2 * pci_link.c - ACPI PCI Interrupt Link Device Driver ($Revision: 34 $)
4 * Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
5 * Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
6 * Copyright (C) 2002 Dominik Brodowski <devel@brodo.de>
8 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or (at
13 * your option) any later version.
15 * This program is distributed in the hope that it will be useful, but
16 * WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * General Public License for more details.
20 * You should have received a copy of the GNU General Public License along
21 * with this program; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
24 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
27 * 1. Support more than one IRQ resource entry per link device (index).
28 * 2. Implement start/stop mechanism and use ACPI Bus Driver facilities
29 * for IRQ management (e.g. start()->_SRS).
32 #include <linux/kernel.h>
33 #include <linux/module.h>
34 #include <linux/init.h>
35 #include <linux/types.h>
36 #include <linux/proc_fs.h>
37 #include <linux/spinlock.h>
39 #include <linux/pci.h>
41 #include <acpi/acpi_bus.h>
42 #include <acpi/acpi_drivers.h>
45 #define _COMPONENT ACPI_PCI_COMPONENT
46 ACPI_MODULE_NAME ("pci_link")
48 #define ACPI_PCI_LINK_CLASS "pci_irq_routing"
49 #define ACPI_PCI_LINK_HID "PNP0C0F"
50 #define ACPI_PCI_LINK_DRIVER_NAME "ACPI PCI Interrupt Link Driver"
51 #define ACPI_PCI_LINK_DEVICE_NAME "PCI Interrupt Link"
52 #define ACPI_PCI_LINK_FILE_INFO "info"
53 #define ACPI_PCI_LINK_FILE_STATUS "state"
55 #define ACPI_PCI_LINK_MAX_POSSIBLE 16
57 static int acpi_pci_link_add (struct acpi_device *device);
58 static int acpi_pci_link_remove (struct acpi_device *device, int type);
60 static struct acpi_driver acpi_pci_link_driver = {
61 .name = ACPI_PCI_LINK_DRIVER_NAME,
62 .class = ACPI_PCI_LINK_CLASS,
63 .ids = ACPI_PCI_LINK_HID,
65 .add = acpi_pci_link_add,
66 .remove = acpi_pci_link_remove,
70 struct acpi_pci_link_irq {
71 u8 active; /* Current IRQ */
72 u8 edge_level; /* All IRQs */
73 u8 active_high_low; /* All IRQs */
77 u8 possible[ACPI_PCI_LINK_MAX_POSSIBLE];
80 struct acpi_pci_link {
81 struct list_head node;
82 struct acpi_device *device;
84 struct acpi_pci_link_irq irq;
89 struct list_head entries;
93 /* --------------------------------------------------------------------------
94 PCI Link Device Management
95 -------------------------------------------------------------------------- */
98 * set context (link) possible list from resource list
101 acpi_pci_link_check_possible (
102 struct acpi_resource *resource,
105 struct acpi_pci_link *link = (struct acpi_pci_link *) context;
108 ACPI_FUNCTION_TRACE("acpi_pci_link_check_possible");
110 switch (resource->id) {
111 case ACPI_RSTYPE_START_DPF:
113 case ACPI_RSTYPE_IRQ:
115 struct acpi_resource_irq *p = &resource->data.irq;
116 if (!p || !p->number_of_interrupts) {
117 ACPI_DEBUG_PRINT((ACPI_DB_WARN, "Blank IRQ resource\n"));
120 for (i = 0; (i<p->number_of_interrupts && i<ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
121 if (!p->interrupts[i]) {
122 ACPI_DEBUG_PRINT((ACPI_DB_WARN, "Invalid IRQ %d\n", p->interrupts[i]));
125 link->irq.possible[i] = p->interrupts[i];
126 link->irq.possible_count++;
128 link->irq.edge_level = p->edge_level;
129 link->irq.active_high_low = p->active_high_low;
130 link->irq.resource_type = ACPI_RSTYPE_IRQ;
133 case ACPI_RSTYPE_EXT_IRQ:
135 struct acpi_resource_ext_irq *p = &resource->data.extended_irq;
136 if (!p || !p->number_of_interrupts) {
137 ACPI_DEBUG_PRINT((ACPI_DB_WARN,
138 "Blank EXT IRQ resource\n"));
141 for (i = 0; (i<p->number_of_interrupts && i<ACPI_PCI_LINK_MAX_POSSIBLE); i++) {
142 if (!p->interrupts[i]) {
143 ACPI_DEBUG_PRINT((ACPI_DB_WARN, "Invalid IRQ %d\n", p->interrupts[i]));
146 link->irq.possible[i] = p->interrupts[i];
147 link->irq.possible_count++;
149 link->irq.edge_level = p->edge_level;
150 link->irq.active_high_low = p->active_high_low;
151 link->irq.resource_type = ACPI_RSTYPE_EXT_IRQ;
155 ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
156 "Resource is not an IRQ entry\n"));
160 return AE_CTRL_TERMINATE;
165 acpi_pci_link_get_possible (
166 struct acpi_pci_link *link)
170 ACPI_FUNCTION_TRACE("acpi_pci_link_get_possible");
173 return_VALUE(-EINVAL);
175 status = acpi_walk_resources(link->handle, METHOD_NAME__PRS,
176 acpi_pci_link_check_possible, link);
177 if (ACPI_FAILURE(status)) {
178 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _PRS\n"));
179 return_VALUE(-ENODEV);
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
183 "Found %d possible IRQs\n", link->irq.possible_count));
190 acpi_pci_link_check_current (
191 struct acpi_resource *resource,
194 int *irq = (int *) context;
196 ACPI_FUNCTION_TRACE("acpi_pci_link_check_current");
198 switch (resource->id) {
199 case ACPI_RSTYPE_IRQ:
201 struct acpi_resource_irq *p = &resource->data.irq;
202 if (!p || !p->number_of_interrupts) {
204 * IRQ descriptors may have no IRQ# bits set,
205 * particularly those those w/ _STA disabled
207 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
208 "Blank IRQ resource\n"));
211 *irq = p->interrupts[0];
214 case ACPI_RSTYPE_EXT_IRQ:
216 struct acpi_resource_ext_irq *p = &resource->data.extended_irq;
217 if (!p || !p->number_of_interrupts) {
219 * extended IRQ descriptors must
220 * return at least 1 IRQ
222 ACPI_DEBUG_PRINT((ACPI_DB_WARN,
223 "Blank EXT IRQ resource\n"));
226 *irq = p->interrupts[0];
230 ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
231 "Resource isn't an IRQ\n"));
234 return AE_CTRL_TERMINATE;
238 * Run _CRS and set link->irq.active
245 acpi_pci_link_get_current (
246 struct acpi_pci_link *link)
249 acpi_status status = AE_OK;
252 ACPI_FUNCTION_TRACE("acpi_pci_link_get_current");
254 if (!link || !link->handle)
255 return_VALUE(-EINVAL);
257 link->irq.active = 0;
259 /* in practice, status disabled is meaningless, ignore it */
261 /* Query _STA, set link->device->status */
262 result = acpi_bus_get_status(link->device);
264 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Unable to read status\n"));
268 if (!link->device->status.enabled) {
269 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link disabled\n"));
275 * Query and parse _CRS to get the current IRQ assignment.
278 status = acpi_walk_resources(link->handle, METHOD_NAME__CRS,
279 acpi_pci_link_check_current, &irq);
280 if (ACPI_FAILURE(status)) {
281 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _CRS\n"));
286 if (acpi_strict && !irq) {
287 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "_CRS returned 0\n"));
291 link->irq.active = irq;
293 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link at IRQ %d \n", link->irq.active));
296 return_VALUE(result);
301 struct acpi_pci_link *link,
305 acpi_status status = AE_OK;
307 struct acpi_resource res;
308 struct acpi_resource end;
310 struct acpi_buffer buffer = {sizeof(resource)+1, &resource};
314 ACPI_FUNCTION_TRACE("acpi_pci_link_set");
317 return_VALUE(-EINVAL);
319 /* We don't check irqs the first time around */
320 if (link->irq.setonboot) {
321 /* See if we're already at the target IRQ. */
322 if (irq == link->irq.active)
325 /* Make sure the target IRQ in the list of possible IRQs. */
326 for (i=0; i<link->irq.possible_count; i++) {
327 if (irq == link->irq.possible[i])
331 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Target IRQ %d invalid\n", irq));
332 return_VALUE(-EINVAL);
336 memset(&resource, 0, sizeof(resource));
338 switch(link->irq.resource_type) {
339 case ACPI_RSTYPE_IRQ:
340 resource.res.id = ACPI_RSTYPE_IRQ;
341 resource.res.length = sizeof(struct acpi_resource);
342 resource.res.data.irq.edge_level = link->irq.edge_level;
343 resource.res.data.irq.active_high_low = link->irq.active_high_low;
344 if (link->irq.edge_level == ACPI_EDGE_SENSITIVE)
345 resource.res.data.irq.shared_exclusive = ACPI_EXCLUSIVE;
347 resource.res.data.irq.shared_exclusive = ACPI_SHARED;
348 resource.res.data.irq.number_of_interrupts = 1;
349 resource.res.data.irq.interrupts[0] = irq;
352 case ACPI_RSTYPE_EXT_IRQ:
353 resource.res.id = ACPI_RSTYPE_EXT_IRQ;
354 resource.res.length = sizeof(struct acpi_resource);
355 resource.res.data.extended_irq.producer_consumer = ACPI_CONSUMER;
356 resource.res.data.extended_irq.edge_level = link->irq.edge_level;
357 resource.res.data.extended_irq.active_high_low = link->irq.active_high_low;
358 if (link->irq.edge_level == ACPI_EDGE_SENSITIVE)
359 resource.res.data.irq.shared_exclusive = ACPI_EXCLUSIVE;
361 resource.res.data.irq.shared_exclusive = ACPI_SHARED;
362 resource.res.data.extended_irq.number_of_interrupts = 1;
363 resource.res.data.extended_irq.interrupts[0] = irq;
364 /* ignore resource_source, it's optional */
367 printk("ACPI BUG: resource_type %d\n", link->irq.resource_type);
368 return_VALUE(-EINVAL);
371 resource.end.id = ACPI_RSTYPE_END_TAG;
373 /* Attempt to set the resource */
374 status = acpi_set_current_resources(link->handle, &buffer);
376 /* check for total failure */
377 if (ACPI_FAILURE(status)) {
378 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Error evaluating _SRS\n"));
379 return_VALUE(-ENODEV);
382 /* Query _STA, set device->status */
383 result = acpi_bus_get_status(link->device);
385 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Unable to read status\n"));
386 return_VALUE(result);
388 if (!link->device->status.enabled) {
389 printk(KERN_WARNING PREFIX
390 "%s [%s] disabled and referenced, BIOS bug.\n",
391 acpi_device_name(link->device),
392 acpi_device_bid(link->device));
395 /* Query _CRS, set link->irq.active */
396 result = acpi_pci_link_get_current(link);
398 return_VALUE(result);
402 * Is current setting not what we set?
403 * set link->irq.active
405 if (link->irq.active != irq) {
407 * policy: when _CRS doesn't return what we just _SRS
408 * assume _SRS worked and override _CRS value.
410 printk(KERN_WARNING PREFIX
411 "%s [%s] BIOS reported IRQ %d, using IRQ %d\n",
412 acpi_device_name(link->device),
413 acpi_device_bid(link->device),
414 link->irq.active, irq);
415 link->irq.active = irq;
418 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Set IRQ %d\n", link->irq.active));
424 /* --------------------------------------------------------------------------
425 PCI Link IRQ Management
426 -------------------------------------------------------------------------- */
429 * "acpi_irq_balance" (default in APIC mode) enables ACPI to use PIC Interrupt
430 * Link Devices to move the PIRQs around to minimize sharing.
432 * "acpi_irq_nobalance" (default in PIC mode) tells ACPI not to move any PIC IRQs
433 * that the BIOS has already set to active. This is necessary because
434 * ACPI has no automatic means of knowing what ISA IRQs are used. Note that
435 * if the BIOS doesn't set a Link Device active, ACPI needs to program it
436 * even if acpi_irq_nobalance is set.
438 * A tables of penalties avoids directing PCI interrupts to well known
439 * ISA IRQs. Boot params are available to over-ride the default table:
441 * List interrupts that are free for PCI use.
444 * List interrupts that should not be used for PCI:
447 * Note that PCI IRQ routers have a list of possible IRQs,
448 * which may not include the IRQs this table says are available.
450 * Since this heuristic can't tell the difference between a link
451 * that no device will attach to, vs. a link which may be shared
452 * by multiple active devices -- it is not optimal.
454 * If interrupt performance is that important, get an IO-APIC system
455 * with a pin dedicated to each device. Or for that matter, an MSI
459 #define ACPI_MAX_IRQS 256
460 #define ACPI_MAX_ISA_IRQ 16
462 #define PIRQ_PENALTY_PCI_AVAILABLE (0)
463 #define PIRQ_PENALTY_PCI_POSSIBLE (16*16)
464 #define PIRQ_PENALTY_PCI_USING (16*16*16)
465 #define PIRQ_PENALTY_ISA_TYPICAL (16*16*16*16)
466 #define PIRQ_PENALTY_ISA_USED (16*16*16*16*16)
467 #define PIRQ_PENALTY_ISA_ALWAYS (16*16*16*16*16*16)
469 static int __initdata acpi_irq_penalty[ACPI_MAX_IRQS] = {
470 PIRQ_PENALTY_ISA_ALWAYS, /* IRQ0 timer */
471 PIRQ_PENALTY_ISA_ALWAYS, /* IRQ1 keyboard */
472 PIRQ_PENALTY_ISA_ALWAYS, /* IRQ2 cascade */
473 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ3 serial */
474 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ4 serial */
475 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ5 sometimes SoundBlaster */
476 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ6 */
477 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ7 parallel, spurious */
478 PIRQ_PENALTY_ISA_TYPICAL, /* IRQ8 rtc, sometimes */
479 PIRQ_PENALTY_PCI_AVAILABLE, /* IRQ9 PCI, often acpi */
480 PIRQ_PENALTY_PCI_AVAILABLE, /* IRQ10 PCI */
481 PIRQ_PENALTY_PCI_AVAILABLE, /* IRQ11 PCI */
482 PIRQ_PENALTY_ISA_USED, /* IRQ12 mouse */
483 PIRQ_PENALTY_ISA_USED, /* IRQ13 fpe, sometimes */
484 PIRQ_PENALTY_ISA_USED, /* IRQ14 ide0 */
485 PIRQ_PENALTY_ISA_USED, /* IRQ15 ide1 */
490 acpi_pci_link_check (void)
492 struct list_head *node = NULL;
493 struct acpi_pci_link *link = NULL;
496 ACPI_FUNCTION_TRACE("acpi_pci_link_check");
499 * Update penalties to facilitate IRQ balancing.
501 list_for_each(node, &acpi_link.entries) {
503 link = list_entry(node, struct acpi_pci_link, node);
505 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link context\n"));
510 * reflect the possible and active irqs in the penalty table --
511 * useful for breaking ties.
513 if (link->irq.possible_count) {
514 int penalty = PIRQ_PENALTY_PCI_POSSIBLE / link->irq.possible_count;
516 for (i = 0; i < link->irq.possible_count; i++) {
517 if (link->irq.possible[i] < ACPI_MAX_ISA_IRQ)
518 acpi_irq_penalty[link->irq.possible[i]] += penalty;
521 } else if (link->irq.active) {
522 acpi_irq_penalty[link->irq.active] += PIRQ_PENALTY_PCI_POSSIBLE;
525 /* Add a penalty for the SCI */
526 acpi_irq_penalty[acpi_fadt.sci_int] += PIRQ_PENALTY_PCI_USING;
531 static int acpi_irq_balance; /* 0: static, 1: balance */
533 static int acpi_pci_link_allocate(struct acpi_pci_link* link) {
537 ACPI_FUNCTION_TRACE("acpi_pci_link_allocate");
539 if (link->irq.setonboot)
543 * search for active IRQ in list of possible IRQs.
545 for (i = 0; i < link->irq.possible_count; ++i) {
546 if (link->irq.active == link->irq.possible[i])
550 * forget active IRQ that is not in possible list
552 if (i == link->irq.possible_count) {
554 printk(KERN_WARNING PREFIX "_CRS %d not found"
555 " in _PRS\n", link->irq.active);
556 link->irq.active = 0;
560 * if active found, use it; else pick entry from end of possible list.
562 if (link->irq.active) {
563 irq = link->irq.active;
565 irq = link->irq.possible[link->irq.possible_count - 1];
568 if (acpi_irq_balance || !link->irq.active) {
570 * Select the best IRQ. This is done in reverse to promote
571 * the use of IRQs 9, 10, 11, and >15.
573 for (i = (link->irq.possible_count - 1); i >= 0; i--) {
574 if (acpi_irq_penalty[irq] > acpi_irq_penalty[link->irq.possible[i]])
575 irq = link->irq.possible[i];
579 /* Attempt to enable the link device at this IRQ. */
580 if (acpi_pci_link_set(link, irq)) {
581 printk(PREFIX "Unable to set IRQ for %s [%s] (likely buggy ACPI BIOS).\n"
582 "Try pci=noacpi or acpi=off\n",
583 acpi_device_name(link->device),
584 acpi_device_bid(link->device));
585 return_VALUE(-ENODEV);
587 acpi_irq_penalty[link->irq.active] += PIRQ_PENALTY_PCI_USING;
588 printk(PREFIX "%s [%s] enabled at IRQ %d\n",
589 acpi_device_name(link->device),
590 acpi_device_bid(link->device), link->irq.active);
593 link->irq.setonboot = 1;
600 acpi_pci_link_get_irq (
604 int* active_high_low)
607 struct acpi_device *device = NULL;
608 struct acpi_pci_link *link = NULL;
610 ACPI_FUNCTION_TRACE("acpi_pci_link_get_irq");
612 result = acpi_bus_get_device(handle, &device);
614 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link device\n"));
618 link = (struct acpi_pci_link *) acpi_driver_data(device);
620 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid link context\n"));
624 /* TBD: Support multiple index (IRQ) entries per Link Device */
626 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Invalid index %d\n", index));
630 if (acpi_pci_link_allocate(link))
633 if (!link->irq.active) {
634 ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "Link active IRQ is 0!\n"));
638 if (edge_level) *edge_level = link->irq.edge_level;
639 if (active_high_low) *active_high_low = link->irq.active_high_low;
640 return_VALUE(link->irq.active);
644 /* --------------------------------------------------------------------------
646 -------------------------------------------------------------------------- */
650 struct acpi_device *device)
653 struct acpi_pci_link *link = NULL;
657 ACPI_FUNCTION_TRACE("acpi_pci_link_add");
660 return_VALUE(-EINVAL);
662 link = kmalloc(sizeof(struct acpi_pci_link), GFP_KERNEL);
664 return_VALUE(-ENOMEM);
665 memset(link, 0, sizeof(struct acpi_pci_link));
667 link->device = device;
668 link->handle = device->handle;
669 strcpy(acpi_device_name(device), ACPI_PCI_LINK_DEVICE_NAME);
670 strcpy(acpi_device_class(device), ACPI_PCI_LINK_CLASS);
671 acpi_driver_data(device) = link;
673 result = acpi_pci_link_get_possible(link);
677 /* query and set link->irq.active */
678 acpi_pci_link_get_current(link);
680 printk(PREFIX "%s [%s] (IRQs", acpi_device_name(device),
681 acpi_device_bid(device));
682 for (i = 0; i < link->irq.possible_count; i++) {
683 if (link->irq.active == link->irq.possible[i]) {
684 printk(" *%d", link->irq.possible[i]);
688 printk(" %d", link->irq.possible[i]);
694 printk(" *%d", link->irq.active);
696 if(!link->device->status.enabled)
697 printk(", disabled.");
701 /* TBD: Acquire/release lock */
702 list_add_tail(&link->node, &acpi_link.entries);
709 return_VALUE(result);
714 acpi_pci_link_remove (
715 struct acpi_device *device,
718 struct acpi_pci_link *link = NULL;
720 ACPI_FUNCTION_TRACE("acpi_pci_link_remove");
722 if (!device || !acpi_driver_data(device))
723 return_VALUE(-EINVAL);
725 link = (struct acpi_pci_link *) acpi_driver_data(device);
727 /* TBD: Acquire/release lock */
728 list_del(&link->node);
736 * modify acpi_irq_penalty[] from cmdline
738 static int __init acpi_irq_penalty_update(char *str, int used)
742 for (i = 0; i < 16; i++) {
746 retval = get_option(&str,&irq);
749 break; /* no number found */
754 if (irq >= ACPI_MAX_IRQS)
758 acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_USED;
760 acpi_irq_penalty[irq] = PIRQ_PENALTY_PCI_AVAILABLE;
762 if (retval != 2) /* no next number */
769 * Over-ride default table to reserve additional IRQs for use by ISA
770 * e.g. acpi_irq_isa=5
771 * Useful for telling ACPI how not to interfere with your ISA sound card.
773 static int __init acpi_irq_isa(char *str)
775 return(acpi_irq_penalty_update(str, 1));
777 __setup("acpi_irq_isa=", acpi_irq_isa);
780 * Over-ride default table to free additional IRQs for use by PCI
781 * e.g. acpi_irq_pci=7,15
782 * Used for acpi_irq_balance to free up IRQs to reduce PCI IRQ sharing.
784 static int __init acpi_irq_pci(char *str)
786 return(acpi_irq_penalty_update(str, 0));
788 __setup("acpi_irq_pci=", acpi_irq_pci);
790 static int __init acpi_irq_nobalance_set(char *str)
792 acpi_irq_balance = 0;
795 __setup("acpi_irq_nobalance", acpi_irq_nobalance_set);
797 int __init acpi_irq_balance_set(char *str)
799 acpi_irq_balance = 1;
802 __setup("acpi_irq_balance", acpi_irq_balance_set);
805 static int __init acpi_pci_link_init (void)
807 ACPI_FUNCTION_TRACE("acpi_pci_link_init");
809 if (acpi_pci_disabled)
813 INIT_LIST_HEAD(&acpi_link.entries);
815 if (acpi_bus_register_driver(&acpi_pci_link_driver) < 0)
816 return_VALUE(-ENODEV);
821 subsys_initcall(acpi_pci_link_init);