xref: /openbmc/linux/drivers/acpi/button.c (revision 63705da3)
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 		 * Lenovo Yoga 9 14ITL5, initial notification of the LID device
83 		 * never happens.
84 		 */
85 		.matches = {
86 			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
87 			DMI_MATCH(DMI_PRODUCT_NAME, "82BG"),
88 		},
89 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
90 	},
91 	{
92 		/*
93 		 * Medion Akoya E2215T, 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, "E2215T"),
99 		},
100 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
101 	},
102 	{
103 		/*
104 		 * Medion Akoya E2228T, notification of the LID device only
105 		 * happens on close, not on open and _LID always returns closed.
106 		 */
107 		.matches = {
108 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
109 			DMI_MATCH(DMI_PRODUCT_NAME, "E2228T"),
110 		},
111 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
112 	},
113 	{
114 		/*
115 		 * Razer Blade Stealth 13 late 2019, notification of the LID device
116 		 * only happens on close, not on open and _LID always returns closed.
117 		 */
118 		.matches = {
119 			DMI_MATCH(DMI_SYS_VENDOR, "Razer"),
120 			DMI_MATCH(DMI_PRODUCT_NAME, "Razer Blade Stealth 13 Late 2019"),
121 		},
122 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
123 	},
124 	{}
125 };
126 
127 static int acpi_button_add(struct acpi_device *device);
128 static int acpi_button_remove(struct acpi_device *device);
129 static void acpi_button_notify(struct acpi_device *device, u32 event);
130 
131 #ifdef CONFIG_PM_SLEEP
132 static int acpi_button_suspend(struct device *dev);
133 static int acpi_button_resume(struct device *dev);
134 #else
135 #define acpi_button_suspend NULL
136 #define acpi_button_resume NULL
137 #endif
138 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
139 
140 static struct acpi_driver acpi_button_driver = {
141 	.name = "button",
142 	.class = ACPI_BUTTON_CLASS,
143 	.ids = button_device_ids,
144 	.ops = {
145 		.add = acpi_button_add,
146 		.remove = acpi_button_remove,
147 		.notify = acpi_button_notify,
148 	},
149 	.drv.pm = &acpi_button_pm,
150 };
151 
152 struct acpi_button {
153 	unsigned int type;
154 	struct input_dev *input;
155 	char phys[32];			/* for input device */
156 	unsigned long pushed;
157 	int last_state;
158 	ktime_t last_time;
159 	bool suspended;
160 	bool lid_state_initialized;
161 };
162 
163 static struct acpi_device *lid_device;
164 static long lid_init_state = -1;
165 
166 static unsigned long lid_report_interval __read_mostly = 500;
167 module_param(lid_report_interval, ulong, 0644);
168 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
169 
170 /* FS Interface (/proc) */
171 static struct proc_dir_entry *acpi_button_dir;
172 static struct proc_dir_entry *acpi_lid_dir;
173 
174 static int acpi_lid_evaluate_state(struct acpi_device *device)
175 {
176 	unsigned long long lid_state;
177 	acpi_status status;
178 
179 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
180 	if (ACPI_FAILURE(status))
181 		return -ENODEV;
182 
183 	return lid_state ? 1 : 0;
184 }
185 
186 static int acpi_lid_notify_state(struct acpi_device *device, int state)
187 {
188 	struct acpi_button *button = acpi_driver_data(device);
189 	ktime_t next_report;
190 	bool do_update;
191 
192 	/*
193 	 * In lid_init_state=ignore mode, if user opens/closes lid
194 	 * frequently with "open" missing, and "last_time" is also updated
195 	 * frequently, "close" cannot be delivered to the userspace.
196 	 * So "last_time" is only updated after a timeout or an actual
197 	 * switch.
198 	 */
199 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
200 	    button->last_state != !!state)
201 		do_update = true;
202 	else
203 		do_update = false;
204 
205 	next_report = ktime_add(button->last_time,
206 				ms_to_ktime(lid_report_interval));
207 	if (button->last_state == !!state &&
208 	    ktime_after(ktime_get(), next_report)) {
209 		/* Complain the buggy firmware */
210 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
211 
212 		/*
213 		 * Send the unreliable complement switch event:
214 		 *
215 		 * On most platforms, the lid device is reliable. However
216 		 * there are exceptions:
217 		 * 1. Platforms returning initial lid state as "close" by
218 		 *    default after booting/resuming:
219 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
220 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
221 		 * 2. Platforms never reporting "open" events:
222 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
223 		 * On these buggy platforms, the usage model of the ACPI
224 		 * lid device actually is:
225 		 * 1. The initial returning value of _LID may not be
226 		 *    reliable.
227 		 * 2. The open event may not be reliable.
228 		 * 3. The close event is reliable.
229 		 *
230 		 * But SW_LID is typed as input switch event, the input
231 		 * layer checks if the event is redundant. Hence if the
232 		 * state is not switched, the userspace cannot see this
233 		 * platform triggered reliable event. By inserting a
234 		 * complement switch event, it then is guaranteed that the
235 		 * platform triggered reliable one can always be seen by
236 		 * the userspace.
237 		 */
238 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
239 			do_update = true;
240 			/*
241 			 * Do generate complement switch event for "close"
242 			 * as "close" is reliable and wrong "open" won't
243 			 * trigger unexpected behaviors.
244 			 * Do not generate complement switch event for
245 			 * "open" as "open" is not reliable and wrong
246 			 * "close" will trigger unexpected behaviors.
247 			 */
248 			if (!state) {
249 				input_report_switch(button->input,
250 						    SW_LID, state);
251 				input_sync(button->input);
252 			}
253 		}
254 	}
255 	/* Send the platform triggered reliable event */
256 	if (do_update) {
257 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
258 				  state ? "open" : "closed");
259 		input_report_switch(button->input, SW_LID, !state);
260 		input_sync(button->input);
261 		button->last_state = !!state;
262 		button->last_time = ktime_get();
263 	}
264 
265 	return 0;
266 }
267 
268 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
269 						     void *offset)
270 {
271 	struct acpi_device *device = seq->private;
272 	int state;
273 
274 	state = acpi_lid_evaluate_state(device);
275 	seq_printf(seq, "state:      %s\n",
276 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
277 	return 0;
278 }
279 
280 static int acpi_button_add_fs(struct acpi_device *device)
281 {
282 	struct acpi_button *button = acpi_driver_data(device);
283 	struct proc_dir_entry *entry = NULL;
284 	int ret = 0;
285 
286 	/* procfs I/F for ACPI lid device only */
287 	if (button->type != ACPI_BUTTON_TYPE_LID)
288 		return 0;
289 
290 	if (acpi_button_dir || acpi_lid_dir) {
291 		pr_info("More than one Lid device found!\n");
292 		return -EEXIST;
293 	}
294 
295 	/* create /proc/acpi/button */
296 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
297 	if (!acpi_button_dir)
298 		return -ENODEV;
299 
300 	/* create /proc/acpi/button/lid */
301 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
302 	if (!acpi_lid_dir) {
303 		ret = -ENODEV;
304 		goto remove_button_dir;
305 	}
306 
307 	/* create /proc/acpi/button/lid/LID/ */
308 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
309 	if (!acpi_device_dir(device)) {
310 		ret = -ENODEV;
311 		goto remove_lid_dir;
312 	}
313 
314 	/* create /proc/acpi/button/lid/LID/state */
315 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
316 			acpi_device_dir(device), acpi_button_state_seq_show,
317 			device);
318 	if (!entry) {
319 		ret = -ENODEV;
320 		goto remove_dev_dir;
321 	}
322 
323 done:
324 	return ret;
325 
326 remove_dev_dir:
327 	remove_proc_entry(acpi_device_bid(device),
328 			  acpi_lid_dir);
329 	acpi_device_dir(device) = NULL;
330 remove_lid_dir:
331 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
332 	acpi_lid_dir = NULL;
333 remove_button_dir:
334 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
335 	acpi_button_dir = NULL;
336 	goto done;
337 }
338 
339 static int acpi_button_remove_fs(struct acpi_device *device)
340 {
341 	struct acpi_button *button = acpi_driver_data(device);
342 
343 	if (button->type != ACPI_BUTTON_TYPE_LID)
344 		return 0;
345 
346 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
347 			  acpi_device_dir(device));
348 	remove_proc_entry(acpi_device_bid(device),
349 			  acpi_lid_dir);
350 	acpi_device_dir(device) = NULL;
351 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
352 	acpi_lid_dir = NULL;
353 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
354 	acpi_button_dir = NULL;
355 
356 	return 0;
357 }
358 
359 /* Driver Interface */
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 	struct acpi_button *button = acpi_driver_data(device);
387 
388 	switch (lid_init_state) {
389 	case ACPI_BUTTON_LID_INIT_OPEN:
390 		(void)acpi_lid_notify_state(device, 1);
391 		break;
392 	case ACPI_BUTTON_LID_INIT_METHOD:
393 		(void)acpi_lid_update_state(device, false);
394 		break;
395 	case ACPI_BUTTON_LID_INIT_IGNORE:
396 	default:
397 		break;
398 	}
399 
400 	button->lid_state_initialized = true;
401 }
402 
403 static void acpi_button_notify(struct acpi_device *device, u32 event)
404 {
405 	struct acpi_button *button = acpi_driver_data(device);
406 	struct input_dev *input;
407 
408 	switch (event) {
409 	case ACPI_FIXED_HARDWARE_EVENT:
410 		event = ACPI_BUTTON_NOTIFY_STATUS;
411 		fallthrough;
412 	case ACPI_BUTTON_NOTIFY_STATUS:
413 		input = button->input;
414 		if (button->type == ACPI_BUTTON_TYPE_LID) {
415 			if (button->lid_state_initialized)
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_handle_debug(device->handle, "Unsupported event [0x%x]\n",
439 				  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) {
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 		pr_info("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 	pr_info("%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