drivers/acpi/button.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  button.c - ACPI Button Driver
   4  *
   5  *  Copyright (C) 2001, 2002 Andy Grover <[email protected]>
   6  *  Copyright (C) 2001, 2002 Paul Diefenbaugh <[email protected]>
   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 MD60198"),
  93                 },
  94                 .driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
  95         },
  96         {
  97                 /*
  98                  * Razer Blade Stealth 13 late 2019, notification of the LID device
  99                  * only happens on close, not on open and _LID always returns closed.
 100                  */
 101                 .matches = {
 102                         DMI_MATCH(DMI_SYS_VENDOR, "Razer"),
 103                         DMI_MATCH(DMI_PRODUCT_NAME, "Razer Blade Stealth 13 Late 2019"),
 104                 },
 105                 .driver_data = (void *)(long)ACPI_BUTTON_LID_INIT_OPEN,
 106         },
 107         {}
 108 };
 109
 110 static int acpi_button_add(struct acpi_device *device);
 111 static int acpi_button_remove(struct acpi_device *device);
 112 static void acpi_button_notify(struct acpi_device *device, u32 event);
 113
 114 #ifdef CONFIG_PM_SLEEP
 115 static int acpi_button_suspend(struct device *dev);
 116 static int acpi_button_resume(struct device *dev);
 117 #else
 118 #define acpi_button_suspend NULL
 119 #define acpi_button_resume NULL
 120 #endif
 121 static SIMPLE_DEV_PM_OPS(acpi_button_pm, acpi_button_suspend, acpi_button_resume);
 122
 123 static struct acpi_driver acpi_button_driver = {
 124         .name = "button",
 125         .class = ACPI_BUTTON_CLASS,
 126         .ids = button_device_ids,
 127         .ops = {
 128                 .add = acpi_button_add,
 129                 .remove = acpi_button_remove,
 130                 .notify = acpi_button_notify,
 131         },
 132         .drv.pm = &acpi_button_pm,
 133 };
 134
 135 struct acpi_button {
 136         unsigned int type;
 137         struct input_dev *input;
 138         char phys[32];                  /* for input device */
 139         unsigned long pushed;
 140         int last_state;
 141         ktime_t last_time;
 142         bool suspended;
 143         bool lid_state_initialized;
 144 };
 145
 146 static struct acpi_device *lid_device;
 147 static long lid_init_state = -1;
 148
 149 static unsigned long lid_report_interval __read_mostly = 500;
 150 module_param(lid_report_interval, ulong, 0644);
 151 MODULE_PARM_DESC(lid_report_interval, "Interval (ms) between lid key events");
 152
 153 /* --------------------------------------------------------------------------
 154                               FS Interface (/proc)
 155    -------------------------------------------------------------------------- */
 156
 157 static struct proc_dir_entry *acpi_button_dir;
 158 static struct proc_dir_entry *acpi_lid_dir;
 159
 160 static int acpi_lid_evaluate_state(struct acpi_device *device)
 161 {
 162         unsigned long long lid_state;
 163         acpi_status status;
 164
 165         status = acpi_evaluate_integer(device->handle, "_LID", NULL, &lid_state);
 166         if (ACPI_FAILURE(status))
 167                 return -ENODEV;
 168
 169         return lid_state ? 1 : 0;
 170 }
 171
 172 static int acpi_lid_notify_state(struct acpi_device *device, int state)
 173 {
 174         struct acpi_button *button = acpi_driver_data(device);
 175         ktime_t next_report;
 176         bool do_update;
 177
 178         /*
 179          * In lid_init_state=ignore mode, if user opens/closes lid
 180          * frequently with "open" missing, and "last_time" is also updated
 181          * frequently, "close" cannot be delivered to the userspace.
 182          * So "last_time" is only updated after a timeout or an actual
 183          * switch.
 184          */
 185         if (lid_init_state != ACPI_BUTTON_LID_INIT_IGNORE ||
 186             button->last_state != !!state)
 187                 do_update = true;
 188         else
 189                 do_update = false;
 190
 191         next_report = ktime_add(button->last_time,
 192                                 ms_to_ktime(lid_report_interval));
 193         if (button->last_state == !!state &&
 194             ktime_after(ktime_get(), next_report)) {
 195                 /* Complain the buggy firmware */
 196                 pr_warn_once("The lid device is not compliant to SW_LID.\n");
 197
 198                 /*
 199                  * Send the unreliable complement switch event:
 200                  *
 201                  * On most platforms, the lid device is reliable. However
 202                  * there are exceptions:
 203                  * 1. Platforms returning initial lid state as "close" by
 204                  *    default after booting/resuming:
 205                  *     https://bugzilla.kernel.org/show_bug.cgi?id=89211
 206                  *     https://bugzilla.kernel.org/show_bug.cgi?id=106151
 207                  * 2. Platforms never reporting "open" events:
 208                  *     https://bugzilla.kernel.org/show_bug.cgi?id=106941
 209                  * On these buggy platforms, the usage model of the ACPI
 210                  * lid device actually is:
 211                  * 1. The initial returning value of _LID may not be
 212                  *    reliable.
 213                  * 2. The open event may not be reliable.
 214                  * 3. The close event is reliable.
 215                  *
 216                  * But SW_LID is typed as input switch event, the input
 217                  * layer checks if the event is redundant. Hence if the
 218                  * state is not switched, the userspace cannot see this
 219                  * platform triggered reliable event. By inserting a
 220                  * complement switch event, it then is guaranteed that the
 221                  * platform triggered reliable one can always be seen by
 222                  * the userspace.
 223                  */
 224                 if (lid_init_state == ACPI_BUTTON_LID_INIT_IGNORE) {
 225                         do_update = true;
 226                         /*
 227                          * Do generate complement switch event for "close"
 228                          * as "close" is reliable and wrong "open" won't
 229                          * trigger unexpected behaviors.
 230                          * Do not generate complement switch event for
 231                          * "open" as "open" is not reliable and wrong
 232                          * "close" will trigger unexpected behaviors.
 233                          */
 234                         if (!state) {
 235                                 input_report_switch(button->input,
 236                                                     SW_LID, state);
 237                                 input_sync(button->input);
 238                         }
 239                 }
 240         }
 241         /* Send the platform triggered reliable event */
 242         if (do_update) {
 243                 acpi_handle_debug(device->handle, "ACPI LID %s\n",
 244                                   state ? "open" : "closed");
 245                 input_report_switch(button->input, SW_LID, !state);
 246                 input_sync(button->input);
 247                 button->last_state = !!state;
 248                 button->last_time = ktime_get();
 249         }
 250
 251         return 0;
 252 }
 253
 254 static int __maybe_unused acpi_button_state_seq_show(struct seq_file *seq,
 255                                                      void *offset)
 256 {
 257         struct acpi_device *device = seq->private;
 258         int state;
 259
 260         state = acpi_lid_evaluate_state(device);
 261         seq_printf(seq, "state:      %s\n",
 262                    state < 0 ? "unsupported" : (state ? "open" : "closed"));
 263         return 0;
 264 }
 265
 266 static int acpi_button_add_fs(struct acpi_device *device)
 267 {
 268         struct acpi_button *button = acpi_driver_data(device);
 269         struct proc_dir_entry *entry = NULL;
 270         int ret = 0;
 271
 272         /* procfs I/F for ACPI lid device only */
 273         if (button->type != ACPI_BUTTON_TYPE_LID)
 274                 return 0;
 275
 276         if (acpi_button_dir || acpi_lid_dir) {
 277                 printk(KERN_ERR PREFIX "More than one Lid device found!\n");
 278                 return -EEXIST;
 279         }
 280
 281         /* create /proc/acpi/button */
 282         acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
 283         if (!acpi_button_dir)
 284                 return -ENODEV;
 285
 286         /* create /proc/acpi/button/lid */
 287         acpi_lid_dir = proc_mkdir(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 288         if (!acpi_lid_dir) {
 289                 ret = -ENODEV;
 290                 goto remove_button_dir;
 291         }
 292
 293         /* create /proc/acpi/button/lid/LID/ */
 294         acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), acpi_lid_dir);
 295         if (!acpi_device_dir(device)) {
 296                 ret = -ENODEV;
 297                 goto remove_lid_dir;
 298         }
 299
 300         /* create /proc/acpi/button/lid/LID/state */
 301         entry = proc_create_single_data(ACPI_BUTTON_FILE_STATE, S_IRUGO,
 302                         acpi_device_dir(device), acpi_button_state_seq_show,
 303                         device);
 304         if (!entry) {
 305                 ret = -ENODEV;
 306                 goto remove_dev_dir;
 307         }
 308
 309 done:
 310         return ret;
 311
 312 remove_dev_dir:
 313         remove_proc_entry(acpi_device_bid(device),
 314                           acpi_lid_dir);
 315         acpi_device_dir(device) = NULL;
 316 remove_lid_dir:
 317         remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 318         acpi_lid_dir = NULL;
 319 remove_button_dir:
 320         remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
 321         acpi_button_dir = NULL;
 322         goto done;
 323 }
 324
 325 static int acpi_button_remove_fs(struct acpi_device *device)
 326 {
 327         struct acpi_button *button = acpi_driver_data(device);
 328
 329         if (button->type != ACPI_BUTTON_TYPE_LID)
 330                 return 0;
 331
 332         remove_proc_entry(ACPI_BUTTON_FILE_STATE,
 333                           acpi_device_dir(device));
 334         remove_proc_entry(acpi_device_bid(device),
 335                           acpi_lid_dir);
 336         acpi_device_dir(device) = NULL;
 337         remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
 338         acpi_lid_dir = NULL;
 339         remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
 340         acpi_button_dir = NULL;
 341
 342         return 0;
 343 }
 344
 345 /* --------------------------------------------------------------------------
 346                                 Driver Interface
 347    -------------------------------------------------------------------------- */
 348 int acpi_lid_open(void)
 349 {
 350         if (!lid_device)
 351                 return -ENODEV;
 352
 353         return acpi_lid_evaluate_state(lid_device);
 354 }
 355 EXPORT_SYMBOL(acpi_lid_open);
 356
 357 static int acpi_lid_update_state(struct acpi_device *device,
 358                                  bool signal_wakeup)
 359 {
 360         int state;
 361
 362         state = acpi_lid_evaluate_state(device);
 363         if (state < 0)
 364                 return state;
 365
 366         if (state && signal_wakeup)
 367                 acpi_pm_wakeup_event(&device->dev);
 368
 369         return acpi_lid_notify_state(device, state);
 370 }
 371
 372 static void acpi_lid_initialize_state(struct acpi_device *device)
 373 {
 374         struct acpi_button *button = acpi_driver_data(device);
 375
 376         switch (lid_init_state) {
 377         case ACPI_BUTTON_LID_INIT_OPEN:
 378                 (void)acpi_lid_notify_state(device, 1);
 379                 break;
 380         case ACPI_BUTTON_LID_INIT_METHOD:
 381                 (void)acpi_lid_update_state(device, false);
 382                 break;
 383         case ACPI_BUTTON_LID_INIT_IGNORE:
 384         default:
 385                 break;
 386         }
 387
 388         button->lid_state_initialized = true;
 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
 396         switch (event) {
 397         case ACPI_FIXED_HARDWARE_EVENT:
 398                 event = ACPI_BUTTON_NOTIFY_STATUS;
 399                 fallthrough;
 400         case ACPI_BUTTON_NOTIFY_STATUS:
 401                 input = button->input;
 402                 if (button->type == ACPI_BUTTON_TYPE_LID) {
 403                         if (button->lid_state_initialized)
 404                                 acpi_lid_update_state(device, true);
 405                 } else {
 406                         int keycode;
 407
 408                         acpi_pm_wakeup_event(&device->dev);
 409                         if (button->suspended)
 410                                 break;
 411
 412                         keycode = test_bit(KEY_SLEEP, input->keybit) ?
 413                                                 KEY_SLEEP : KEY_POWER;
 414                         input_report_key(input, keycode, 1);
 415                         input_sync(input);
 416                         input_report_key(input, keycode, 0);
 417                         input_sync(input);
 418
 419                         acpi_bus_generate_netlink_event(
 420                                         device->pnp.device_class,
 421                                         dev_name(&device->dev),
 422                                         event, ++button->pushed);
 423                 }
 424                 break;
 425         default:
 426                 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 427                                   "Unsupported event [0x%x]\n", event));
 428                 break;
 429         }
 430 }
 431
 432 #ifdef CONFIG_PM_SLEEP
 433 static int acpi_button_suspend(struct device *dev)
 434 {
 435         struct acpi_device *device = to_acpi_device(dev);
 436         struct acpi_button *button = acpi_driver_data(device);
 437
 438         button->suspended = true;
 439         return 0;
 440 }
 441
 442 static int acpi_button_resume(struct device *dev)
 443 {
 444         struct acpi_device *device = to_acpi_device(dev);
 445         struct acpi_button *button = acpi_driver_data(device);
 446
 447         button->suspended = false;
 448         if (button->type == ACPI_BUTTON_TYPE_LID) {
 449                 button->last_state = !!acpi_lid_evaluate_state(device);
 450                 button->last_time = ktime_get();
 451                 acpi_lid_initialize_state(device);
 452         }
 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         if (!strcmp(hid, ACPI_BUTTON_HID_LID) &&
 478              lid_init_state == ACPI_BUTTON_LID_INIT_DISABLED)
 479                 return -ENODEV;
 480
 481         button = kzalloc(sizeof(struct acpi_button), GFP_KERNEL);
 482         if (!button)
 483                 return -ENOMEM;
 484
 485         device->driver_data = button;
 486
 487         button->input = input = input_allocate_device();
 488         if (!input) {
 489                 error = -ENOMEM;
 490                 goto err_free_button;
 491         }
 492
 493         name = acpi_device_name(device);
 494         class = acpi_device_class(device);
 495
 496         if (!strcmp(hid, ACPI_BUTTON_HID_POWER) ||
 497             !strcmp(hid, ACPI_BUTTON_HID_POWERF)) {
 498                 button->type = ACPI_BUTTON_TYPE_POWER;
 499                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_POWER);
 500                 sprintf(class, "%s/%s",
 501                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_POWER);
 502         } else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEP) ||
 503                    !strcmp(hid, ACPI_BUTTON_HID_SLEEPF)) {
 504                 button->type = ACPI_BUTTON_TYPE_SLEEP;
 505                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_SLEEP);
 506                 sprintf(class, "%s/%s",
 507                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_SLEEP);
 508         } else if (!strcmp(hid, ACPI_BUTTON_HID_LID)) {
 509                 button->type = ACPI_BUTTON_TYPE_LID;
 510                 strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
 511                 sprintf(class, "%s/%s",
 512                         ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
 513                 input->open = acpi_lid_input_open;
 514         } else {
 515                 printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
 516                 error = -ENODEV;
 517                 goto err_free_input;
 518         }
 519
 520         error = acpi_button_add_fs(device);
 521         if (error)
 522                 goto err_free_input;
 523
 524         snprintf(button->phys, sizeof(button->phys), "%s/button/input0", hid);
 525
 526         input->name = name;
 527         input->phys = button->phys;
 528         input->id.bustype = BUS_HOST;
 529         input->id.product = button->type;
 530         input->dev.parent = &device->dev;
 531
 532         switch (button->type) {
 533         case ACPI_BUTTON_TYPE_POWER:
 534                 input_set_capability(input, EV_KEY, KEY_POWER);
 535                 break;
 536
 537         case ACPI_BUTTON_TYPE_SLEEP:
 538                 input_set_capability(input, EV_KEY, KEY_SLEEP);
 539                 break;
 540
 541         case ACPI_BUTTON_TYPE_LID:
 542                 input_set_capability(input, EV_SW, SW_LID);
 543                 break;
 544         }
 545
 546         input_set_drvdata(input, device);
 547         error = input_register_device(input);
 548         if (error)
 549                 goto err_remove_fs;
 550         if (button->type == ACPI_BUTTON_TYPE_LID) {
 551                 /*
 552                  * This assumes there's only one lid device, or if there are
 553                  * more we only care about the last one...
 554                  */
 555                 lid_device = device;
 556         }
 557
 558         device_init_wakeup(&device->dev, true);
 559         printk(KERN_INFO PREFIX "%s [%s]\n", name, acpi_device_bid(device));
 560         return 0;
 561
 562  err_remove_fs:
 563         acpi_button_remove_fs(device);
 564  err_free_input:
 565         input_free_device(input);
 566  err_free_button:
 567         kfree(button);
 568         return error;
 569 }
 570
 571 static int acpi_button_remove(struct acpi_device *device)
 572 {
 573         struct acpi_button *button = acpi_driver_data(device);
 574
 575         acpi_button_remove_fs(device);
 576         input_unregister_device(button->input);
 577         kfree(button);
 578         return 0;
 579 }
 580
 581 static int param_set_lid_init_state(const char *val,
 582                                     const struct kernel_param *kp)
 583 {
 584         int i;
 585
 586         i = sysfs_match_string(lid_init_state_str, val);
 587         if (i < 0)
 588                 return i;
 589
 590         lid_init_state = i;
 591         pr_info("Initial lid state set to '%s'\n", lid_init_state_str[i]);
 592         return 0;
 593 }
 594
 595 static int param_get_lid_init_state(char *buf, const struct kernel_param *kp)
 596 {
 597         int i, c = 0;
 598
 599         for (i = 0; i < ARRAY_SIZE(lid_init_state_str); i++)
 600                 if (i == lid_init_state)
 601                         c += sprintf(buf + c, "[%s] ", lid_init_state_str[i]);
 602                 else
 603                         c += sprintf(buf + c, "%s ", lid_init_state_str[i]);
 604
 605         buf[c - 1] = '\n'; /* Replace the final space with a newline */
 606
 607         return c;
 608 }
 609
 610 module_param_call(lid_init_state,
 611                   param_set_lid_init_state, param_get_lid_init_state,
 612                   NULL, 0644);
 613 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
 614
 615 static int acpi_button_register_driver(struct acpi_driver *driver)
 616 {
 617         const struct dmi_system_id *dmi_id;
 618
 619         if (lid_init_state == -1) {
 620                 dmi_id = dmi_first_match(dmi_lid_quirks);
 621                 if (dmi_id)
 622                         lid_init_state = (long)dmi_id->driver_data;
 623                 else
 624                         lid_init_state = ACPI_BUTTON_LID_INIT_METHOD;
 625         }
 626
 627         /*
 628          * Modules such as nouveau.ko and i915.ko have a link time dependency
 629          * on acpi_lid_open(), and would therefore not be loadable on ACPI
 630          * capable kernels booted in non-ACPI mode if the return value of
 631          * acpi_bus_register_driver() is returned from here with ACPI disabled
 632          * when this driver is built as a module.
 633          */
 634         if (acpi_disabled)
 635                 return 0;
 636
 637         return acpi_bus_register_driver(driver);
 638 }
 639
 640 static void acpi_button_unregister_driver(struct acpi_driver *driver)
 641 {
 642         if (!acpi_disabled)
 643                 acpi_bus_unregister_driver(driver);
 644 }
 645
 646 module_driver(acpi_button_driver, acpi_button_register_driver,
 647                acpi_button_unregister_driver);