2 * fs/sysfs/file.c - sysfs regular (text) file implementation
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 * This file is released under the GPLv2.
10 * Please see Documentation/filesystems/sysfs.txt for more information.
13 #include <linux/module.h>
14 #include <linux/kobject.h>
15 #include <linux/kallsyms.h>
16 #include <linux/slab.h>
17 #include <linux/fsnotify.h>
18 #include <linux/namei.h>
19 #include <linux/poll.h>
20 #include <linux/list.h>
21 #include <linux/mutex.h>
22 #include <linux/limits.h>
23 #include <linux/uaccess.h>
24 #include <linux/seq_file.h>
29 * There's one sysfs_open_file for each open file and one sysfs_open_dirent
30 * for each sysfs_dirent with one or more open files.
32 * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open is
33 * protected by sysfs_open_dirent_lock.
35 * filp->private_data points to seq_file whose ->private points to
36 * sysfs_open_file. sysfs_open_files are chained at
37 * sysfs_open_dirent->files, which is protected by sysfs_open_file_mutex.
39 static DEFINE_SPINLOCK(sysfs_open_dirent_lock);
40 static DEFINE_MUTEX(sysfs_open_file_mutex);
42 struct sysfs_open_dirent {
45 wait_queue_head_t poll;
46 struct list_head files; /* goes through sysfs_open_file.list */
49 struct sysfs_open_file {
50 struct sysfs_dirent *sd;
54 struct list_head list;
57 static bool sysfs_is_bin(struct sysfs_dirent *sd)
59 return sysfs_type(sd) == SYSFS_KOBJ_BIN_ATTR;
62 static struct sysfs_open_file *sysfs_of(struct file *file)
64 return ((struct seq_file *)file->private_data)->private;
68 * Determine ktype->sysfs_ops for the given sysfs_dirent. This function
69 * must be called while holding an active reference.
71 static const struct sysfs_ops *sysfs_file_ops(struct sysfs_dirent *sd)
73 struct kobject *kobj = sd->s_parent->s_dir.kobj;
75 lockdep_assert_held(sd);
76 return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
80 * Reads on sysfs are handled through seq_file, which takes care of hairy
81 * details like buffering and seeking. The following function pipes
82 * sysfs_ops->show() result through seq_file.
84 static int sysfs_seq_show(struct seq_file *sf, void *v)
86 struct sysfs_open_file *of = sf->private;
87 struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
88 const struct sysfs_ops *ops;
92 /* acquire buffer and ensure that it's >= PAGE_SIZE */
93 count = seq_get_buf(sf, &buf);
94 if (count < PAGE_SIZE) {
100 * Need @of->sd for attr and ops, its parent for kobj. @of->mutex
101 * nests outside active ref and is just to ensure that the ops
102 * aren't called concurrently for the same open file.
104 mutex_lock(&of->mutex);
105 if (!sysfs_get_active(of->sd)) {
106 mutex_unlock(&of->mutex);
110 of->event = atomic_read(&of->sd->s_attr.open->event);
113 * Lookup @ops and invoke show(). Control may reach here via seq
114 * file lseek even if @ops->show() isn't implemented.
116 ops = sysfs_file_ops(of->sd);
118 count = ops->show(kobj, of->sd->s_attr.attr, buf);
122 sysfs_put_active(of->sd);
123 mutex_unlock(&of->mutex);
129 * The code works fine with PAGE_SIZE return but it's likely to
130 * indicate truncated result or overflow in normal use cases.
132 if (count >= (ssize_t)PAGE_SIZE) {
133 print_symbol("fill_read_buffer: %s returned bad count\n",
134 (unsigned long)ops->show);
135 /* Try to struggle along */
136 count = PAGE_SIZE - 1;
138 seq_commit(sf, count);
143 * flush_write_buffer - push buffer to kobject
145 * @buf: data buffer for file
146 * @off: file offset to write to
147 * @count: number of bytes
149 * Get the correct pointers for the kobject and the attribute we're dealing
150 * with, then call the store() method for it with @buf.
152 static int flush_write_buffer(struct sysfs_open_file *of, char *buf, loff_t off,
155 struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
159 * Need @of->sd for attr and ops, its parent for kobj. @of->mutex
160 * nests outside active ref and is just to ensure that the ops
161 * aren't called concurrently for the same open file.
163 mutex_lock(&of->mutex);
164 if (!sysfs_get_active(of->sd)) {
165 mutex_unlock(&of->mutex);
169 if (sysfs_is_bin(of->sd)) {
170 struct bin_attribute *battr = of->sd->s_bin_attr.bin_attr;
174 rc = battr->write(of->file, kobj, battr, buf, off,
177 const struct sysfs_ops *ops = sysfs_file_ops(of->sd);
179 rc = ops->store(kobj, of->sd->s_attr.attr, buf, count);
182 sysfs_put_active(of->sd);
183 mutex_unlock(&of->mutex);
189 * sysfs_write_file - write an attribute
190 * @file: file pointer
191 * @user_buf: data to write
192 * @count: number of bytes
193 * @ppos: starting offset
195 * Copy data in from userland and pass it to the matching
196 * sysfs_ops->store() by invoking flush_write_buffer().
198 * There is no easy way for us to know if userspace is only doing a partial
199 * write, so we don't support them. We expect the entire buffer to come on
200 * the first write. Hint: if you're writing a value, first read the file,
201 * modify only the the value you're changing, then write entire buffer
204 static ssize_t sysfs_write_file(struct file *file, const char __user *user_buf,
205 size_t count, loff_t *ppos)
207 struct sysfs_open_file *of = sysfs_of(file);
208 ssize_t len = min_t(size_t, count, PAGE_SIZE);
211 if (sysfs_is_bin(of->sd)) {
212 loff_t size = file_inode(file)->i_size;
216 len = min_t(ssize_t, len, size - *ppos);
222 buf = kmalloc(len + 1, GFP_KERNEL);
226 if (copy_from_user(buf, user_buf, len)) {
230 buf[len] = '\0'; /* guarantee string termination */
232 len = flush_write_buffer(of, buf, *ppos, len);
241 * sysfs_get_open_dirent - get or create sysfs_open_dirent
242 * @sd: target sysfs_dirent
243 * @of: sysfs_open_file for this instance of open
245 * If @sd->s_attr.open exists, increment its reference count;
246 * otherwise, create one. @of is chained to the files list.
249 * Kernel thread context (may sleep).
252 * 0 on success, -errno on failure.
254 static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
255 struct sysfs_open_file *of)
257 struct sysfs_open_dirent *od, *new_od = NULL;
260 mutex_lock(&sysfs_open_file_mutex);
261 spin_lock_irq(&sysfs_open_dirent_lock);
263 if (!sd->s_attr.open && new_od) {
264 sd->s_attr.open = new_od;
268 od = sd->s_attr.open;
270 atomic_inc(&od->refcnt);
271 list_add_tail(&of->list, &od->files);
274 spin_unlock_irq(&sysfs_open_dirent_lock);
275 mutex_unlock(&sysfs_open_file_mutex);
282 /* not there, initialize a new one and retry */
283 new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);
287 atomic_set(&new_od->refcnt, 0);
288 atomic_set(&new_od->event, 1);
289 init_waitqueue_head(&new_od->poll);
290 INIT_LIST_HEAD(&new_od->files);
295 * sysfs_put_open_dirent - put sysfs_open_dirent
296 * @sd: target sysfs_dirent
297 * @of: associated sysfs_open_file
299 * Put @sd->s_attr.open and unlink @of from the files list. If
300 * reference count reaches zero, disassociate and free it.
305 static void sysfs_put_open_dirent(struct sysfs_dirent *sd,
306 struct sysfs_open_file *of)
308 struct sysfs_open_dirent *od = sd->s_attr.open;
311 mutex_lock(&sysfs_open_file_mutex);
312 spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
315 if (atomic_dec_and_test(&od->refcnt))
316 sd->s_attr.open = NULL;
320 spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
321 mutex_unlock(&sysfs_open_file_mutex);
326 static int sysfs_open_file(struct inode *inode, struct file *file)
328 struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
329 struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
330 struct sysfs_open_file *of;
331 const struct sysfs_ops *ops;
334 /* need attr_sd for attr and ops, its parent for kobj */
335 if (!sysfs_get_active(attr_sd))
338 /* every kobject with an attribute needs a ktype assigned */
339 ops = sysfs_file_ops(attr_sd);
340 if (WARN(!ops, KERN_ERR
341 "missing sysfs attribute operations for kobject: %s\n",
345 /* File needs write support.
346 * The inode's perms must say it's ok,
347 * and we must have a store method.
349 if (file->f_mode & FMODE_WRITE) {
350 if (!(inode->i_mode & S_IWUGO) || !ops->store)
354 /* File needs read support.
355 * The inode's perms must say it's ok, and we there
356 * must be a show method for it.
358 if (file->f_mode & FMODE_READ) {
359 if (!(inode->i_mode & S_IRUGO) || !ops->show)
363 /* allocate a sysfs_open_file for the file */
365 of = kzalloc(sizeof(struct sysfs_open_file), GFP_KERNEL);
369 mutex_init(&of->mutex);
374 * Always instantiate seq_file even if read access is not
375 * implemented or requested. This unifies private data access and
376 * most files are readable anyway.
378 error = single_open(file, sysfs_seq_show, of);
382 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
383 if (file->f_mode & FMODE_WRITE)
384 file->f_mode |= FMODE_PWRITE;
386 /* make sure we have open dirent struct */
387 error = sysfs_get_open_dirent(attr_sd, of);
391 /* open succeeded, put active references */
392 sysfs_put_active(attr_sd);
396 single_release(inode, file);
400 sysfs_put_active(attr_sd);
404 static int sysfs_release(struct inode *inode, struct file *filp)
406 struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;
407 struct sysfs_open_file *of = sysfs_of(filp);
409 sysfs_put_open_dirent(sd, of);
410 single_release(inode, filp);
416 /* Sysfs attribute files are pollable. The idea is that you read
417 * the content and then you use 'poll' or 'select' to wait for
418 * the content to change. When the content changes (assuming the
419 * manager for the kobject supports notification), poll will
420 * return POLLERR|POLLPRI, and select will return the fd whether
421 * it is waiting for read, write, or exceptions.
422 * Once poll/select indicates that the value has changed, you
423 * need to close and re-open the file, or seek to 0 and read again.
424 * Reminder: this only works for attributes which actively support
425 * it, and it is not possible to test an attribute from userspace
426 * to see if it supports poll (Neither 'poll' nor 'select' return
427 * an appropriate error code). When in doubt, set a suitable timeout value.
429 static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
431 struct sysfs_open_file *of = sysfs_of(filp);
432 struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
433 struct sysfs_open_dirent *od = attr_sd->s_attr.open;
435 /* need parent for the kobj, grab both */
436 if (!sysfs_get_active(attr_sd))
439 poll_wait(filp, &od->poll, wait);
441 sysfs_put_active(attr_sd);
443 if (of->event != atomic_read(&od->event))
446 return DEFAULT_POLLMASK;
449 return DEFAULT_POLLMASK|POLLERR|POLLPRI;
452 void sysfs_notify_dirent(struct sysfs_dirent *sd)
454 struct sysfs_open_dirent *od;
457 spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
459 if (!WARN_ON(sysfs_type(sd) != SYSFS_KOBJ_ATTR)) {
460 od = sd->s_attr.open;
462 atomic_inc(&od->event);
463 wake_up_interruptible(&od->poll);
467 spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
469 EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
471 void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
473 struct sysfs_dirent *sd = k->sd;
475 mutex_lock(&sysfs_mutex);
478 sd = sysfs_find_dirent(sd, dir, NULL);
480 sd = sysfs_find_dirent(sd, attr, NULL);
482 sysfs_notify_dirent(sd);
484 mutex_unlock(&sysfs_mutex);
486 EXPORT_SYMBOL_GPL(sysfs_notify);
488 const struct file_operations sysfs_file_operations = {
490 .write = sysfs_write_file,
492 .open = sysfs_open_file,
493 .release = sysfs_release,
497 const struct file_operations sysfs_bin_operations = {
498 .write = sysfs_write_file,
499 .llseek = generic_file_llseek,
502 int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
503 const struct attribute *attr, int type,
504 umode_t amode, const void *ns)
506 umode_t mode = (amode & S_IALLUGO) | S_IFREG;
507 struct sysfs_addrm_cxt acxt;
508 struct sysfs_dirent *sd;
511 sd = sysfs_new_dirent(attr->name, mode, type);
516 sd->s_attr.attr = (void *)attr;
517 sysfs_dirent_init_lockdep(sd);
519 sysfs_addrm_start(&acxt);
520 rc = sysfs_add_one(&acxt, sd, dir_sd);
521 sysfs_addrm_finish(&acxt);
530 int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
533 return sysfs_add_file_mode_ns(dir_sd, attr, type, attr->mode, NULL);
537 * sysfs_create_file_ns - create an attribute file for an object with custom ns
538 * @kobj: object we're creating for
539 * @attr: attribute descriptor
540 * @ns: namespace the new file should belong to
542 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
545 BUG_ON(!kobj || !kobj->sd || !attr);
547 return sysfs_add_file_mode_ns(kobj->sd, attr, SYSFS_KOBJ_ATTR,
551 EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
553 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
558 for (i = 0; ptr[i] && !err; i++)
559 err = sysfs_create_file(kobj, ptr[i]);
562 sysfs_remove_file(kobj, ptr[i]);
565 EXPORT_SYMBOL_GPL(sysfs_create_files);
568 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
569 * @kobj: object we're acting for.
570 * @attr: attribute descriptor.
571 * @group: group name.
573 int sysfs_add_file_to_group(struct kobject *kobj,
574 const struct attribute *attr, const char *group)
576 struct sysfs_dirent *dir_sd;
580 dir_sd = sysfs_get_dirent(kobj->sd, group);
582 dir_sd = sysfs_get(kobj->sd);
587 error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR);
592 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
595 * sysfs_chmod_file - update the modified mode value on an object attribute.
596 * @kobj: object we're acting for.
597 * @attr: attribute descriptor.
598 * @mode: file permissions.
601 int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
604 struct sysfs_dirent *sd;
605 struct iattr newattrs;
608 mutex_lock(&sysfs_mutex);
611 sd = sysfs_find_dirent(kobj->sd, attr->name, NULL);
615 newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
616 newattrs.ia_valid = ATTR_MODE;
617 rc = sysfs_sd_setattr(sd, &newattrs);
620 mutex_unlock(&sysfs_mutex);
623 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
626 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
627 * @kobj: object we're acting for
628 * @attr: attribute descriptor
629 * @ns: namespace tag of the file to remove
631 * Hash the attribute name and namespace tag and kill the victim.
633 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
636 struct sysfs_dirent *dir_sd = kobj->sd;
638 sysfs_hash_and_remove(dir_sd, attr->name, ns);
640 EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
642 void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
645 for (i = 0; ptr[i]; i++)
646 sysfs_remove_file(kobj, ptr[i]);
648 EXPORT_SYMBOL_GPL(sysfs_remove_files);
651 * sysfs_remove_file_from_group - remove an attribute file from a group.
652 * @kobj: object we're acting for.
653 * @attr: attribute descriptor.
654 * @group: group name.
656 void sysfs_remove_file_from_group(struct kobject *kobj,
657 const struct attribute *attr, const char *group)
659 struct sysfs_dirent *dir_sd;
662 dir_sd = sysfs_get_dirent(kobj->sd, group);
664 dir_sd = sysfs_get(kobj->sd);
666 sysfs_hash_and_remove(dir_sd, attr->name, NULL);
670 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
672 struct sysfs_schedule_callback_struct {
673 struct list_head workq_list;
674 struct kobject *kobj;
675 void (*func)(void *);
677 struct module *owner;
678 struct work_struct work;
681 static struct workqueue_struct *sysfs_workqueue;
682 static DEFINE_MUTEX(sysfs_workq_mutex);
683 static LIST_HEAD(sysfs_workq);
684 static void sysfs_schedule_callback_work(struct work_struct *work)
686 struct sysfs_schedule_callback_struct *ss = container_of(work,
687 struct sysfs_schedule_callback_struct, work);
689 (ss->func)(ss->data);
690 kobject_put(ss->kobj);
691 module_put(ss->owner);
692 mutex_lock(&sysfs_workq_mutex);
693 list_del(&ss->workq_list);
694 mutex_unlock(&sysfs_workq_mutex);
699 * sysfs_schedule_callback - helper to schedule a callback for a kobject
700 * @kobj: object we're acting for.
701 * @func: callback function to invoke later.
702 * @data: argument to pass to @func.
703 * @owner: module owning the callback code
705 * sysfs attribute methods must not unregister themselves or their parent
706 * kobject (which would amount to the same thing). Attempts to do so will
707 * deadlock, since unregistration is mutually exclusive with driver
710 * Instead methods can call this routine, which will attempt to allocate
711 * and schedule a workqueue request to call back @func with @data as its
712 * argument in the workqueue's process context. @kobj will be pinned
713 * until @func returns.
715 * Returns 0 if the request was submitted, -ENOMEM if storage could not
716 * be allocated, -ENODEV if a reference to @owner isn't available,
717 * -EAGAIN if a callback has already been scheduled for @kobj.
719 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
720 void *data, struct module *owner)
722 struct sysfs_schedule_callback_struct *ss, *tmp;
724 if (!try_module_get(owner))
727 mutex_lock(&sysfs_workq_mutex);
728 list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
729 if (ss->kobj == kobj) {
731 mutex_unlock(&sysfs_workq_mutex);
734 mutex_unlock(&sysfs_workq_mutex);
736 if (sysfs_workqueue == NULL) {
737 sysfs_workqueue = create_singlethread_workqueue("sysfsd");
738 if (sysfs_workqueue == NULL) {
744 ss = kmalloc(sizeof(*ss), GFP_KERNEL);
754 INIT_WORK(&ss->work, sysfs_schedule_callback_work);
755 INIT_LIST_HEAD(&ss->workq_list);
756 mutex_lock(&sysfs_workq_mutex);
757 list_add_tail(&ss->workq_list, &sysfs_workq);
758 mutex_unlock(&sysfs_workq_mutex);
759 queue_work(sysfs_workqueue, &ss->work);
762 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);