xref: /linux/drivers/acpi/button.c (revision c79c3c34f75d72a066e292b10aa50fc758c97c89)
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 ACPI_BUTTON_CLASS		"button"
25 #define ACPI_BUTTON_FILE_STATE		"state"
26 #define ACPI_BUTTON_TYPE_UNKNOWN	0x00
27 #define ACPI_BUTTON_NOTIFY_STATUS	0x80
28 
29 #define ACPI_BUTTON_SUBCLASS_POWER	"power"
30 #define ACPI_BUTTON_DEVICE_NAME_POWER	"Power Button"
31 #define ACPI_BUTTON_TYPE_POWER		0x01
32 
33 #define ACPI_BUTTON_SUBCLASS_SLEEP	"sleep"
34 #define ACPI_BUTTON_DEVICE_NAME_SLEEP	"Sleep Button"
35 #define ACPI_BUTTON_TYPE_SLEEP		0x03
36 
37 #define ACPI_BUTTON_SUBCLASS_LID	"lid"
38 #define ACPI_BUTTON_DEVICE_NAME_LID	"Lid Switch"
39 #define ACPI_BUTTON_TYPE_LID		0x05
40 
41 enum {
42 	ACPI_BUTTON_LID_INIT_IGNORE,
43 	ACPI_BUTTON_LID_INIT_OPEN,
44 	ACPI_BUTTON_LID_INIT_METHOD,
45 	ACPI_BUTTON_LID_INIT_DISABLED,
46 };
47 
48 static const char * const lid_init_state_str[] = {
49 	[ACPI_BUTTON_LID_INIT_IGNORE]		= "ignore",
50 	[ACPI_BUTTON_LID_INIT_OPEN]		= "open",
51 	[ACPI_BUTTON_LID_INIT_METHOD]		= "method",
52 	[ACPI_BUTTON_LID_INIT_DISABLED]		= "disabled",
53 };
54 
55 MODULE_AUTHOR("Paul Diefenbaugh");
56 MODULE_DESCRIPTION("ACPI Button Driver");
57 MODULE_LICENSE("GPL");
58 
59 static const struct acpi_device_id button_device_ids[] = {
60 	{ACPI_BUTTON_HID_LID,    0},
61 	{ACPI_BUTTON_HID_SLEEP,  0},
62 	{ACPI_BUTTON_HID_SLEEPF, 0},
63 	{ACPI_BUTTON_HID_POWER,  0},
64 	{ACPI_BUTTON_HID_POWERF, 0},
65 	{"", 0},
66 };
67 MODULE_DEVICE_TABLE(acpi, button_device_ids);
68 
69 /* Please keep this list sorted alphabetically by vendor and model */
70 static const struct dmi_system_id dmi_lid_quirks[] = {
71 	{
72 		/* GP-electronic T701, _LID method points to a floating GPIO */
73 		.matches = {
74 			DMI_MATCH(DMI_SYS_VENDOR, "Insyde"),
75 			DMI_MATCH(DMI_PRODUCT_NAME, "T701"),
76 			DMI_MATCH(DMI_BIOS_VERSION, "BYT70A.YNCHENG.WIN.007"),
77 		},
78 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_DISABLED,
79 	},
80 	{
81 		/*
82 		 * Medion Akoya E2215T, notification of the LID device only
83 		 * happens on close, not on open and _LID always returns closed.
84 		 */
85 		.matches = {
86 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
87 			DMI_MATCH(DMI_PRODUCT_NAME, "E2215T"),
88 		},
89 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
90 	},
91 	{
92 		/*
93 		 * Medion Akoya E2228T, notification of the LID device only
94 		 * happens on close, not on open and _LID always returns closed.
95 		 */
96 		.matches = {
97 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
98 			DMI_MATCH(DMI_PRODUCT_NAME, "E2228T"),
99 		},
100 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
101 	},
102 	{
103 		/*
104 		 * Razer Blade Stealth 13 late 2019, notification of the LID device
105 		 * only happens on close, not on open and _LID always returns closed.
106 		 */
107 		.matches = {
108 			DMI_MATCH(DMI_SYS_VENDOR, "Razer"),
109 			DMI_MATCH(DMI_PRODUCT_NAME, "Razer Blade Stealth 13 Late 2019"),
110 		},
111 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
112 	},
113 	{}
114 };
115 
116 static int acpi_button_add(struct acpi_device *device);
117 static int acpi_button_remove(struct acpi_device *device);
118 static void acpi_button_notify(struct acpi_device *device, u32 event);
119 
120 #ifdef CONFIG_PM_SLEEP
121 static int acpi_button_suspend(struct device *dev);
122 static int acpi_button_resume(struct device *dev);
123 #else
124 #define acpi_button_suspend NULL
125 #define acpi_button_resume NULL
126 #endif
127 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
128 
129 static struct acpi_driver acpi_button_driver = {
130 	.name = "button",
131 	.class = ACPI_BUTTON_CLASS,
132 	.ids = button_device_ids,
133 	.ops = {
134 		.add = acpi_button_add,
135 		.remove = acpi_button_remove,
136 		.notify = acpi_button_notify,
137 	},
138 	.drv.pm = &acpi_button_pm,
139 };
140 
141 struct acpi_button {
142 	unsigned int type;
143 	struct input_dev *input;
144 	char phys[32];			/* for input device */
145 	unsigned long pushed;
146 	int last_state;
147 	ktime_t last_time;
148 	bool suspended;
149 	bool lid_state_initialized;
150 };
151 
152 static struct acpi_device *lid_device;
153 static long lid_init_state = -1;
154 
155 static unsigned long lid_report_interval __read_mostly = 500;
156 module_param(lid_report_interval, ulong, 0644);
157 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
158 
159 /* --------------------------------------------------------------------------
160                               FS Interface (/proc)
161    -------------------------------------------------------------------------- */
162 
163 static struct proc_dir_entry *acpi_button_dir;
164 static struct proc_dir_entry *acpi_lid_dir;
165 
166 static int acpi_lid_evaluate_state(struct acpi_device *device)
167 {
168 	unsigned long long lid_state;
169 	acpi_status status;
170 
171 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
172 	if (ACPI_FAILURE(status))
173 		return -ENODEV;
174 
175 	return lid_state ? 1 : 0;
176 }
177 
178 static int acpi_lid_notify_state(struct acpi_device *device, int state)
179 {
180 	struct acpi_button *button = acpi_driver_data(device);
181 	ktime_t next_report;
182 	bool do_update;
183 
184 	/*
185 	 * In lid_init_state=ignore mode, if user opens/closes lid
186 	 * frequently with "open" missing, and "last_time" is also updated
187 	 * frequently, "close" cannot be delivered to the userspace.
188 	 * So "last_time" is only updated after a timeout or an actual
189 	 * switch.
190 	 */
191 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
192 	    button->last_state != !!state)
193 		do_update = true;
194 	else
195 		do_update = false;
196 
197 	next_report = ktime_add(button->last_time,
198 				ms_to_ktime(lid_report_interval));
199 	if (button->last_state == !!state &&
200 	    ktime_after(ktime_get(), next_report)) {
201 		/* Complain the buggy firmware */
202 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
203 
204 		/*
205 		 * Send the unreliable complement switch event:
206 		 *
207 		 * On most platforms, the lid device is reliable. However
208 		 * there are exceptions:
209 		 * 1. Platforms returning initial lid state as "close" by
210 		 *    default after booting/resuming:
211 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
212 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
213 		 * 2. Platforms never reporting "open" events:
214 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
215 		 * On these buggy platforms, the usage model of the ACPI
216 		 * lid device actually is:
217 		 * 1. The initial returning value of _LID may not be
218 		 *    reliable.
219 		 * 2. The open event may not be reliable.
220 		 * 3. The close event is reliable.
221 		 *
222 		 * But SW_LID is typed as input switch event, the input
223 		 * layer checks if the event is redundant. Hence if the
224 		 * state is not switched, the userspace cannot see this
225 		 * platform triggered reliable event. By inserting a
226 		 * complement switch event, it then is guaranteed that the
227 		 * platform triggered reliable one can always be seen by
228 		 * the userspace.
229 		 */
230 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
231 			do_update = true;
232 			/*
233 			 * Do generate complement switch event for "close"
234 			 * as "close" is reliable and wrong "open" won't
235 			 * trigger unexpected behaviors.
236 			 * Do not generate complement switch event for
237 			 * "open" as "open" is not reliable and wrong
238 			 * "close" will trigger unexpected behaviors.
239 			 */
240 			if (!state) {
241 				input_report_switch(button->input,
242 						    SW_LID, state);
243 				input_sync(button->input);
244 			}
245 		}
246 	}
247 	/* Send the platform triggered reliable event */
248 	if (do_update) {
249 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
250 				  state ? "open" : "closed");
251 		input_report_switch(button->input, SW_LID, !state);
252 		input_sync(button->input);
253 		button->last_state = !!state;
254 		button->last_time = ktime_get();
255 	}
256 
257 	return 0;
258 }
259 
260 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
261 						     void *offset)
262 {
263 	struct acpi_device *device = seq->private;
264 	int state;
265 
266 	state = acpi_lid_evaluate_state(device);
267 	seq_printf(seq, "state:      %s\n",
268 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
269 	return 0;
270 }
271 
272 static int acpi_button_add_fs(struct acpi_device *device)
273 {
274 	struct acpi_button *button = acpi_driver_data(device);
275 	struct proc_dir_entry *entry = NULL;
276 	int ret = 0;
277 
278 	/* procfs I/F for ACPI lid device only */
279 	if (button->type != ACPI_BUTTON_TYPE_LID)
280 		return 0;
281 
282 	if (acpi_button_dir || acpi_lid_dir) {
283 		pr_info("More than one Lid device found!\n");
284 		return -EEXIST;
285 	}
286 
287 	/* create /proc/acpi/button */
288 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
289 	if (!acpi_button_dir)
290 		return -ENODEV;
291 
292 	/* create /proc/acpi/button/lid */
293 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
294 	if (!acpi_lid_dir) {
295 		ret = -ENODEV;
296 		goto remove_button_dir;
297 	}
298 
299 	/* create /proc/acpi/button/lid/LID/ */
300 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
301 	if (!acpi_device_dir(device)) {
302 		ret = -ENODEV;
303 		goto remove_lid_dir;
304 	}
305 
306 	/* create /proc/acpi/button/lid/LID/state */
307 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
308 			acpi_device_dir(device), acpi_button_state_seq_show,
309 			device);
310 	if (!entry) {
311 		ret = -ENODEV;
312 		goto remove_dev_dir;
313 	}
314 
315 done:
316 	return ret;
317 
318 remove_dev_dir:
319 	remove_proc_entry(acpi_device_bid(device),
320 			  acpi_lid_dir);
321 	acpi_device_dir(device) = NULL;
322 remove_lid_dir:
323 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
324 	acpi_lid_dir = NULL;
325 remove_button_dir:
326 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
327 	acpi_button_dir = NULL;
328 	goto done;
329 }
330 
331 static int acpi_button_remove_fs(struct acpi_device *device)
332 {
333 	struct acpi_button *button = acpi_driver_data(device);
334 
335 	if (button->type != ACPI_BUTTON_TYPE_LID)
336 		return 0;
337 
338 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
339 			  acpi_device_dir(device));
340 	remove_proc_entry(acpi_device_bid(device),
341 			  acpi_lid_dir);
342 	acpi_device_dir(device) = NULL;
343 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
344 	acpi_lid_dir = NULL;
345 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
346 	acpi_button_dir = NULL;
347 
348 	return 0;
349 }
350 
351 /* --------------------------------------------------------------------------
352                                 Driver Interface
353    -------------------------------------------------------------------------- */
354 int acpi_lid_open(void)
355 {
356 	if (!lid_device)
357 		return -ENODEV;
358 
359 	return acpi_lid_evaluate_state(lid_device);
360 }
361 EXPORT_SYMBOL(acpi_lid_open);
362 
363 static int acpi_lid_update_state(struct acpi_device *device,
364 				 bool signal_wakeup)
365 {
366 	int state;
367 
368 	state = acpi_lid_evaluate_state(device);
369 	if (state < 0)
370 		return state;
371 
372 	if (state && signal_wakeup)
373 		acpi_pm_wakeup_event(&device->dev);
374 
375 	return acpi_lid_notify_state(device, state);
376 }
377 
378 static void acpi_lid_initialize_state(struct acpi_device *device)
379 {
380 	struct acpi_button *button = acpi_driver_data(device);
381 
382 	switch (lid_init_state) {
383 	case ACPI_BUTTON_LID_INIT_OPEN:
384 		(void)acpi_lid_notify_state(device, 1);
385 		break;
386 	case ACPI_BUTTON_LID_INIT_METHOD:
387 		(void)acpi_lid_update_state(device, false);
388 		break;
389 	case ACPI_BUTTON_LID_INIT_IGNORE:
390 	default:
391 		break;
392 	}
393 
394 	button->lid_state_initialized = true;
395 }
396 
397 static void acpi_button_notify(struct acpi_device *device, u32 event)
398 {
399 	struct acpi_button *button = acpi_driver_data(device);
400 	struct input_dev *input;
401 
402 	switch (event) {
403 	case ACPI_FIXED_HARDWARE_EVENT:
404 		event = ACPI_BUTTON_NOTIFY_STATUS;
405 		fallthrough;
406 	case ACPI_BUTTON_NOTIFY_STATUS:
407 		input = button->input;
408 		if (button->type == ACPI_BUTTON_TYPE_LID) {
409 			if (button->lid_state_initialized)
410 				acpi_lid_update_state(device, true);
411 		} else {
412 			int keycode;
413 
414 			acpi_pm_wakeup_event(&device->dev);
415 			if (button->suspended)
416 				break;
417 
418 			keycode = test_bit(KEY_SLEEP, input->keybit) ?
419 						KEY_SLEEP : KEY_POWER;
420 			input_report_key(input, keycode, 1);
421 			input_sync(input);
422 			input_report_key(input, keycode, 0);
423 			input_sync(input);
424 
425 			acpi_bus_generate_netlink_event(
426 					device->pnp.device_class,
427 					dev_name(&device->dev),
428 					event, ++button->pushed);
429 		}
430 		break;
431 	default:
432 		acpi_handle_debug(device->handle, "Unsupported event [0x%x]\n",
433 				  event);
434 		break;
435 	}
436 }
437 
438 #ifdef CONFIG_PM_SLEEP
439 static int acpi_button_suspend(struct device *dev)
440 {
441 	struct acpi_device *device = to_acpi_device(dev);
442 	struct acpi_button *button = acpi_driver_data(device);
443 
444 	button->suspended = true;
445 	return 0;
446 }
447 
448 static int acpi_button_resume(struct device *dev)
449 {
450 	struct acpi_device *device = to_acpi_device(dev);
451 	struct acpi_button *button = acpi_driver_data(device);
452 
453 	button->suspended = false;
454 	if (button->type == ACPI_BUTTON_TYPE_LID) {
455 		button->last_state = !!acpi_lid_evaluate_state(device);
456 		button->last_time = ktime_get();
457 		acpi_lid_initialize_state(device);
458 	}
459 	return 0;
460 }
461 #endif
462 
463 static int acpi_lid_input_open(struct input_dev *input)
464 {
465 	struct acpi_device *device = input_get_drvdata(input);
466 	struct acpi_button *button = acpi_driver_data(device);
467 
468 	button->last_state = !!acpi_lid_evaluate_state(device);
469 	button->last_time = ktime_get();
470 	acpi_lid_initialize_state(device);
471 
472 	return 0;
473 }
474 
475 static int acpi_button_add(struct acpi_device *device)
476 {
477 	struct acpi_button *button;
478 	struct input_dev *input;
479 	const char *hid = acpi_device_hid(device);
480 	char *name, *class;
481 	int error;
482 
483 	if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
484 	     lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
485 		return -ENODEV;
486 
487 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
488 	if (!button)
489 		return -ENOMEM;
490 
491 	device->driver_data = button;
492 
493 	button->input = input = input_allocate_device();
494 	if (!input) {
495 		error = -ENOMEM;
496 		goto err_free_button;
497 	}
498 
499 	name = acpi_device_name(device);
500 	class = acpi_device_class(device);
501 
502 	if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
503 	    !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
504 		button->type = ACPI_BUTTON_TYPE_POWER;
505 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
506 		sprintf(class, "%s/%s",
507 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
508 	} else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
509 		   !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
510 		button->type = ACPI_BUTTON_TYPE_SLEEP;
511 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
512 		sprintf(class, "%s/%s",
513 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
514 	} else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
515 		button->type = ACPI_BUTTON_TYPE_LID;
516 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
517 		sprintf(class, "%s/%s",
518 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
519 		input->open = acpi_lid_input_open;
520 	} else {
521 		pr_info("Unsupported hid [%s]\n", hid);
522 		error = -ENODEV;
523 		goto err_free_input;
524 	}
525 
526 	error = acpi_button_add_fs(device);
527 	if (error)
528 		goto err_free_input;
529 
530 	snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
531 
532 	input->name = name;
533 	input->phys = button->phys;
534 	input->id.bustype = BUS_HOST;
535 	input->id.product = button->type;
536 	input->dev.parent = &device->dev;
537 
538 	switch (button->type) {
539 	case ACPI_BUTTON_TYPE_POWER:
540 		input_set_capability(input, EV_KEY, KEY_POWER);
541 		break;
542 
543 	case ACPI_BUTTON_TYPE_SLEEP:
544 		input_set_capability(input, EV_KEY, KEY_SLEEP);
545 		break;
546 
547 	case ACPI_BUTTON_TYPE_LID:
548 		input_set_capability(input, EV_SW, SW_LID);
549 		break;
550 	}
551 
552 	input_set_drvdata(input, device);
553 	error = input_register_device(input);
554 	if (error)
555 		goto err_remove_fs;
556 	if (button->type == ACPI_BUTTON_TYPE_LID) {
557 		/*
558 		 * This assumes there's only one lid device, or if there are
559 		 * more we only care about the last one...
560 		 */
561 		lid_device = device;
562 	}
563 
564 	device_init_wakeup(&device->dev, true);
565 	pr_info("%s [%s]\n", name, acpi_device_bid(device));
566 	return 0;
567 
568  err_remove_fs:
569 	acpi_button_remove_fs(device);
570  err_free_input:
571 	input_free_device(input);
572  err_free_button:
573 	kfree(button);
574 	return error;
575 }
576 
577 static int acpi_button_remove(struct acpi_device *device)
578 {
579 	struct acpi_button *button = acpi_driver_data(device);
580 
581 	acpi_button_remove_fs(device);
582 	input_unregister_device(button->input);
583 	kfree(button);
584 	return 0;
585 }
586 
587 static int param_set_lid_init_state(const char *val,
588 				    const struct kernel_param *kp)
589 {
590 	int i;
591 
592 	i = sysfs_match_string(lid_init_state_str, val);
593 	if (i < 0)
594 		return i;
595 
596 	lid_init_state = i;
597 	pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
598 	return 0;
599 }
600 
601 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
602 {
603 	int i, c = 0;
604 
605 	for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
606 		if (i == lid_init_state)
607 			c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
608 		else
609 			c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
610 
611 	buf[c - 1] = '\n'; /* Replace the final space with a newline */
612 
613 	return c;
614 }
615 
616 module_param_call(lid_init_state,
617 		  param_set_lid_init_state, param_get_lid_init_state,
618 		  NULL, 0644);
619 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
620 
621 static int acpi_button_register_driver(struct acpi_driver *driver)
622 {
623 	const struct dmi_system_id *dmi_id;
624 
625 	if (lid_init_state == -1) {
626 		dmi_id = dmi_first_match(dmi_lid_quirks);
627 		if (dmi_id)
628 			lid_init_state = (long)dmi_id->driver_data;
629 		else
630 			lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
631 	}
632 
633 	/*
634 	 * Modules such as nouveau.ko and i915.ko have a link time dependency
635 	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
636 	 * capable kernels booted in non-ACPI mode if the return value of
637 	 * acpi_bus_register_driver() is returned from here with ACPI disabled
638 	 * when this driver is built as a module.
639 	 */
640 	if (acpi_disabled)
641 		return 0;
642 
643 	return acpi_bus_register_driver(driver);
644 }
645 
646 static void acpi_button_unregister_driver(struct acpi_driver *driver)
647 {
648 	if (!acpi_disabled)
649 		acpi_bus_unregister_driver(driver);
650 }
651 
652 module_driver(acpi_button_driver, acpi_button_register_driver,
653 	       acpi_button_unregister_driver);
654