// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *  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>
   *

   * 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/syscore_ops.h>

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/types.h>

  #include <linux/spinlock.h>
  #include <linux/pm.h>
  #include <linux/pci.h>

  #include <linux/mutex.h>

  #include <linux/slab.h>

  #include <linux/acpi.h>

  #include <linux/irq.h>

  #include "internal.h"

  #define _COMPONENT			ACPI_PCI_COMPONENT

  ACPI_MODULE_NAME("pci_link");

  #define ACPI_PCI_LINK_CLASS		"pci_irq_routing"

  #define ACPI_PCI_LINK_DEVICE_NAME	"PCI Interrupt Link"

  #define ACPI_PCI_LINK_MAX_POSSIBLE	16

  static int acpi_pci_link_add(struct acpi_device *device,
  			     const struct acpi_device_id *not_used);
  static void acpi_pci_link_remove(struct acpi_device *device);

  static const struct acpi_device_id link_device_ids[] = {

  	{"PNP0C0F", 0},
  	{"", 0},
  };

  static struct acpi_scan_handler pci_link_handler = {

  	.ids = link_device_ids,

  	.attach = acpi_pci_link_add,
  	.detach = 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 {

  	u32 active;		/* Current IRQ */

  	u8 triggering;		/* All IRQs */

  	u8 polarity;		/* All IRQs */

  	u8 resource_type;
  	u8 possible_count;

  	u32 possible[ACPI_PCI_LINK_MAX_POSSIBLE];

  	u8 initialized:1;
  	u8 reserved:7;

  };
  
  struct acpi_pci_link {

  	struct list_head		list;

  	struct acpi_device		*device;
  	struct acpi_pci_link_irq	irq;
  	int				refcnt;

  };

  static LIST_HEAD(acpi_link_list);

  static DEFINE_MUTEX(acpi_link_lock);

  static int sci_irq = -1, sci_penalty;

  /* --------------------------------------------------------------------------
                              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 = context;

  	u32 i;

  	switch (resource->type) {

  	case ACPI_RESOURCE_TYPE_START_DEPENDENT:

  	case ACPI_RESOURCE_TYPE_END_TAG:

  		return 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_INFO,
  						  "Blank _PRS IRQ resource
  "));

  				return AE_OK;

  			}

  			for (i = 0;

  			     (i < p->interrupt_count

  			      && i < ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
  				if (!p->interrupts[i]) {

  					printk(KERN_WARNING PREFIX
  					       "Invalid _PRS IRQ %d
  ",
  					       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) {

  				printk(KERN_WARNING PREFIX

  					      "Blank _PRS EXT IRQ resource
  ");

  				return AE_OK;

  			}
  			for (i = 0;

  			     (i < p->interrupt_count

  			      && i < ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
  				if (!p->interrupts[i]) {

  					printk(KERN_WARNING PREFIX
  					       "Invalid _PRS IRQ %d
  ",
  					       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:

  		printk(KERN_ERR PREFIX "_PRS resource type 0x%x isn't an IRQ
  ",
  		       resource->type);

  		return AE_OK;

  	}

  	return AE_CTRL_TERMINATE;

  }

  static int acpi_pci_link_get_possible(struct acpi_pci_link *link)

  {

  	acpi_status status;

  	status = acpi_walk_resources(link->device->handle, METHOD_NAME__PRS,

  				     acpi_pci_link_check_possible, link);

  	if (ACPI_FAILURE(status)) {

  		acpi_handle_debug(link->device->handle, "_PRS not present or invalid");
  		return 0;

  	}

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

  	return 0;

  }

  static acpi_status acpi_pci_link_check_current(struct acpi_resource *resource,
  					       void *context)

  {

  	int *irq = context;

  	switch (resource->type) {

  	case ACPI_RESOURCE_TYPE_START_DEPENDENT:
  	case ACPI_RESOURCE_TYPE_END_TAG:
  		return AE_OK;

  	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 _CRS IRQ resource
  "));

  				return 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
  				 */

  				printk(KERN_WARNING PREFIX

  					      "Blank _CRS EXT IRQ resource
  ");

  				return AE_OK;

  			}
  			*irq = p->interrupts[0];
  			break;

  		}

  		break;

  	default:

  		printk(KERN_ERR PREFIX "_CRS resource type 0x%x isn't an IRQ
  ",
  		       resource->type);

  		return AE_OK;

  	}

  	return 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;

  	int irq = 0;

  	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) {

  			printk(KERN_ERR PREFIX "Unable to read status
  ");

  			goto end;
  		}
  
  		if (!link->device->status.enabled) {
  			ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link disabled
  "));

  			return 0;

  		}
  	}

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

  	 */

  	status = acpi_walk_resources(link->device->handle, METHOD_NAME__CRS,

  				     acpi_pci_link_check_current, &irq);

  	if (ACPI_FAILURE(status)) {

  		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _CRS"));

  		result = -ENODEV;
  		goto end;
  	}
  
  	if (acpi_strict && !irq) {

  		printk(KERN_ERR PREFIX "_CRS returned 0
  ");

  		result = -ENODEV;
  	}
  
  	link->irq.active = irq;
  
  	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link at IRQ %d 
  ", link->irq.active));

        end:

  	return result;

  }

  static int acpi_pci_link_set(struct acpi_pci_link *link, int irq)

  {

  	int result;
  	acpi_status status;

  	struct {

  		struct acpi_resource res;
  		struct acpi_resource end;
  	} *resource;
  	struct acpi_buffer buffer = { 0, NULL };

  	if (!irq)

  		return -EINVAL;

  	resource = kzalloc(sizeof(*resource) + 1, irqs_disabled() ? GFP_ATOMIC: GFP_KERNEL);

  	if (!resource)

  		return -ENOMEM;

  	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.shareable =

  			    ACPI_EXCLUSIVE;

  		else

  			resource->res.data.irq.shareable = 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.extended_irq.shareable =

  			    ACPI_EXCLUSIVE;

  		else

  			resource->res.data.extended_irq.shareable = 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(KERN_ERR PREFIX "Invalid Resource_type %d
  ", link->irq.resource_type);

  		result = -EINVAL;
  		goto end;
  
  	}

  	resource->end.type = ACPI_RESOURCE_TYPE_END_TAG;

  	resource->end.length = sizeof(struct acpi_resource);

  
  	/* Attempt to set the resource */

  	status = acpi_set_current_resources(link->device->handle, &buffer);

  
  	/* check for total failure */
  	if (ACPI_FAILURE(status)) {

  		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _SRS"));

  		result = -ENODEV;
  		goto end;
  	}
  
  	/* Query _STA, set device->status */
  	result = acpi_bus_get_status(link->device);
  	if (result) {

  		printk(KERN_ERR PREFIX "Unable to read status
  ");

  		goto end;
  	}
  	if (!link->device->status.enabled) {

  		printk(KERN_WARNING PREFIX
  			      "%s [%s] disabled and referenced, BIOS bug
  ",

  			      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
  ",

  			      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
  ", link->irq.active));

  
        end:

  	kfree(resource);

  	return 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_ISA_IRQS	16

  #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_isa_irq_penalty[ACPI_MAX_ISA_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 */

  	0,				/* IRQ9  PCI, often acpi */
  	0,				/* IRQ10 PCI */
  	0,				/* 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 */

  };

  static int acpi_irq_pci_sharing_penalty(int irq)
  {
  	struct acpi_pci_link *link;
  	int penalty = 0;

  	int i;

  
  	list_for_each_entry(link, &acpi_link_list, list) {
  		/*
  		 * If a link is active, penalize its IRQ heavily
  		 * so we try to choose a different IRQ.
  		 */
  		if (link->irq.active && link->irq.active == irq)
  			penalty += PIRQ_PENALTY_PCI_USING;

  
  		/*
  		 * penalize the IRQs PCI might use, but not as severely.
  		 */
  		for (i = 0; i < link->irq.possible_count; i++)
  			if (link->irq.possible[i] == irq)
  				penalty += PIRQ_PENALTY_PCI_POSSIBLE /
  					link->irq.possible_count;

  	}
  
  	return penalty;
  }
  
  static int acpi_irq_get_penalty(int irq)
  {
  	int penalty = 0;

  	if (irq == sci_irq)
  		penalty += sci_penalty;

  	if (irq < ACPI_MAX_ISA_IRQS)
  		return penalty + acpi_isa_irq_penalty[irq];

  	return penalty + acpi_irq_pci_sharing_penalty(irq);

  }

  int __init acpi_irq_penalty_init(void)
  {
  	struct acpi_pci_link *link;
  	int i;
  
  	/*
  	 * Update penalties to facilitate IRQ balancing.
  	 */
  	list_for_each_entry(link, &acpi_link_list, list) {
  
  		/*
  		 * 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_IRQS)
  					acpi_isa_irq_penalty[link->irq.
  							 possible[i]] +=
  					    penalty;
  			}
  
  		} else if (link->irq.active &&
  				(link->irq.active < ACPI_MAX_ISA_IRQS)) {
  			acpi_isa_irq_penalty[link->irq.active] +=
  			    PIRQ_PENALTY_PCI_POSSIBLE;
  		}
  	}
  
  	return 0;
  }

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

  static int acpi_pci_link_allocate(struct acpi_pci_link *link)

  {

  	int irq;
  	int i;

  	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 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
  ", 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_get_penalty(irq) >
  			    acpi_irq_get_penalty(link->irq.possible[i]))

  				irq = link->irq.possible[i];
  		}
  	}

  	if (acpi_irq_get_penalty(irq) >= PIRQ_PENALTY_ISA_ALWAYS) {

  		printk(KERN_ERR PREFIX "No IRQ available for %s [%s]. "
  			    "Try pci=noacpi or acpi=off
  ",
  			    acpi_device_name(link->device),
  			    acpi_device_bid(link->device));
  		return -ENODEV;
  	}

  
  	/* Attempt to enable the link device at this IRQ. */
  	if (acpi_pci_link_set(link, irq)) {

  		printk(KERN_ERR PREFIX "Unable to set IRQ for %s [%s]. "
  			    "Try pci=noacpi or acpi=off
  ",

  			    acpi_device_name(link->device),

  			    acpi_device_bid(link->device));

  		return -ENODEV;

  	} else {

  		if (link->irq.active < ACPI_MAX_ISA_IRQS)
  			acpi_isa_irq_penalty[link->irq.active] +=
  				PIRQ_PENALTY_PCI_USING;

  		pr_info("%s [%s] enabled at IRQ %d
  ",

  		       acpi_device_name(link->device),
  		       acpi_device_bid(link->device), link->irq.active);

  	}
  
  	link->irq.initialized = 1;

  	return 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;
  	struct acpi_device *device;
  	struct acpi_pci_link *link;

  	result = acpi_bus_get_device(handle, &device);
  	if (result) {

  		printk(KERN_ERR PREFIX "Invalid link device
  ");

  		return -1;

  	}

  	link = acpi_driver_data(device);

  	if (!link) {

  		printk(KERN_ERR PREFIX "Invalid link context
  ");

  		return -1;

  	}
  
  	/* TBD: Support multiple index (IRQ) entries per Link Device */
  	if (index) {

  		printk(KERN_ERR PREFIX "Invalid index %d
  ", index);

  		return -1;

  	}

  	mutex_lock(&acpi_link_lock);

  	if (acpi_pci_link_allocate(link)) {

  		mutex_unlock(&acpi_link_lock);

  		return -1;

  	}

  	if (!link->irq.active) {

  		mutex_unlock(&acpi_link_lock);

  		printk(KERN_ERR PREFIX "Link active IRQ is 0!
  ");

  		return -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
  ",
  			  acpi_device_bid(link->device)));

  	return 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;
  	struct acpi_pci_link *link;

  	acpi_status result;

  	result = acpi_bus_get_device(handle, &device);
  	if (result) {

  		printk(KERN_ERR PREFIX "Invalid link device
  ");

  		return -1;

  	}

  	link = acpi_driver_data(device);

  	if (!link) {

  		printk(KERN_ERR PREFIX "Invalid link context
  ");

  		return -1;

  	}

  	mutex_lock(&acpi_link_lock);

  	if (!link->irq.initialized) {

  		mutex_unlock(&acpi_link_lock);

  		printk(KERN_ERR PREFIX "Link isn't initialized
  ");

  		return -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
  ",
  			  acpi_device_bid(link->device)));

  	if (link->refcnt == 0)

  		acpi_evaluate_object(link->device->handle, "_DIS", NULL, NULL);

  	mutex_unlock(&acpi_link_lock);

  	return link->irq.active;

  }

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

  static int acpi_pci_link_add(struct acpi_device *device,
  			     const struct acpi_device_id *not_used)

  {

  	int result;
  	struct acpi_pci_link *link;
  	int i;

  	int found = 0;

  	link = kzalloc(sizeof(struct acpi_pci_link), GFP_KERNEL);

  	if (!link)

  		return -ENOMEM;

  
  	link->device = device;

  	strcpy(acpi_device_name(device), ACPI_PCI_LINK_DEVICE_NAME);
  	strcpy(acpi_device_class(device), ACPI_PCI_LINK_CLASS);

  	device->driver_data = 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(KERN_INFO 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(KERN_CONT " *%d", link->irq.possible[i]);

  			found = 1;

  		} else

  			printk(KERN_CONT " %d", link->irq.possible[i]);

  	}

  	printk(KERN_CONT ")");

  
  	if (!found)

  		printk(KERN_CONT " *%d", link->irq.active);

  	if (!link->device->status.enabled)

  		printk(KERN_CONT ", disabled.");

  	printk(KERN_CONT "
  ");

  	list_add_tail(&link->list, &acpi_link_list);

        end:

  	/* disable all links -- to be activated on use */

  	acpi_evaluate_object(device->handle, "_DIS", NULL, NULL);

  	mutex_unlock(&acpi_link_lock);

  
  	if (result)
  		kfree(link);

  	return result < 0 ? result : 1;

  }

  static int acpi_pci_link_resume(struct acpi_pci_link *link)

  {

  	if (link->refcnt && link->irq.active && link->irq.initialized)

  		return (acpi_pci_link_set(link, link->irq.active));

  
  	return 0;

  }

  static void irqrouter_resume(void)

  {

  	struct acpi_pci_link *link;

  	list_for_each_entry(link, &acpi_link_list, list) {

  		acpi_pci_link_resume(link);

  	}

  }

  static void acpi_pci_link_remove(struct acpi_device *device)

  {

  	struct acpi_pci_link *link;

  	link = acpi_driver_data(device);

  	mutex_lock(&acpi_link_lock);

  	list_del(&link->list);

  	mutex_unlock(&acpi_link_lock);

  
  	kfree(link);

  }
  
  /*

   * modify acpi_isa_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;

  		int new_penalty;

  		retval = get_option(&str, &irq);

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

  		/* see if this is a ISA IRQ */
  		if ((irq < 0) || (irq >= ACPI_MAX_ISA_IRQS))

  			continue;

  		if (used)

  			new_penalty = acpi_isa_irq_penalty[irq] +

  					PIRQ_PENALTY_ISA_USED;

  		else

  			new_penalty = 0;

  		acpi_isa_irq_penalty[irq] = new_penalty;

  		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 ((irq >= 0) && (irq < ARRAY_SIZE(acpi_isa_irq_penalty)))

  		acpi_isa_irq_penalty[irq] +=

  		  (active ? PIRQ_PENALTY_ISA_USED : PIRQ_PENALTY_PCI_USING);

  }

  bool acpi_isa_irq_available(int irq)
  {

  	return irq >= 0 && (irq >= ARRAY_SIZE(acpi_isa_irq_penalty) ||

  		    acpi_irq_get_penalty(irq) < PIRQ_PENALTY_ISA_ALWAYS);

  }

  void acpi_penalize_sci_irq(int irq, int trigger, int polarity)
  {
  	sci_irq = irq;
  
  	if (trigger == ACPI_MADT_TRIGGER_LEVEL &&
  	    polarity == ACPI_MADT_POLARITY_ACTIVE_LOW)
  		sci_penalty = PIRQ_PENALTY_PCI_USING;
  	else
  		sci_penalty = PIRQ_PENALTY_ISA_ALWAYS;
  }

  /*

   * 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);

  static int __init acpi_irq_balance_set(char *str)

  {
  	acpi_irq_balance = 1;
  	return 1;
  }

  __setup("acpi_irq_balance", acpi_irq_balance_set);

  static struct syscore_ops irqrouter_syscore_ops = {

  	.resume = irqrouter_resume,

  };

  void __init acpi_pci_link_init(void)

  {

  	if (acpi_noirq)

  		return;

  	if (acpi_irq_balance == -1) {
  		/* no command line switch: enable balancing in IOAPIC mode */
  		if (acpi_irq_model == ACPI_IRQ_MODEL_IOAPIC)
  			acpi_irq_balance = 1;
  		else
  			acpi_irq_balance = 0;
  	}

  	register_syscore_ops(&irqrouter_syscore_ops);
  	acpi_scan_add_handler(&pci_link_handler);

  }