xref: /linux/drivers/acpi/button.c (revision 2634682fdffd9ba6e74b76be8aa91cf8b2e05c41)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  button.c - ACPI Button Driver
4  *
5  *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
6  *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
7  */
8 
9 #define pr_fmt(fmt) "ACPI: button: " fmt
10 
11 #include <linux/compiler.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/types.h>
16 #include <linux/proc_fs.h>
17 #include <linux/seq_file.h>
18 #include <linux/input.h>
19 #include <linux/slab.h>
20 #include <linux/acpi.h>
21 #include <linux/dmi.h>
22 #include <acpi/button.h>
23 
24 #define PREFIX "ACPI: "
25 
26 #define ACPI_BUTTON_CLASS		"button"
27 #define ACPI_BUTTON_FILE_STATE		"state"
28 #define ACPI_BUTTON_TYPE_UNKNOWN	0x00
29 #define ACPI_BUTTON_NOTIFY_STATUS	0x80
30 
31 #define ACPI_BUTTON_SUBCLASS_POWER	"power"
32 #define ACPI_BUTTON_DEVICE_NAME_POWER	"Power Button"
33 #define ACPI_BUTTON_TYPE_POWER		0x01
34 
35 #define ACPI_BUTTON_SUBCLASS_SLEEP	"sleep"
36 #define ACPI_BUTTON_DEVICE_NAME_SLEEP	"Sleep Button"
37 #define ACPI_BUTTON_TYPE_SLEEP		0x03
38 
39 #define ACPI_BUTTON_SUBCLASS_LID	"lid"
40 #define ACPI_BUTTON_DEVICE_NAME_LID	"Lid Switch"
41 #define ACPI_BUTTON_TYPE_LID		0x05
42 
43 enum {
44 	ACPI_BUTTON_LID_INIT_IGNORE,
45 	ACPI_BUTTON_LID_INIT_OPEN,
46 	ACPI_BUTTON_LID_INIT_METHOD,
47 	ACPI_BUTTON_LID_INIT_DISABLED,
48 };
49 
50 static const char * const lid_init_state_str[] = {
51 	[ACPI_BUTTON_LID_INIT_IGNORE]		= "ignore",
52 	[ACPI_BUTTON_LID_INIT_OPEN]		= "open",
53 	[ACPI_BUTTON_LID_INIT_METHOD]		= "method",
54 	[ACPI_BUTTON_LID_INIT_DISABLED]		= "disabled",
55 };
56 
57 #define _COMPONENT		ACPI_BUTTON_COMPONENT
58 ACPI_MODULE_NAME("button");
59 
60 MODULE_AUTHOR("Paul Diefenbaugh");
61 MODULE_DESCRIPTION("ACPI Button Driver");
62 MODULE_LICENSE("GPL");
63 
64 static const struct acpi_device_id button_device_ids[] = {
65 	{ACPI_BUTTON_HID_LID,    0},
66 	{ACPI_BUTTON_HID_SLEEP,  0},
67 	{ACPI_BUTTON_HID_SLEEPF, 0},
68 	{ACPI_BUTTON_HID_POWER,  0},
69 	{ACPI_BUTTON_HID_POWERF, 0},
70 	{"", 0},
71 };
72 MODULE_DEVICE_TABLE(acpi, button_device_ids);
73 
74 /* Please keep this list sorted alphabetically by vendor and model */
75 static const struct dmi_system_id dmi_lid_quirks[] = {
76 	{
77 		/*
78 		 * Acer Switch 10 SW5-012. _LID method messes with home and
79 		 * power button GPIO IRQ settings causing an interrupt storm on
80 		 * both GPIOs. This is unfixable without a DSDT override, so we
81 		 * have to disable the lid-switch functionality altogether :|
82 		 */
83 		.matches = {
84 			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
85 			DMI_MATCH(DMI_PRODUCT_NAME, "Aspire SW5-012"),
86 		},
87 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_DISABLED,
88 	},
89 	{
90 		/* GP-electronic T701, _LID method points to a floating GPIO */
91 		.matches = {
92 			DMI_MATCH(DMI_SYS_VENDOR, "Insyde"),
93 			DMI_MATCH(DMI_PRODUCT_NAME, "T701"),
94 			DMI_MATCH(DMI_BIOS_VERSION, "BYT70A.YNCHENG.WIN.007"),
95 		},
96 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_DISABLED,
97 	},
98 	{
99 		/*
100 		 * Medion Akoya E2215T, notification of the LID device only
101 		 * happens on close, not on open and _LID always returns closed.
102 		 */
103 		.matches = {
104 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
105 			DMI_MATCH(DMI_PRODUCT_NAME, "E2215T MD60198"),
106 		},
107 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
108 	},
109 	{
110 		/*
111 		 * Razer Blade Stealth 13 late 2019, notification of the LID device
112 		 * only happens on close, not on open and _LID always returns closed.
113 		 */
114 		.matches = {
115 			DMI_MATCH(DMI_SYS_VENDOR, "Razer"),
116 			DMI_MATCH(DMI_PRODUCT_NAME, "Razer Blade Stealth 13 Late 2019"),
117 		},
118 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
119 	},
120 	{}
121 };
122 
123 static int acpi_button_add(struct acpi_device *device);
124 static int acpi_button_remove(struct acpi_device *device);
125 static void acpi_button_notify(struct acpi_device *device, u32 event);
126 
127 #ifdef CONFIG_PM_SLEEP
128 static int acpi_button_suspend(struct device *dev);
129 static int acpi_button_resume(struct device *dev);
130 #else
131 #define acpi_button_suspend NULL
132 #define acpi_button_resume NULL
133 #endif
134 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
135 
136 static struct acpi_driver acpi_button_driver = {
137 	.name = "button",
138 	.class = ACPI_BUTTON_CLASS,
139 	.ids = button_device_ids,
140 	.ops = {
141 		.add = acpi_button_add,
142 		.remove = acpi_button_remove,
143 		.notify = acpi_button_notify,
144 	},
145 	.drv.pm = &acpi_button_pm,
146 };
147 
148 struct acpi_button {
149 	unsigned int type;
150 	struct input_dev *input;
151 	char phys[32];			/* for input device */
152 	unsigned long pushed;
153 	int last_state;
154 	ktime_t last_time;
155 	bool suspended;
156 };
157 
158 static struct acpi_device *lid_device;
159 static long lid_init_state = -1;
160 
161 static unsigned long lid_report_interval __read_mostly = 500;
162 module_param(lid_report_interval, ulong, 0644);
163 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
164 
165 /* --------------------------------------------------------------------------
166                               FS Interface (/proc)
167    -------------------------------------------------------------------------- */
168 
169 static struct proc_dir_entry *acpi_button_dir;
170 static struct proc_dir_entry *acpi_lid_dir;
171 
172 static int acpi_lid_evaluate_state(struct acpi_device *device)
173 {
174 	unsigned long long lid_state;
175 	acpi_status status;
176 
177 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
178 	if (ACPI_FAILURE(status))
179 		return -ENODEV;
180 
181 	return lid_state ? 1 : 0;
182 }
183 
184 static int acpi_lid_notify_state(struct acpi_device *device, int state)
185 {
186 	struct acpi_button *button = acpi_driver_data(device);
187 	ktime_t next_report;
188 	bool do_update;
189 
190 	/*
191 	 * In lid_init_state=ignore mode, if user opens/closes lid
192 	 * frequently with "open" missing, and "last_time" is also updated
193 	 * frequently, "close" cannot be delivered to the userspace.
194 	 * So "last_time" is only updated after a timeout or an actual
195 	 * switch.
196 	 */
197 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
198 	    button->last_state != !!state)
199 		do_update = true;
200 	else
201 		do_update = false;
202 
203 	next_report = ktime_add(button->last_time,
204 				ms_to_ktime(lid_report_interval));
205 	if (button->last_state == !!state &&
206 	    ktime_after(ktime_get(), next_report)) {
207 		/* Complain the buggy firmware */
208 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
209 
210 		/*
211 		 * Send the unreliable complement switch event:
212 		 *
213 		 * On most platforms, the lid device is reliable. However
214 		 * there are exceptions:
215 		 * 1. Platforms returning initial lid state as "close" by
216 		 *    default after booting/resuming:
217 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
218 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
219 		 * 2. Platforms never reporting "open" events:
220 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
221 		 * On these buggy platforms, the usage model of the ACPI
222 		 * lid device actually is:
223 		 * 1. The initial returning value of _LID may not be
224 		 *    reliable.
225 		 * 2. The open event may not be reliable.
226 		 * 3. The close event is reliable.
227 		 *
228 		 * But SW_LID is typed as input switch event, the input
229 		 * layer checks if the event is redundant. Hence if the
230 		 * state is not switched, the userspace cannot see this
231 		 * platform triggered reliable event. By inserting a
232 		 * complement switch event, it then is guaranteed that the
233 		 * platform triggered reliable one can always be seen by
234 		 * the userspace.
235 		 */
236 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
237 			do_update = true;
238 			/*
239 			 * Do generate complement switch event for "close"
240 			 * as "close" is reliable and wrong "open" won't
241 			 * trigger unexpected behaviors.
242 			 * Do not generate complement switch event for
243 			 * "open" as "open" is not reliable and wrong
244 			 * "close" will trigger unexpected behaviors.
245 			 */
246 			if (!state) {
247 				input_report_switch(button->input,
248 						    SW_LID, state);
249 				input_sync(button->input);
250 			}
251 		}
252 	}
253 	/* Send the platform triggered reliable event */
254 	if (do_update) {
255 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
256 				  state ? "open" : "closed");
257 		input_report_switch(button->input, SW_LID, !state);
258 		input_sync(button->input);
259 		button->last_state = !!state;
260 		button->last_time = ktime_get();
261 	}
262 
263 	return 0;
264 }
265 
266 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
267 						     void *offset)
268 {
269 	struct acpi_device *device = seq->private;
270 	int state;
271 
272 	state = acpi_lid_evaluate_state(device);
273 	seq_printf(seq, "state:      %s\n",
274 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
275 	return 0;
276 }
277 
278 static int acpi_button_add_fs(struct acpi_device *device)
279 {
280 	struct acpi_button *button = acpi_driver_data(device);
281 	struct proc_dir_entry *entry = NULL;
282 	int ret = 0;
283 
284 	/* procfs I/F for ACPI lid device only */
285 	if (button->type != ACPI_BUTTON_TYPE_LID)
286 		return 0;
287 
288 	if (acpi_button_dir || acpi_lid_dir) {
289 		printk(KERN_ERR PREFIX "More than one Lid device found!\n");
290 		return -EEXIST;
291 	}
292 
293 	/* create /proc/acpi/button */
294 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
295 	if (!acpi_button_dir)
296 		return -ENODEV;
297 
298 	/* create /proc/acpi/button/lid */
299 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
300 	if (!acpi_lid_dir) {
301 		ret = -ENODEV;
302 		goto remove_button_dir;
303 	}
304 
305 	/* create /proc/acpi/button/lid/LID/ */
306 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
307 	if (!acpi_device_dir(device)) {
308 		ret = -ENODEV;
309 		goto remove_lid_dir;
310 	}
311 
312 	/* create /proc/acpi/button/lid/LID/state */
313 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
314 			acpi_device_dir(device), acpi_button_state_seq_show,
315 			device);
316 	if (!entry) {
317 		ret = -ENODEV;
318 		goto remove_dev_dir;
319 	}
320 
321 done:
322 	return ret;
323 
324 remove_dev_dir:
325 	remove_proc_entry(acpi_device_bid(device),
326 			  acpi_lid_dir);
327 	acpi_device_dir(device) = NULL;
328 remove_lid_dir:
329 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
330 	acpi_lid_dir = NULL;
331 remove_button_dir:
332 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
333 	acpi_button_dir = NULL;
334 	goto done;
335 }
336 
337 static int acpi_button_remove_fs(struct acpi_device *device)
338 {
339 	struct acpi_button *button = acpi_driver_data(device);
340 
341 	if (button->type != ACPI_BUTTON_TYPE_LID)
342 		return 0;
343 
344 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
345 			  acpi_device_dir(device));
346 	remove_proc_entry(acpi_device_bid(device),
347 			  acpi_lid_dir);
348 	acpi_device_dir(device) = NULL;
349 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
350 	acpi_lid_dir = NULL;
351 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
352 	acpi_button_dir = NULL;
353 
354 	return 0;
355 }
356 
357 /* --------------------------------------------------------------------------
358                                 Driver Interface
359    -------------------------------------------------------------------------- */
360 int acpi_lid_open(void)
361 {
362 	if (!lid_device)
363 		return -ENODEV;
364 
365 	return acpi_lid_evaluate_state(lid_device);
366 }
367 EXPORT_SYMBOL(acpi_lid_open);
368 
369 static int acpi_lid_update_state(struct acpi_device *device,
370 				 bool signal_wakeup)
371 {
372 	int state;
373 
374 	state = acpi_lid_evaluate_state(device);
375 	if (state < 0)
376 		return state;
377 
378 	if (state && signal_wakeup)
379 		acpi_pm_wakeup_event(&device->dev);
380 
381 	return acpi_lid_notify_state(device, state);
382 }
383 
384 static void acpi_lid_initialize_state(struct acpi_device *device)
385 {
386 	switch (lid_init_state) {
387 	case ACPI_BUTTON_LID_INIT_OPEN:
388 		(void)acpi_lid_notify_state(device, 1);
389 		break;
390 	case ACPI_BUTTON_LID_INIT_METHOD:
391 		(void)acpi_lid_update_state(device, false);
392 		break;
393 	case ACPI_BUTTON_LID_INIT_IGNORE:
394 	default:
395 		break;
396 	}
397 }
398 
399 static void acpi_button_notify(struct acpi_device *device, u32 event)
400 {
401 	struct acpi_button *button = acpi_driver_data(device);
402 	struct input_dev *input;
403 	int users;
404 
405 	switch (event) {
406 	case ACPI_FIXED_HARDWARE_EVENT:
407 		event = ACPI_BUTTON_NOTIFY_STATUS;
408 		fallthrough;
409 	case ACPI_BUTTON_NOTIFY_STATUS:
410 		input = button->input;
411 		if (button->type == ACPI_BUTTON_TYPE_LID) {
412 			mutex_lock(&button->input->mutex);
413 			users = button->input->users;
414 			mutex_unlock(&button->input->mutex);
415 			if (users)
416 				acpi_lid_update_state(device, true);
417 		} else {
418 			int keycode;
419 
420 			acpi_pm_wakeup_event(&device->dev);
421 			if (button->suspended)
422 				break;
423 
424 			keycode = test_bit(KEY_SLEEP, input->keybit) ?
425 						KEY_SLEEP : KEY_POWER;
426 			input_report_key(input, keycode, 1);
427 			input_sync(input);
428 			input_report_key(input, keycode, 0);
429 			input_sync(input);
430 
431 			acpi_bus_generate_netlink_event(
432 					device->pnp.device_class,
433 					dev_name(&device->dev),
434 					event, ++button->pushed);
435 		}
436 		break;
437 	default:
438 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
439 				  "Unsupported event [0x%x]\n", event));
440 		break;
441 	}
442 }
443 
444 #ifdef CONFIG_PM_SLEEP
445 static int acpi_button_suspend(struct device *dev)
446 {
447 	struct acpi_device *device = to_acpi_device(dev);
448 	struct acpi_button *button = acpi_driver_data(device);
449 
450 	button->suspended = true;
451 	return 0;
452 }
453 
454 static int acpi_button_resume(struct device *dev)
455 {
456 	struct acpi_device *device = to_acpi_device(dev);
457 	struct acpi_button *button = acpi_driver_data(device);
458 
459 	button->suspended = false;
460 	if (button->type == ACPI_BUTTON_TYPE_LID && button->input->users) {
461 		button->last_state = !!acpi_lid_evaluate_state(device);
462 		button->last_time = ktime_get();
463 		acpi_lid_initialize_state(device);
464 	}
465 	return 0;
466 }
467 #endif
468 
469 static int acpi_lid_input_open(struct input_dev *input)
470 {
471 	struct acpi_device *device = input_get_drvdata(input);
472 	struct acpi_button *button = acpi_driver_data(device);
473 
474 	button->last_state = !!acpi_lid_evaluate_state(device);
475 	button->last_time = ktime_get();
476 	acpi_lid_initialize_state(device);
477 
478 	return 0;
479 }
480 
481 static int acpi_button_add(struct acpi_device *device)
482 {
483 	struct acpi_button *button;
484 	struct input_dev *input;
485 	const char *hid = acpi_device_hid(device);
486 	char *name, *class;
487 	int error;
488 
489 	if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
490 	     lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
491 		return -ENODEV;
492 
493 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
494 	if (!button)
495 		return -ENOMEM;
496 
497 	device->driver_data = button;
498 
499 	button->input = input = input_allocate_device();
500 	if (!input) {
501 		error = -ENOMEM;
502 		goto err_free_button;
503 	}
504 
505 	name = acpi_device_name(device);
506 	class = acpi_device_class(device);
507 
508 	if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
509 	    !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
510 		button->type = ACPI_BUTTON_TYPE_POWER;
511 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
512 		sprintf(class, "%s/%s",
513 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
514 	} else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
515 		   !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
516 		button->type = ACPI_BUTTON_TYPE_SLEEP;
517 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
518 		sprintf(class, "%s/%s",
519 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
520 	} else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
521 		button->type = ACPI_BUTTON_TYPE_LID;
522 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
523 		sprintf(class, "%s/%s",
524 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
525 		input->open = acpi_lid_input_open;
526 	} else {
527 		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
528 		error = -ENODEV;
529 		goto err_free_input;
530 	}
531 
532 	error = acpi_button_add_fs(device);
533 	if (error)
534 		goto err_free_input;
535 
536 	snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
537 
538 	input->name = name;
539 	input->phys = button->phys;
540 	input->id.bustype = BUS_HOST;
541 	input->id.product = button->type;
542 	input->dev.parent = &device->dev;
543 
544 	switch (button->type) {
545 	case ACPI_BUTTON_TYPE_POWER:
546 		input_set_capability(input, EV_KEY, KEY_POWER);
547 		break;
548 
549 	case ACPI_BUTTON_TYPE_SLEEP:
550 		input_set_capability(input, EV_KEY, KEY_SLEEP);
551 		break;
552 
553 	case ACPI_BUTTON_TYPE_LID:
554 		input_set_capability(input, EV_SW, SW_LID);
555 		break;
556 	}
557 
558 	input_set_drvdata(input, device);
559 	error = input_register_device(input);
560 	if (error)
561 		goto err_remove_fs;
562 	if (button->type == ACPI_BUTTON_TYPE_LID) {
563 		/*
564 		 * This assumes there's only one lid device, or if there are
565 		 * more we only care about the last one...
566 		 */
567 		lid_device = device;
568 	}
569 
570 	device_init_wakeup(&device->dev, true);
571 	printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
572 	return 0;
573 
574  err_remove_fs:
575 	acpi_button_remove_fs(device);
576  err_free_input:
577 	input_free_device(input);
578  err_free_button:
579 	kfree(button);
580 	return error;
581 }
582 
583 static int acpi_button_remove(struct acpi_device *device)
584 {
585 	struct acpi_button *button = acpi_driver_data(device);
586 
587 	acpi_button_remove_fs(device);
588 	input_unregister_device(button->input);
589 	kfree(button);
590 	return 0;
591 }
592 
593 static int param_set_lid_init_state(const char *val,
594 				    const struct kernel_param *kp)
595 {
596 	int i;
597 
598 	i = sysfs_match_string(lid_init_state_str, val);
599 	if (i < 0)
600 		return i;
601 
602 	lid_init_state = i;
603 	pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
604 	return 0;
605 }
606 
607 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
608 {
609 	int i, c = 0;
610 
611 	for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
612 		if (i == lid_init_state)
613 			c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
614 		else
615 			c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
616 
617 	buf[c - 1] = '\n'; /* Replace the final space with a newline */
618 
619 	return c;
620 }
621 
622 module_param_call(lid_init_state,
623 		  param_set_lid_init_state, param_get_lid_init_state,
624 		  NULL, 0644);
625 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
626 
627 static int acpi_button_register_driver(struct acpi_driver *driver)
628 {
629 	const struct dmi_system_id *dmi_id;
630 
631 	if (lid_init_state == -1) {
632 		dmi_id = dmi_first_match(dmi_lid_quirks);
633 		if (dmi_id)
634 			lid_init_state = (long)dmi_id->driver_data;
635 		else
636 			lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
637 	}
638 
639 	/*
640 	 * Modules such as nouveau.ko and i915.ko have a link time dependency
641 	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
642 	 * capable kernels booted in non-ACPI mode if the return value of
643 	 * acpi_bus_register_driver() is returned from here with ACPI disabled
644 	 * when this driver is built as a module.
645 	 */
646 	if (acpi_disabled)
647 		return 0;
648 
649 	return acpi_bus_register_driver(driver);
650 }
651 
652 static void acpi_button_unregister_driver(struct acpi_driver *driver)
653 {
654 	if (!acpi_disabled)
655 		acpi_bus_unregister_driver(driver);
656 }
657 
658 module_driver(acpi_button_driver, acpi_button_register_driver,
659 	       acpi_button_unregister_driver);
660