fs/sysfs/file.c

   1 /*
   2  * fs/sysfs/file.c - sysfs regular (text) file implementation
   3  *
   4  * Copyright (c) 2001-3 Patrick Mochel
   5  * Copyright (c) 2007 SUSE Linux Products GmbH
   6  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7  *
   8  * This file is released under the GPLv2.
   9  *
  10  * Please see Documentation/filesystems/sysfs.txt for more information.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/kobject.h>
  15 #include <linux/namei.h>
  16 #include <linux/poll.h>
  17 #include <linux/list.h>
  18 #include <linux/mutex.h>
  19 #include <asm/uaccess.h>
  20
  21 #include "sysfs.h"
  22
  23 /*
  24  * There's one sysfs_buffer for each open file and one
  25  * sysfs_open_dirent for each sysfs_dirent with one or more open
  26  * files.
  27  *
  28  * filp->private_data points to sysfs_buffer and
  29  * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open
  30  * is protected by sysfs_open_dirent_lock.
  31  */
  32 static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
  33
  34 struct sysfs_open_dirent {
  35         atomic_t                refcnt;
  36         atomic_t                event;
  37         wait_queue_head_t       poll;
  38         struct list_head        buffers; /* goes through sysfs_buffer.list */
  39 };
  40
  41 struct sysfs_buffer {
  42         size_t                  count;
  43         loff_t                  pos;
  44         char                    * page;
  45         struct sysfs_ops        * ops;
  46         struct mutex            mutex;
  47         int                     needs_read_fill;
  48         int                     event;
  49         struct list_head        list;
  50 };
  51
  52 /**
  53  *      fill_read_buffer - allocate and fill buffer from object.
  54  *      @dentry:        dentry pointer.
  55  *      @buffer:        data buffer for file.
  56  *
  57  *      Allocate @buffer->page, if it hasn't been already, then call the
  58  *      kobject's show() method to fill the buffer with this attribute's
  59  *      data.
  60  *      This is called only once, on the file's first read unless an error
  61  *      is returned.
  62  */
  63 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
  64 {
  65         struct sysfs_dirent *attr_sd = dentry->d_fsdata;
  66         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
  67         struct sysfs_ops * ops = buffer->ops;
  68         int ret = 0;
  69         ssize_t count;
  70
  71         if (!buffer->page)
  72                 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
  73         if (!buffer->page)
  74                 return -ENOMEM;
  75
  76         /* need attr_sd for attr and ops, its parent for kobj */
  77         if (!sysfs_get_active_two(attr_sd))
  78                 return -ENODEV;
  79
  80         buffer->event = atomic_read(&attr_sd->s_attr.open->event);
  81         count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
  82
  83         sysfs_put_active_two(attr_sd);
  84
  85         /*
  86          * The code works fine with PAGE_SIZE return but it's likely to
  87          * indicate truncated result or overflow in normal use cases.
  88          */
  89         BUG_ON(count >= (ssize_t)PAGE_SIZE);
  90         if (count >= 0) {
  91                 buffer->needs_read_fill = 0;
  92                 buffer->count = count;
  93         } else {
  94                 ret = count;
  95         }
  96         return ret;
  97 }
  98
  99 /**
 100  *      sysfs_read_file - read an attribute.
 101  *      @file:  file pointer.
 102  *      @buf:   buffer to fill.
 103  *      @count: number of bytes to read.
 104  *      @ppos:  starting offset in file.
 105  *
 106  *      Userspace wants to read an attribute file. The attribute descriptor
 107  *      is in the file's ->d_fsdata. The target object is in the directory's
 108  *      ->d_fsdata.
 109  *
 110  *      We call fill_read_buffer() to allocate and fill the buffer from the
 111  *      object's show() method exactly once (if the read is happening from
 112  *      the beginning of the file). That should fill the entire buffer with
 113  *      all the data the object has to offer for that attribute.
 114  *      We then call flush_read_buffer() to copy the buffer to userspace
 115  *      in the increments specified.
 116  */
 117
 118 static ssize_t
 119 sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 120 {
 121         struct sysfs_buffer * buffer = file->private_data;
 122         ssize_t retval = 0;
 123
 124         mutex_lock(&buffer->mutex);
 125         if (buffer->needs_read_fill) {
 126                 retval = fill_read_buffer(file->f_path.dentry,buffer);
 127                 if (retval)
 128                         goto out;
 129         }
 130         pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
 131                  __FUNCTION__, count, *ppos, buffer->page);
 132         retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
 133                                          buffer->count);
 134 out:
 135         mutex_unlock(&buffer->mutex);
 136         return retval;
 137 }
 138
 139 /**
 140  *      fill_write_buffer - copy buffer from userspace.
 141  *      @buffer:        data buffer for file.
 142  *      @buf:           data from user.
 143  *      @count:         number of bytes in @userbuf.
 144  *
 145  *      Allocate @buffer->page if it hasn't been already, then
 146  *      copy the user-supplied buffer into it.
 147  */
 148
 149 static int
 150 fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
 151 {
 152         int error;
 153
 154         if (!buffer->page)
 155                 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
 156         if (!buffer->page)
 157                 return -ENOMEM;
 158
 159         if (count >= PAGE_SIZE)
 160                 count = PAGE_SIZE - 1;
 161         error = copy_from_user(buffer->page,buf,count);
 162         buffer->needs_read_fill = 1;
 163         /* if buf is assumed to contain a string, terminate it by \0,
 164            so e.g. sscanf() can scan the string easily */
 165         buffer->page[count] = 0;
 166         return error ? -EFAULT : count;
 167 }
 168
 169
 170 /**
 171  *      flush_write_buffer - push buffer to kobject.
 172  *      @dentry:        dentry to the attribute
 173  *      @buffer:        data buffer for file.
 174  *      @count:         number of bytes
 175  *
 176  *      Get the correct pointers for the kobject and the attribute we're
 177  *      dealing with, then call the store() method for the attribute,
 178  *      passing the buffer that we acquired in fill_write_buffer().
 179  */
 180
 181 static int
 182 flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
 183 {
 184         struct sysfs_dirent *attr_sd = dentry->d_fsdata;
 185         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
 186         struct sysfs_ops * ops = buffer->ops;
 187         int rc;
 188
 189         /* need attr_sd for attr and ops, its parent for kobj */
 190         if (!sysfs_get_active_two(attr_sd))
 191                 return -ENODEV;
 192
 193         rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
 194
 195         sysfs_put_active_two(attr_sd);
 196
 197         return rc;
 198 }
 199
 200
 201 /**
 202  *      sysfs_write_file - write an attribute.
 203  *      @file:  file pointer
 204  *      @buf:   data to write
 205  *      @count: number of bytes
 206  *      @ppos:  starting offset
 207  *
 208  *      Similar to sysfs_read_file(), though working in the opposite direction.
 209  *      We allocate and fill the data from the user in fill_write_buffer(),
 210  *      then push it to the kobject in flush_write_buffer().
 211  *      There is no easy way for us to know if userspace is only doing a partial
 212  *      write, so we don't support them. We expect the entire buffer to come
 213  *      on the first write.
 214  *      Hint: if you're writing a value, first read the file, modify only the
 215  *      the value you're changing, then write entire buffer back.
 216  */
 217
 218 static ssize_t
 219 sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 220 {
 221         struct sysfs_buffer * buffer = file->private_data;
 222         ssize_t len;
 223
 224         mutex_lock(&buffer->mutex);
 225         len = fill_write_buffer(buffer, buf, count);
 226         if (len > 0)
 227                 len = flush_write_buffer(file->f_path.dentry, buffer, len);
 228         if (len > 0)
 229                 *ppos += len;
 230         mutex_unlock(&buffer->mutex);
 231         return len;
 232 }
 233
 234 /**
 235  *      sysfs_get_open_dirent - get or create sysfs_open_dirent
 236  *      @sd: target sysfs_dirent
 237  *      @buffer: sysfs_buffer for this instance of open
 238  *
 239  *      If @sd->s_attr.open exists, increment its reference count;
 240  *      otherwise, create one.  @buffer is chained to the buffers
 241  *      list.
 242  *
 243  *      LOCKING:
 244  *      Kernel thread context (may sleep).
 245  *
 246  *      RETURNS:
 247  *      0 on success, -errno on failure.
 248  */
 249 static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
 250                                  struct sysfs_buffer *buffer)
 251 {
 252         struct sysfs_open_dirent *od, *new_od = NULL;
 253
 254  retry:
 255         spin_lock(&sysfs_open_dirent_lock);
 256
 257         if (!sd->s_attr.open && new_od) {
 258                 sd->s_attr.open = new_od;
 259                 new_od = NULL;
 260         }
 261
 262         od = sd->s_attr.open;
 263         if (od) {
 264                 atomic_inc(&od->refcnt);
 265                 list_add_tail(&buffer->list, &od->buffers);
 266         }
 267
 268         spin_unlock(&sysfs_open_dirent_lock);
 269
 270         if (od) {
 271                 kfree(new_od);
 272                 return 0;
 273         }
 274
 275         /* not there, initialize a new one and retry */
 276         new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
 277         if (!new_od)
 278                 return -ENOMEM;
 279
 280         atomic_set(&new_od->refcnt, 0);
 281         atomic_set(&new_od->event, 1);
 282         init_waitqueue_head(&new_od->poll);
 283         INIT_LIST_HEAD(&new_od->buffers);
 284         goto retry;
 285 }
 286
 287 /**
 288  *      sysfs_put_open_dirent - put sysfs_open_dirent
 289  *      @sd: target sysfs_dirent
 290  *      @buffer: associated sysfs_buffer
 291  *
 292  *      Put @sd->s_attr.open and unlink @buffer from the buffers list.
 293  *      If reference count reaches zero, disassociate and free it.
 294  *
 295  *      LOCKING:
 296  *      None.
 297  */
 298 static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
 299                                   struct sysfs_buffer *buffer)
 300 {
 301         struct sysfs_open_dirent *od = sd->s_attr.open;
 302
 303         spin_lock(&sysfs_open_dirent_lock);
 304
 305         list_del(&buffer->list);
 306         if (atomic_dec_and_test(&od->refcnt))
 307                 sd->s_attr.open = NULL;
 308         else
 309                 od = NULL;
 310
 311         spin_unlock(&sysfs_open_dirent_lock);
 312
 313         kfree(od);
 314 }
 315
 316 static int sysfs_open_file(struct inode *inode, struct file *file)
 317 {
 318         struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
 319         struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
 320         struct sysfs_buffer *buffer;
 321         struct sysfs_ops *ops;
 322         int error = -EACCES;
 323
 324         /* need attr_sd for attr and ops, its parent for kobj */
 325         if (!sysfs_get_active_two(attr_sd))
 326                 return -ENODEV;
 327
 328         /* every kobject with an attribute needs a ktype assigned */
 329         if (kobj->ktype && kobj->ktype->sysfs_ops)
 330                 ops = kobj->ktype->sysfs_ops;
 331         else {
 332                 printk(KERN_ERR "missing sysfs attribute operations for "
 333                        "kobject: %s\n", kobject_name(kobj));
 334                 WARN_ON(1);
 335                 goto err_out;
 336         }
 337
 338         /* File needs write support.
 339          * The inode's perms must say it's ok,
 340          * and we must have a store method.
 341          */
 342         if (file->f_mode & FMODE_WRITE) {
 343                 if (!(inode->i_mode & S_IWUGO) || !ops->store)
 344                         goto err_out;
 345         }
 346
 347         /* File needs read support.
 348          * The inode's perms must say it's ok, and we there
 349          * must be a show method for it.
 350          */
 351         if (file->f_mode & FMODE_READ) {
 352                 if (!(inode->i_mode & S_IRUGO) || !ops->show)
 353                         goto err_out;
 354         }
 355
 356         /* No error? Great, allocate a buffer for the file, and store it
 357          * it in file->private_data for easy access.
 358          */
 359         error = -ENOMEM;
 360         buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
 361         if (!buffer)
 362                 goto err_out;
 363
 364         mutex_init(&buffer->mutex);
 365         buffer->needs_read_fill = 1;
 366         buffer->ops = ops;
 367         file->private_data = buffer;
 368
 369         /* make sure we have open dirent struct */
 370         error = sysfs_get_open_dirent(attr_sd, buffer);
 371         if (error)
 372                 goto err_free;
 373
 374         /* open succeeded, put active references */
 375         sysfs_put_active_two(attr_sd);
 376         return 0;
 377
 378  err_free:
 379         kfree(buffer);
 380  err_out:
 381         sysfs_put_active_two(attr_sd);
 382         return error;
 383 }
 384
 385 static int sysfs_release(struct inode *inode, struct file *filp)
 386 {
 387         struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
 388         struct sysfs_buffer *buffer = filp->private_data;
 389
 390         sysfs_put_open_dirent(sd, buffer);
 391
 392         if (buffer->page)
 393                 free_page((unsigned long)buffer->page);
 394         kfree(buffer);
 395
 396         return 0;
 397 }
 398
 399 /* Sysfs attribute files are pollable.  The idea is that you read
 400  * the content and then you use 'poll' or 'select' to wait for
 401  * the content to change.  When the content changes (assuming the
 402  * manager for the kobject supports notification), poll will
 403  * return POLLERR|POLLPRI, and select will return the fd whether
 404  * it is waiting for read, write, or exceptions.
 405  * Once poll/select indicates that the value has changed, you
 406  * need to close and re-open the file, as simply seeking and reading
 407  * again will not get new data, or reset the state of 'poll'.
 408  * Reminder: this only works for attributes which actively support
 409  * it, and it is not possible to test an attribute from userspace
 410  * to see if it supports poll (Neither 'poll' nor 'select' return
 411  * an appropriate error code).  When in doubt, set a suitable timeout value.
 412  */
 413 static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
 414 {
 415         struct sysfs_buffer * buffer = filp->private_data;
 416         struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
 417         struct sysfs_open_dirent *od = attr_sd->s_attr.open;
 418
 419         /* need parent for the kobj, grab both */
 420         if (!sysfs_get_active_two(attr_sd))
 421                 goto trigger;
 422
 423         poll_wait(filp, &od->poll, wait);
 424
 425         sysfs_put_active_two(attr_sd);
 426
 427         if (buffer->event != atomic_read(&od->event))
 428                 goto trigger;
 429
 430         return 0;
 431
 432  trigger:
 433         buffer->needs_read_fill = 1;
 434         return POLLERR|POLLPRI;
 435 }
 436
 437 void sysfs_notify(struct kobject *k, char *dir, char *attr)
 438 {
 439         struct sysfs_dirent *sd = k->sd;
 440
 441         mutex_lock(&sysfs_mutex);
 442
 443         if (sd && dir)
 444                 sd = sysfs_find_dirent(sd, dir);
 445         if (sd && attr)
 446                 sd = sysfs_find_dirent(sd, attr);
 447         if (sd) {
 448                 struct sysfs_open_dirent *od;
 449
 450                 spin_lock(&sysfs_open_dirent_lock);
 451
 452                 od = sd->s_attr.open;
 453                 if (od) {
 454                         atomic_inc(&od->event);
 455                         wake_up_interruptible(&od->poll);
 456                 }
 457
 458                 spin_unlock(&sysfs_open_dirent_lock);
 459         }
 460
 461         mutex_unlock(&sysfs_mutex);
 462 }
 463 EXPORT_SYMBOL_GPL(sysfs_notify);
 464
 465 const struct file_operations sysfs_file_operations = {
 466         .read           = sysfs_read_file,
 467         .write          = sysfs_write_file,
 468         .llseek         = generic_file_llseek,
 469         .open           = sysfs_open_file,
 470         .release        = sysfs_release,
 471         .poll           = sysfs_poll,
 472 };
 473
 474
 475 int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
 476                    int type)
 477 {
 478         umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
 479         struct sysfs_addrm_cxt acxt;
 480         struct sysfs_dirent *sd;
 481         int rc;
 482
 483         sd = sysfs_new_dirent(attr->name, mode, type);
 484         if (!sd)
 485                 return -ENOMEM;
 486         sd->s_attr.attr = (void *)attr;
 487
 488         sysfs_addrm_start(&acxt, dir_sd);
 489         rc = sysfs_add_one(&acxt, sd);
 490         sysfs_addrm_finish(&acxt);
 491
 492         if (rc)
 493                 sysfs_put(sd);
 494
 495         return rc;
 496 }
 497
 498
 499 /**
 500  *      sysfs_create_file - create an attribute file for an object.
 501  *      @kobj:  object we're creating for.
 502  *      @attr:  attribute descriptor.
 503  */
 504
 505 int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 506 {
 507         BUG_ON(!kobj || !kobj->sd || !attr);
 508
 509         return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
 510
 511 }
 512
 513
 514 /**
 515  * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
 516  * @kobj: object we're acting for.
 517  * @attr: attribute descriptor.
 518  * @group: group name.
 519  */
 520 int sysfs_add_file_to_group(struct kobject *kobj,
 521                 const struct attribute *attr, const char *group)
 522 {
 523         struct sysfs_dirent *dir_sd;
 524         int error;
 525
 526         if (group)
 527                 dir_sd = sysfs_get_dirent(kobj->sd, group);
 528         else
 529                 dir_sd = sysfs_get(kobj->sd);
 530
 531         if (!dir_sd)
 532                 return -ENOENT;
 533
 534         error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
 535         sysfs_put(dir_sd);
 536
 537         return error;
 538 }
 539 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
 540
 541 /**
 542  * sysfs_chmod_file - update the modified mode value on an object attribute.
 543  * @kobj: object we're acting for.
 544  * @attr: attribute descriptor.
 545  * @mode: file permissions.
 546  *
 547  */
 548 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 549 {
 550         struct sysfs_dirent *victim_sd = NULL;
 551         struct dentry *victim = NULL;
 552         struct inode * inode;
 553         struct iattr newattrs;
 554         int rc;
 555
 556         rc = -ENOENT;
 557         victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
 558         if (!victim_sd)
 559                 goto out;
 560
 561         mutex_lock(&sysfs_rename_mutex);
 562         victim = sysfs_get_dentry(victim_sd);
 563         mutex_unlock(&sysfs_rename_mutex);
 564         if (IS_ERR(victim)) {
 565                 rc = PTR_ERR(victim);
 566                 victim = NULL;
 567                 goto out;
 568         }
 569
 570         inode = victim->d_inode;
 571
 572         mutex_lock(&inode->i_mutex);
 573
 574         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 575         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 576         rc = notify_change(victim, &newattrs);
 577
 578         if (rc == 0) {
 579                 mutex_lock(&sysfs_mutex);
 580                 victim_sd->s_mode = newattrs.ia_mode;
 581                 mutex_unlock(&sysfs_mutex);
 582         }
 583
 584         mutex_unlock(&inode->i_mutex);
 585  out:
 586         dput(victim);
 587         sysfs_put(victim_sd);
 588         return rc;
 589 }
 590 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 591
 592
 593 /**
 594  *      sysfs_remove_file - remove an object attribute.
 595  *      @kobj:  object we're acting for.
 596  *      @attr:  attribute descriptor.
 597  *
 598  *      Hash the attribute name and kill the victim.
 599  */
 600
 601 void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
 602 {
 603         sysfs_hash_and_remove(kobj->sd, attr->name);
 604 }
 605
 606
 607 /**
 608  * sysfs_remove_file_from_group - remove an attribute file from a group.
 609  * @kobj: object we're acting for.
 610  * @attr: attribute descriptor.
 611  * @group: group name.
 612  */
 613 void sysfs_remove_file_from_group(struct kobject *kobj,
 614                 const struct attribute *attr, const char *group)
 615 {
 616         struct sysfs_dirent *dir_sd;
 617
 618         if (group)
 619                 dir_sd = sysfs_get_dirent(kobj->sd, group);
 620         else
 621                 dir_sd = sysfs_get(kobj->sd);
 622         if (dir_sd) {
 623                 sysfs_hash_and_remove(dir_sd, attr->name);
 624                 sysfs_put(dir_sd);
 625         }
 626 }
 627 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
 628
 629 struct sysfs_schedule_callback_struct {
 630         struct kobject          *kobj;
 631         void                    (*func)(void *);
 632         void                    *data;
 633         struct module           *owner;
 634         struct work_struct      work;
 635 };
 636
 637 static void sysfs_schedule_callback_work(struct work_struct *work)
 638 {
 639         struct sysfs_schedule_callback_struct *ss = container_of(work,
 640                         struct sysfs_schedule_callback_struct, work);
 641
 642         (ss->func)(ss->data);
 643         kobject_put(ss->kobj);
 644         module_put(ss->owner);
 645         kfree(ss);
 646 }
 647
 648 /**
 649  * sysfs_schedule_callback - helper to schedule a callback for a kobject
 650  * @kobj: object we're acting for.
 651  * @func: callback function to invoke later.
 652  * @data: argument to pass to @func.
 653  * @owner: module owning the callback code
 654  *
 655  * sysfs attribute methods must not unregister themselves or their parent
 656  * kobject (which would amount to the same thing).  Attempts to do so will
 657  * deadlock, since unregistration is mutually exclusive with driver
 658  * callbacks.
 659  *
 660  * Instead methods can call this routine, which will attempt to allocate
 661  * and schedule a workqueue request to call back @func with @data as its
 662  * argument in the workqueue's process context.  @kobj will be pinned
 663  * until @func returns.
 664  *
 665  * Returns 0 if the request was submitted, -ENOMEM if storage could not
 666  * be allocated, -ENODEV if a reference to @owner isn't available.
 667  */
 668 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 669                 void *data, struct module *owner)
 670 {
 671         struct sysfs_schedule_callback_struct *ss;
 672
 673         if (!try_module_get(owner))
 674                 return -ENODEV;
 675         ss = kmalloc(sizeof(*ss), GFP_KERNEL);
 676         if (!ss) {
 677                 module_put(owner);
 678                 return -ENOMEM;
 679         }
 680         kobject_get(kobj);
 681         ss->kobj = kobj;
 682         ss->func = func;
 683         ss->data = data;
 684         ss->owner = owner;
 685         INIT_WORK(&ss->work, sysfs_schedule_callback_work);
 686         schedule_work(&ss->work);
 687         return 0;
 688 }
 689 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
 690
 691
 692 EXPORT_SYMBOL_GPL(sysfs_create_file);
 693 EXPORT_SYMBOL_GPL(sysfs_remove_file);