drivers/acpi/button.c

   1 /*
   2  *  button.c - ACPI Button Driver
   3  *
   4  *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
   5  *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
   6  *
   7  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   8  *
   9  *  This program is free software; you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation; either version 2 of the License, or (at
  12  *  your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful, but
  15  *  WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  *  General Public License for more details.
  18  *
  19  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  20  */
  21
  22 #define pr_fmt(fmt) "ACPI: button: " fmt
  23
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/init.h>
  27 #include <linux/types.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/seq_file.h>
  30 #include <linux/input.h>
  31 #include <linux/slab.h>
  32 #include <linux/acpi.h>
  33 #include <acpi/button.h>
  34
  35 #define PREFIX "ACPI: "
  36
  37 #define ACPI_BUTTON_CLASS               "button"
  38 #define ACPI_BUTTON_FILE_INFO           "info"
  39 #define ACPI_BUTTON_FILE_STATE          "state"
  40 #define ACPI_BUTTON_TYPE_UNKNOWN        0x00
  41 #define ACPI_BUTTON_NOTIFY_STATUS       0x80
  42
  43 #define ACPI_BUTTON_SUBCLASS_POWER      "power"
  44 #define ACPI_BUTTON_HID_POWER           "PNP0C0C"
  45 #define ACPI_BUTTON_DEVICE_NAME_POWER   "Power Button"
  46 #define ACPI_BUTTON_TYPE_POWER          0x01
  47
  48 #define ACPI_BUTTON_SUBCLASS_SLEEP      "sleep"
  49 #define ACPI_BUTTON_HID_SLEEP           "PNP0C0E"
  50 #define ACPI_BUTTON_DEVICE_NAME_SLEEP   "Sleep Button"
  51 #define ACPI_BUTTON_TYPE_SLEEP          0x03
  52
  53 #define ACPI_BUTTON_SUBCLASS_LID        "lid"
  54 #define ACPI_BUTTON_HID_LID             "PNP0C0D"
  55 #define ACPI_BUTTON_DEVICE_NAME_LID     "Lid Switch"
  56 #define ACPI_BUTTON_TYPE_LID            0x05
  57
  58 #define ACPI_BUTTON_LID_INIT_IGNORE     0x00
  59 #define ACPI_BUTTON_LID_INIT_OPEN       0x01
  60 #define ACPI_BUTTON_LID_INIT_METHOD     0x02
  61
  62 #define _COMPONENT              ACPI_BUTTON_COMPONENT
  63 ACPI_MODULE_NAME("button");
  64
  65 MODULE_AUTHOR("Paul Diefenbaugh");
  66 MODULE_DESCRIPTION("ACPI Button Driver");
  67 MODULE_LICENSE("GPL");
  68
  69 static const struct acpi_device_id button_device_ids[] = {
  70         {ACPI_BUTTON_HID_LID,    0},
  71         {ACPI_BUTTON_HID_SLEEP,  0},
  72         {ACPI_BUTTON_HID_SLEEPF, 0},
  73         {ACPI_BUTTON_HID_POWER,  0},
  74         {ACPI_BUTTON_HID_POWERF, 0},
  75         {"", 0},
  76 };
  77 MODULE_DEVICE_TABLE(acpi, button_device_ids);
  78
  79 static int acpi_button_add(struct acpi_device *device);
  80 static int acpi_button_remove(struct acpi_device *device);
  81 static void acpi_button_notify(struct acpi_device *device, u32 event);
  82
  83 #ifdef CONFIG_PM_SLEEP
  84 static int acpi_button_suspend(struct device *dev);
  85 static int acpi_button_resume(struct device *dev);
  86 #else
  87 #define acpi_button_suspend NULL
  88 #define acpi_button_resume NULL
  89 #endif
  90 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
  91
  92 static struct acpi_driver acpi_button_driver = {
  93         .name = "button",
  94         .class = ACPI_BUTTON_CLASS,
  95         .ids = button_device_ids,
  96         .ops = {
  97                 .add = acpi_button_add,
  98                 .remove = acpi_button_remove,
  99                 .notify = acpi_button_notify,
 100         },
 101         .drv.pm = &acpi_button_pm,
 102 };
 103
 104 struct acpi_button {
 105         unsigned int type;
 106         struct input_dev *input;
 107         char phys[32];                  /* for input device */
 108         unsigned long pushed;
 109         int last_state;
 110         ktime_t last_time;
 111         bool suspended;
 112 };
 113
 114 static BLOCKING_NOTIFIER_HEAD(acpi_lid_notifier);
 115 static struct acpi_device *lid_device;
 116 static u8 lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
 117
 118 static unsigned long lid_report_interval __read_mostly = 500;
 119 module_param(lid_report_interval, ulong, 0644);
 120 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
 121
 122 /* --------------------------------------------------------------------------
 123                               FS Interface (/proc)
 124    -------------------------------------------------------------------------- */
 125
 126 static struct proc_dir_entry *acpi_button_dir;
 127 static struct proc_dir_entry *acpi_lid_dir;
 128
 129 static int acpi_lid_evaluate_state(struct acpi_device *device)
 130 {
 131         unsigned long long lid_state;
 132         acpi_status status;
 133
 134         status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
 135         if (ACPI_FAILURE(status))
 136                 return -ENODEV;
 137
 138         return lid_state ? 1 : 0;
 139 }
 140
 141 static int acpi_lid_notify_state(struct acpi_device *device, int state)
 142 {
 143         struct acpi_button *button = acpi_driver_data(device);
 144         int ret;
 145         ktime_t next_report;
 146         bool do_update;
 147
 148         /*
 149          * In lid_init_state=ignore mode, if user opens/closes lid
 150          * frequently with "open" missing, and "last_time" is also updated
 151          * frequently, "close" cannot be delivered to the userspace.
 152          * So "last_time" is only updated after a timeout or an actual
 153          * switch.
 154          */
 155         if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
 156             button->last_state != !!state)
 157                 do_update = true;
 158         else
 159                 do_update = false;
 160
 161         next_report = ktime_add(button->last_time,
 162                                 ms_to_ktime(lid_report_interval));
 163         if (button->last_state == !!state &&
 164             ktime_after(ktime_get(), next_report)) {
 165                 /* Complain the buggy firmware */
 166                 pr_warn_once("The lid device is not compliant to SW_LID.\n");
 167
 168                 /*
 169                  * Send the unreliable complement switch event:
 170                  *
 171                  * On most platforms, the lid device is reliable. However
 172                  * there are exceptions:
 173                  * 1. Platforms returning initial lid state as "close" by
 174                  *    default after booting/resuming:
 175                  *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
 176                  *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
 177                  * 2. Platforms never reporting "open" events:
 178                  *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
 179                  * On these buggy platforms, the usage model of the ACPI
 180                  * lid device actually is:
 181                  * 1. The initial returning value of _LID may not be
 182                  *    reliable.
 183                  * 2. The open event may not be reliable.
 184                  * 3. The close event is reliable.
 185                  *
 186                  * But SW_LID is typed as input switch event, the input
 187                  * layer checks if the event is redundant. Hence if the
 188                  * state is not switched, the userspace cannot see this
 189                  * platform triggered reliable event. By inserting a
 190                  * complement switch event, it then is guaranteed that the
 191                  * platform triggered reliable one can always be seen by
 192                  * the userspace.
 193                  */
 194                 if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
 195                         do_update = true;
 196                         /*
 197                          * Do generate complement switch event for "close"
 198                          * as "close" is reliable and wrong "open" won't
 199                          * trigger unexpected behaviors.
 200                          * Do not generate complement switch event for
 201                          * "open" as "open" is not reliable and wrong
 202                          * "close" will trigger unexpected behaviors.
 203                          */
 204                         if (!state) {
 205                                 input_report_switch(button->input,
 206                                                     SW_LID, state);
 207                                 input_sync(button->input);
 208                         }
 209                 }
 210         }
 211         /* Send the platform triggered reliable event */
 212         if (do_update) {
 213                 input_report_switch(button->input, SW_LID, !state);
 214                 input_sync(button->input);
 215                 button->last_state = !!state;
 216                 button->last_time = ktime_get();
 217         }
 218
 219         ret = blocking_notifier_call_chain(&acpi_lid_notifier, state, device);
 220         if (ret == NOTIFY_DONE)
 221                 ret = blocking_notifier_call_chain(&acpi_lid_notifier, state,
 222                                                    device);
 223         if (ret == NOTIFY_DONE || ret == NOTIFY_OK) {
 224                 /*
 225                  * It is also regarded as success if the notifier_chain
 226                  * returns NOTIFY_OK or NOTIFY_DONE.
 227                  */
 228                 ret = 0;
 229         }
 230         return ret;
 231 }
 232
 233 static int acpi_button_state_seq_show(struct seq_file *seq, void *offset)
 234 {
 235         struct acpi_device *device = seq->private;
 236         int state;
 237
 238         state = acpi_lid_evaluate_state(device);
 239         seq_printf(seq, "state:      %s\n",
 240                    state < 0 ? "unsupported" : (state ? "open" : "closed"));
 241         return 0;
 242 }
 243
 244 static int acpi_button_state_open_fs(struct inode *inode, struct file *file)
 245 {
 246         return single_open(file, acpi_button_state_seq_show, PDE_DATA(inode));
 247 }
 248
 249 static const struct file_operations acpi_button_state_fops = {
 250         .owner = THIS_MODULE,
 251         .open = acpi_button_state_open_fs,
 252         .read = seq_read,
 253         .llseek = seq_lseek,
 254         .release = single_release,
 255 };
 256
 257 static int acpi_button_add_fs(struct acpi_device *device)
 258 {
 259         struct acpi_button *button = acpi_driver_data(device);
 260         struct proc_dir_entry *entry = NULL;
 261         int ret = 0;
 262
 263         /* procfs I/F for ACPI lid device only */
 264         if (button->type != ACPI_BUTTON_TYPE_LID)
 265                 return 0;
 266
 267         if (acpi_button_dir || acpi_lid_dir) {
 268                 printk(KERN_ERR PREFIX "More than one Lid device found!\n");
 269                 return -EEXIST;
 270         }
 271
 272         /* create /proc/acpi/button */
 273         acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
 274         if (!acpi_button_dir)
 275                 return -ENODEV;
 276
 277         /* create /proc/acpi/button/lid */
 278         acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 279         if (!acpi_lid_dir) {
 280                 ret = -ENODEV;
 281                 goto remove_button_dir;
 282         }
 283
 284         /* create /proc/acpi/button/lid/LID/ */
 285         acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
 286         if (!acpi_device_dir(device)) {
 287                 ret = -ENODEV;
 288                 goto remove_lid_dir;
 289         }
 290
 291         /* create /proc/acpi/button/lid/LID/state */
 292         entry = proc_create_data(ACPI_BUTTON_FILE_STATE,
 293                                  S_IRUGO, acpi_device_dir(device),
 294                                  &acpi_button_state_fops, device);
 295         if (!entry) {
 296                 ret = -ENODEV;
 297                 goto remove_dev_dir;
 298         }
 299
 300 done:
 301         return ret;
 302
 303 remove_dev_dir:
 304         remove_proc_entry(acpi_device_bid(device),
 305                           acpi_lid_dir);
 306         acpi_device_dir(device) = NULL;
 307 remove_lid_dir:
 308         remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 309         acpi_lid_dir = NULL;
 310 remove_button_dir:
 311         remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
 312         acpi_button_dir = NULL;
 313         goto done;
 314 }
 315
 316 static int acpi_button_remove_fs(struct acpi_device *device)
 317 {
 318         struct acpi_button *button = acpi_driver_data(device);
 319
 320         if (button->type != ACPI_BUTTON_TYPE_LID)
 321                 return 0;
 322
 323         remove_proc_entry(ACPI_BUTTON_FILE_STATE,
 324                           acpi_device_dir(device));
 325         remove_proc_entry(acpi_device_bid(device),
 326                           acpi_lid_dir);
 327         acpi_device_dir(device) = NULL;
 328         remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 329         acpi_lid_dir = NULL;
 330         remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
 331         acpi_button_dir = NULL;
 332
 333         return 0;
 334 }
 335
 336 /* --------------------------------------------------------------------------
 337                                 Driver Interface
 338    -------------------------------------------------------------------------- */
 339 int acpi_lid_notifier_register(struct notifier_block *nb)
 340 {
 341         return blocking_notifier_chain_register(&acpi_lid_notifier, nb);
 342 }
 343 EXPORT_SYMBOL(acpi_lid_notifier_register);
 344
 345 int acpi_lid_notifier_unregister(struct notifier_block *nb)
 346 {
 347         return blocking_notifier_chain_unregister(&acpi_lid_notifier, nb);
 348 }
 349 EXPORT_SYMBOL(acpi_lid_notifier_unregister);
 350
 351 int acpi_lid_open(void)
 352 {
 353         if (!lid_device)
 354                 return -ENODEV;
 355
 356         return acpi_lid_evaluate_state(lid_device);
 357 }
 358 EXPORT_SYMBOL(acpi_lid_open);
 359
 360 static int acpi_lid_update_state(struct acpi_device *device,
 361                                  bool signal_wakeup)
 362 {
 363         int state;
 364
 365         state = acpi_lid_evaluate_state(device);
 366         if (state < 0)
 367                 return state;
 368
 369         if (state && signal_wakeup)
 370                 acpi_pm_wakeup_event(&device->dev);
 371
 372         return acpi_lid_notify_state(device, state);
 373 }
 374
 375 static void acpi_lid_initialize_state(struct acpi_device *device)
 376 {
 377         switch (lid_init_state) {
 378         case ACPI_BUTTON_LID_INIT_OPEN:
 379                 (void)acpi_lid_notify_state(device, 1);
 380                 break;
 381         case ACPI_BUTTON_LID_INIT_METHOD:
 382                 (void)acpi_lid_update_state(device, false);
 383                 break;
 384         case ACPI_BUTTON_LID_INIT_IGNORE:
 385         default:
 386                 break;
 387         }
 388 }
 389
 390 static void acpi_button_notify(struct acpi_device *device, u32 event)
 391 {
 392         struct acpi_button *button = acpi_driver_data(device);
 393         struct input_dev *input;
 394         int users;
 395
 396         switch (event) {
 397         case ACPI_FIXED_HARDWARE_EVENT:
 398                 event = ACPI_BUTTON_NOTIFY_STATUS;
 399                 /* fall through */
 400         case ACPI_BUTTON_NOTIFY_STATUS:
 401                 input = button->input;
 402                 if (button->type == ACPI_BUTTON_TYPE_LID) {
 403                         mutex_lock(&button->input->mutex);
 404                         users = button->input->users;
 405                         mutex_unlock(&button->input->mutex);
 406                         if (users)
 407                                 acpi_lid_update_state(device, true);
 408                 } else {
 409                         int keycode;
 410
 411                         acpi_pm_wakeup_event(&device->dev);
 412                         if (button->suspended)
 413                                 break;
 414
 415                         keycode = test_bit(KEY_SLEEP, input->keybit) ?
 416                                                 KEY_SLEEP : KEY_POWER;
 417                         input_report_key(input, keycode, 1);
 418                         input_sync(input);
 419                         input_report_key(input, keycode, 0);
 420                         input_sync(input);
 421
 422                         acpi_bus_generate_netlink_event(
 423                                         device->pnp.device_class,
 424                                         dev_name(&device->dev),
 425                                         event, ++button->pushed);
 426                 }
 427                 break;
 428         default:
 429                 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 430                                   "Unsupported event [0x%x]\n", event));
 431                 break;
 432         }
 433 }
 434
 435 #ifdef CONFIG_PM_SLEEP
 436 static int acpi_button_suspend(struct device *dev)
 437 {
 438         struct acpi_device *device = to_acpi_device(dev);
 439         struct acpi_button *button = acpi_driver_data(device);
 440
 441         button->suspended = true;
 442         return 0;
 443 }
 444
 445 static int acpi_button_resume(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 = false;
 451         if (button->type == ACPI_BUTTON_TYPE_LID && button->input->users)
 452                 acpi_lid_initialize_state(device);
 453         return 0;
 454 }
 455 #endif
 456
 457 static int acpi_lid_input_open(struct input_dev *input)
 458 {
 459         struct acpi_device *device = input_get_drvdata(input);
 460         struct acpi_button *button = acpi_driver_data(device);
 461
 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
 469 static int acpi_button_add(struct acpi_device *device)
 470 {
 471         struct acpi_button *button;
 472         struct input_dev *input;
 473         const char *hid = acpi_device_hid(device);
 474         char *name, *class;
 475         int error;
 476
 477         button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
 478         if (!button)
 479                 return -ENOMEM;
 480
 481         device->driver_data = button;
 482
 483         button->input = input = input_allocate_device();
 484         if (!input) {
 485                 error = -ENOMEM;
 486                 goto err_free_button;
 487         }
 488
 489         name = acpi_device_name(device);
 490         class = acpi_device_class(device);
 491
 492         if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
 493             !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
 494                 button->type = ACPI_BUTTON_TYPE_POWER;
 495                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
 496                 sprintf(class, "%s/%s",
 497                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
 498         } else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
 499                    !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
 500                 button->type = ACPI_BUTTON_TYPE_SLEEP;
 501                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
 502                 sprintf(class, "%s/%s",
 503                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
 504         } else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
 505                 button->type = ACPI_BUTTON_TYPE_LID;
 506                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
 507                 sprintf(class, "%s/%s",
 508                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
 509                 input->open = acpi_lid_input_open;
 510         } else {
 511                 printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
 512                 error = -ENODEV;
 513                 goto err_free_input;
 514         }
 515
 516         error = acpi_button_add_fs(device);
 517         if (error)
 518                 goto err_free_input;
 519
 520         snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
 521
 522         input->name = name;
 523         input->phys = button->phys;
 524         input->id.bustype = BUS_HOST;
 525         input->id.product = button->type;
 526         input->dev.parent = &device->dev;
 527
 528         switch (button->type) {
 529         case ACPI_BUTTON_TYPE_POWER:
 530                 input_set_capability(input, EV_KEY, KEY_POWER);
 531                 break;
 532
 533         case ACPI_BUTTON_TYPE_SLEEP:
 534                 input_set_capability(input, EV_KEY, KEY_SLEEP);
 535                 break;
 536
 537         case ACPI_BUTTON_TYPE_LID:
 538                 input_set_capability(input, EV_SW, SW_LID);
 539                 break;
 540         }
 541
 542         input_set_drvdata(input, device);
 543         error = input_register_device(input);
 544         if (error)
 545                 goto err_remove_fs;
 546         if (button->type == ACPI_BUTTON_TYPE_LID) {
 547                 /*
 548                  * This assumes there's only one lid device, or if there are
 549                  * more we only care about the last one...
 550                  */
 551                 lid_device = device;
 552         }
 553
 554         device_init_wakeup(&device->dev, true);
 555         printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
 556         return 0;
 557
 558  err_remove_fs:
 559         acpi_button_remove_fs(device);
 560  err_free_input:
 561         input_free_device(input);
 562  err_free_button:
 563         kfree(button);
 564         return error;
 565 }
 566
 567 static int acpi_button_remove(struct acpi_device *device)
 568 {
 569         struct acpi_button *button = acpi_driver_data(device);
 570
 571         acpi_button_remove_fs(device);
 572         input_unregister_device(button->input);
 573         kfree(button);
 574         return 0;
 575 }
 576
 577 static int param_set_lid_init_state(const char *val,
 578                                     const struct kernel_param *kp)
 579 {
 580         int result = 0;
 581
 582         if (!strncmp(val, "open", sizeof("open") - 1)) {
 583                 lid_init_state = ACPI_BUTTON_LID_INIT_OPEN;
 584                 pr_info("Notify initial lid state as open\n");
 585         } else if (!strncmp(val, "method", sizeof("method") - 1)) {
 586                 lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
 587                 pr_info("Notify initial lid state with _LID return value\n");
 588         } else if (!strncmp(val, "ignore", sizeof("ignore") - 1)) {
 589                 lid_init_state = ACPI_BUTTON_LID_INIT_IGNORE;
 590                 pr_info("Do not notify initial lid state\n");
 591         } else
 592                 result = -EINVAL;
 593         return result;
 594 }
 595
 596 static int param_get_lid_init_state(char *buffer,
 597                                     const struct kernel_param *kp)
 598 {
 599         switch (lid_init_state) {
 600         case ACPI_BUTTON_LID_INIT_OPEN:
 601                 return sprintf(buffer, "open");
 602         case ACPI_BUTTON_LID_INIT_METHOD:
 603                 return sprintf(buffer, "method");
 604         case ACPI_BUTTON_LID_INIT_IGNORE:
 605                 return sprintf(buffer, "ignore");
 606         default:
 607                 return sprintf(buffer, "invalid");
 608         }
 609         return 0;
 610 }
 611
 612 module_param_call(lid_init_state,
 613                   param_set_lid_init_state, param_get_lid_init_state,
 614                   NULL, 0644);
 615 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
 616
 617 static int acpi_button_register_driver(struct acpi_driver *driver)
 618 {
 619         /*
 620          * Modules such as nouveau.ko and i915.ko have a link time dependency
 621          * on acpi_lid_open(), and would therefore not be loadable on ACPI
 622          * capable kernels booted in non-ACPI mode if the return value of
 623          * acpi_bus_register_driver() is returned from here with ACPI disabled
 624          * when this driver is built as a module.
 625          */
 626         if (acpi_disabled)
 627                 return 0;
 628
 629         return acpi_bus_register_driver(driver);
 630 }
 631
 632 static void acpi_button_unregister_driver(struct acpi_driver *driver)
 633 {
 634         if (!acpi_disabled)
 635                 acpi_bus_unregister_driver(driver);
 636 }
 637
 638 module_driver(acpi_button_driver, acpi_button_register_driver,
 639                acpi_button_unregister_driver);