drivers/nvdimm/dimm_devs.c

   1 /*
   2  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  */
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14 #include <linux/vmalloc.h>
  15 #include <linux/device.h>
  16 #include <linux/ndctl.h>
  17 #include <linux/slab.h>
  18 #include <linux/io.h>
  19 #include <linux/fs.h>
  20 #include <linux/mm.h>
  21 #include "nd-core.h"
  22 #include "label.h"
  23 #include "nd.h"
  24
  25 static DEFINE_IDA(dimm_ida);
  26
  27 /*
  28  * Retrieve bus and dimm handle and return if this bus supports
  29  * get_config_data commands
  30  */
  31 int nvdimm_check_config_data(struct device *dev)
  32 {
  33         struct nvdimm *nvdimm = to_nvdimm(dev);
  34
  35         if (!nvdimm->cmd_mask ||
  36             !test_bit(ND_CMD_GET_CONFIG_DATA, &nvdimm->cmd_mask)) {
  37                 if (test_bit(NDD_ALIASING, &nvdimm->flags))
  38                         return -ENXIO;
  39                 else
  40                         return -ENOTTY;
  41         }
  42
  43         return 0;
  44 }
  45
  46 static int validate_dimm(struct nvdimm_drvdata *ndd)
  47 {
  48         int rc;
  49
  50         if (!ndd)
  51                 return -EINVAL;
  52
  53         rc = nvdimm_check_config_data(ndd->dev);
  54         if (rc)
  55                 dev_dbg(ndd->dev, "%pf: %s error: %d\n",
  56                                 __builtin_return_address(0), __func__, rc);
  57         return rc;
  58 }
  59
  60 /**
  61  * nvdimm_init_nsarea - determine the geometry of a dimm's namespace area
  62  * @nvdimm: dimm to initialize
  63  */
  64 int nvdimm_init_nsarea(struct nvdimm_drvdata *ndd)
  65 {
  66         struct nd_cmd_get_config_size *cmd = &ndd->nsarea;
  67         struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
  68         struct nvdimm_bus_descriptor *nd_desc;
  69         int rc = validate_dimm(ndd);
  70         int cmd_rc = 0;
  71
  72         if (rc)
  73                 return rc;
  74
  75         if (cmd->config_size)
  76                 return 0; /* already valid */
  77
  78         memset(cmd, 0, sizeof(*cmd));
  79         nd_desc = nvdimm_bus->nd_desc;
  80         rc = nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
  81                         ND_CMD_GET_CONFIG_SIZE, cmd, sizeof(*cmd), &cmd_rc);
  82         if (rc < 0)
  83                 return rc;
  84         return cmd_rc;
  85 }
  86
  87 int nvdimm_init_config_data(struct nvdimm_drvdata *ndd)
  88 {
  89         struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
  90         struct nd_cmd_get_config_data_hdr *cmd;
  91         struct nvdimm_bus_descriptor *nd_desc;
  92         int rc = validate_dimm(ndd);
  93         u32 max_cmd_size, config_size;
  94         size_t offset;
  95
  96         if (rc)
  97                 return rc;
  98
  99         if (ndd->data)
 100                 return 0;
 101
 102         if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0
 103                         || ndd->nsarea.config_size < ND_LABEL_MIN_SIZE) {
 104                 dev_dbg(ndd->dev, "failed to init config data area: (%d:%d)\n",
 105                                 ndd->nsarea.max_xfer, ndd->nsarea.config_size);
 106                 return -ENXIO;
 107         }
 108
 109         ndd->data = kvmalloc(ndd->nsarea.config_size, GFP_KERNEL);
 110         if (!ndd->data)
 111                 return -ENOMEM;
 112
 113         max_cmd_size = min_t(u32, PAGE_SIZE, ndd->nsarea.max_xfer);
 114         cmd = kzalloc(max_cmd_size + sizeof(*cmd), GFP_KERNEL);
 115         if (!cmd)
 116                 return -ENOMEM;
 117
 118         nd_desc = nvdimm_bus->nd_desc;
 119         for (config_size = ndd->nsarea.config_size, offset = 0;
 120                         config_size; config_size -= cmd->in_length,
 121                         offset += cmd->in_length) {
 122                 cmd->in_length = min(config_size, max_cmd_size);
 123                 cmd->in_offset = offset;
 124                 rc = nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
 125                                 ND_CMD_GET_CONFIG_DATA, cmd,
 126                                 cmd->in_length + sizeof(*cmd), NULL);
 127                 if (rc || cmd->status) {
 128                         rc = -ENXIO;
 129                         break;
 130                 }
 131                 memcpy(ndd->data + offset, cmd->out_buf, cmd->in_length);
 132         }
 133         dev_dbg(ndd->dev, "%s: len: %zu rc: %d\n", __func__, offset, rc);
 134         kfree(cmd);
 135
 136         return rc;
 137 }
 138
 139 int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
 140                 void *buf, size_t len)
 141 {
 142         int rc = validate_dimm(ndd);
 143         size_t max_cmd_size, buf_offset;
 144         struct nd_cmd_set_config_hdr *cmd;
 145         struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
 146         struct nvdimm_bus_descriptor *nd_desc = nvdimm_bus->nd_desc;
 147
 148         if (rc)
 149                 return rc;
 150
 151         if (!ndd->data)
 152                 return -ENXIO;
 153
 154         if (offset + len > ndd->nsarea.config_size)
 155                 return -ENXIO;
 156
 157         max_cmd_size = min_t(u32, PAGE_SIZE, len);
 158         max_cmd_size = min_t(u32, max_cmd_size, ndd->nsarea.max_xfer);
 159         cmd = kzalloc(max_cmd_size + sizeof(*cmd) + sizeof(u32), GFP_KERNEL);
 160         if (!cmd)
 161                 return -ENOMEM;
 162
 163         for (buf_offset = 0; len; len -= cmd->in_length,
 164                         buf_offset += cmd->in_length) {
 165                 size_t cmd_size;
 166                 u32 *status;
 167
 168                 cmd->in_offset = offset + buf_offset;
 169                 cmd->in_length = min(max_cmd_size, len);
 170                 memcpy(cmd->in_buf, buf + buf_offset, cmd->in_length);
 171
 172                 /* status is output in the last 4-bytes of the command buffer */
 173                 cmd_size = sizeof(*cmd) + cmd->in_length + sizeof(u32);
 174                 status = ((void *) cmd) + cmd_size - sizeof(u32);
 175
 176                 rc = nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
 177                                 ND_CMD_SET_CONFIG_DATA, cmd, cmd_size, NULL);
 178                 if (rc || *status) {
 179                         rc = rc ? rc : -ENXIO;
 180                         break;
 181                 }
 182         }
 183         kfree(cmd);
 184
 185         return rc;
 186 }
 187
 188 void nvdimm_set_aliasing(struct device *dev)
 189 {
 190         struct nvdimm *nvdimm = to_nvdimm(dev);
 191
 192         set_bit(NDD_ALIASING, &nvdimm->flags);
 193 }
 194
 195 void nvdimm_set_locked(struct device *dev)
 196 {
 197         struct nvdimm *nvdimm = to_nvdimm(dev);
 198
 199         set_bit(NDD_LOCKED, &nvdimm->flags);
 200 }
 201
 202 static void nvdimm_release(struct device *dev)
 203 {
 204         struct nvdimm *nvdimm = to_nvdimm(dev);
 205
 206         ida_simple_remove(&dimm_ida, nvdimm->id);
 207         kfree(nvdimm);
 208 }
 209
 210 static struct device_type nvdimm_device_type = {
 211         .name = "nvdimm",
 212         .release = nvdimm_release,
 213 };
 214
 215 bool is_nvdimm(struct device *dev)
 216 {
 217         return dev->type == &nvdimm_device_type;
 218 }
 219
 220 struct nvdimm *to_nvdimm(struct device *dev)
 221 {
 222         struct nvdimm *nvdimm = container_of(dev, struct nvdimm, dev);
 223
 224         WARN_ON(!is_nvdimm(dev));
 225         return nvdimm;
 226 }
 227 EXPORT_SYMBOL_GPL(to_nvdimm);
 228
 229 struct nvdimm *nd_blk_region_to_dimm(struct nd_blk_region *ndbr)
 230 {
 231         struct nd_region *nd_region = &ndbr->nd_region;
 232         struct nd_mapping *nd_mapping = &nd_region->mapping[0];
 233
 234         return nd_mapping->nvdimm;
 235 }
 236 EXPORT_SYMBOL_GPL(nd_blk_region_to_dimm);
 237
 238 struct nvdimm_drvdata *to_ndd(struct nd_mapping *nd_mapping)
 239 {
 240         struct nvdimm *nvdimm = nd_mapping->nvdimm;
 241
 242         WARN_ON_ONCE(!is_nvdimm_bus_locked(&nvdimm->dev));
 243
 244         return dev_get_drvdata(&nvdimm->dev);
 245 }
 246 EXPORT_SYMBOL(to_ndd);
 247
 248 void nvdimm_drvdata_release(struct kref *kref)
 249 {
 250         struct nvdimm_drvdata *ndd = container_of(kref, typeof(*ndd), kref);
 251         struct device *dev = ndd->dev;
 252         struct resource *res, *_r;
 253
 254         dev_dbg(dev, "%s\n", __func__);
 255
 256         nvdimm_bus_lock(dev);
 257         for_each_dpa_resource_safe(ndd, res, _r)
 258                 nvdimm_free_dpa(ndd, res);
 259         nvdimm_bus_unlock(dev);
 260
 261         kvfree(ndd->data);
 262         kfree(ndd);
 263         put_device(dev);
 264 }
 265
 266 void get_ndd(struct nvdimm_drvdata *ndd)
 267 {
 268         kref_get(&ndd->kref);
 269 }
 270
 271 void put_ndd(struct nvdimm_drvdata *ndd)
 272 {
 273         if (ndd)
 274                 kref_put(&ndd->kref, nvdimm_drvdata_release);
 275 }
 276
 277 const char *nvdimm_name(struct nvdimm *nvdimm)
 278 {
 279         return dev_name(&nvdimm->dev);
 280 }
 281 EXPORT_SYMBOL_GPL(nvdimm_name);
 282
 283 struct kobject *nvdimm_kobj(struct nvdimm *nvdimm)
 284 {
 285         return &nvdimm->dev.kobj;
 286 }
 287 EXPORT_SYMBOL_GPL(nvdimm_kobj);
 288
 289 unsigned long nvdimm_cmd_mask(struct nvdimm *nvdimm)
 290 {
 291         return nvdimm->cmd_mask;
 292 }
 293 EXPORT_SYMBOL_GPL(nvdimm_cmd_mask);
 294
 295 void *nvdimm_provider_data(struct nvdimm *nvdimm)
 296 {
 297         if (nvdimm)
 298                 return nvdimm->provider_data;
 299         return NULL;
 300 }
 301 EXPORT_SYMBOL_GPL(nvdimm_provider_data);
 302
 303 static ssize_t commands_show(struct device *dev,
 304                 struct device_attribute *attr, char *buf)
 305 {
 306         struct nvdimm *nvdimm = to_nvdimm(dev);
 307         int cmd, len = 0;
 308
 309         if (!nvdimm->cmd_mask)
 310                 return sprintf(buf, "\n");
 311
 312         for_each_set_bit(cmd, &nvdimm->cmd_mask, BITS_PER_LONG)
 313                 len += sprintf(buf + len, "%s ", nvdimm_cmd_name(cmd));
 314         len += sprintf(buf + len, "\n");
 315         return len;
 316 }
 317 static DEVICE_ATTR_RO(commands);
 318
 319 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 320                 char *buf)
 321 {
 322         struct nvdimm *nvdimm = to_nvdimm(dev);
 323
 324         /*
 325          * The state may be in the process of changing, userspace should
 326          * quiesce probing if it wants a static answer
 327          */
 328         nvdimm_bus_lock(dev);
 329         nvdimm_bus_unlock(dev);
 330         return sprintf(buf, "%s\n", atomic_read(&nvdimm->busy)
 331                         ? "active" : "idle");
 332 }
 333 static DEVICE_ATTR_RO(state);
 334
 335 static ssize_t available_slots_show(struct device *dev,
 336                 struct device_attribute *attr, char *buf)
 337 {
 338         struct nvdimm_drvdata *ndd = dev_get_drvdata(dev);
 339         ssize_t rc;
 340         u32 nfree;
 341
 342         if (!ndd)
 343                 return -ENXIO;
 344
 345         nvdimm_bus_lock(dev);
 346         nfree = nd_label_nfree(ndd);
 347         if (nfree - 1 > nfree) {
 348                 dev_WARN_ONCE(dev, 1, "we ate our last label?\n");
 349                 nfree = 0;
 350         } else
 351                 nfree--;
 352         rc = sprintf(buf, "%d\n", nfree);
 353         nvdimm_bus_unlock(dev);
 354         return rc;
 355 }
 356 static DEVICE_ATTR_RO(available_slots);
 357
 358 static struct attribute *nvdimm_attributes[] = {
 359         &dev_attr_state.attr,
 360         &dev_attr_commands.attr,
 361         &dev_attr_available_slots.attr,
 362         NULL,
 363 };
 364
 365 struct attribute_group nvdimm_attribute_group = {
 366         .attrs = nvdimm_attributes,
 367 };
 368 EXPORT_SYMBOL_GPL(nvdimm_attribute_group);
 369
 370 struct nvdimm *nvdimm_create(struct nvdimm_bus *nvdimm_bus, void *provider_data,
 371                 const struct attribute_group **groups, unsigned long flags,
 372                 unsigned long cmd_mask, int num_flush,
 373                 struct resource *flush_wpq)
 374 {
 375         struct nvdimm *nvdimm = kzalloc(sizeof(*nvdimm), GFP_KERNEL);
 376         struct device *dev;
 377
 378         if (!nvdimm)
 379                 return NULL;
 380
 381         nvdimm->id = ida_simple_get(&dimm_ida, 0, 0, GFP_KERNEL);
 382         if (nvdimm->id < 0) {
 383                 kfree(nvdimm);
 384                 return NULL;
 385         }
 386         nvdimm->provider_data = provider_data;
 387         nvdimm->flags = flags;
 388         nvdimm->cmd_mask = cmd_mask;
 389         nvdimm->num_flush = num_flush;
 390         nvdimm->flush_wpq = flush_wpq;
 391         atomic_set(&nvdimm->busy, 0);
 392         dev = &nvdimm->dev;
 393         dev_set_name(dev, "nmem%d", nvdimm->id);
 394         dev->parent = &nvdimm_bus->dev;
 395         dev->type = &nvdimm_device_type;
 396         dev->devt = MKDEV(nvdimm_major, nvdimm->id);
 397         dev->groups = groups;
 398         nd_device_register(dev);
 399
 400         return nvdimm;
 401 }
 402 EXPORT_SYMBOL_GPL(nvdimm_create);
 403
 404 int alias_dpa_busy(struct device *dev, void *data)
 405 {
 406         resource_size_t map_end, blk_start, new;
 407         struct blk_alloc_info *info = data;
 408         struct nd_mapping *nd_mapping;
 409         struct nd_region *nd_region;
 410         struct nvdimm_drvdata *ndd;
 411         struct resource *res;
 412         int i;
 413
 414         if (!is_nd_pmem(dev))
 415                 return 0;
 416
 417         nd_region = to_nd_region(dev);
 418         for (i = 0; i < nd_region->ndr_mappings; i++) {
 419                 nd_mapping  = &nd_region->mapping[i];
 420                 if (nd_mapping->nvdimm == info->nd_mapping->nvdimm)
 421                         break;
 422         }
 423
 424         if (i >= nd_region->ndr_mappings)
 425                 return 0;
 426
 427         ndd = to_ndd(nd_mapping);
 428         map_end = nd_mapping->start + nd_mapping->size - 1;
 429         blk_start = nd_mapping->start;
 430
 431         /*
 432          * In the allocation case ->res is set to free space that we are
 433          * looking to validate against PMEM aliasing collision rules
 434          * (i.e. BLK is allocated after all aliased PMEM).
 435          */
 436         if (info->res) {
 437                 if (info->res->start >= nd_mapping->start
 438                                 && info->res->start < map_end)
 439                         /* pass */;
 440                 else
 441                         return 0;
 442         }
 443
 444  retry:
 445         /*
 446          * Find the free dpa from the end of the last pmem allocation to
 447          * the end of the interleave-set mapping.
 448          */
 449         for_each_dpa_resource(ndd, res) {
 450                 if (strncmp(res->name, "pmem", 4) != 0)
 451                         continue;
 452                 if ((res->start >= blk_start && res->start < map_end)
 453                                 || (res->end >= blk_start
 454                                         && res->end <= map_end)) {
 455                         new = max(blk_start, min(map_end + 1, res->end + 1));
 456                         if (new != blk_start) {
 457                                 blk_start = new;
 458                                 goto retry;
 459                         }
 460                 }
 461         }
 462
 463         /* update the free space range with the probed blk_start */
 464         if (info->res && blk_start > info->res->start) {
 465                 info->res->start = max(info->res->start, blk_start);
 466                 if (info->res->start > info->res->end)
 467                         info->res->end = info->res->start - 1;
 468                 return 1;
 469         }
 470
 471         info->available -= blk_start - nd_mapping->start;
 472
 473         return 0;
 474 }
 475
 476 /**
 477  * nd_blk_available_dpa - account the unused dpa of BLK region
 478  * @nd_mapping: container of dpa-resource-root + labels
 479  *
 480  * Unlike PMEM, BLK namespaces can occupy discontiguous DPA ranges, but
 481  * we arrange for them to never start at an lower dpa than the last
 482  * PMEM allocation in an aliased region.
 483  */
 484 resource_size_t nd_blk_available_dpa(struct nd_region *nd_region)
 485 {
 486         struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(&nd_region->dev);
 487         struct nd_mapping *nd_mapping = &nd_region->mapping[0];
 488         struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
 489         struct blk_alloc_info info = {
 490                 .nd_mapping = nd_mapping,
 491                 .available = nd_mapping->size,
 492                 .res = NULL,
 493         };
 494         struct resource *res;
 495
 496         if (!ndd)
 497                 return 0;
 498
 499         device_for_each_child(&nvdimm_bus->dev, &info, alias_dpa_busy);
 500
 501         /* now account for busy blk allocations in unaliased dpa */
 502         for_each_dpa_resource(ndd, res) {
 503                 if (strncmp(res->name, "blk", 3) != 0)
 504                         continue;
 505                 info.available -= resource_size(res);
 506         }
 507
 508         return info.available;
 509 }
 510
 511 /**
 512  * nd_pmem_available_dpa - for the given dimm+region account unallocated dpa
 513  * @nd_mapping: container of dpa-resource-root + labels
 514  * @nd_region: constrain available space check to this reference region
 515  * @overlap: calculate available space assuming this level of overlap
 516  *
 517  * Validate that a PMEM label, if present, aligns with the start of an
 518  * interleave set and truncate the available size at the lowest BLK
 519  * overlap point.
 520  *
 521  * The expectation is that this routine is called multiple times as it
 522  * probes for the largest BLK encroachment for any single member DIMM of
 523  * the interleave set.  Once that value is determined the PMEM-limit for
 524  * the set can be established.
 525  */
 526 resource_size_t nd_pmem_available_dpa(struct nd_region *nd_region,
 527                 struct nd_mapping *nd_mapping, resource_size_t *overlap)
 528 {
 529         resource_size_t map_start, map_end, busy = 0, available, blk_start;
 530         struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
 531         struct resource *res;
 532         const char *reason;
 533
 534         if (!ndd)
 535                 return 0;
 536
 537         map_start = nd_mapping->start;
 538         map_end = map_start + nd_mapping->size - 1;
 539         blk_start = max(map_start, map_end + 1 - *overlap);
 540         for_each_dpa_resource(ndd, res) {
 541                 if (res->start >= map_start && res->start < map_end) {
 542                         if (strncmp(res->name, "blk", 3) == 0)
 543                                 blk_start = min(blk_start,
 544                                                 max(map_start, res->start));
 545                         else if (res->end > map_end) {
 546                                 reason = "misaligned to iset";
 547                                 goto err;
 548                         } else
 549                                 busy += resource_size(res);
 550                 } else if (res->end >= map_start && res->end <= map_end) {
 551                         if (strncmp(res->name, "blk", 3) == 0) {
 552                                 /*
 553                                  * If a BLK allocation overlaps the start of
 554                                  * PMEM the entire interleave set may now only
 555                                  * be used for BLK.
 556                                  */
 557                                 blk_start = map_start;
 558                         } else
 559                                 busy += resource_size(res);
 560                 } else if (map_start > res->start && map_start < res->end) {
 561                         /* total eclipse of the mapping */
 562                         busy += nd_mapping->size;
 563                         blk_start = map_start;
 564                 }
 565         }
 566
 567         *overlap = map_end + 1 - blk_start;
 568         available = blk_start - map_start;
 569         if (busy < available)
 570                 return available - busy;
 571         return 0;
 572
 573  err:
 574         nd_dbg_dpa(nd_region, ndd, res, "%s\n", reason);
 575         return 0;
 576 }
 577
 578 void nvdimm_free_dpa(struct nvdimm_drvdata *ndd, struct resource *res)
 579 {
 580         WARN_ON_ONCE(!is_nvdimm_bus_locked(ndd->dev));
 581         kfree(res->name);
 582         __release_region(&ndd->dpa, res->start, resource_size(res));
 583 }
 584
 585 struct resource *nvdimm_allocate_dpa(struct nvdimm_drvdata *ndd,
 586                 struct nd_label_id *label_id, resource_size_t start,
 587                 resource_size_t n)
 588 {
 589         char *name = kmemdup(label_id, sizeof(*label_id), GFP_KERNEL);
 590         struct resource *res;
 591
 592         if (!name)
 593                 return NULL;
 594
 595         WARN_ON_ONCE(!is_nvdimm_bus_locked(ndd->dev));
 596         res = __request_region(&ndd->dpa, start, n, name, 0);
 597         if (!res)
 598                 kfree(name);
 599         return res;
 600 }
 601
 602 /**
 603  * nvdimm_allocated_dpa - sum up the dpa currently allocated to this label_id
 604  * @nvdimm: container of dpa-resource-root + labels
 605  * @label_id: dpa resource name of the form {pmem|blk}-<human readable uuid>
 606  */
 607 resource_size_t nvdimm_allocated_dpa(struct nvdimm_drvdata *ndd,
 608                 struct nd_label_id *label_id)
 609 {
 610         resource_size_t allocated = 0;
 611         struct resource *res;
 612
 613         for_each_dpa_resource(ndd, res)
 614                 if (strcmp(res->name, label_id->id) == 0)
 615                         allocated += resource_size(res);
 616
 617         return allocated;
 618 }
 619
 620 static int count_dimms(struct device *dev, void *c)
 621 {
 622         int *count = c;
 623
 624         if (is_nvdimm(dev))
 625                 (*count)++;
 626         return 0;
 627 }
 628
 629 int nvdimm_bus_check_dimm_count(struct nvdimm_bus *nvdimm_bus, int dimm_count)
 630 {
 631         int count = 0;
 632         /* Flush any possible dimm registration failures */
 633         nd_synchronize();
 634
 635         device_for_each_child(&nvdimm_bus->dev, &count, count_dimms);
 636         dev_dbg(&nvdimm_bus->dev, "%s: count: %d\n", __func__, count);
 637         if (count != dimm_count)
 638                 return -ENXIO;
 639         return 0;
 640 }
 641 EXPORT_SYMBOL_GPL(nvdimm_bus_check_dimm_count);
 642
 643 void __exit nvdimm_devs_exit(void)
 644 {
 645         ida_destroy(&dimm_ida);
 646 }