xref: /openbmc/linux/drivers/acpi/button.c (revision 11a163f2)
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 	bool lid_state_initialized;
157 };
158 
159 static struct acpi_device *lid_device;
160 static long lid_init_state = -1;
161 
162 static unsigned long lid_report_interval __read_mostly = 500;
163 module_param(lid_report_interval, ulong, 0644);
164 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
165 
166 /* --------------------------------------------------------------------------
167                               FS Interface (/proc)
168    -------------------------------------------------------------------------- */
169 
170 static struct proc_dir_entry *acpi_button_dir;
171 static struct proc_dir_entry *acpi_lid_dir;
172 
173 static int acpi_lid_evaluate_state(struct acpi_device *device)
174 {
175 	unsigned long long lid_state;
176 	acpi_status status;
177 
178 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
179 	if (ACPI_FAILURE(status))
180 		return -ENODEV;
181 
182 	return lid_state ? 1 : 0;
183 }
184 
185 static int acpi_lid_notify_state(struct acpi_device *device, int state)
186 {
187 	struct acpi_button *button = acpi_driver_data(device);
188 	ktime_t next_report;
189 	bool do_update;
190 
191 	/*
192 	 * In lid_init_state=ignore mode, if user opens/closes lid
193 	 * frequently with "open" missing, and "last_time" is also updated
194 	 * frequently, "close" cannot be delivered to the userspace.
195 	 * So "last_time" is only updated after a timeout or an actual
196 	 * switch.
197 	 */
198 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
199 	    button->last_state != !!state)
200 		do_update = true;
201 	else
202 		do_update = false;
203 
204 	next_report = ktime_add(button->last_time,
205 				ms_to_ktime(lid_report_interval));
206 	if (button->last_state == !!state &&
207 	    ktime_after(ktime_get(), next_report)) {
208 		/* Complain the buggy firmware */
209 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
210 
211 		/*
212 		 * Send the unreliable complement switch event:
213 		 *
214 		 * On most platforms, the lid device is reliable. However
215 		 * there are exceptions:
216 		 * 1. Platforms returning initial lid state as "close" by
217 		 *    default after booting/resuming:
218 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
219 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
220 		 * 2. Platforms never reporting "open" events:
221 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
222 		 * On these buggy platforms, the usage model of the ACPI
223 		 * lid device actually is:
224 		 * 1. The initial returning value of _LID may not be
225 		 *    reliable.
226 		 * 2. The open event may not be reliable.
227 		 * 3. The close event is reliable.
228 		 *
229 		 * But SW_LID is typed as input switch event, the input
230 		 * layer checks if the event is redundant. Hence if the
231 		 * state is not switched, the userspace cannot see this
232 		 * platform triggered reliable event. By inserting a
233 		 * complement switch event, it then is guaranteed that the
234 		 * platform triggered reliable one can always be seen by
235 		 * the userspace.
236 		 */
237 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
238 			do_update = true;
239 			/*
240 			 * Do generate complement switch event for "close"
241 			 * as "close" is reliable and wrong "open" won't
242 			 * trigger unexpected behaviors.
243 			 * Do not generate complement switch event for
244 			 * "open" as "open" is not reliable and wrong
245 			 * "close" will trigger unexpected behaviors.
246 			 */
247 			if (!state) {
248 				input_report_switch(button->input,
249 						    SW_LID, state);
250 				input_sync(button->input);
251 			}
252 		}
253 	}
254 	/* Send the platform triggered reliable event */
255 	if (do_update) {
256 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
257 				  state ? "open" : "closed");
258 		input_report_switch(button->input, SW_LID, !state);
259 		input_sync(button->input);
260 		button->last_state = !!state;
261 		button->last_time = ktime_get();
262 	}
263 
264 	return 0;
265 }
266 
267 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
268 						     void *offset)
269 {
270 	struct acpi_device *device = seq->private;
271 	int state;
272 
273 	state = acpi_lid_evaluate_state(device);
274 	seq_printf(seq, "state:      %s\n",
275 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
276 	return 0;
277 }
278 
279 static int acpi_button_add_fs(struct acpi_device *device)
280 {
281 	struct acpi_button *button = acpi_driver_data(device);
282 	struct proc_dir_entry *entry = NULL;
283 	int ret = 0;
284 
285 	/* procfs I/F for ACPI lid device only */
286 	if (button->type != ACPI_BUTTON_TYPE_LID)
287 		return 0;
288 
289 	if (acpi_button_dir || acpi_lid_dir) {
290 		printk(KERN_ERR PREFIX "More than one Lid device found!\n");
291 		return -EEXIST;
292 	}
293 
294 	/* create /proc/acpi/button */
295 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
296 	if (!acpi_button_dir)
297 		return -ENODEV;
298 
299 	/* create /proc/acpi/button/lid */
300 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
301 	if (!acpi_lid_dir) {
302 		ret = -ENODEV;
303 		goto remove_button_dir;
304 	}
305 
306 	/* create /proc/acpi/button/lid/LID/ */
307 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
308 	if (!acpi_device_dir(device)) {
309 		ret = -ENODEV;
310 		goto remove_lid_dir;
311 	}
312 
313 	/* create /proc/acpi/button/lid/LID/state */
314 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
315 			acpi_device_dir(device), acpi_button_state_seq_show,
316 			device);
317 	if (!entry) {
318 		ret = -ENODEV;
319 		goto remove_dev_dir;
320 	}
321 
322 done:
323 	return ret;
324 
325 remove_dev_dir:
326 	remove_proc_entry(acpi_device_bid(device),
327 			  acpi_lid_dir);
328 	acpi_device_dir(device) = NULL;
329 remove_lid_dir:
330 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
331 	acpi_lid_dir = NULL;
332 remove_button_dir:
333 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
334 	acpi_button_dir = NULL;
335 	goto done;
336 }
337 
338 static int acpi_button_remove_fs(struct acpi_device *device)
339 {
340 	struct acpi_button *button = acpi_driver_data(device);
341 
342 	if (button->type != ACPI_BUTTON_TYPE_LID)
343 		return 0;
344 
345 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
346 			  acpi_device_dir(device));
347 	remove_proc_entry(acpi_device_bid(device),
348 			  acpi_lid_dir);
349 	acpi_device_dir(device) = NULL;
350 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
351 	acpi_lid_dir = NULL;
352 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
353 	acpi_button_dir = NULL;
354 
355 	return 0;
356 }
357 
358 /* --------------------------------------------------------------------------
359                                 Driver Interface
360    -------------------------------------------------------------------------- */
361 int acpi_lid_open(void)
362 {
363 	if (!lid_device)
364 		return -ENODEV;
365 
366 	return acpi_lid_evaluate_state(lid_device);
367 }
368 EXPORT_SYMBOL(acpi_lid_open);
369 
370 static int acpi_lid_update_state(struct acpi_device *device,
371 				 bool signal_wakeup)
372 {
373 	int state;
374 
375 	state = acpi_lid_evaluate_state(device);
376 	if (state < 0)
377 		return state;
378 
379 	if (state && signal_wakeup)
380 		acpi_pm_wakeup_event(&device->dev);
381 
382 	return acpi_lid_notify_state(device, state);
383 }
384 
385 static void acpi_lid_initialize_state(struct acpi_device *device)
386 {
387 	struct acpi_button *button = acpi_driver_data(device);
388 
389 	switch (lid_init_state) {
390 	case ACPI_BUTTON_LID_INIT_OPEN:
391 		(void)acpi_lid_notify_state(device, 1);
392 		break;
393 	case ACPI_BUTTON_LID_INIT_METHOD:
394 		(void)acpi_lid_update_state(device, false);
395 		break;
396 	case ACPI_BUTTON_LID_INIT_IGNORE:
397 	default:
398 		break;
399 	}
400 
401 	button->lid_state_initialized = true;
402 }
403 
404 static void acpi_button_notify(struct acpi_device *device, u32 event)
405 {
406 	struct acpi_button *button = acpi_driver_data(device);
407 	struct input_dev *input;
408 
409 	switch (event) {
410 	case ACPI_FIXED_HARDWARE_EVENT:
411 		event = ACPI_BUTTON_NOTIFY_STATUS;
412 		fallthrough;
413 	case ACPI_BUTTON_NOTIFY_STATUS:
414 		input = button->input;
415 		if (button->type == ACPI_BUTTON_TYPE_LID) {
416 			if (button->lid_state_initialized)
417 				acpi_lid_update_state(device, true);
418 		} else {
419 			int keycode;
420 
421 			acpi_pm_wakeup_event(&device->dev);
422 			if (button->suspended)
423 				break;
424 
425 			keycode = test_bit(KEY_SLEEP, input->keybit) ?
426 						KEY_SLEEP : KEY_POWER;
427 			input_report_key(input, keycode, 1);
428 			input_sync(input);
429 			input_report_key(input, keycode, 0);
430 			input_sync(input);
431 
432 			acpi_bus_generate_netlink_event(
433 					device->pnp.device_class,
434 					dev_name(&device->dev),
435 					event, ++button->pushed);
436 		}
437 		break;
438 	default:
439 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
440 				  "Unsupported event [0x%x]\n", event));
441 		break;
442 	}
443 }
444 
445 #ifdef CONFIG_PM_SLEEP
446 static int acpi_button_suspend(struct device *dev)
447 {
448 	struct acpi_device *device = to_acpi_device(dev);
449 	struct acpi_button *button = acpi_driver_data(device);
450 
451 	button->suspended = true;
452 	return 0;
453 }
454 
455 static int acpi_button_resume(struct device *dev)
456 {
457 	struct acpi_device *device = to_acpi_device(dev);
458 	struct acpi_button *button = acpi_driver_data(device);
459 
460 	button->suspended = false;
461 	if (button->type == ACPI_BUTTON_TYPE_LID) {
462 		button->last_state = !!acpi_lid_evaluate_state(device);
463 		button->last_time = ktime_get();
464 		acpi_lid_initialize_state(device);
465 	}
466 	return 0;
467 }
468 #endif
469 
470 static int acpi_lid_input_open(struct input_dev *input)
471 {
472 	struct acpi_device *device = input_get_drvdata(input);
473 	struct acpi_button *button = acpi_driver_data(device);
474 
475 	button->last_state = !!acpi_lid_evaluate_state(device);
476 	button->last_time = ktime_get();
477 	acpi_lid_initialize_state(device);
478 
479 	return 0;
480 }
481 
482 static int acpi_button_add(struct acpi_device *device)
483 {
484 	struct acpi_button *button;
485 	struct input_dev *input;
486 	const char *hid = acpi_device_hid(device);
487 	char *name, *class;
488 	int error;
489 
490 	if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
491 	     lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
492 		return -ENODEV;
493 
494 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
495 	if (!button)
496 		return -ENOMEM;
497 
498 	device->driver_data = button;
499 
500 	button->input = input = input_allocate_device();
501 	if (!input) {
502 		error = -ENOMEM;
503 		goto err_free_button;
504 	}
505 
506 	name = acpi_device_name(device);
507 	class = acpi_device_class(device);
508 
509 	if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
510 	    !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
511 		button->type = ACPI_BUTTON_TYPE_POWER;
512 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
513 		sprintf(class, "%s/%s",
514 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
515 	} else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
516 		   !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
517 		button->type = ACPI_BUTTON_TYPE_SLEEP;
518 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
519 		sprintf(class, "%s/%s",
520 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
521 	} else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
522 		button->type = ACPI_BUTTON_TYPE_LID;
523 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
524 		sprintf(class, "%s/%s",
525 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
526 		input->open = acpi_lid_input_open;
527 	} else {
528 		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
529 		error = -ENODEV;
530 		goto err_free_input;
531 	}
532 
533 	error = acpi_button_add_fs(device);
534 	if (error)
535 		goto err_free_input;
536 
537 	snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
538 
539 	input->name = name;
540 	input->phys = button->phys;
541 	input->id.bustype = BUS_HOST;
542 	input->id.product = button->type;
543 	input->dev.parent = &device->dev;
544 
545 	switch (button->type) {
546 	case ACPI_BUTTON_TYPE_POWER:
547 		input_set_capability(input, EV_KEY, KEY_POWER);
548 		break;
549 
550 	case ACPI_BUTTON_TYPE_SLEEP:
551 		input_set_capability(input, EV_KEY, KEY_SLEEP);
552 		break;
553 
554 	case ACPI_BUTTON_TYPE_LID:
555 		input_set_capability(input, EV_SW, SW_LID);
556 		break;
557 	}
558 
559 	input_set_drvdata(input, device);
560 	error = input_register_device(input);
561 	if (error)
562 		goto err_remove_fs;
563 	if (button->type == ACPI_BUTTON_TYPE_LID) {
564 		/*
565 		 * This assumes there's only one lid device, or if there are
566 		 * more we only care about the last one...
567 		 */
568 		lid_device = device;
569 	}
570 
571 	device_init_wakeup(&device->dev, true);
572 	printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
573 	return 0;
574 
575  err_remove_fs:
576 	acpi_button_remove_fs(device);
577  err_free_input:
578 	input_free_device(input);
579  err_free_button:
580 	kfree(button);
581 	return error;
582 }
583 
584 static int acpi_button_remove(struct acpi_device *device)
585 {
586 	struct acpi_button *button = acpi_driver_data(device);
587 
588 	acpi_button_remove_fs(device);
589 	input_unregister_device(button->input);
590 	kfree(button);
591 	return 0;
592 }
593 
594 static int param_set_lid_init_state(const char *val,
595 				    const struct kernel_param *kp)
596 {
597 	int i;
598 
599 	i = sysfs_match_string(lid_init_state_str, val);
600 	if (i < 0)
601 		return i;
602 
603 	lid_init_state = i;
604 	pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
605 	return 0;
606 }
607 
608 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
609 {
610 	int i, c = 0;
611 
612 	for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
613 		if (i == lid_init_state)
614 			c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
615 		else
616 			c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
617 
618 	buf[c - 1] = '\n'; /* Replace the final space with a newline */
619 
620 	return c;
621 }
622 
623 module_param_call(lid_init_state,
624 		  param_set_lid_init_state, param_get_lid_init_state,
625 		  NULL, 0644);
626 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
627 
628 static int acpi_button_register_driver(struct acpi_driver *driver)
629 {
630 	const struct dmi_system_id *dmi_id;
631 
632 	if (lid_init_state == -1) {
633 		dmi_id = dmi_first_match(dmi_lid_quirks);
634 		if (dmi_id)
635 			lid_init_state = (long)dmi_id->driver_data;
636 		else
637 			lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
638 	}
639 
640 	/*
641 	 * Modules such as nouveau.ko and i915.ko have a link time dependency
642 	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
643 	 * capable kernels booted in non-ACPI mode if the return value of
644 	 * acpi_bus_register_driver() is returned from here with ACPI disabled
645 	 * when this driver is built as a module.
646 	 */
647 	if (acpi_disabled)
648 		return 0;
649 
650 	return acpi_bus_register_driver(driver);
651 }
652 
653 static void acpi_button_unregister_driver(struct acpi_driver *driver)
654 {
655 	if (!acpi_disabled)
656 		acpi_bus_unregister_driver(driver);
657 }
658 
659 module_driver(acpi_button_driver, acpi_button_register_driver,
660 	       acpi_button_unregister_driver);
661