fs/sysfs/file.c

   1 /*
   2  * file.c - operations for regular (text) files.
   3  */
   4
   5 #include <linux/module.h>
   6 #include <linux/fsnotify.h>
   7 #include <linux/kobject.h>
   8 #include <linux/namei.h>
   9 #include <linux/poll.h>
  10 #include <linux/list.h>
  11 #include <asm/uaccess.h>
  12 #include <asm/semaphore.h>
  13
  14 #include "sysfs.h"
  15
  16 #define to_sattr(a) container_of(a,struct subsys_attribute, attr)
  17
  18 /*
  19  * Subsystem file operations.
  20  * These operations allow subsystems to have files that can be
  21  * read/written.
  22  */
  23 static ssize_t
  24 subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page)
  25 {
  26         struct kset *kset = to_kset(kobj);
  27         struct subsys_attribute * sattr = to_sattr(attr);
  28         ssize_t ret = -EIO;
  29
  30         if (sattr->show)
  31                 ret = sattr->show(kset, page);
  32         return ret;
  33 }
  34
  35 static ssize_t
  36 subsys_attr_store(struct kobject * kobj, struct attribute * attr,
  37                   const char * page, size_t count)
  38 {
  39         struct kset *kset = to_kset(kobj);
  40         struct subsys_attribute * sattr = to_sattr(attr);
  41         ssize_t ret = -EIO;
  42
  43         if (sattr->store)
  44                 ret = sattr->store(kset, page, count);
  45         return ret;
  46 }
  47
  48 static struct sysfs_ops subsys_sysfs_ops = {
  49         .show   = subsys_attr_show,
  50         .store  = subsys_attr_store,
  51 };
  52
  53 /**
  54  *      add_to_collection - add buffer to a collection
  55  *      @buffer:        buffer to be added
  56  *      @node:          inode of set to add to
  57  */
  58
  59 static inline void
  60 add_to_collection(struct sysfs_buffer *buffer, struct inode *node)
  61 {
  62         struct sysfs_buffer_collection *set = node->i_private;
  63
  64         mutex_lock(&node->i_mutex);
  65         list_add(&buffer->associates, &set->associates);
  66         mutex_unlock(&node->i_mutex);
  67 }
  68
  69 static inline void
  70 remove_from_collection(struct sysfs_buffer *buffer, struct inode *node)
  71 {
  72         mutex_lock(&node->i_mutex);
  73         list_del(&buffer->associates);
  74         mutex_unlock(&node->i_mutex);
  75 }
  76
  77 /**
  78  *      fill_read_buffer - allocate and fill buffer from object.
  79  *      @dentry:        dentry pointer.
  80  *      @buffer:        data buffer for file.
  81  *
  82  *      Allocate @buffer->page, if it hasn't been already, then call the
  83  *      kobject's show() method to fill the buffer with this attribute's
  84  *      data.
  85  *      This is called only once, on the file's first read unless an error
  86  *      is returned.
  87  */
  88 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
  89 {
  90         struct sysfs_dirent * sd = dentry->d_fsdata;
  91         struct attribute * attr = to_attr(dentry);
  92         struct kobject * kobj = to_kobj(dentry->d_parent);
  93         struct sysfs_ops * ops = buffer->ops;
  94         int ret = 0;
  95         ssize_t count;
  96
  97         if (!buffer->page)
  98                 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
  99         if (!buffer->page)
 100                 return -ENOMEM;
 101
 102         buffer->event = atomic_read(&sd->s_event);
 103         count = ops->show(kobj,attr,buffer->page);
 104         BUG_ON(count > (ssize_t)PAGE_SIZE);
 105         if (count >= 0) {
 106                 buffer->needs_read_fill = 0;
 107                 buffer->count = count;
 108         } else {
 109                 ret = count;
 110         }
 111         return ret;
 112 }
 113
 114
 115 /**
 116  *      flush_read_buffer - push buffer to userspace.
 117  *      @buffer:        data buffer for file.
 118  *      @buf:           user-passed buffer.
 119  *      @count:         number of bytes requested.
 120  *      @ppos:          file position.
 121  *
 122  *      Copy the buffer we filled in fill_read_buffer() to userspace.
 123  *      This is done at the reader's leisure, copying and advancing
 124  *      the amount they specify each time.
 125  *      This may be called continuously until the buffer is empty.
 126  */
 127 static int flush_read_buffer(struct sysfs_buffer * buffer, char __user * buf,
 128                              size_t count, loff_t * ppos)
 129 {
 130         int error;
 131
 132         if (*ppos > buffer->count)
 133                 return 0;
 134
 135         if (count > (buffer->count - *ppos))
 136                 count = buffer->count - *ppos;
 137
 138         error = copy_to_user(buf,buffer->page + *ppos,count);
 139         if (!error)
 140                 *ppos += count;
 141         return error ? -EFAULT : count;
 142 }
 143
 144 /**
 145  *      sysfs_read_file - read an attribute.
 146  *      @file:  file pointer.
 147  *      @buf:   buffer to fill.
 148  *      @count: number of bytes to read.
 149  *      @ppos:  starting offset in file.
 150  *
 151  *      Userspace wants to read an attribute file. The attribute descriptor
 152  *      is in the file's ->d_fsdata. The target object is in the directory's
 153  *      ->d_fsdata.
 154  *
 155  *      We call fill_read_buffer() to allocate and fill the buffer from the
 156  *      object's show() method exactly once (if the read is happening from
 157  *      the beginning of the file). That should fill the entire buffer with
 158  *      all the data the object has to offer for that attribute.
 159  *      We then call flush_read_buffer() to copy the buffer to userspace
 160  *      in the increments specified.
 161  */
 162
 163 static ssize_t
 164 sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 165 {
 166         struct sysfs_buffer * buffer = file->private_data;
 167         ssize_t retval = 0;
 168
 169         down(&buffer->sem);
 170         if (buffer->needs_read_fill) {
 171                 if (buffer->orphaned)
 172                         retval = -ENODEV;
 173                 else
 174                         retval = fill_read_buffer(file->f_path.dentry,buffer);
 175                 if (retval)
 176                         goto out;
 177         }
 178         pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
 179                  __FUNCTION__, count, *ppos, buffer->page);
 180         retval = flush_read_buffer(buffer,buf,count,ppos);
 181 out:
 182         up(&buffer->sem);
 183         return retval;
 184 }
 185
 186 /**
 187  *      fill_write_buffer - copy buffer from userspace.
 188  *      @buffer:        data buffer for file.
 189  *      @buf:           data from user.
 190  *      @count:         number of bytes in @userbuf.
 191  *
 192  *      Allocate @buffer->page if it hasn't been already, then
 193  *      copy the user-supplied buffer into it.
 194  */
 195
 196 static int
 197 fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
 198 {
 199         int error;
 200
 201         if (!buffer->page)
 202                 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
 203         if (!buffer->page)
 204                 return -ENOMEM;
 205
 206         if (count >= PAGE_SIZE)
 207                 count = PAGE_SIZE - 1;
 208         error = copy_from_user(buffer->page,buf,count);
 209         buffer->needs_read_fill = 1;
 210         /* if buf is assumed to contain a string, terminate it by \0,
 211            so e.g. sscanf() can scan the string easily */
 212         buffer->page[count] = 0;
 213         return error ? -EFAULT : count;
 214 }
 215
 216
 217 /**
 218  *      flush_write_buffer - push buffer to kobject.
 219  *      @dentry:        dentry to the attribute
 220  *      @buffer:        data buffer for file.
 221  *      @count:         number of bytes
 222  *
 223  *      Get the correct pointers for the kobject and the attribute we're
 224  *      dealing with, then call the store() method for the attribute,
 225  *      passing the buffer that we acquired in fill_write_buffer().
 226  */
 227
 228 static int
 229 flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
 230 {
 231         struct attribute * attr = to_attr(dentry);
 232         struct kobject * kobj = to_kobj(dentry->d_parent);
 233         struct sysfs_ops * ops = buffer->ops;
 234
 235         return ops->store(kobj,attr,buffer->page,count);
 236 }
 237
 238
 239 /**
 240  *      sysfs_write_file - write an attribute.
 241  *      @file:  file pointer
 242  *      @buf:   data to write
 243  *      @count: number of bytes
 244  *      @ppos:  starting offset
 245  *
 246  *      Similar to sysfs_read_file(), though working in the opposite direction.
 247  *      We allocate and fill the data from the user in fill_write_buffer(),
 248  *      then push it to the kobject in flush_write_buffer().
 249  *      There is no easy way for us to know if userspace is only doing a partial
 250  *      write, so we don't support them. We expect the entire buffer to come
 251  *      on the first write.
 252  *      Hint: if you're writing a value, first read the file, modify only the
 253  *      the value you're changing, then write entire buffer back.
 254  */
 255
 256 static ssize_t
 257 sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 258 {
 259         struct sysfs_buffer * buffer = file->private_data;
 260         ssize_t len;
 261
 262         down(&buffer->sem);
 263         if (buffer->orphaned) {
 264                 len = -ENODEV;
 265                 goto out;
 266         }
 267         len = fill_write_buffer(buffer, buf, count);
 268         if (len > 0)
 269                 len = flush_write_buffer(file->f_path.dentry, buffer, len);
 270         if (len > 0)
 271                 *ppos += len;
 272 out:
 273         up(&buffer->sem);
 274         return len;
 275 }
 276
 277 static int sysfs_open_file(struct inode *inode, struct file *file)
 278 {
 279         struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
 280         struct attribute * attr = to_attr(file->f_path.dentry);
 281         struct sysfs_buffer_collection *set;
 282         struct sysfs_buffer * buffer;
 283         struct sysfs_ops * ops = NULL;
 284         int error = 0;
 285
 286         if (!kobj || !attr)
 287                 goto Einval;
 288
 289         /* Grab the module reference for this attribute if we have one */
 290         if (!try_module_get(attr->owner)) {
 291                 error = -ENODEV;
 292                 goto Done;
 293         }
 294
 295         /* if the kobject has no ktype, then we assume that it is a subsystem
 296          * itself, and use ops for it.
 297          */
 298         if (kobj->kset && kobj->kset->ktype)
 299                 ops = kobj->kset->ktype->sysfs_ops;
 300         else if (kobj->ktype)
 301                 ops = kobj->ktype->sysfs_ops;
 302         else
 303                 ops = &subsys_sysfs_ops;
 304
 305         /* No sysfs operations, either from having no subsystem,
 306          * or the subsystem have no operations.
 307          */
 308         if (!ops)
 309                 goto Eaccess;
 310
 311         /* make sure we have a collection to add our buffers to */
 312         mutex_lock(&inode->i_mutex);
 313         if (!(set = inode->i_private)) {
 314                 if (!(set = inode->i_private = kmalloc(sizeof(struct sysfs_buffer_collection), GFP_KERNEL))) {
 315                         error = -ENOMEM;
 316                         goto Done;
 317                 } else {
 318                         INIT_LIST_HEAD(&set->associates);
 319                 }
 320         }
 321         mutex_unlock(&inode->i_mutex);
 322
 323         /* File needs write support.
 324          * The inode's perms must say it's ok,
 325          * and we must have a store method.
 326          */
 327         if (file->f_mode & FMODE_WRITE) {
 328
 329                 if (!(inode->i_mode & S_IWUGO) || !ops->store)
 330                         goto Eaccess;
 331
 332         }
 333
 334         /* File needs read support.
 335          * The inode's perms must say it's ok, and we there
 336          * must be a show method for it.
 337          */
 338         if (file->f_mode & FMODE_READ) {
 339                 if (!(inode->i_mode & S_IRUGO) || !ops->show)
 340                         goto Eaccess;
 341         }
 342
 343         /* No error? Great, allocate a buffer for the file, and store it
 344          * it in file->private_data for easy access.
 345          */
 346         buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
 347         if (buffer) {
 348                 INIT_LIST_HEAD(&buffer->associates);
 349                 init_MUTEX(&buffer->sem);
 350                 buffer->needs_read_fill = 1;
 351                 buffer->ops = ops;
 352                 add_to_collection(buffer, inode);
 353                 file->private_data = buffer;
 354         } else
 355                 error = -ENOMEM;
 356         goto Done;
 357
 358  Einval:
 359         error = -EINVAL;
 360         goto Done;
 361  Eaccess:
 362         error = -EACCES;
 363         module_put(attr->owner);
 364  Done:
 365         if (error)
 366                 kobject_put(kobj);
 367         return error;
 368 }
 369
 370 static int sysfs_release(struct inode * inode, struct file * filp)
 371 {
 372         struct kobject * kobj = to_kobj(filp->f_path.dentry->d_parent);
 373         struct attribute * attr = to_attr(filp->f_path.dentry);
 374         struct module * owner = attr->owner;
 375         struct sysfs_buffer * buffer = filp->private_data;
 376
 377         if (buffer)
 378                 remove_from_collection(buffer, inode);
 379         kobject_put(kobj);
 380         /* After this point, attr should not be accessed. */
 381         module_put(owner);
 382
 383         if (buffer) {
 384                 if (buffer->page)
 385                         free_page((unsigned long)buffer->page);
 386                 kfree(buffer);
 387         }
 388         return 0;
 389 }
 390
 391 /* Sysfs attribute files are pollable.  The idea is that you read
 392  * the content and then you use 'poll' or 'select' to wait for
 393  * the content to change.  When the content changes (assuming the
 394  * manager for the kobject supports notification), poll will
 395  * return POLLERR|POLLPRI, and select will return the fd whether
 396  * it is waiting for read, write, or exceptions.
 397  * Once poll/select indicates that the value has changed, you
 398  * need to close and re-open the file, as simply seeking and reading
 399  * again will not get new data, or reset the state of 'poll'.
 400  * Reminder: this only works for attributes which actively support
 401  * it, and it is not possible to test an attribute from userspace
 402  * to see if it supports poll (Nether 'poll' or 'select' return
 403  * an appropriate error code).  When in doubt, set a suitable timeout value.
 404  */
 405 static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
 406 {
 407         struct sysfs_buffer * buffer = filp->private_data;
 408         struct kobject * kobj = to_kobj(filp->f_path.dentry->d_parent);
 409         struct sysfs_dirent * sd = filp->f_path.dentry->d_fsdata;
 410         int res = 0;
 411
 412         poll_wait(filp, &kobj->poll, wait);
 413
 414         if (buffer->event != atomic_read(&sd->s_event)) {
 415                 res = POLLERR|POLLPRI;
 416                 buffer->needs_read_fill = 1;
 417         }
 418
 419         return res;
 420 }
 421
 422
 423 static struct dentry *step_down(struct dentry *dir, const char * name)
 424 {
 425         struct dentry * de;
 426
 427         if (dir == NULL || dir->d_inode == NULL)
 428                 return NULL;
 429
 430         mutex_lock(&dir->d_inode->i_mutex);
 431         de = lookup_one_len(name, dir, strlen(name));
 432         mutex_unlock(&dir->d_inode->i_mutex);
 433         dput(dir);
 434         if (IS_ERR(de))
 435                 return NULL;
 436         if (de->d_inode == NULL) {
 437                 dput(de);
 438                 return NULL;
 439         }
 440         return de;
 441 }
 442
 443 void sysfs_notify(struct kobject * k, char *dir, char *attr)
 444 {
 445         struct dentry *de = k->dentry;
 446         if (de)
 447                 dget(de);
 448         if (de && dir)
 449                 de = step_down(de, dir);
 450         if (de && attr)
 451                 de = step_down(de, attr);
 452         if (de) {
 453                 struct sysfs_dirent * sd = de->d_fsdata;
 454                 if (sd)
 455                         atomic_inc(&sd->s_event);
 456                 wake_up_interruptible(&k->poll);
 457                 dput(de);
 458         }
 459 }
 460 EXPORT_SYMBOL_GPL(sysfs_notify);
 461
 462 const struct file_operations sysfs_file_operations = {
 463         .read           = sysfs_read_file,
 464         .write          = sysfs_write_file,
 465         .llseek         = generic_file_llseek,
 466         .open           = sysfs_open_file,
 467         .release        = sysfs_release,
 468         .poll           = sysfs_poll,
 469 };
 470
 471
 472 int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type)
 473 {
 474         struct sysfs_dirent * parent_sd = dir->d_fsdata;
 475         umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
 476         int error = -EEXIST;
 477
 478         mutex_lock(&dir->d_inode->i_mutex);
 479         if (!sysfs_dirent_exist(parent_sd, attr->name))
 480                 error = sysfs_make_dirent(parent_sd, NULL, (void *)attr,
 481                                           mode, type);
 482         mutex_unlock(&dir->d_inode->i_mutex);
 483
 484         return error;
 485 }
 486
 487
 488 /**
 489  *      sysfs_create_file - create an attribute file for an object.
 490  *      @kobj:  object we're creating for.
 491  *      @attr:  atrribute descriptor.
 492  */
 493
 494 int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 495 {
 496         BUG_ON(!kobj || !kobj->dentry || !attr);
 497
 498         return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR);
 499
 500 }
 501
 502
 503 /**
 504  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 505  * @kobj: object we're acting for.
 506  * @attr: attribute descriptor.
 507  * @group: group name.
 508  */
 509 int sysfs_add_file_to_group(struct kobject *kobj,
 510                 const struct attribute *attr, const char *group)
 511 {
 512         struct dentry *dir;
 513         int error;
 514
 515         dir = lookup_one_len(group, kobj->dentry, strlen(group));
 516         if (IS_ERR(dir))
 517                 error = PTR_ERR(dir);
 518         else {
 519                 error = sysfs_add_file(dir, attr, SYSFS_KOBJ_ATTR);
 520                 dput(dir);
 521         }
 522         return error;
 523 }
 524 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 525
 526
 527 /**
 528  * sysfs_update_file - update the modified timestamp on an object attribute.
 529  * @kobj: object we're acting for.
 530  * @attr: attribute descriptor.
 531  */
 532 int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
 533 {
 534         struct dentry * dir = kobj->dentry;
 535         struct dentry * victim;
 536         int res = -ENOENT;
 537
 538         mutex_lock(&dir->d_inode->i_mutex);
 539         victim = lookup_one_len(attr->name, dir, strlen(attr->name));
 540         if (!IS_ERR(victim)) {
 541                 /* make sure dentry is really there */
 542                 if (victim->d_inode &&
 543                     (victim->d_parent->d_inode == dir->d_inode)) {
 544                         victim->d_inode->i_mtime = CURRENT_TIME;
 545                         fsnotify_modify(victim);
 546                         res = 0;
 547                 } else
 548                         d_drop(victim);
 549
 550                 /**
 551                  * Drop the reference acquired from lookup_one_len() above.
 552                  */
 553                 dput(victim);
 554         }
 555         mutex_unlock(&dir->d_inode->i_mutex);
 556
 557         return res;
 558 }
 559
 560
 561 /**
 562  * sysfs_chmod_file - update the modified mode value on an object attribute.
 563  * @kobj: object we're acting for.
 564  * @attr: attribute descriptor.
 565  * @mode: file permissions.
 566  *
 567  */
 568 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 569 {
 570         struct dentry *dir = kobj->dentry;
 571         struct dentry *victim;
 572         struct inode * inode;
 573         struct iattr newattrs;
 574         int res = -ENOENT;
 575
 576         mutex_lock(&dir->d_inode->i_mutex);
 577         victim = lookup_one_len(attr->name, dir, strlen(attr->name));
 578         if (!IS_ERR(victim)) {
 579                 if (victim->d_inode &&
 580                     (victim->d_parent->d_inode == dir->d_inode)) {
 581                         inode = victim->d_inode;
 582                         mutex_lock(&inode->i_mutex);
 583                         newattrs.ia_mode = (mode & S_IALLUGO) |
 584                                                 (inode->i_mode & ~S_IALLUGO);
 585                         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 586                         res = notify_change(victim, &newattrs);
 587                         mutex_unlock(&inode->i_mutex);
 588                 }
 589                 dput(victim);
 590         }
 591         mutex_unlock(&dir->d_inode->i_mutex);
 592
 593         return res;
 594 }
 595 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 596
 597
 598 /**
 599  *      sysfs_remove_file - remove an object attribute.
 600  *      @kobj:  object we're acting for.
 601  *      @attr:  attribute descriptor.
 602  *
 603  *      Hash the attribute name and kill the victim.
 604  */
 605
 606 void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
 607 {
 608         sysfs_hash_and_remove(kobj->dentry, attr->name);
 609 }
 610
 611
 612 /**
 613  * sysfs_remove_file_from_group - remove an attribute file from a group.
 614  * @kobj: object we're acting for.
 615  * @attr: attribute descriptor.
 616  * @group: group name.
 617  */
 618 void sysfs_remove_file_from_group(struct kobject *kobj,
 619                 const struct attribute *attr, const char *group)
 620 {
 621         struct dentry *dir;
 622
 623         dir = lookup_one_len(group, kobj->dentry, strlen(group));
 624         if (!IS_ERR(dir)) {
 625                 sysfs_hash_and_remove(dir, attr->name);
 626                 dput(dir);
 627         }
 628 }
 629 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 630
 631 struct sysfs_schedule_callback_struct {
 632         struct kobject          *kobj;
 633         void                    (*func)(void *);
 634         void                    *data;
 635         struct module           *owner;
 636         struct work_struct      work;
 637 };
 638
 639 static void sysfs_schedule_callback_work(struct work_struct *work)
 640 {
 641         struct sysfs_schedule_callback_struct *ss = container_of(work,
 642                         struct sysfs_schedule_callback_struct, work);
 643
 644         (ss->func)(ss->data);
 645         kobject_put(ss->kobj);
 646         module_put(ss->owner);
 647         kfree(ss);
 648 }
 649
 650 /**
 651  * sysfs_schedule_callback - helper to schedule a callback for a kobject
 652  * @kobj: object we're acting for.
 653  * @func: callback function to invoke later.
 654  * @data: argument to pass to @func.
 655  * @owner: module owning the callback code
 656  *
 657  * sysfs attribute methods must not unregister themselves or their parent
 658  * kobject (which would amount to the same thing).  Attempts to do so will
 659  * deadlock, since unregistration is mutually exclusive with driver
 660  * callbacks.
 661  *
 662  * Instead methods can call this routine, which will attempt to allocate
 663  * and schedule a workqueue request to call back @func with @data as its
 664  * argument in the workqueue's process context.  @kobj will be pinned
 665  * until @func returns.
 666  *
 667  * Returns 0 if the request was submitted, -ENOMEM if storage could not
 668  * be allocated, -ENODEV if a reference to @owner isn't available.
 669  */
 670 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 671                 void *data, struct module *owner)
 672 {
 673         struct sysfs_schedule_callback_struct *ss;
 674
 675         if (!try_module_get(owner))
 676                 return -ENODEV;
 677         ss = kmalloc(sizeof(*ss), GFP_KERNEL);
 678         if (!ss) {
 679                 module_put(owner);
 680                 return -ENOMEM;
 681         }
 682         kobject_get(kobj);
 683         ss->kobj = kobj;
 684         ss->func = func;
 685         ss->data = data;
 686         ss->owner = owner;
 687         INIT_WORK(&ss->work, sysfs_schedule_callback_work);
 688         schedule_work(&ss->work);
 689         return 0;
 690 }
 691 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
 692
 693
 694 EXPORT_SYMBOL_GPL(sysfs_create_file);
 695 EXPORT_SYMBOL_GPL(sysfs_remove_file);
 696 EXPORT_SYMBOL_GPL(sysfs_update_file);