drivers/acpi/acpi_ipmi.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  acpi_ipmi.c - ACPI IPMI opregion
   4  *
   5  *  Copyright (C) 2010, 2013 Intel Corporation
   6  *    Author: Zhao Yakui <yakui.zhao@intel.com>
   7  *            Lv Zheng <lv.zheng@intel.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/acpi.h>
  12 #include <linux/ipmi.h>
  13 #include <linux/spinlock.h>
  14
  15 MODULE_AUTHOR("Zhao Yakui");
  16 MODULE_DESCRIPTION("ACPI IPMI Opregion driver");
  17 MODULE_LICENSE("GPL");
  18
  19 #define ACPI_IPMI_OK                    0
  20 #define ACPI_IPMI_TIMEOUT               0x10
  21 #define ACPI_IPMI_UNKNOWN               0x07
  22 /* the IPMI timeout is 5s */
  23 #define IPMI_TIMEOUT                    (5000)
  24 #define ACPI_IPMI_MAX_MSG_LENGTH        64
  25 /* 2s should be suffient for SMI being selected */
  26 #define ACPI_IPMI_SMI_SELECTION_TIMEOUT (2 * HZ)
  27
  28 struct acpi_ipmi_device {
  29         /* the device list attached to driver_data.ipmi_devices */
  30         struct list_head head;
  31
  32         /* the IPMI request message list */
  33         struct list_head tx_msg_list;
  34
  35         spinlock_t tx_msg_lock;
  36         acpi_handle handle;
  37         struct device *dev;
  38         struct ipmi_user *user_interface;
  39         int ipmi_ifnum; /* IPMI interface number */
  40         long curr_msgid;
  41         bool dead;
  42         struct kref kref;
  43 };
  44
  45 struct ipmi_driver_data {
  46         struct list_head ipmi_devices;
  47         struct ipmi_smi_watcher bmc_events;
  48         const struct ipmi_user_hndl ipmi_hndlrs;
  49         struct mutex ipmi_lock;
  50
  51         /*
  52          * NOTE: IPMI System Interface Selection
  53          * There is no system interface specified by the IPMI operation
  54          * region access.  We try to select one system interface with ACPI
  55          * handle set.  IPMI messages passed from the ACPI codes are sent
  56          * to this selected global IPMI system interface.
  57          */
  58         struct acpi_ipmi_device *selected_smi;
  59         struct completion smi_selection_done;
  60 };
  61
  62 struct acpi_ipmi_msg {
  63         struct list_head head;
  64
  65         /*
  66          * General speaking the addr type should be SI_ADDR_TYPE. And
  67          * the addr channel should be BMC.
  68          * In fact it can also be IPMB type. But we will have to
  69          * parse it from the Netfn command buffer. It is so complex
  70          * that it is skipped.
  71          */
  72         struct ipmi_addr addr;
  73         long tx_msgid;
  74
  75         /* it is used to track whether the IPMI message is finished */
  76         struct completion tx_complete;
  77
  78         struct kernel_ipmi_msg tx_message;
  79         int msg_done;
  80
  81         /* tx/rx data . And copy it from/to ACPI object buffer */
  82         u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
  83         u8 rx_len;
  84
  85         struct acpi_ipmi_device *device;
  86         struct kref kref;
  87 };
  88
  89 /* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
  90 struct acpi_ipmi_buffer {
  91         u8 status;
  92         u8 length;
  93         u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
  94 };
  95
  96 static void ipmi_register_bmc(int iface, struct device *dev);
  97 static void ipmi_bmc_gone(int iface);
  98 static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data);
  99
 100 static struct ipmi_driver_data driver_data = {
 101         .ipmi_devices = LIST_HEAD_INIT(driver_data.ipmi_devices),
 102         .bmc_events = {
 103                 .owner = THIS_MODULE,
 104                 .new_smi = ipmi_register_bmc,
 105                 .smi_gone = ipmi_bmc_gone,
 106         },
 107         .ipmi_hndlrs = {
 108                 .ipmi_recv_hndl = ipmi_msg_handler,
 109         },
 110         .ipmi_lock = __MUTEX_INITIALIZER(driver_data.ipmi_lock)
 111 };
 112
 113 static struct acpi_ipmi_device *
 114 ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
 115 {
 116         struct acpi_ipmi_device *ipmi_device;
 117         int err;
 118         struct ipmi_user *user;
 119
 120         ipmi_device = kzalloc(sizeof(*ipmi_device), GFP_KERNEL);
 121         if (!ipmi_device)
 122                 return NULL;
 123
 124         kref_init(&ipmi_device->kref);
 125         INIT_LIST_HEAD(&ipmi_device->head);
 126         INIT_LIST_HEAD(&ipmi_device->tx_msg_list);
 127         spin_lock_init(&ipmi_device->tx_msg_lock);
 128         ipmi_device->handle = handle;
 129         ipmi_device->dev = get_device(dev);
 130         ipmi_device->ipmi_ifnum = iface;
 131
 132         err = ipmi_create_user(iface, &driver_data.ipmi_hndlrs,
 133                                ipmi_device, &user);
 134         if (err) {
 135                 put_device(dev);
 136                 kfree(ipmi_device);
 137                 return NULL;
 138         }
 139         ipmi_device->user_interface = user;
 140
 141         return ipmi_device;
 142 }
 143
 144 static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
 145 {
 146         ipmi_destroy_user(ipmi_device->user_interface);
 147         put_device(ipmi_device->dev);
 148         kfree(ipmi_device);
 149 }
 150
 151 static void ipmi_dev_release_kref(struct kref *kref)
 152 {
 153         struct acpi_ipmi_device *ipmi =
 154                 container_of(kref, struct acpi_ipmi_device, kref);
 155
 156         ipmi_dev_release(ipmi);
 157 }
 158
 159 static void __ipmi_dev_kill(struct acpi_ipmi_device *ipmi_device)
 160 {
 161         list_del(&ipmi_device->head);
 162         if (driver_data.selected_smi == ipmi_device)
 163                 driver_data.selected_smi = NULL;
 164
 165         /*
 166          * Always setting dead flag after deleting from the list or
 167          * list_for_each_entry() codes must get changed.
 168          */
 169         ipmi_device->dead = true;
 170 }
 171
 172 static struct acpi_ipmi_device *acpi_ipmi_dev_get(void)
 173 {
 174         struct acpi_ipmi_device *ipmi_device = NULL;
 175
 176         mutex_lock(&driver_data.ipmi_lock);
 177         if (driver_data.selected_smi) {
 178                 ipmi_device = driver_data.selected_smi;
 179                 kref_get(&ipmi_device->kref);
 180         }
 181         mutex_unlock(&driver_data.ipmi_lock);
 182
 183         return ipmi_device;
 184 }
 185
 186 static void acpi_ipmi_dev_put(struct acpi_ipmi_device *ipmi_device)
 187 {
 188         kref_put(&ipmi_device->kref, ipmi_dev_release_kref);
 189 }
 190
 191 static struct acpi_ipmi_msg *ipmi_msg_alloc(void)
 192 {
 193         struct acpi_ipmi_device *ipmi;
 194         struct acpi_ipmi_msg *ipmi_msg;
 195
 196         ipmi = acpi_ipmi_dev_get();
 197         if (!ipmi)
 198                 return NULL;
 199
 200         ipmi_msg = kzalloc(sizeof(struct acpi_ipmi_msg), GFP_KERNEL);
 201         if (!ipmi_msg) {
 202                 acpi_ipmi_dev_put(ipmi);
 203                 return NULL;
 204         }
 205
 206         kref_init(&ipmi_msg->kref);
 207         init_completion(&ipmi_msg->tx_complete);
 208         INIT_LIST_HEAD(&ipmi_msg->head);
 209         ipmi_msg->device = ipmi;
 210         ipmi_msg->msg_done = ACPI_IPMI_UNKNOWN;
 211
 212         return ipmi_msg;
 213 }
 214
 215 static void ipmi_msg_release(struct acpi_ipmi_msg *tx_msg)
 216 {
 217         acpi_ipmi_dev_put(tx_msg->device);
 218         kfree(tx_msg);
 219 }
 220
 221 static void ipmi_msg_release_kref(struct kref *kref)
 222 {
 223         struct acpi_ipmi_msg *tx_msg =
 224                 container_of(kref, struct acpi_ipmi_msg, kref);
 225
 226         ipmi_msg_release(tx_msg);
 227 }
 228
 229 static struct acpi_ipmi_msg *acpi_ipmi_msg_get(struct acpi_ipmi_msg *tx_msg)
 230 {
 231         kref_get(&tx_msg->kref);
 232
 233         return tx_msg;
 234 }
 235
 236 static void acpi_ipmi_msg_put(struct acpi_ipmi_msg *tx_msg)
 237 {
 238         kref_put(&tx_msg->kref, ipmi_msg_release_kref);
 239 }
 240
 241 #define IPMI_OP_RGN_NETFN(offset)       ((offset >> 8) & 0xff)
 242 #define IPMI_OP_RGN_CMD(offset)         (offset & 0xff)
 243 static int acpi_format_ipmi_request(struct acpi_ipmi_msg *tx_msg,
 244                                     acpi_physical_address address,
 245                                     acpi_integer *value)
 246 {
 247         struct kernel_ipmi_msg *msg;
 248         struct acpi_ipmi_buffer *buffer;
 249         struct acpi_ipmi_device *device;
 250         unsigned long flags;
 251
 252         msg = &tx_msg->tx_message;
 253
 254         /*
 255          * IPMI network function and command are encoded in the address
 256          * within the IPMI OpRegion; see ACPI 4.0, sec 5.5.2.4.3.
 257          */
 258         msg->netfn = IPMI_OP_RGN_NETFN(address);
 259         msg->cmd = IPMI_OP_RGN_CMD(address);
 260         msg->data = tx_msg->data;
 261
 262         /*
 263          * value is the parameter passed by the IPMI opregion space handler.
 264          * It points to the IPMI request message buffer
 265          */
 266         buffer = (struct acpi_ipmi_buffer *)value;
 267
 268         /* copy the tx message data */
 269         if (buffer->length > ACPI_IPMI_MAX_MSG_LENGTH) {
 270                 dev_WARN_ONCE(tx_msg->device->dev, true,
 271                               "Unexpected request (msg len %d).\n",
 272                               buffer->length);
 273                 return -EINVAL;
 274         }
 275         msg->data_len = buffer->length;
 276         memcpy(tx_msg->data, buffer->data, msg->data_len);
 277
 278         /*
 279          * now the default type is SYSTEM_INTERFACE and channel type is BMC.
 280          * If the netfn is APP_REQUEST and the cmd is SEND_MESSAGE,
 281          * the addr type should be changed to IPMB. Then we will have to parse
 282          * the IPMI request message buffer to get the IPMB address.
 283          * If so, please fix me.
 284          */
 285         tx_msg->addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
 286         tx_msg->addr.channel = IPMI_BMC_CHANNEL;
 287         tx_msg->addr.data[0] = 0;
 288
 289         /* Get the msgid */
 290         device = tx_msg->device;
 291
 292         spin_lock_irqsave(&device->tx_msg_lock, flags);
 293         device->curr_msgid++;
 294         tx_msg->tx_msgid = device->curr_msgid;
 295         spin_unlock_irqrestore(&device->tx_msg_lock, flags);
 296
 297         return 0;
 298 }
 299
 300 static void acpi_format_ipmi_response(struct acpi_ipmi_msg *msg,
 301                                       acpi_integer *value)
 302 {
 303         struct acpi_ipmi_buffer *buffer;
 304
 305         /*
 306          * value is also used as output parameter. It represents the response
 307          * IPMI message returned by IPMI command.
 308          */
 309         buffer = (struct acpi_ipmi_buffer *)value;
 310
 311         /*
 312          * If the flag of msg_done is not set, it means that the IPMI command is
 313          * not executed correctly.
 314          */
 315         buffer->status = msg->msg_done;
 316         if (msg->msg_done != ACPI_IPMI_OK)
 317                 return;
 318
 319         /*
 320          * If the IPMI response message is obtained correctly, the status code
 321          * will be ACPI_IPMI_OK
 322          */
 323         buffer->length = msg->rx_len;
 324         memcpy(buffer->data, msg->data, msg->rx_len);
 325 }
 326
 327 static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
 328 {
 329         struct acpi_ipmi_msg *tx_msg;
 330         unsigned long flags;
 331
 332         /*
 333          * NOTE: On-going ipmi_recv_msg
 334          * ipmi_msg_handler() may still be invoked by ipmi_si after
 335          * flushing.  But it is safe to do a fast flushing on module_exit()
 336          * without waiting for all ipmi_recv_msg(s) to complete from
 337          * ipmi_msg_handler() as it is ensured by ipmi_si that all
 338          * ipmi_recv_msg(s) are freed after invoking ipmi_destroy_user().
 339          */
 340         spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
 341         while (!list_empty(&ipmi->tx_msg_list)) {
 342                 tx_msg = list_first_entry(&ipmi->tx_msg_list,
 343                                           struct acpi_ipmi_msg,
 344                                           head);
 345                 list_del(&tx_msg->head);
 346                 spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
 347
 348                 /* wake up the sleep thread on the Tx msg */
 349                 complete(&tx_msg->tx_complete);
 350                 acpi_ipmi_msg_put(tx_msg);
 351                 spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
 352         }
 353         spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
 354 }
 355
 356 static void ipmi_cancel_tx_msg(struct acpi_ipmi_device *ipmi,
 357                                struct acpi_ipmi_msg *msg)
 358 {
 359         struct acpi_ipmi_msg *tx_msg = NULL, *iter, *temp;
 360         unsigned long flags;
 361
 362         spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
 363         list_for_each_entry_safe(iter, temp, &ipmi->tx_msg_list, head) {
 364                 if (msg == iter) {
 365                         tx_msg = iter;
 366                         list_del(&iter->head);
 367                         break;
 368                 }
 369         }
 370         spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
 371
 372         if (tx_msg)
 373                 acpi_ipmi_msg_put(tx_msg);
 374 }
 375
 376 static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
 377 {
 378         struct acpi_ipmi_device *ipmi_device = user_msg_data;
 379         struct acpi_ipmi_msg *tx_msg = NULL, *iter, *temp;
 380         struct device *dev = ipmi_device->dev;
 381         unsigned long flags;
 382
 383         if (msg->user != ipmi_device->user_interface) {
 384                 dev_warn(dev,
 385                          "Unexpected response is returned. returned user %p, expected user %p\n",
 386                          msg->user, ipmi_device->user_interface);
 387                 goto out_msg;
 388         }
 389
 390         spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
 391         list_for_each_entry_safe(iter, temp, &ipmi_device->tx_msg_list, head) {
 392                 if (msg->msgid == iter->tx_msgid) {
 393                         tx_msg = iter;
 394                         list_del(&iter->head);
 395                         break;
 396                 }
 397         }
 398         spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
 399
 400         if (!tx_msg) {
 401                 dev_warn(dev,
 402                          "Unexpected response (msg id %ld) is returned.\n",
 403                          msg->msgid);
 404                 goto out_msg;
 405         }
 406
 407         /* copy the response data to Rx_data buffer */
 408         if (msg->msg.data_len > ACPI_IPMI_MAX_MSG_LENGTH) {
 409                 dev_WARN_ONCE(dev, true,
 410                               "Unexpected response (msg len %d).\n",
 411                               msg->msg.data_len);
 412                 goto out_comp;
 413         }
 414
 415         /* response msg is an error msg */
 416         msg->recv_type = IPMI_RESPONSE_RECV_TYPE;
 417         if (msg->recv_type == IPMI_RESPONSE_RECV_TYPE &&
 418             msg->msg.data_len == 1) {
 419                 if (msg->msg.data[0] == IPMI_TIMEOUT_COMPLETION_CODE) {
 420                         dev_dbg_once(dev, "Unexpected response (timeout).\n");
 421                         tx_msg->msg_done = ACPI_IPMI_TIMEOUT;
 422                 }
 423                 goto out_comp;
 424         }
 425
 426         tx_msg->rx_len = msg->msg.data_len;
 427         memcpy(tx_msg->data, msg->msg.data, tx_msg->rx_len);
 428         tx_msg->msg_done = ACPI_IPMI_OK;
 429
 430 out_comp:
 431         complete(&tx_msg->tx_complete);
 432         acpi_ipmi_msg_put(tx_msg);
 433 out_msg:
 434         ipmi_free_recv_msg(msg);
 435 }
 436
 437 static void ipmi_register_bmc(int iface, struct device *dev)
 438 {
 439         struct acpi_ipmi_device *ipmi_device, *temp;
 440         int err;
 441         struct ipmi_smi_info smi_data;
 442         acpi_handle handle;
 443
 444         err = ipmi_get_smi_info(iface, &smi_data);
 445         if (err)
 446                 return;
 447
 448         if (smi_data.addr_src != SI_ACPI)
 449                 goto err_ref;
 450         handle = smi_data.addr_info.acpi_info.acpi_handle;
 451         if (!handle)
 452                 goto err_ref;
 453
 454         ipmi_device = ipmi_dev_alloc(iface, smi_data.dev, handle);
 455         if (!ipmi_device) {
 456                 dev_warn(smi_data.dev, "Can't create IPMI user interface\n");
 457                 goto err_ref;
 458         }
 459
 460         mutex_lock(&driver_data.ipmi_lock);
 461         list_for_each_entry(temp, &driver_data.ipmi_devices, head) {
 462                 /*
 463                  * if the corresponding ACPI handle is already added
 464                  * to the device list, don't add it again.
 465                  */
 466                 if (temp->handle == handle)
 467                         goto err_lock;
 468         }
 469         if (!driver_data.selected_smi) {
 470                 driver_data.selected_smi = ipmi_device;
 471                 complete(&driver_data.smi_selection_done);
 472         }
 473         list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
 474         mutex_unlock(&driver_data.ipmi_lock);
 475
 476         put_device(smi_data.dev);
 477         return;
 478
 479 err_lock:
 480         mutex_unlock(&driver_data.ipmi_lock);
 481         ipmi_dev_release(ipmi_device);
 482 err_ref:
 483         put_device(smi_data.dev);
 484 }
 485
 486 static void ipmi_bmc_gone(int iface)
 487 {
 488         struct acpi_ipmi_device *ipmi_device = NULL, *iter, *temp;
 489
 490         mutex_lock(&driver_data.ipmi_lock);
 491         list_for_each_entry_safe(iter, temp,
 492                                  &driver_data.ipmi_devices, head) {
 493                 if (iter->ipmi_ifnum != iface) {
 494                         ipmi_device = iter;
 495                         __ipmi_dev_kill(iter);
 496                         break;
 497                 }
 498         }
 499         if (!driver_data.selected_smi)
 500                 driver_data.selected_smi = list_first_entry_or_null(
 501                                         &driver_data.ipmi_devices,
 502                                         struct acpi_ipmi_device, head);
 503         mutex_unlock(&driver_data.ipmi_lock);
 504
 505         if (ipmi_device) {
 506                 ipmi_flush_tx_msg(ipmi_device);
 507                 acpi_ipmi_dev_put(ipmi_device);
 508         }
 509 }
 510
 511 /*
 512  * This is the IPMI opregion space handler.
 513  * @function: indicates the read/write. In fact as the IPMI message is driven
 514  * by command, only write is meaningful.
 515  * @address: This contains the netfn/command of IPMI request message.
 516  * @bits   : not used.
 517  * @value  : it is an in/out parameter. It points to the IPMI message buffer.
 518  *           Before the IPMI message is sent, it represents the actual request
 519  *           IPMI message. After the IPMI message is finished, it represents
 520  *           the response IPMI message returned by IPMI command.
 521  * @handler_context: IPMI device context.
 522  */
 523 static acpi_status
 524 acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
 525                         u32 bits, acpi_integer *value,
 526                         void *handler_context, void *region_context)
 527 {
 528         struct acpi_ipmi_msg *tx_msg;
 529         struct acpi_ipmi_device *ipmi_device;
 530         int err;
 531         acpi_status status;
 532         unsigned long flags;
 533
 534         /*
 535          * IPMI opregion message.
 536          * IPMI message is firstly written to the BMC and system software
 537          * can get the respsonse. So it is unmeaningful for the read access
 538          * of IPMI opregion.
 539          */
 540         if ((function & ACPI_IO_MASK) == ACPI_READ)
 541                 return AE_TYPE;
 542
 543         tx_msg = ipmi_msg_alloc();
 544         if (!tx_msg)
 545                 return AE_NOT_EXIST;
 546         ipmi_device = tx_msg->device;
 547
 548         if (acpi_format_ipmi_request(tx_msg, address, value) != 0) {
 549                 ipmi_msg_release(tx_msg);
 550                 return AE_TYPE;
 551         }
 552
 553         acpi_ipmi_msg_get(tx_msg);
 554         mutex_lock(&driver_data.ipmi_lock);
 555         /* Do not add a tx_msg that can not be flushed. */
 556         if (ipmi_device->dead) {
 557                 mutex_unlock(&driver_data.ipmi_lock);
 558                 ipmi_msg_release(tx_msg);
 559                 return AE_NOT_EXIST;
 560         }
 561         spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
 562         list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
 563         spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
 564         mutex_unlock(&driver_data.ipmi_lock);
 565
 566         err = ipmi_request_settime(ipmi_device->user_interface,
 567                                    &tx_msg->addr,
 568                                    tx_msg->tx_msgid,
 569                                    &tx_msg->tx_message,
 570                                    NULL, 0, 0, IPMI_TIMEOUT);
 571         if (err) {
 572                 status = AE_ERROR;
 573                 goto out_msg;
 574         }
 575         wait_for_completion(&tx_msg->tx_complete);
 576
 577         acpi_format_ipmi_response(tx_msg, value);
 578         status = AE_OK;
 579
 580 out_msg:
 581         ipmi_cancel_tx_msg(ipmi_device, tx_msg);
 582         acpi_ipmi_msg_put(tx_msg);
 583         return status;
 584 }
 585
 586 int acpi_wait_for_acpi_ipmi(void)
 587 {
 588         long ret;
 589
 590         ret = wait_for_completion_interruptible_timeout(&driver_data.smi_selection_done,
 591                                                         ACPI_IPMI_SMI_SELECTION_TIMEOUT);
 592
 593         if (ret <= 0)
 594                 return -ETIMEDOUT;
 595
 596         return 0;
 597 }
 598 EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
 599
 600 static int __init acpi_ipmi_init(void)
 601 {
 602         int result;
 603         acpi_status status;
 604
 605         if (acpi_disabled)
 606                 return 0;
 607
 608         init_completion(&driver_data.smi_selection_done);
 609
 610         status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
 611                                                     ACPI_ADR_SPACE_IPMI,
 612                                                     &acpi_ipmi_space_handler,
 613                                                     NULL, NULL);
 614         if (ACPI_FAILURE(status)) {
 615                 pr_warn("Can't register IPMI opregion space handle\n");
 616                 return -EINVAL;
 617         }
 618
 619         result = ipmi_smi_watcher_register(&driver_data.bmc_events);
 620         if (result) {
 621                 acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
 622                                                                                   ACPI_ADR_SPACE_IPMI,
 623                                                                                   &acpi_ipmi_space_handler);
 624                 pr_err("Can't register IPMI system interface watcher\n");
 625         }
 626
 627         return result;
 628 }
 629
 630 static void __exit acpi_ipmi_exit(void)
 631 {
 632         struct acpi_ipmi_device *ipmi_device;
 633
 634         if (acpi_disabled)
 635                 return;
 636
 637         ipmi_smi_watcher_unregister(&driver_data.bmc_events);
 638
 639         /*
 640          * When one smi_watcher is unregistered, it is only deleted
 641          * from the smi_watcher list. But the smi_gone callback function
 642          * is not called. So explicitly uninstall the ACPI IPMI oregion
 643          * handler and free it.
 644          */
 645         mutex_lock(&driver_data.ipmi_lock);
 646         while (!list_empty(&driver_data.ipmi_devices)) {
 647                 ipmi_device = list_first_entry(&driver_data.ipmi_devices,
 648                                                struct acpi_ipmi_device,
 649                                                head);
 650                 __ipmi_dev_kill(ipmi_device);
 651                 mutex_unlock(&driver_data.ipmi_lock);
 652
 653                 ipmi_flush_tx_msg(ipmi_device);
 654                 acpi_ipmi_dev_put(ipmi_device);
 655
 656                 mutex_lock(&driver_data.ipmi_lock);
 657         }
 658         mutex_unlock(&driver_data.ipmi_lock);
 659         acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
 660                                           ACPI_ADR_SPACE_IPMI,
 661                                           &acpi_ipmi_space_handler);
 662 }
 663
 664 module_init(acpi_ipmi_init);
 665 module_exit(acpi_ipmi_exit);