xref: /openbmc/linux/drivers/acpi/button.c (revision 323dd2c3)
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_INFO		"info"
28 #define ACPI_BUTTON_FILE_STATE		"state"
29 #define ACPI_BUTTON_TYPE_UNKNOWN	0x00
30 #define ACPI_BUTTON_NOTIFY_STATUS	0x80
31 
32 #define ACPI_BUTTON_SUBCLASS_POWER	"power"
33 #define ACPI_BUTTON_HID_POWER		"PNP0C0C"
34 #define ACPI_BUTTON_DEVICE_NAME_POWER	"Power Button"
35 #define ACPI_BUTTON_TYPE_POWER		0x01
36 
37 #define ACPI_BUTTON_SUBCLASS_SLEEP	"sleep"
38 #define ACPI_BUTTON_HID_SLEEP		"PNP0C0E"
39 #define ACPI_BUTTON_DEVICE_NAME_SLEEP	"Sleep Button"
40 #define ACPI_BUTTON_TYPE_SLEEP		0x03
41 
42 #define ACPI_BUTTON_SUBCLASS_LID	"lid"
43 #define ACPI_BUTTON_HID_LID		"PNP0C0D"
44 #define ACPI_BUTTON_DEVICE_NAME_LID	"Lid Switch"
45 #define ACPI_BUTTON_TYPE_LID		0x05
46 
47 enum {
48 	ACPI_BUTTON_LID_INIT_IGNORE,
49 	ACPI_BUTTON_LID_INIT_OPEN,
50 	ACPI_BUTTON_LID_INIT_METHOD,
51 	ACPI_BUTTON_LID_INIT_DISABLED,
52 };
53 
54 static const char * const lid_init_state_str[] = {
55 	[ACPI_BUTTON_LID_INIT_IGNORE]		= "ignore",
56 	[ACPI_BUTTON_LID_INIT_OPEN]		= "open",
57 	[ACPI_BUTTON_LID_INIT_METHOD]		= "method",
58 	[ACPI_BUTTON_LID_INIT_DISABLED]		= "disabled",
59 };
60 
61 #define _COMPONENT		ACPI_BUTTON_COMPONENT
62 ACPI_MODULE_NAME("button");
63 
64 MODULE_AUTHOR("Paul Diefenbaugh");
65 MODULE_DESCRIPTION("ACPI Button Driver");
66 MODULE_LICENSE("GPL");
67 
68 static const struct acpi_device_id button_device_ids[] = {
69 	{ACPI_BUTTON_HID_LID,    0},
70 	{ACPI_BUTTON_HID_SLEEP,  0},
71 	{ACPI_BUTTON_HID_SLEEPF, 0},
72 	{ACPI_BUTTON_HID_POWER,  0},
73 	{ACPI_BUTTON_HID_POWERF, 0},
74 	{"", 0},
75 };
76 MODULE_DEVICE_TABLE(acpi, button_device_ids);
77 
78 /* Please keep this list sorted alphabetically by vendor and model */
79 static const struct dmi_system_id dmi_lid_quirks[] = {
80 	{
81 		/*
82 		 * Asus T200TA, _LID keeps reporting closed after every second
83 		 * openening of the lid. Causing immediate re-suspend after
84 		 * opening every other open. Using LID_INIT_OPEN fixes this.
85 		 */
86 		.matches = {
87 			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
88 			DMI_MATCH(DMI_PRODUCT_NAME, "T200TA"),
89 		},
90 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
91 	},
92 	{
93 		/* GP-electronic T701, _LID method points to a floating GPIO */
94 		.matches = {
95 			DMI_MATCH(DMI_SYS_VENDOR, "Insyde"),
96 			DMI_MATCH(DMI_PRODUCT_NAME, "T701"),
97 			DMI_MATCH(DMI_BIOS_VERSION, "BYT70A.YNCHENG.WIN.007"),
98 		},
99 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_DISABLED,
100 	},
101 	{
102 		/*
103 		 * Medion Akoya E2215T, notification of the LID device only
104 		 * happens on close, not on open and _LID always returns closed.
105 		 */
106 		.matches = {
107 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
108 			DMI_MATCH(DMI_PRODUCT_NAME, "E2215T MD60198"),
109 		},
110 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
111 	},
112 	{}
113 };
114 
115 static int acpi_button_add(struct acpi_device *device);
116 static int acpi_button_remove(struct acpi_device *device);
117 static void acpi_button_notify(struct acpi_device *device, u32 event);
118 
119 #ifdef CONFIG_PM_SLEEP
120 static int acpi_button_suspend(struct device *dev);
121 static int acpi_button_resume(struct device *dev);
122 #else
123 #define acpi_button_suspend NULL
124 #define acpi_button_resume NULL
125 #endif
126 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
127 
128 static struct acpi_driver acpi_button_driver = {
129 	.name = "button",
130 	.class = ACPI_BUTTON_CLASS,
131 	.ids = button_device_ids,
132 	.ops = {
133 		.add = acpi_button_add,
134 		.remove = acpi_button_remove,
135 		.notify = acpi_button_notify,
136 	},
137 	.drv.pm = &acpi_button_pm,
138 };
139 
140 struct acpi_button {
141 	unsigned int type;
142 	struct input_dev *input;
143 	char phys[32];			/* for input device */
144 	unsigned long pushed;
145 	int last_state;
146 	ktime_t last_time;
147 	bool suspended;
148 };
149 
150 static struct acpi_device *lid_device;
151 static long lid_init_state = -1;
152 
153 static unsigned long lid_report_interval __read_mostly = 500;
154 module_param(lid_report_interval, ulong, 0644);
155 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
156 
157 /* --------------------------------------------------------------------------
158                               FS Interface (/proc)
159    -------------------------------------------------------------------------- */
160 
161 static struct proc_dir_entry *acpi_button_dir;
162 static struct proc_dir_entry *acpi_lid_dir;
163 
164 static int acpi_lid_evaluate_state(struct acpi_device *device)
165 {
166 	unsigned long long lid_state;
167 	acpi_status status;
168 
169 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
170 	if (ACPI_FAILURE(status))
171 		return -ENODEV;
172 
173 	return lid_state ? 1 : 0;
174 }
175 
176 static int acpi_lid_notify_state(struct acpi_device *device, int state)
177 {
178 	struct acpi_button *button = acpi_driver_data(device);
179 	ktime_t next_report;
180 	bool do_update;
181 
182 	/*
183 	 * In lid_init_state=ignore mode, if user opens/closes lid
184 	 * frequently with "open" missing, and "last_time" is also updated
185 	 * frequently, "close" cannot be delivered to the userspace.
186 	 * So "last_time" is only updated after a timeout or an actual
187 	 * switch.
188 	 */
189 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
190 	    button->last_state != !!state)
191 		do_update = true;
192 	else
193 		do_update = false;
194 
195 	next_report = ktime_add(button->last_time,
196 				ms_to_ktime(lid_report_interval));
197 	if (button->last_state == !!state &&
198 	    ktime_after(ktime_get(), next_report)) {
199 		/* Complain the buggy firmware */
200 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
201 
202 		/*
203 		 * Send the unreliable complement switch event:
204 		 *
205 		 * On most platforms, the lid device is reliable. However
206 		 * there are exceptions:
207 		 * 1. Platforms returning initial lid state as "close" by
208 		 *    default after booting/resuming:
209 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
210 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
211 		 * 2. Platforms never reporting "open" events:
212 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
213 		 * On these buggy platforms, the usage model of the ACPI
214 		 * lid device actually is:
215 		 * 1. The initial returning value of _LID may not be
216 		 *    reliable.
217 		 * 2. The open event may not be reliable.
218 		 * 3. The close event is reliable.
219 		 *
220 		 * But SW_LID is typed as input switch event, the input
221 		 * layer checks if the event is redundant. Hence if the
222 		 * state is not switched, the userspace cannot see this
223 		 * platform triggered reliable event. By inserting a
224 		 * complement switch event, it then is guaranteed that the
225 		 * platform triggered reliable one can always be seen by
226 		 * the userspace.
227 		 */
228 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
229 			do_update = true;
230 			/*
231 			 * Do generate complement switch event for "close"
232 			 * as "close" is reliable and wrong "open" won't
233 			 * trigger unexpected behaviors.
234 			 * Do not generate complement switch event for
235 			 * "open" as "open" is not reliable and wrong
236 			 * "close" will trigger unexpected behaviors.
237 			 */
238 			if (!state) {
239 				input_report_switch(button->input,
240 						    SW_LID, state);
241 				input_sync(button->input);
242 			}
243 		}
244 	}
245 	/* Send the platform triggered reliable event */
246 	if (do_update) {
247 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
248 				  state ? "open" : "closed");
249 		input_report_switch(button->input, SW_LID, !state);
250 		input_sync(button->input);
251 		button->last_state = !!state;
252 		button->last_time = ktime_get();
253 	}
254 
255 	return 0;
256 }
257 
258 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
259 						     void *offset)
260 {
261 	struct acpi_device *device = seq->private;
262 	int state;
263 
264 	state = acpi_lid_evaluate_state(device);
265 	seq_printf(seq, "state:      %s\n",
266 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
267 	return 0;
268 }
269 
270 static int acpi_button_add_fs(struct acpi_device *device)
271 {
272 	struct acpi_button *button = acpi_driver_data(device);
273 	struct proc_dir_entry *entry = NULL;
274 	int ret = 0;
275 
276 	/* procfs I/F for ACPI lid device only */
277 	if (button->type != ACPI_BUTTON_TYPE_LID)
278 		return 0;
279 
280 	if (acpi_button_dir || acpi_lid_dir) {
281 		printk(KERN_ERR PREFIX "More than one Lid device found!\n");
282 		return -EEXIST;
283 	}
284 
285 	/* create /proc/acpi/button */
286 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
287 	if (!acpi_button_dir)
288 		return -ENODEV;
289 
290 	/* create /proc/acpi/button/lid */
291 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
292 	if (!acpi_lid_dir) {
293 		ret = -ENODEV;
294 		goto remove_button_dir;
295 	}
296 
297 	/* create /proc/acpi/button/lid/LID/ */
298 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
299 	if (!acpi_device_dir(device)) {
300 		ret = -ENODEV;
301 		goto remove_lid_dir;
302 	}
303 
304 	/* create /proc/acpi/button/lid/LID/state */
305 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
306 			acpi_device_dir(device), acpi_button_state_seq_show,
307 			device);
308 	if (!entry) {
309 		ret = -ENODEV;
310 		goto remove_dev_dir;
311 	}
312 
313 done:
314 	return ret;
315 
316 remove_dev_dir:
317 	remove_proc_entry(acpi_device_bid(device),
318 			  acpi_lid_dir);
319 	acpi_device_dir(device) = NULL;
320 remove_lid_dir:
321 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
322 	acpi_lid_dir = NULL;
323 remove_button_dir:
324 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
325 	acpi_button_dir = NULL;
326 	goto done;
327 }
328 
329 static int acpi_button_remove_fs(struct acpi_device *device)
330 {
331 	struct acpi_button *button = acpi_driver_data(device);
332 
333 	if (button->type != ACPI_BUTTON_TYPE_LID)
334 		return 0;
335 
336 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
337 			  acpi_device_dir(device));
338 	remove_proc_entry(acpi_device_bid(device),
339 			  acpi_lid_dir);
340 	acpi_device_dir(device) = NULL;
341 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
342 	acpi_lid_dir = NULL;
343 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
344 	acpi_button_dir = NULL;
345 
346 	return 0;
347 }
348 
349 /* --------------------------------------------------------------------------
350                                 Driver Interface
351    -------------------------------------------------------------------------- */
352 int acpi_lid_open(void)
353 {
354 	if (!lid_device)
355 		return -ENODEV;
356 
357 	return acpi_lid_evaluate_state(lid_device);
358 }
359 EXPORT_SYMBOL(acpi_lid_open);
360 
361 static int acpi_lid_update_state(struct acpi_device *device,
362 				 bool signal_wakeup)
363 {
364 	int state;
365 
366 	state = acpi_lid_evaluate_state(device);
367 	if (state < 0)
368 		return state;
369 
370 	if (state && signal_wakeup)
371 		acpi_pm_wakeup_event(&device->dev);
372 
373 	return acpi_lid_notify_state(device, state);
374 }
375 
376 static void acpi_lid_initialize_state(struct acpi_device *device)
377 {
378 	switch (lid_init_state) {
379 	case ACPI_BUTTON_LID_INIT_OPEN:
380 		(void)acpi_lid_notify_state(device, 1);
381 		break;
382 	case ACPI_BUTTON_LID_INIT_METHOD:
383 		(void)acpi_lid_update_state(device, false);
384 		break;
385 	case ACPI_BUTTON_LID_INIT_IGNORE:
386 	default:
387 		break;
388 	}
389 }
390 
391 static void acpi_button_notify(struct acpi_device *device, u32 event)
392 {
393 	struct acpi_button *button = acpi_driver_data(device);
394 	struct input_dev *input;
395 	int users;
396 
397 	switch (event) {
398 	case ACPI_FIXED_HARDWARE_EVENT:
399 		event = ACPI_BUTTON_NOTIFY_STATUS;
400 		/* fall through */
401 	case ACPI_BUTTON_NOTIFY_STATUS:
402 		input = button->input;
403 		if (button->type == ACPI_BUTTON_TYPE_LID) {
404 			mutex_lock(&button->input->mutex);
405 			users = button->input->users;
406 			mutex_unlock(&button->input->mutex);
407 			if (users)
408 				acpi_lid_update_state(device, true);
409 		} else {
410 			int keycode;
411 
412 			acpi_pm_wakeup_event(&device->dev);
413 			if (button->suspended)
414 				break;
415 
416 			keycode = test_bit(KEY_SLEEP, input->keybit) ?
417 						KEY_SLEEP : KEY_POWER;
418 			input_report_key(input, keycode, 1);
419 			input_sync(input);
420 			input_report_key(input, keycode, 0);
421 			input_sync(input);
422 
423 			acpi_bus_generate_netlink_event(
424 					device->pnp.device_class,
425 					dev_name(&device->dev),
426 					event, ++button->pushed);
427 		}
428 		break;
429 	default:
430 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
431 				  "Unsupported event [0x%x]\n", event));
432 		break;
433 	}
434 }
435 
436 #ifdef CONFIG_PM_SLEEP
437 static int acpi_button_suspend(struct device *dev)
438 {
439 	struct acpi_device *device = to_acpi_device(dev);
440 	struct acpi_button *button = acpi_driver_data(device);
441 
442 	button->suspended = true;
443 	return 0;
444 }
445 
446 static int acpi_button_resume(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 = false;
452 	if (button->type == ACPI_BUTTON_TYPE_LID && button->input->users) {
453 		button->last_state = !!acpi_lid_evaluate_state(device);
454 		button->last_time = ktime_get();
455 		acpi_lid_initialize_state(device);
456 	}
457 	return 0;
458 }
459 #endif
460 
461 static int acpi_lid_input_open(struct input_dev *input)
462 {
463 	struct acpi_device *device = input_get_drvdata(input);
464 	struct acpi_button *button = acpi_driver_data(device);
465 
466 	button->last_state = !!acpi_lid_evaluate_state(device);
467 	button->last_time = ktime_get();
468 	acpi_lid_initialize_state(device);
469 
470 	return 0;
471 }
472 
473 static int acpi_button_add(struct acpi_device *device)
474 {
475 	struct acpi_button *button;
476 	struct input_dev *input;
477 	const char *hid = acpi_device_hid(device);
478 	char *name, *class;
479 	int error;
480 
481 	if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
482 	     lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
483 		return -ENODEV;
484 
485 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
486 	if (!button)
487 		return -ENOMEM;
488 
489 	device->driver_data = button;
490 
491 	button->input = input = input_allocate_device();
492 	if (!input) {
493 		error = -ENOMEM;
494 		goto err_free_button;
495 	}
496 
497 	name = acpi_device_name(device);
498 	class = acpi_device_class(device);
499 
500 	if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
501 	    !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
502 		button->type = ACPI_BUTTON_TYPE_POWER;
503 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
504 		sprintf(class, "%s/%s",
505 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
506 	} else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
507 		   !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
508 		button->type = ACPI_BUTTON_TYPE_SLEEP;
509 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
510 		sprintf(class, "%s/%s",
511 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
512 	} else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
513 		button->type = ACPI_BUTTON_TYPE_LID;
514 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
515 		sprintf(class, "%s/%s",
516 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
517 		input->open = acpi_lid_input_open;
518 	} else {
519 		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
520 		error = -ENODEV;
521 		goto err_free_input;
522 	}
523 
524 	error = acpi_button_add_fs(device);
525 	if (error)
526 		goto err_free_input;
527 
528 	snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
529 
530 	input->name = name;
531 	input->phys = button->phys;
532 	input->id.bustype = BUS_HOST;
533 	input->id.product = button->type;
534 	input->dev.parent = &device->dev;
535 
536 	switch (button->type) {
537 	case ACPI_BUTTON_TYPE_POWER:
538 		input_set_capability(input, EV_KEY, KEY_POWER);
539 		break;
540 
541 	case ACPI_BUTTON_TYPE_SLEEP:
542 		input_set_capability(input, EV_KEY, KEY_SLEEP);
543 		break;
544 
545 	case ACPI_BUTTON_TYPE_LID:
546 		input_set_capability(input, EV_SW, SW_LID);
547 		break;
548 	}
549 
550 	input_set_drvdata(input, device);
551 	error = input_register_device(input);
552 	if (error)
553 		goto err_remove_fs;
554 	if (button->type == ACPI_BUTTON_TYPE_LID) {
555 		/*
556 		 * This assumes there's only one lid device, or if there are
557 		 * more we only care about the last one...
558 		 */
559 		lid_device = device;
560 	}
561 
562 	device_init_wakeup(&device->dev, true);
563 	printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
564 	return 0;
565 
566  err_remove_fs:
567 	acpi_button_remove_fs(device);
568  err_free_input:
569 	input_free_device(input);
570  err_free_button:
571 	kfree(button);
572 	return error;
573 }
574 
575 static int acpi_button_remove(struct acpi_device *device)
576 {
577 	struct acpi_button *button = acpi_driver_data(device);
578 
579 	acpi_button_remove_fs(device);
580 	input_unregister_device(button->input);
581 	kfree(button);
582 	return 0;
583 }
584 
585 static int param_set_lid_init_state(const char *val,
586 				    const struct kernel_param *kp)
587 {
588 	int i;
589 
590 	i = sysfs_match_string(lid_init_state_str, val);
591 	if (i < 0)
592 		return i;
593 
594 	lid_init_state = i;
595 	pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
596 	return 0;
597 }
598 
599 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
600 {
601 	int i, c = 0;
602 
603 	for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
604 		if (i == lid_init_state)
605 			c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
606 		else
607 			c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
608 
609 	buf[c - 1] = '\n'; /* Replace the final space with a newline */
610 
611 	return c;
612 }
613 
614 module_param_call(lid_init_state,
615 		  param_set_lid_init_state, param_get_lid_init_state,
616 		  NULL, 0644);
617 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
618 
619 static int acpi_button_register_driver(struct acpi_driver *driver)
620 {
621 	const struct dmi_system_id *dmi_id;
622 
623 	if (lid_init_state == -1) {
624 		dmi_id = dmi_first_match(dmi_lid_quirks);
625 		if (dmi_id)
626 			lid_init_state = (long)dmi_id->driver_data;
627 		else
628 			lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
629 	}
630 
631 	/*
632 	 * Modules such as nouveau.ko and i915.ko have a link time dependency
633 	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
634 	 * capable kernels booted in non-ACPI mode if the return value of
635 	 * acpi_bus_register_driver() is returned from here with ACPI disabled
636 	 * when this driver is built as a module.
637 	 */
638 	if (acpi_disabled)
639 		return 0;
640 
641 	return acpi_bus_register_driver(driver);
642 }
643 
644 static void acpi_button_unregister_driver(struct acpi_driver *driver)
645 {
646 	if (!acpi_disabled)
647 		acpi_bus_unregister_driver(driver);
648 }
649 
650 module_driver(acpi_button_driver, acpi_button_register_driver,
651 	       acpi_button_unregister_driver);
652