->irq.active = 0;

	/* in practice, status disabled is meaningless, ignore it */
	if (acpi_strict) {
		/* Query _STA, set link->device->status */
		result = acpi_bus_get_status(link->device);
		if (result) {
			ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
					  "Unable to read status\n"));
			goto end;
		}

		if (!link->device->status.enabled) {
			ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link disabled\n"));
			return_VALUE(0);
		}
	}

	/* 
	 * Query and parse _CRS to get the current IRQ assignment. 
	 */

	status = acpi_walk_resources(link->handle, METHOD_NAME__CRS,
				     acpi_pci_link_check_current, &irq);
	if (ACPI_FAILURE(status)) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _CRS\n"));
		result = -ENODEV;
		goto end;
	}

	if (acpi_strict && !irq) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "_CRS returned 0\n"));
		result = -ENODEV;
	}

	link->irq.active = irq;

	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link at IRQ %d \n", link->irq.active));

      end:
	return_VALUE(result);
}

static int acpi_pci_link_set(struct acpi_pci_link *link, int irq)
{
	int result = 0;
	acpi_status status = AE_OK;
	struct {
		struct acpi_resource res;
		struct acpi_resource end;
	} *resource;
	struct acpi_buffer buffer = { 0, NULL };

	ACPI_FUNCTION_TRACE("acpi_pci_link_set");

	if (!link || !irq)
		return_VALUE(-EINVAL);

	resource = kmalloc(sizeof(*resource) + 1, GFP_ATOMIC);
	if (!resource)
		return_VALUE(-ENOMEM);

	memset(resource, 0, sizeof(*resource) + 1);
	buffer.length = sizeof(*resource) + 1;
	buffer.pointer = resource;

	switch (link->irq.resource_type) {
	case ACPI_RESOURCE_TYPE_IRQ:
		resource->res.type = ACPI_RESOURCE_TYPE_IRQ;
		resource->res.length = sizeof(struct acpi_resource);
		resource->res.data.irq.triggering = link->irq.triggering;
		resource->res.data.irq.polarity =
		    link->irq.polarity;
		if (link->irq.triggering == ACPI_EDGE_SENSITIVE)
			resource->res.data.irq.sharable =
			    ACPI_EXCLUSIVE;
		else
			resource->res.data.irq.sharable = ACPI_SHARED;
		resource->res.data.irq.interrupt_count = 1;
		resource->res.data.irq.interrupts[0] = irq;
		break;

	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
		resource->res.type = ACPI_RESOURCE_TYPE_EXTENDED_IRQ;
		resource->res.length = sizeof(struct acpi_resource);
		resource->res.data.extended_irq.producer_consumer =
		    ACPI_CONSUMER;
		resource->res.data.extended_irq.triggering =
		    link->irq.triggering;
		resource->res.data.extended_irq.polarity =
		    link->irq.polarity;
		if (link->irq.triggering == ACPI_EDGE_SENSITIVE)
			resource->res.data.irq.sharable =
			    ACPI_EXCLUSIVE;
		else
			resource->res.data.irq.sharable = ACPI_SHARED;
		resource->res.data.extended_irq.interrupt_count = 1;
		resource->res.data.extended_irq.interrupts[0] = irq;
		/* ignore resource_source, it's optional */
		break;
	default:
		printk("ACPI BUG: resource_type %d\n", link->irq.resource_type);
		result = -EINVAL;
		goto end;

	}
	resource->end.type = ACPI_RESOURCE_TYPE_END_TAG;

	/* Attempt to set the resource */
	status = acpi_set_current_resources(link->handle, &buffer);

	/* check for total failure */
	if (ACPI_FAILURE(status)) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _SRS\n"));
		result = -ENODEV;
		goto end;
	}

	/* Query _STA, set device->status */
	result = acpi_bus_get_status(link->device);
	if (result) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Unable to read status\n"));
		goto end;
	}
	if (!link->device->status.enabled) {
		printk(KERN_WARNING PREFIX
		       "%s [%s] disabled and referenced, BIOS bug.\n",
		       acpi_device_name(link->device),
		       acpi_device_bid(link->device));
	}

	/* Query _CRS, set link->irq.active */
	result = acpi_pci_link_get_current(link);
	if (result) {
		goto end;
	}

	/*
	 * Is current setting not what we set?
	 * set link->irq.active
	 */
	if (link->irq.active != irq) {
		/*
		 * policy: when _CRS doesn't return what we just _SRS
		 * assume _SRS worked and override _CRS value.
		 */
		printk(KERN_WARNING PREFIX
		       "%s [%s] BIOS reported IRQ %d, using IRQ %d\n",
		       acpi_device_name(link->device),
		       acpi_device_bid(link->device), link->irq.active, irq);
		link->irq.active = irq;
	}

	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Set IRQ %d\n", link->irq.active));

      end:
	kfree(resource);
	return_VALUE(result);
}

/* --------------------------------------------------------------------------
                            PCI Link IRQ Management
   -------------------------------------------------------------------------- */

/*
 * "acpi_irq_balance" (default in APIC mode) enables ACPI to use PIC Interrupt
 * Link Devices to move the PIRQs around to minimize sharing.
 * 
 * "acpi_irq_nobalance" (default in PIC mode) tells ACPI not to move any PIC IRQs
 * that the BIOS has already set to active.  This is necessary because
 * ACPI has no automatic means of knowing what ISA IRQs are used.  Note that
 * if the BIOS doesn't set a Link Device active, ACPI needs to program it
 * even if acpi_irq_nobalance is set.
 *
 * A tables of penalties avoids directing PCI interrupts to well known
 * ISA IRQs. Boot params are available to over-ride the default table:
 *
 * List interrupts that are free for PCI use.
 * acpi_irq_pci=n[,m]
 *
 * List interrupts that should not be used for PCI:
 * acpi_irq_isa=n[,m]
 *
 * Note that PCI IRQ routers have a list of possible IRQs,
 * which may not include the IRQs this table says are available.
 * 
 * Since this heuristic can't tell the difference between a link
 * that no device will attach to, vs. a link which may be shared
 * by multiple active devices -- it is not optimal.
 *
 * If interrupt performance is that important, get an IO-APIC system
 * with a pin dedicated to each device.  Or for that matter, an MSI
 * enabled system.
 */

#define ACPI_MAX_IRQS		256
#define ACPI_MAX_ISA_IRQ	16

#define PIRQ_PENALTY_PCI_AVAILABLE	(0)
#define PIRQ_PENALTY_PCI_POSSIBLE	(16*16)
#define PIRQ_PENALTY_PCI_USING		(16*16*16)
#define PIRQ_PENALTY_ISA_TYPICAL	(16*16*16*16)
#define PIRQ_PENALTY_ISA_USED		(16*16*16*16*16)
#define PIRQ_PENALTY_ISA_ALWAYS		(16*16*16*16*16*16)

static int acpi_irq_penalty[ACPI_MAX_IRQS] = {
	PIRQ_PENALTY_ISA_ALWAYS,	/* IRQ0 timer */
	PIRQ_PENALTY_ISA_ALWAYS,	/* IRQ1 keyboard */
	PIRQ_PENALTY_ISA_ALWAYS,	/* IRQ2 cascade */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ3 serial */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ4 serial */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ5 sometimes SoundBlaster */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ6 */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ7 parallel, spurious */
	PIRQ_PENALTY_ISA_TYPICAL,	/* IRQ8 rtc, sometimes */
	PIRQ_PENALTY_PCI_AVAILABLE,	/* IRQ9  PCI, often acpi */
	PIRQ_PENALTY_PCI_AVAILABLE,	/* IRQ10 PCI */
	PIRQ_PENALTY_PCI_AVAILABLE,	/* IRQ11 PCI */
	PIRQ_PENALTY_ISA_USED,	/* IRQ12 mouse */
	PIRQ_PENALTY_ISA_USED,	/* IRQ13 fpe, sometimes */
	PIRQ_PENALTY_ISA_USED,	/* IRQ14 ide0 */
	PIRQ_PENALTY_ISA_USED,	/* IRQ15 ide1 */
	/* >IRQ15 */
};

int __init acpi_irq_penalty_init(void)
{
	struct list_head *node = NULL;
	struct acpi_pci_link *link = NULL;
	int i = 0;

	ACPI_FUNCTION_TRACE("acpi_irq_penalty_init");

	/*
	 * Update penalties to facilitate IRQ balancing.
	 */
	list_for_each(node, &acpi_link.entries) {

		link = list_entry(node, struct acpi_pci_link, node);
		if (!link) {
			ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
					  "Invalid link context\n"));
			continue;
		}

		/*
		 * reflect the possible and active irqs in the penalty table --
		 * useful for breaking ties.
		 */
		if (link->irq.possible_count) {
			int penalty =
			    PIRQ_PENALTY_PCI_POSSIBLE /
			    link->irq.possible_count;

			for (i = 0; i < link->irq.possible_count; i++) {
				if (link->irq.possible[i] < ACPI_MAX_ISA_IRQ)
					acpi_irq_penalty[link->irq.
							 possible[i]] +=
					    penalty;
			}

		} else if (link->irq.active) {
			acpi_irq_penalty[link->irq.active] +=
			    PIRQ_PENALTY_PCI_POSSIBLE;
		}
	}
	/* Add a penalty for the SCI */
	acpi_irq_penalty[acpi_fadt.sci_int] += PIRQ_PENALTY_PCI_USING;

	return_VALUE(0);
}

static int acpi_irq_balance;	/* 0: static, 1: balance */

static int acpi_pci_link_allocate(struct acpi_pci_link *link)
{
	int irq;
	int i;

	ACPI_FUNCTION_TRACE("acpi_pci_link_allocate");

	if (link->irq.initialized) {
		if (link->refcnt == 0)
			/* This means the link is disabled but initialized */
			acpi_pci_link_set(link, link->irq.active);
		return_VALUE(0);
	}

	/*
	 * search for active IRQ in list of possible IRQs.
	 */
	for (i = 0; i < link->irq.possible_count; ++i) {
		if (link->irq.active == link->irq.possible[i])
			break;
	}
	/*
	 * forget active IRQ that is not in possible list
	 */
	if (i == link->irq.possible_count) {
		if (acpi_strict)
			printk(KERN_WARNING PREFIX "_CRS %d not found"
			       " in _PRS\n", link->irq.active);
		link->irq.active = 0;
	}

	/*
	 * if active found, use it; else pick entry from end of possible list.
	 */
	if (link->irq.active) {
		irq = link->irq.active;
	} else {
		irq = link->irq.possible[link->irq.possible_count - 1];
	}

	if (acpi_irq_balance || !link->irq.active) {
		/*
		 * Select the best IRQ.  This is done in reverse to promote
		 * the use of IRQs 9, 10, 11, and >15.
		 */
		for (i = (link->irq.possible_count - 1); i >= 0; i--) {
			if (acpi_irq_penalty[irq] >
			    acpi_irq_penalty[link->irq.possible[i]])
				irq = link->irq.possible[i];
		}
	}

	/* Attempt to enable the link device at this IRQ. */
	if (acpi_pci_link_set(link, irq)) {
		printk(PREFIX
		       "Unable to set IRQ for %s [%s] (likely buggy ACPI BIOS).\n"
		       "Try pci=noacpi or acpi=off\n",
		       acpi_device_name(link->device),
		       acpi_device_bid(link->device));
		return_VALUE(-ENODEV);
	} else {
		acpi_irq_penalty[link->irq.active] += PIRQ_PENALTY_PCI_USING;
		printk(PREFIX "%s [%s] enabled at IRQ %d\n",
		       acpi_device_name(link->device),
		       acpi_device_bid(link->device), link->irq.active);
	}

	link->irq.initialized = 1;

	return_VALUE(0);
}

/*
 * acpi_pci_link_allocate_irq
 * success: return IRQ >= 0
 * failure: return -1
 */

int
acpi_pci_link_allocate_irq(acpi_handle handle,
			   int index,
			   int *triggering, int *polarity, char **name)
{
	int result = 0;
	struct acpi_device *device = NULL;
	struct acpi_pci_link *link = NULL;

	ACPI_FUNCTION_TRACE("acpi_pci_link_allocate_irq");

	result = acpi_bus_get_device(handle, &device);
	if (result) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link device\n"));
		return_VALUE(-1);
	}

	link = (struct acpi_pci_link *)acpi_driver_data(device);
	if (!link) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link context\n"));
		return_VALUE(-1);
	}

	/* TBD: Support multiple index (IRQ) entries per Link Device */
	if (index) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid index %d\n", index));
		return_VALUE(-1);
	}

	mutex_lock(&acpi_link_lock);
	if (acpi_pci_link_allocate(link)) {
		mutex_unlock(&acpi_link_lock);
		return_VALUE(-1);
	}

	if (!link->irq.active) {
		mutex_unlock(&acpi_link_lock);
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Link active IRQ is 0!\n"));
		return_VALUE(-1);
	}
	link->refcnt++;
	mutex_unlock(&acpi_link_lock);

	if (triggering)
		*triggering = link->irq.triggering;
	if (polarity)
		*polarity = link->irq.polarity;
	if (name)
		*name = acpi_device_bid(link->device);
	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
			  "Link %s is referenced\n",
			  acpi_device_bid(link->device)));
	return_VALUE(link->irq.active);
}

/*
 * We don't change link's irq information here.  After it is reenabled, we
 * continue use the info
 */
int acpi_pci_link_free_irq(acpi_handle handle)
{
	struct acpi_device *device = NULL;
	struct acpi_pci_link *link = NULL;
	acpi_status result;

	ACPI_FUNCTION_TRACE("acpi_pci_link_free_irq");

	result = acpi_bus_get_device(handle, &device);
	if (result) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link device\n"));
		return_VALUE(-1);
	}

	link = (struct acpi_pci_link *)acpi_driver_data(device);
	if (!link) {
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link context\n"));
		return_VALUE(-1);
	}

	mutex_lock(&acpi_link_lock);
	if (!link->irq.initialized) {
		mutex_unlock(&acpi_link_lock);
		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Link isn't initialized\n"));
		return_VALUE(-1);
	}
#ifdef	FUTURE_USE
	/*
	 * The Link reference count allows us to _DISable an unused link
	 * and suspend time, and set it again  on resume.
	 * However, 2.6.12 still has irq_router.resume
	 * which blindly restores the link state.
	 * So we disable the reference count method
	 * to prevent duplicate acpi_pci_link_set()
	 * which would harm some systems
	 */
	link->refcnt--;
#endif
	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
			  "Link %s is dereferenced\n",
			  acpi_device_bid(link->device)));

	if (link->refcnt == 0) {
		acpi_ut_evaluate_object(link->handle, "_DIS", 0, NULL);
	}
	mutex_unlock(&acpi_link_lock);
	return_VALUE(link->irq.active);
}

/* --------------------------------------------------------------------------
                                 Driver Interface
   -------------------------------------------------------------------------- */

static int acpi_pci_link_add(struct acpi_device *device)
{
	int result = 0;
	struct acpi_pci_link *link = NULL;
	int i = 0;
	int found = 0;

	ACPI_FUNCTION_TRACE("acpi_pci_link_add");

	if (!device)
		return_VALUE(-EINVAL);

	link = kmalloc(sizeof(struct acpi_pci_link), GFP_KERNEL);
	if (!link)
		return_VALUE(-ENOMEM);
	memset(link, 0, sizeof(struct acpi_pci_link));

	link->device = device;
	link->handle = device->handle;
	strcpy(acpi_device_name(device), ACPI_PCI_LINK_DEVICE_NAME);
	strcpy(acpi_device_class(device), ACPI_PCI_LINK_CLASS);
	acpi_driver_data(device) = link;

	mutex_lock(&acpi_link_lock);
	result = acpi_pci_link_get_possible(link);
	if (result)
		goto end;

	/* query and set link->irq.active */
	acpi_pci_link_get_current(link);

	printk(PREFIX "%s [%s] (IRQs", acpi_device_name(device),
	       acpi_device_bid(device));
	for (i = 0; i < link->irq.possible_count; i++) {
		if (link->irq.active == link->irq.possible[i]) {
			printk(" *%d", link->irq.possible[i]);
			found = 1;
		} else
			printk(" %d", link->irq.possible[i]);
	}

	printk(")");

	if (!found)
		printk(" *%d", link->irq.active);

	if (!link->device->status.enabled)
		printk(", disabled.");

	printk("\n");

	/* TBD: Acquire/release lock */
	list_add_tail(&link->node, &acpi_link.entries);
	acpi_link.count++;

      end:
	/* disable all links -- to be activated on use */
	acpi_ut_evaluate_object(link->handle, "_DIS", 0, NULL);
	mutex_unlock(&acpi_link_lock);

	if (result)
		kfree(link);

	return_VALUE(result);
}

static int acpi_pci_link_resume(struct acpi_pci_link *link)
{
	ACPI_FUNCTION_TRACE("acpi_pci_link_resume");

	if (link->refcnt && link->irq.active && link->irq.initialized)
		return_VALUE(acpi_pci_link_set(link, link->irq.active));
	else
		return_VALUE(0);
}

/*
 * FIXME: this is a workaround to avoid nasty warning.  It will be removed
 * after every device calls pci_disable_device in .resume.
 */
int acpi_in_resume;
static int irqrouter_resume(struct sys_device *dev)
{
	struct list_head *node = NULL;
	struct acpi_pci_link *link = NULL;

	ACPI_FUNCTION_TRACE("irqrouter_resume");

	/* Make sure SCI is enabled again (Apple firmware bug?) */
	acpi_set_register(ACPI_BITREG_SCI_ENABLE, 1, ACPI_MTX_DO_NOT_LOCK);

	acpi_in_resume = 1;
	list_for_each(node, &acpi_link.entries) {
		link = list_entry(node, struct acpi_pci_link, node);
		if (!link) {
			ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
					  "Invalid link context\n"));
			continue;
		}
		acpi_pci_link_resume(link);
	}
	acpi_in_resume = 0;
	return_VALUE(0);
}

static int acpi_pci_link_remove(struct acpi_device *device, int type)
{
	struct acpi_pci_link *link = NULL;

	ACPI_FUNCTION_TRACE("acpi_pci_link_remove");

	if (!device || !acpi_driver_data(device))
		return_VALUE(-EINVAL);

	link = (struct acpi_pci_link *)acpi_driver_data(device);

	mutex_lock(&acpi_link_lock);
	list_del(&link->node);
	mutex_unlock(&acpi_link_lock);

	kfree(link);

	return_VALUE(0);
}

/*
 * modify acpi_irq_penalty[] from cmdline
 */
static int __init acpi_irq_penalty_update(char *str, int used)
{
	int i;

	for (i = 0; i < 16; i++) {
		int retval;
		int irq;

		retval = get_option(&str, &irq);

		if (!retval)
			break;	/* no number found */

		if (irq < 0)
			continue;

		if (irq >= ACPI_MAX_IRQS)
			continue;

		if (used)
			acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_USED;
		else
			acpi_irq_penalty[irq] = PIRQ_PENALTY_PCI_AVAILABLE;

		if (retval != 2)	/* no next number */
			break;
	}
	return 1;
}

/*
 * We'd like PNP to call this routine for the
 * single ISA_USED value for each legacy device.
 * But instead it calls us with each POSSIBLE setting.
 * There is no ISA_POSSIBLE weight, so we simply use
 * the (small) PCI_USING penalty.
 */
void acpi_penalize_isa_irq(int irq, int active)
{
	if (active)
		acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_USED;
	else
		acpi_irq_penalty[irq] += PIRQ_PENALTY_PCI_USING;
}

/*
 * Over-ride default table to reserve additional IRQs for use by ISA
 * e.g. acpi_irq_isa=5
 * Useful for telling ACPI how not to interfere with your ISA sound card.
 */
static int __init acpi_irq_isa(char *str)
{
	return acpi_irq_penalty_update(str, 1);
}

__setup("acpi_irq_isa=", acpi_irq_isa);

/*
 * Over-ride default table to free additional IRQs for use by PCI
 * e.g. acpi_irq_pci=7,15
 * Used for acpi_irq_balance to free up IRQs to reduce PCI IRQ sharing.
 */
static int __init acpi_irq_pci(char *str)
{
	return acpi_irq_penalty_update(str, 0);
}

__setup("acpi_irq_pci=", acpi_irq_pci);

static int __init acpi_irq_nobalance_set(char *str)
{
	acpi_irq_balance = 0;
	return 1;
}

__setup("acpi_irq_nobalance", acpi_irq_nobalance_set);

int __init acpi_irq_balance_set(char *str)
{
	acpi_irq_balance = 1;
	return 1;
}

__setup("acpi_irq_balance", acpi_irq_balance_set);

/* FIXME: we will remove this interface after all drivers call pci_disable_device */
static struct sysdev_class irqrouter_sysdev_class = {
	set_kset_name("irqrouter"),
	.resume = irqrouter_resume,
};

static struct sys_device device_irqrouter = {
	.id = 0,
	.cls = &irqrouter_sysdev_class,
};

static int __init irqrouter_init_sysfs(void)
{
	int error;

	ACPI_FUNCTION_TRACE("irqrouter_init_sysfs");

	if (acpi_disabled || acpi_noirq)
		return_VALUE(0);

	error = sysdev_class_register(&irqrouter_sysdev_class);
	if (!error)
		error = sysdev_register(&device_irqrouter);

	return_VALUE(error);
}

device_initcall(irqrouter_init_sysfs);

static int __init acpi_pci_link_init(void)
{
	ACPI_FUNCTION_TRACE("acpi_pci_link_init");

	if (acpi_noirq)
		return_VALUE(0);

	acpi_link.count = 0;
	INIT_LIST_HEAD(&acpi_link.entries);

	if (acpi_bus_register_driver(&acpi_pci_link_driver) < 0)
		return_VALUE(-ENODEV);

	return_VALUE(0);
}

subsys_initcall(acpi_pci_link_init);