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