drivers/scsi/device_handler/scsi_dh.c

   1 /*
   2  * SCSI device handler infrastruture.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License as published by the
   6  * Free Software Foundation; either version 2 of the License, or (at your
   7  * option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright IBM Corporation, 2007
  19  *      Authors:
  20  *               Chandra Seetharaman <sekharan@us.ibm.com>
  21  *               Mike Anderson <andmike@linux.vnet.ibm.com>
  22  */
  23
  24 #include <linux/slab.h>
  25 #include <linux/module.h>
  26 #include <scsi/scsi_dh.h>
  27 #include "../scsi_priv.h"
  28
  29 static DEFINE_SPINLOCK(list_lock);
  30 static LIST_HEAD(scsi_dh_list);
  31
  32 static struct scsi_device_handler *get_device_handler(const char *name)
  33 {
  34         struct scsi_device_handler *tmp, *found = NULL;
  35
  36         spin_lock(&list_lock);
  37         list_for_each_entry(tmp, &scsi_dh_list, list) {
  38                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
  39                         found = tmp;
  40                         break;
  41                 }
  42         }
  43         spin_unlock(&list_lock);
  44         return found;
  45 }
  46
  47 /*
  48  * device_handler_match_function - Match a device handler to a device
  49  * @sdev - SCSI device to be tested
  50  *
  51  * Tests @sdev against the match function of all registered device_handler.
  52  * Returns the found device handler or NULL if not found.
  53  */
  54 static struct scsi_device_handler *
  55 device_handler_match_function(struct scsi_device *sdev)
  56 {
  57         struct scsi_device_handler *tmp_dh, *found_dh = NULL;
  58
  59         spin_lock(&list_lock);
  60         list_for_each_entry(tmp_dh, &scsi_dh_list, list) {
  61                 if (tmp_dh->match && tmp_dh->match(sdev)) {
  62                         found_dh = tmp_dh;
  63                         break;
  64                 }
  65         }
  66         spin_unlock(&list_lock);
  67         return found_dh;
  68 }
  69
  70 /*
  71  * device_handler_match - Attach a device handler to a device
  72  * @scsi_dh - The device handler to match against or NULL
  73  * @sdev - SCSI device to be tested against @scsi_dh
  74  *
  75  * Tests @sdev against the device handler @scsi_dh or against
  76  * all registered device_handler if @scsi_dh == NULL.
  77  * Returns the found device handler or NULL if not found.
  78  */
  79 static struct scsi_device_handler *
  80 device_handler_match(struct scsi_device_handler *scsi_dh,
  81                      struct scsi_device *sdev)
  82 {
  83         struct scsi_device_handler *found_dh;
  84
  85         found_dh = device_handler_match_function(sdev);
  86
  87         if (scsi_dh && found_dh != scsi_dh)
  88                 found_dh = NULL;
  89
  90         return found_dh;
  91 }
  92
  93 /*
  94  * scsi_dh_handler_attach - Attach a device handler to a device
  95  * @sdev - SCSI device the device handler should attach to
  96  * @scsi_dh - The device handler to attach
  97  */
  98 static int scsi_dh_handler_attach(struct scsi_device *sdev,
  99                                   struct scsi_device_handler *scsi_dh)
 100 {
 101         int err = 0;
 102
 103         if (sdev->scsi_dh_data) {
 104                 if (sdev->scsi_dh_data->scsi_dh != scsi_dh)
 105                         err = -EBUSY;
 106                 else
 107                         kref_get(&sdev->scsi_dh_data->kref);
 108         } else if (scsi_dh->attach) {
 109                 err = scsi_dh->attach(sdev);
 110                 if (!err) {
 111                         kref_init(&sdev->scsi_dh_data->kref);
 112                         sdev->scsi_dh_data->sdev = sdev;
 113                 }
 114         }
 115         return err;
 116 }
 117
 118 static void __detach_handler (struct kref *kref)
 119 {
 120         struct scsi_dh_data *scsi_dh_data = container_of(kref, struct scsi_dh_data, kref);
 121         scsi_dh_data->scsi_dh->detach(scsi_dh_data->sdev);
 122 }
 123
 124 /*
 125  * scsi_dh_handler_detach - Detach a device handler from a device
 126  * @sdev - SCSI device the device handler should be detached from
 127  * @scsi_dh - Device handler to be detached
 128  *
 129  * Detach from a device handler. If a device handler is specified,
 130  * only detach if the currently attached handler matches @scsi_dh.
 131  */
 132 static void scsi_dh_handler_detach(struct scsi_device *sdev,
 133                                    struct scsi_device_handler *scsi_dh)
 134 {
 135         if (!sdev->scsi_dh_data)
 136                 return;
 137
 138         if (scsi_dh && scsi_dh != sdev->scsi_dh_data->scsi_dh)
 139                 return;
 140
 141         if (!scsi_dh)
 142                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 143
 144         if (scsi_dh && scsi_dh->detach)
 145                 kref_put(&sdev->scsi_dh_data->kref, __detach_handler);
 146 }
 147
 148 /*
 149  * Functions for sysfs attribute 'dh_state'
 150  */
 151 static ssize_t
 152 store_dh_state(struct device *dev, struct device_attribute *attr,
 153                const char *buf, size_t count)
 154 {
 155         struct scsi_device *sdev = to_scsi_device(dev);
 156         struct scsi_device_handler *scsi_dh;
 157         int err = -EINVAL;
 158
 159         if (sdev->sdev_state == SDEV_CANCEL ||
 160             sdev->sdev_state == SDEV_DEL)
 161                 return -ENODEV;
 162
 163         if (!sdev->scsi_dh_data) {
 164                 /*
 165                  * Attach to a device handler
 166                  */
 167                 if (!(scsi_dh = get_device_handler(buf)))
 168                         return err;
 169                 err = scsi_dh_handler_attach(sdev, scsi_dh);
 170         } else {
 171                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 172                 if (!strncmp(buf, "detach", 6)) {
 173                         /*
 174                          * Detach from a device handler
 175                          */
 176                         scsi_dh_handler_detach(sdev, scsi_dh);
 177                         err = 0;
 178                 } else if (!strncmp(buf, "activate", 8)) {
 179                         /*
 180                          * Activate a device handler
 181                          */
 182                         if (scsi_dh->activate)
 183                                 err = scsi_dh->activate(sdev, NULL, NULL);
 184                         else
 185                                 err = 0;
 186                 }
 187         }
 188
 189         return err<0?err:count;
 190 }
 191
 192 static ssize_t
 193 show_dh_state(struct device *dev, struct device_attribute *attr, char *buf)
 194 {
 195         struct scsi_device *sdev = to_scsi_device(dev);
 196
 197         if (!sdev->scsi_dh_data)
 198                 return snprintf(buf, 20, "detached\n");
 199
 200         return snprintf(buf, 20, "%s\n", sdev->scsi_dh_data->scsi_dh->name);
 201 }
 202
 203 static struct device_attribute scsi_dh_state_attr =
 204         __ATTR(dh_state, S_IRUGO | S_IWUSR, show_dh_state,
 205                store_dh_state);
 206
 207 /*
 208  * scsi_dh_sysfs_attr_add - Callback for scsi_init_dh
 209  */
 210 static int scsi_dh_sysfs_attr_add(struct device *dev, void *data)
 211 {
 212         struct scsi_device *sdev;
 213         int err;
 214
 215         if (!scsi_is_sdev_device(dev))
 216                 return 0;
 217
 218         sdev = to_scsi_device(dev);
 219
 220         err = device_create_file(&sdev->sdev_gendev,
 221                                  &scsi_dh_state_attr);
 222
 223         return 0;
 224 }
 225
 226 /*
 227  * scsi_dh_sysfs_attr_remove - Callback for scsi_exit_dh
 228  */
 229 static int scsi_dh_sysfs_attr_remove(struct device *dev, void *data)
 230 {
 231         struct scsi_device *sdev;
 232
 233         if (!scsi_is_sdev_device(dev))
 234                 return 0;
 235
 236         sdev = to_scsi_device(dev);
 237
 238         device_remove_file(&sdev->sdev_gendev,
 239                            &scsi_dh_state_attr);
 240
 241         return 0;
 242 }
 243
 244 /*
 245  * scsi_dh_notifier - notifier chain callback
 246  */
 247 static int scsi_dh_notifier(struct notifier_block *nb,
 248                             unsigned long action, void *data)
 249 {
 250         struct device *dev = data;
 251         struct scsi_device *sdev;
 252         int err = 0;
 253         struct scsi_device_handler *devinfo = NULL;
 254
 255         if (!scsi_is_sdev_device(dev))
 256                 return 0;
 257
 258         sdev = to_scsi_device(dev);
 259
 260         if (action == BUS_NOTIFY_ADD_DEVICE) {
 261                 err = device_create_file(dev, &scsi_dh_state_attr);
 262                 /* don't care about err */
 263                 devinfo = device_handler_match(NULL, sdev);
 264                 if (devinfo)
 265                         err = scsi_dh_handler_attach(sdev, devinfo);
 266         } else if (action == BUS_NOTIFY_DEL_DEVICE) {
 267                 device_remove_file(dev, &scsi_dh_state_attr);
 268                 scsi_dh_handler_detach(sdev, NULL);
 269         }
 270         return err;
 271 }
 272
 273 /*
 274  * scsi_dh_notifier_add - Callback for scsi_register_device_handler
 275  */
 276 static int scsi_dh_notifier_add(struct device *dev, void *data)
 277 {
 278         struct scsi_device_handler *scsi_dh = data;
 279         struct scsi_device *sdev;
 280
 281         if (!scsi_is_sdev_device(dev))
 282                 return 0;
 283
 284         if (!get_device(dev))
 285                 return 0;
 286
 287         sdev = to_scsi_device(dev);
 288
 289         if (device_handler_match(scsi_dh, sdev))
 290                 scsi_dh_handler_attach(sdev, scsi_dh);
 291
 292         put_device(dev);
 293
 294         return 0;
 295 }
 296
 297 /*
 298  * scsi_dh_notifier_remove - Callback for scsi_unregister_device_handler
 299  */
 300 static int scsi_dh_notifier_remove(struct device *dev, void *data)
 301 {
 302         struct scsi_device_handler *scsi_dh = data;
 303         struct scsi_device *sdev;
 304
 305         if (!scsi_is_sdev_device(dev))
 306                 return 0;
 307
 308         if (!get_device(dev))
 309                 return 0;
 310
 311         sdev = to_scsi_device(dev);
 312
 313         scsi_dh_handler_detach(sdev, scsi_dh);
 314
 315         put_device(dev);
 316
 317         return 0;
 318 }
 319
 320 /*
 321  * scsi_register_device_handler - register a device handler personality
 322  *      module.
 323  * @scsi_dh - device handler to be registered.
 324  *
 325  * Returns 0 on success, -EBUSY if handler already registered.
 326  */
 327 int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
 328 {
 329
 330         if (get_device_handler(scsi_dh->name))
 331                 return -EBUSY;
 332
 333         spin_lock(&list_lock);
 334         list_add(&scsi_dh->list, &scsi_dh_list);
 335         spin_unlock(&list_lock);
 336
 337         bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh, scsi_dh_notifier_add);
 338         printk(KERN_INFO "%s: device handler registered\n", scsi_dh->name);
 339
 340         return SCSI_DH_OK;
 341 }
 342 EXPORT_SYMBOL_GPL(scsi_register_device_handler);
 343
 344 /*
 345  * scsi_unregister_device_handler - register a device handler personality
 346  *      module.
 347  * @scsi_dh - device handler to be unregistered.
 348  *
 349  * Returns 0 on success, -ENODEV if handler not registered.
 350  */
 351 int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)
 352 {
 353
 354         if (!get_device_handler(scsi_dh->name))
 355                 return -ENODEV;
 356
 357         bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh,
 358                          scsi_dh_notifier_remove);
 359
 360         spin_lock(&list_lock);
 361         list_del(&scsi_dh->list);
 362         spin_unlock(&list_lock);
 363         printk(KERN_INFO "%s: device handler unregistered\n", scsi_dh->name);
 364
 365         return SCSI_DH_OK;
 366 }
 367 EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);
 368
 369 /*
 370  * scsi_dh_activate - activate the path associated with the scsi_device
 371  *      corresponding to the given request queue.
 372  *     Returns immediately without waiting for activation to be completed.
 373  * @q    - Request queue that is associated with the scsi_device to be
 374  *         activated.
 375  * @fn   - Function to be called upon completion of the activation.
 376  *         Function fn is called with data (below) and the error code.
 377  *         Function fn may be called from the same calling context. So,
 378  *         do not hold the lock in the caller which may be needed in fn.
 379  * @data - data passed to the function fn upon completion.
 380  *
 381  */
 382 int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
 383 {
 384         int err = 0;
 385         unsigned long flags;
 386         struct scsi_device *sdev;
 387         struct scsi_device_handler *scsi_dh = NULL;
 388         struct device *dev = NULL;
 389
 390         spin_lock_irqsave(q->queue_lock, flags);
 391         sdev = q->queuedata;
 392         if (!sdev) {
 393                 spin_unlock_irqrestore(q->queue_lock, flags);
 394                 err = SCSI_DH_NOSYS;
 395                 if (fn)
 396                         fn(data, err);
 397                 return err;
 398         }
 399
 400         if (sdev->scsi_dh_data)
 401                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 402         dev = get_device(&sdev->sdev_gendev);
 403         if (!scsi_dh || !dev ||
 404             sdev->sdev_state == SDEV_CANCEL ||
 405             sdev->sdev_state == SDEV_DEL)
 406                 err = SCSI_DH_NOSYS;
 407         if (sdev->sdev_state == SDEV_OFFLINE)
 408                 err = SCSI_DH_DEV_OFFLINED;
 409         spin_unlock_irqrestore(q->queue_lock, flags);
 410
 411         if (err) {
 412                 if (fn)
 413                         fn(data, err);
 414                 goto out;
 415         }
 416
 417         if (scsi_dh->activate)
 418                 err = scsi_dh->activate(sdev, fn, data);
 419 out:
 420         put_device(dev);
 421         return err;
 422 }
 423 EXPORT_SYMBOL_GPL(scsi_dh_activate);
 424
 425 /*
 426  * scsi_dh_set_params - set the parameters for the device as per the
 427  *      string specified in params.
 428  * @q - Request queue that is associated with the scsi_device for
 429  *      which the parameters to be set.
 430  * @params - parameters in the following format
 431  *      "no_of_params\0param1\0param2\0param3\0...\0"
 432  *      for example, string for 2 parameters with value 10 and 21
 433  *      is specified as "2\010\021\0".
 434  */
 435 int scsi_dh_set_params(struct request_queue *q, const char *params)
 436 {
 437         int err = -SCSI_DH_NOSYS;
 438         unsigned long flags;
 439         struct scsi_device *sdev;
 440         struct scsi_device_handler *scsi_dh = NULL;
 441
 442         spin_lock_irqsave(q->queue_lock, flags);
 443         sdev = q->queuedata;
 444         if (sdev && sdev->scsi_dh_data)
 445                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 446         if (scsi_dh && scsi_dh->set_params && get_device(&sdev->sdev_gendev))
 447                 err = 0;
 448         spin_unlock_irqrestore(q->queue_lock, flags);
 449
 450         if (err)
 451                 return err;
 452         err = scsi_dh->set_params(sdev, params);
 453         put_device(&sdev->sdev_gendev);
 454         return err;
 455 }
 456 EXPORT_SYMBOL_GPL(scsi_dh_set_params);
 457
 458 /*
 459  * scsi_dh_handler_exist - Return TRUE(1) if a device handler exists for
 460  *      the given name. FALSE(0) otherwise.
 461  * @name - name of the device handler.
 462  */
 463 int scsi_dh_handler_exist(const char *name)
 464 {
 465         return (get_device_handler(name) != NULL);
 466 }
 467 EXPORT_SYMBOL_GPL(scsi_dh_handler_exist);
 468
 469 /*
 470  * scsi_dh_attach - Attach device handler
 471  * @q - Request queue that is associated with the scsi_device
 472  *      the handler should be attached to
 473  * @name - name of the handler to attach
 474  */
 475 int scsi_dh_attach(struct request_queue *q, const char *name)
 476 {
 477         unsigned long flags;
 478         struct scsi_device *sdev;
 479         struct scsi_device_handler *scsi_dh;
 480         int err = 0;
 481
 482         scsi_dh = get_device_handler(name);
 483         if (!scsi_dh)
 484                 return -EINVAL;
 485
 486         spin_lock_irqsave(q->queue_lock, flags);
 487         sdev = q->queuedata;
 488         if (!sdev || !get_device(&sdev->sdev_gendev))
 489                 err = -ENODEV;
 490         spin_unlock_irqrestore(q->queue_lock, flags);
 491
 492         if (!err) {
 493                 err = scsi_dh_handler_attach(sdev, scsi_dh);
 494                 put_device(&sdev->sdev_gendev);
 495         }
 496         return err;
 497 }
 498 EXPORT_SYMBOL_GPL(scsi_dh_attach);
 499
 500 /*
 501  * scsi_dh_detach - Detach device handler
 502  * @q - Request queue that is associated with the scsi_device
 503  *      the handler should be detached from
 504  *
 505  * This function will detach the device handler only
 506  * if the sdev is not part of the internal list, ie
 507  * if it has been attached manually.
 508  */
 509 void scsi_dh_detach(struct request_queue *q)
 510 {
 511         unsigned long flags;
 512         struct scsi_device *sdev;
 513         struct scsi_device_handler *scsi_dh = NULL;
 514
 515         spin_lock_irqsave(q->queue_lock, flags);
 516         sdev = q->queuedata;
 517         if (!sdev || !get_device(&sdev->sdev_gendev))
 518                 sdev = NULL;
 519         spin_unlock_irqrestore(q->queue_lock, flags);
 520
 521         if (!sdev)
 522                 return;
 523
 524         if (sdev->scsi_dh_data) {
 525                 scsi_dh = sdev->scsi_dh_data->scsi_dh;
 526                 scsi_dh_handler_detach(sdev, scsi_dh);
 527         }
 528         put_device(&sdev->sdev_gendev);
 529 }
 530 EXPORT_SYMBOL_GPL(scsi_dh_detach);
 531
 532 /*
 533  * scsi_dh_attached_handler_name - Get attached device handler's name
 534  * @q - Request queue that is associated with the scsi_device
 535  *      that may have a device handler attached
 536  * @gfp - the GFP mask used in the kmalloc() call when allocating memory
 537  *
 538  * Returns name of attached handler, NULL if no handler is attached.
 539  * Caller must take care to free the returned string.
 540  */
 541 const char *scsi_dh_attached_handler_name(struct request_queue *q, gfp_t gfp)
 542 {
 543         unsigned long flags;
 544         struct scsi_device *sdev;
 545         const char *handler_name = NULL;
 546
 547         spin_lock_irqsave(q->queue_lock, flags);
 548         sdev = q->queuedata;
 549         if (!sdev || !get_device(&sdev->sdev_gendev))
 550                 sdev = NULL;
 551         spin_unlock_irqrestore(q->queue_lock, flags);
 552
 553         if (!sdev)
 554                 return NULL;
 555
 556         if (sdev->scsi_dh_data)
 557                 handler_name = kstrdup(sdev->scsi_dh_data->scsi_dh->name, gfp);
 558
 559         put_device(&sdev->sdev_gendev);
 560         return handler_name;
 561 }
 562 EXPORT_SYMBOL_GPL(scsi_dh_attached_handler_name);
 563
 564 static struct notifier_block scsi_dh_nb = {
 565         .notifier_call = scsi_dh_notifier
 566 };
 567
 568 static int __init scsi_dh_init(void)
 569 {
 570         int r;
 571
 572         r = bus_register_notifier(&scsi_bus_type, &scsi_dh_nb);
 573
 574         if (!r)
 575                 bus_for_each_dev(&scsi_bus_type, NULL, NULL,
 576                                  scsi_dh_sysfs_attr_add);
 577
 578         return r;
 579 }
 580
 581 static void __exit scsi_dh_exit(void)
 582 {
 583         bus_for_each_dev(&scsi_bus_type, NULL, NULL,
 584                          scsi_dh_sysfs_attr_remove);
 585         bus_unregister_notifier(&scsi_bus_type, &scsi_dh_nb);
 586 }
 587
 588 module_init(scsi_dh_init);
 589 module_exit(scsi_dh_exit);
 590
 591 MODULE_DESCRIPTION("SCSI device handler");
 592 MODULE_AUTHOR("Chandra Seetharaman <sekharan@us.ibm.com>");
 593 MODULE_LICENSE("GPL");