xref: /openbmc/linux/drivers/acpi/button.c (revision 384b77fd)
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 		/* GP-electronic T701, _LID method points to a floating GPIO */
78 		.matches = {
79 			DMI_MATCH(DMI_SYS_VENDOR, "Insyde"),
80 			DMI_MATCH(DMI_PRODUCT_NAME, "T701"),
81 			DMI_MATCH(DMI_BIOS_VERSION, "BYT70A.YNCHENG.WIN.007"),
82 		},
83 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_DISABLED,
84 	},
85 	{
86 		/*
87 		 * Medion Akoya E2215T, notification of the LID device only
88 		 * happens on close, not on open and _LID always returns closed.
89 		 */
90 		.matches = {
91 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
92 			DMI_MATCH(DMI_PRODUCT_NAME, "E2215T"),
93 		},
94 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
95 	},
96 	{
97 		/*
98 		 * Medion Akoya E2228T, notification of the LID device only
99 		 * happens on close, not on open and _LID always returns closed.
100 		 */
101 		.matches = {
102 			DMI_MATCH(DMI_SYS_VENDOR, "MEDION"),
103 			DMI_MATCH(DMI_PRODUCT_NAME, "E2228T"),
104 		},
105 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
106 	},
107 	{
108 		/*
109 		 * Razer Blade Stealth 13 late 2019, notification of the LID device
110 		 * only happens on close, not on open and _LID always returns closed.
111 		 */
112 		.matches = {
113 			DMI_MATCH(DMI_SYS_VENDOR, "Razer"),
114 			DMI_MATCH(DMI_PRODUCT_NAME, "Razer Blade Stealth 13 Late 2019"),
115 		},
116 		.driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
117 	},
118 	{}
119 };
120 
121 static int acpi_button_add(struct acpi_device *device);
122 static int acpi_button_remove(struct acpi_device *device);
123 static void acpi_button_notify(struct acpi_device *device, u32 event);
124 
125 #ifdef CONFIG_PM_SLEEP
126 static int acpi_button_suspend(struct device *dev);
127 static int acpi_button_resume(struct device *dev);
128 #else
129 #define acpi_button_suspend NULL
130 #define acpi_button_resume NULL
131 #endif
132 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
133 
134 static struct acpi_driver acpi_button_driver = {
135 	.name = "button",
136 	.class = ACPI_BUTTON_CLASS,
137 	.ids = button_device_ids,
138 	.ops = {
139 		.add = acpi_button_add,
140 		.remove = acpi_button_remove,
141 		.notify = acpi_button_notify,
142 	},
143 	.drv.pm = &acpi_button_pm,
144 };
145 
146 struct acpi_button {
147 	unsigned int type;
148 	struct input_dev *input;
149 	char phys[32];			/* for input device */
150 	unsigned long pushed;
151 	int last_state;
152 	ktime_t last_time;
153 	bool suspended;
154 	bool lid_state_initialized;
155 };
156 
157 static struct acpi_device *lid_device;
158 static long lid_init_state = -1;
159 
160 static unsigned long lid_report_interval __read_mostly = 500;
161 module_param(lid_report_interval, ulong, 0644);
162 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
163 
164 /* --------------------------------------------------------------------------
165                               FS Interface (/proc)
166    -------------------------------------------------------------------------- */
167 
168 static struct proc_dir_entry *acpi_button_dir;
169 static struct proc_dir_entry *acpi_lid_dir;
170 
171 static int acpi_lid_evaluate_state(struct acpi_device *device)
172 {
173 	unsigned long long lid_state;
174 	acpi_status status;
175 
176 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
177 	if (ACPI_FAILURE(status))
178 		return -ENODEV;
179 
180 	return lid_state ? 1 : 0;
181 }
182 
183 static int acpi_lid_notify_state(struct acpi_device *device, int state)
184 {
185 	struct acpi_button *button = acpi_driver_data(device);
186 	ktime_t next_report;
187 	bool do_update;
188 
189 	/*
190 	 * In lid_init_state=ignore mode, if user opens/closes lid
191 	 * frequently with "open" missing, and "last_time" is also updated
192 	 * frequently, "close" cannot be delivered to the userspace.
193 	 * So "last_time" is only updated after a timeout or an actual
194 	 * switch.
195 	 */
196 	if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
197 	    button->last_state != !!state)
198 		do_update = true;
199 	else
200 		do_update = false;
201 
202 	next_report = ktime_add(button->last_time,
203 				ms_to_ktime(lid_report_interval));
204 	if (button->last_state == !!state &&
205 	    ktime_after(ktime_get(), next_report)) {
206 		/* Complain the buggy firmware */
207 		pr_warn_once("The lid device is not compliant to SW_LID.\n");
208 
209 		/*
210 		 * Send the unreliable complement switch event:
211 		 *
212 		 * On most platforms, the lid device is reliable. However
213 		 * there are exceptions:
214 		 * 1. Platforms returning initial lid state as "close" by
215 		 *    default after booting/resuming:
216 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
217 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
218 		 * 2. Platforms never reporting "open" events:
219 		 *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
220 		 * On these buggy platforms, the usage model of the ACPI
221 		 * lid device actually is:
222 		 * 1. The initial returning value of _LID may not be
223 		 *    reliable.
224 		 * 2. The open event may not be reliable.
225 		 * 3. The close event is reliable.
226 		 *
227 		 * But SW_LID is typed as input switch event, the input
228 		 * layer checks if the event is redundant. Hence if the
229 		 * state is not switched, the userspace cannot see this
230 		 * platform triggered reliable event. By inserting a
231 		 * complement switch event, it then is guaranteed that the
232 		 * platform triggered reliable one can always be seen by
233 		 * the userspace.
234 		 */
235 		if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
236 			do_update = true;
237 			/*
238 			 * Do generate complement switch event for "close"
239 			 * as "close" is reliable and wrong "open" won't
240 			 * trigger unexpected behaviors.
241 			 * Do not generate complement switch event for
242 			 * "open" as "open" is not reliable and wrong
243 			 * "close" will trigger unexpected behaviors.
244 			 */
245 			if (!state) {
246 				input_report_switch(button->input,
247 						    SW_LID, state);
248 				input_sync(button->input);
249 			}
250 		}
251 	}
252 	/* Send the platform triggered reliable event */
253 	if (do_update) {
254 		acpi_handle_debug(device->handle, "ACPI LID %s\n",
255 				  state ? "open" : "closed");
256 		input_report_switch(button->input, SW_LID, !state);
257 		input_sync(button->input);
258 		button->last_state = !!state;
259 		button->last_time = ktime_get();
260 	}
261 
262 	return 0;
263 }
264 
265 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
266 						     void *offset)
267 {
268 	struct acpi_device *device = seq->private;
269 	int state;
270 
271 	state = acpi_lid_evaluate_state(device);
272 	seq_printf(seq, "state:      %s\n",
273 		   state < 0 ? "unsupported" : (state ? "open" : "closed"));
274 	return 0;
275 }
276 
277 static int acpi_button_add_fs(struct acpi_device *device)
278 {
279 	struct acpi_button *button = acpi_driver_data(device);
280 	struct proc_dir_entry *entry = NULL;
281 	int ret = 0;
282 
283 	/* procfs I/F for ACPI lid device only */
284 	if (button->type != ACPI_BUTTON_TYPE_LID)
285 		return 0;
286 
287 	if (acpi_button_dir || acpi_lid_dir) {
288 		printk(KERN_ERR PREFIX "More than one Lid device found!\n");
289 		return -EEXIST;
290 	}
291 
292 	/* create /proc/acpi/button */
293 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
294 	if (!acpi_button_dir)
295 		return -ENODEV;
296 
297 	/* create /proc/acpi/button/lid */
298 	acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
299 	if (!acpi_lid_dir) {
300 		ret = -ENODEV;
301 		goto remove_button_dir;
302 	}
303 
304 	/* create /proc/acpi/button/lid/LID/ */
305 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
306 	if (!acpi_device_dir(device)) {
307 		ret = -ENODEV;
308 		goto remove_lid_dir;
309 	}
310 
311 	/* create /proc/acpi/button/lid/LID/state */
312 	entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
313 			acpi_device_dir(device), acpi_button_state_seq_show,
314 			device);
315 	if (!entry) {
316 		ret = -ENODEV;
317 		goto remove_dev_dir;
318 	}
319 
320 done:
321 	return ret;
322 
323 remove_dev_dir:
324 	remove_proc_entry(acpi_device_bid(device),
325 			  acpi_lid_dir);
326 	acpi_device_dir(device) = NULL;
327 remove_lid_dir:
328 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
329 	acpi_lid_dir = NULL;
330 remove_button_dir:
331 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
332 	acpi_button_dir = NULL;
333 	goto done;
334 }
335 
336 static int acpi_button_remove_fs(struct acpi_device *device)
337 {
338 	struct acpi_button *button = acpi_driver_data(device);
339 
340 	if (button->type != ACPI_BUTTON_TYPE_LID)
341 		return 0;
342 
343 	remove_proc_entry(ACPI_BUTTON_FILE_STATE,
344 			  acpi_device_dir(device));
345 	remove_proc_entry(acpi_device_bid(device),
346 			  acpi_lid_dir);
347 	acpi_device_dir(device) = NULL;
348 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
349 	acpi_lid_dir = NULL;
350 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
351 	acpi_button_dir = NULL;
352 
353 	return 0;
354 }
355 
356 /* --------------------------------------------------------------------------
357                                 Driver Interface
358    -------------------------------------------------------------------------- */
359 int acpi_lid_open(void)
360 {
361 	if (!lid_device)
362 		return -ENODEV;
363 
364 	return acpi_lid_evaluate_state(lid_device);
365 }
366 EXPORT_SYMBOL(acpi_lid_open);
367 
368 static int acpi_lid_update_state(struct acpi_device *device,
369 				 bool signal_wakeup)
370 {
371 	int state;
372 
373 	state = acpi_lid_evaluate_state(device);
374 	if (state < 0)
375 		return state;
376 
377 	if (state && signal_wakeup)
378 		acpi_pm_wakeup_event(&device->dev);
379 
380 	return acpi_lid_notify_state(device, state);
381 }
382 
383 static void acpi_lid_initialize_state(struct acpi_device *device)
384 {
385 	struct acpi_button *button = acpi_driver_data(device);
386 
387 	switch (lid_init_state) {
388 	case ACPI_BUTTON_LID_INIT_OPEN:
389 		(void)acpi_lid_notify_state(device, 1);
390 		break;
391 	case ACPI_BUTTON_LID_INIT_METHOD:
392 		(void)acpi_lid_update_state(device, false);
393 		break;
394 	case ACPI_BUTTON_LID_INIT_IGNORE:
395 	default:
396 		break;
397 	}
398 
399 	button->lid_state_initialized = true;
400 }
401 
402 static void acpi_button_notify(struct acpi_device *device, u32 event)
403 {
404 	struct acpi_button *button = acpi_driver_data(device);
405 	struct input_dev *input;
406 
407 	switch (event) {
408 	case ACPI_FIXED_HARDWARE_EVENT:
409 		event = ACPI_BUTTON_NOTIFY_STATUS;
410 		fallthrough;
411 	case ACPI_BUTTON_NOTIFY_STATUS:
412 		input = button->input;
413 		if (button->type == ACPI_BUTTON_TYPE_LID) {
414 			if (button->lid_state_initialized)
415 				acpi_lid_update_state(device, true);
416 		} else {
417 			int keycode;
418 
419 			acpi_pm_wakeup_event(&device->dev);
420 			if (button->suspended)
421 				break;
422 
423 			keycode = test_bit(KEY_SLEEP, input->keybit) ?
424 						KEY_SLEEP : KEY_POWER;
425 			input_report_key(input, keycode, 1);
426 			input_sync(input);
427 			input_report_key(input, keycode, 0);
428 			input_sync(input);
429 
430 			acpi_bus_generate_netlink_event(
431 					device->pnp.device_class,
432 					dev_name(&device->dev),
433 					event, ++button->pushed);
434 		}
435 		break;
436 	default:
437 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
438 				  "Unsupported event [0x%x]\n", event));
439 		break;
440 	}
441 }
442 
443 #ifdef CONFIG_PM_SLEEP
444 static int acpi_button_suspend(struct device *dev)
445 {
446 	struct acpi_device *device = to_acpi_device(dev);
447 	struct acpi_button *button = acpi_driver_data(device);
448 
449 	button->suspended = true;
450 	return 0;
451 }
452 
453 static int acpi_button_resume(struct device *dev)
454 {
455 	struct acpi_device *device = to_acpi_device(dev);
456 	struct acpi_button *button = acpi_driver_data(device);
457 
458 	button->suspended = false;
459 	if (button->type == ACPI_BUTTON_TYPE_LID) {
460 		button->last_state = !!acpi_lid_evaluate_state(device);
461 		button->last_time = ktime_get();
462 		acpi_lid_initialize_state(device);
463 	}
464 	return 0;
465 }
466 #endif
467 
468 static int acpi_lid_input_open(struct input_dev *input)
469 {
470 	struct acpi_device *device = input_get_drvdata(input);
471 	struct acpi_button *button = acpi_driver_data(device);
472 
473 	button->last_state = !!acpi_lid_evaluate_state(device);
474 	button->last_time = ktime_get();
475 	acpi_lid_initialize_state(device);
476 
477 	return 0;
478 }
479 
480 static int acpi_button_add(struct acpi_device *device)
481 {
482 	struct acpi_button *button;
483 	struct input_dev *input;
484 	const char *hid = acpi_device_hid(device);
485 	char *name, *class;
486 	int error;
487 
488 	if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
489 	     lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
490 		return -ENODEV;
491 
492 	button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
493 	if (!button)
494 		return -ENOMEM;
495 
496 	device->driver_data = button;
497 
498 	button->input = input = input_allocate_device();
499 	if (!input) {
500 		error = -ENOMEM;
501 		goto err_free_button;
502 	}
503 
504 	name = acpi_device_name(device);
505 	class = acpi_device_class(device);
506 
507 	if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
508 	    !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
509 		button->type = ACPI_BUTTON_TYPE_POWER;
510 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
511 		sprintf(class, "%s/%s",
512 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
513 	} else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
514 		   !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
515 		button->type = ACPI_BUTTON_TYPE_SLEEP;
516 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
517 		sprintf(class, "%s/%s",
518 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
519 	} else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
520 		button->type = ACPI_BUTTON_TYPE_LID;
521 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
522 		sprintf(class, "%s/%s",
523 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
524 		input->open = acpi_lid_input_open;
525 	} else {
526 		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
527 		error = -ENODEV;
528 		goto err_free_input;
529 	}
530 
531 	error = acpi_button_add_fs(device);
532 	if (error)
533 		goto err_free_input;
534 
535 	snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
536 
537 	input->name = name;
538 	input->phys = button->phys;
539 	input->id.bustype = BUS_HOST;
540 	input->id.product = button->type;
541 	input->dev.parent = &device->dev;
542 
543 	switch (button->type) {
544 	case ACPI_BUTTON_TYPE_POWER:
545 		input_set_capability(input, EV_KEY, KEY_POWER);
546 		break;
547 
548 	case ACPI_BUTTON_TYPE_SLEEP:
549 		input_set_capability(input, EV_KEY, KEY_SLEEP);
550 		break;
551 
552 	case ACPI_BUTTON_TYPE_LID:
553 		input_set_capability(input, EV_SW, SW_LID);
554 		break;
555 	}
556 
557 	input_set_drvdata(input, device);
558 	error = input_register_device(input);
559 	if (error)
560 		goto err_remove_fs;
561 	if (button->type == ACPI_BUTTON_TYPE_LID) {
562 		/*
563 		 * This assumes there's only one lid device, or if there are
564 		 * more we only care about the last one...
565 		 */
566 		lid_device = device;
567 	}
568 
569 	device_init_wakeup(&device->dev, true);
570 	printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
571 	return 0;
572 
573  err_remove_fs:
574 	acpi_button_remove_fs(device);
575  err_free_input:
576 	input_free_device(input);
577  err_free_button:
578 	kfree(button);
579 	return error;
580 }
581 
582 static int acpi_button_remove(struct acpi_device *device)
583 {
584 	struct acpi_button *button = acpi_driver_data(device);
585 
586 	acpi_button_remove_fs(device);
587 	input_unregister_device(button->input);
588 	kfree(button);
589 	return 0;
590 }
591 
592 static int param_set_lid_init_state(const char *val,
593 				    const struct kernel_param *kp)
594 {
595 	int i;
596 
597 	i = sysfs_match_string(lid_init_state_str, val);
598 	if (i < 0)
599 		return i;
600 
601 	lid_init_state = i;
602 	pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
603 	return 0;
604 }
605 
606 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
607 {
608 	int i, c = 0;
609 
610 	for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
611 		if (i == lid_init_state)
612 			c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
613 		else
614 			c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
615 
616 	buf[c - 1] = '\n'; /* Replace the final space with a newline */
617 
618 	return c;
619 }
620 
621 module_param_call(lid_init_state,
622 		  param_set_lid_init_state, param_get_lid_init_state,
623 		  NULL, 0644);
624 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
625 
626 static int acpi_button_register_driver(struct acpi_driver *driver)
627 {
628 	const struct dmi_system_id *dmi_id;
629 
630 	if (lid_init_state == -1) {
631 		dmi_id = dmi_first_match(dmi_lid_quirks);
632 		if (dmi_id)
633 			lid_init_state = (long)dmi_id->driver_data;
634 		else
635 			lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
636 	}
637 
638 	/*
639 	 * Modules such as nouveau.ko and i915.ko have a link time dependency
640 	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
641 	 * capable kernels booted in non-ACPI mode if the return value of
642 	 * acpi_bus_register_driver() is returned from here with ACPI disabled
643 	 * when this driver is built as a module.
644 	 */
645 	if (acpi_disabled)
646 		return 0;
647 
648 	return acpi_bus_register_driver(driver);
649 }
650 
651 static void acpi_button_unregister_driver(struct acpi_driver *driver)
652 {
653 	if (!acpi_disabled)
654 		acpi_bus_unregister_driver(driver);
655 }
656 
657 module_driver(acpi_button_driver, acpi_button_register_driver,
658 	       acpi_button_unregister_driver);
659