2 * file.c - operations for regular (text) files.
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>
16 #define to_sattr(a) container_of(a,struct subsys_attribute, attr)
19 * Subsystem file operations.
20 * These operations allow subsystems to have files that can be
24 subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page)
26 struct kset *kset = to_kset(kobj);
27 struct subsys_attribute * sattr = to_sattr(attr);
31 ret = sattr->show(kset, page);
36 subsys_attr_store(struct kobject * kobj, struct attribute * attr,
37 const char * page, size_t count)
39 struct kset *kset = to_kset(kobj);
40 struct subsys_attribute * sattr = to_sattr(attr);
44 ret = sattr->store(kset, page, count);
48 static struct sysfs_ops subsys_sysfs_ops = {
49 .show = subsys_attr_show,
50 .store = subsys_attr_store,
54 * add_to_collection - add buffer to a collection
55 * @buffer: buffer to be added
56 * @node: inode of set to add to
60 add_to_collection(struct sysfs_buffer *buffer, struct inode *node)
62 struct sysfs_buffer_collection *set = node->i_private;
64 mutex_lock(&node->i_mutex);
65 list_add(&buffer->associates, &set->associates);
66 mutex_unlock(&node->i_mutex);
70 remove_from_collection(struct sysfs_buffer *buffer, struct inode *node)
72 mutex_lock(&node->i_mutex);
73 list_del(&buffer->associates);
74 mutex_unlock(&node->i_mutex);
78 * fill_read_buffer - allocate and fill buffer from object.
79 * @dentry: dentry pointer.
80 * @buffer: data buffer for file.
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
85 * This is called only once, on the file's first read unless an error
88 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
90 struct sysfs_dirent *attr_sd = dentry->d_fsdata;
91 struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
92 struct sysfs_ops * ops = buffer->ops;
97 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
101 /* need attr_sd for attr and ops, its parent for kobj */
102 if (!sysfs_get_active_two(attr_sd))
105 buffer->event = atomic_read(&attr_sd->s_event);
106 count = ops->show(kobj, attr_sd->s_elem.attr.attr, buffer->page);
108 sysfs_put_active_two(attr_sd);
110 BUG_ON(count > (ssize_t)PAGE_SIZE);
112 buffer->needs_read_fill = 0;
113 buffer->count = count;
121 * sysfs_read_file - read an attribute.
122 * @file: file pointer.
123 * @buf: buffer to fill.
124 * @count: number of bytes to read.
125 * @ppos: starting offset in file.
127 * Userspace wants to read an attribute file. The attribute descriptor
128 * is in the file's ->d_fsdata. The target object is in the directory's
131 * We call fill_read_buffer() to allocate and fill the buffer from the
132 * object's show() method exactly once (if the read is happening from
133 * the beginning of the file). That should fill the entire buffer with
134 * all the data the object has to offer for that attribute.
135 * We then call flush_read_buffer() to copy the buffer to userspace
136 * in the increments specified.
140 sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
142 struct sysfs_buffer * buffer = file->private_data;
146 if (buffer->needs_read_fill) {
147 if (buffer->orphaned)
150 retval = fill_read_buffer(file->f_path.dentry,buffer);
154 pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
155 __FUNCTION__, count, *ppos, buffer->page);
156 retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
164 * fill_write_buffer - copy buffer from userspace.
165 * @buffer: data buffer for file.
166 * @buf: data from user.
167 * @count: number of bytes in @userbuf.
169 * Allocate @buffer->page if it hasn't been already, then
170 * copy the user-supplied buffer into it.
174 fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count)
179 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
183 if (count >= PAGE_SIZE)
184 count = PAGE_SIZE - 1;
185 error = copy_from_user(buffer->page,buf,count);
186 buffer->needs_read_fill = 1;
187 /* if buf is assumed to contain a string, terminate it by \0,
188 so e.g. sscanf() can scan the string easily */
189 buffer->page[count] = 0;
190 return error ? -EFAULT : count;
195 * flush_write_buffer - push buffer to kobject.
196 * @dentry: dentry to the attribute
197 * @buffer: data buffer for file.
198 * @count: number of bytes
200 * Get the correct pointers for the kobject and the attribute we're
201 * dealing with, then call the store() method for the attribute,
202 * passing the buffer that we acquired in fill_write_buffer().
206 flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
208 struct sysfs_dirent *attr_sd = dentry->d_fsdata;
209 struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
210 struct sysfs_ops * ops = buffer->ops;
213 /* need attr_sd for attr and ops, its parent for kobj */
214 if (!sysfs_get_active_two(attr_sd))
217 rc = ops->store(kobj, attr_sd->s_elem.attr.attr, buffer->page, count);
219 sysfs_put_active_two(attr_sd);
226 * sysfs_write_file - write an attribute.
227 * @file: file pointer
228 * @buf: data to write
229 * @count: number of bytes
230 * @ppos: starting offset
232 * Similar to sysfs_read_file(), though working in the opposite direction.
233 * We allocate and fill the data from the user in fill_write_buffer(),
234 * then push it to the kobject in flush_write_buffer().
235 * There is no easy way for us to know if userspace is only doing a partial
236 * write, so we don't support them. We expect the entire buffer to come
237 * on the first write.
238 * Hint: if you're writing a value, first read the file, modify only the
239 * the value you're changing, then write entire buffer back.
243 sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
245 struct sysfs_buffer * buffer = file->private_data;
249 if (buffer->orphaned) {
253 len = fill_write_buffer(buffer, buf, count);
255 len = flush_write_buffer(file->f_path.dentry, buffer, len);
263 static int sysfs_open_file(struct inode *inode, struct file *file)
265 struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
266 struct attribute *attr = attr_sd->s_elem.attr.attr;
267 struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
268 struct sysfs_buffer_collection *set;
269 struct sysfs_buffer * buffer;
270 struct sysfs_ops * ops = NULL;
273 /* need attr_sd for attr and ops, its parent for kobj */
274 if (!sysfs_get_active_two(attr_sd))
277 /* Grab the module reference for this attribute */
279 if (!try_module_get(attr->owner))
282 /* if the kobject has no ktype, then we assume that it is a subsystem
283 * itself, and use ops for it.
285 if (kobj->kset && kobj->kset->ktype)
286 ops = kobj->kset->ktype->sysfs_ops;
287 else if (kobj->ktype)
288 ops = kobj->ktype->sysfs_ops;
290 ops = &subsys_sysfs_ops;
292 /* No sysfs operations, either from having no subsystem,
293 * or the subsystem have no operations.
299 /* make sure we have a collection to add our buffers to */
300 mutex_lock(&inode->i_mutex);
301 if (!(set = inode->i_private)) {
303 if (!(set = inode->i_private = kmalloc(sizeof(struct sysfs_buffer_collection), GFP_KERNEL)))
306 INIT_LIST_HEAD(&set->associates);
308 mutex_unlock(&inode->i_mutex);
312 /* File needs write support.
313 * The inode's perms must say it's ok,
314 * and we must have a store method.
316 if (file->f_mode & FMODE_WRITE) {
317 if (!(inode->i_mode & S_IWUGO) || !ops->store)
321 /* File needs read support.
322 * The inode's perms must say it's ok, and we there
323 * must be a show method for it.
325 if (file->f_mode & FMODE_READ) {
326 if (!(inode->i_mode & S_IRUGO) || !ops->show)
330 /* No error? Great, allocate a buffer for the file, and store it
331 * it in file->private_data for easy access.
334 buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
338 INIT_LIST_HEAD(&buffer->associates);
339 init_MUTEX(&buffer->sem);
340 buffer->needs_read_fill = 1;
342 add_to_collection(buffer, inode);
343 file->private_data = buffer;
345 /* open succeeded, put active references and pin attr_sd */
346 sysfs_put_active_two(attr_sd);
351 module_put(attr->owner);
353 sysfs_put_active_two(attr_sd);
357 static int sysfs_release(struct inode * inode, struct file * filp)
359 struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
360 struct attribute *attr = attr_sd->s_elem.attr.attr;
361 struct sysfs_buffer * buffer = filp->private_data;
364 remove_from_collection(buffer, inode);
366 /* After this point, attr should not be accessed. */
367 module_put(attr->owner);
371 free_page((unsigned long)buffer->page);
377 /* Sysfs attribute files are pollable. The idea is that you read
378 * the content and then you use 'poll' or 'select' to wait for
379 * the content to change. When the content changes (assuming the
380 * manager for the kobject supports notification), poll will
381 * return POLLERR|POLLPRI, and select will return the fd whether
382 * it is waiting for read, write, or exceptions.
383 * Once poll/select indicates that the value has changed, you
384 * need to close and re-open the file, as simply seeking and reading
385 * again will not get new data, or reset the state of 'poll'.
386 * Reminder: this only works for attributes which actively support
387 * it, and it is not possible to test an attribute from userspace
388 * to see if it supports poll (Nether 'poll' or 'select' return
389 * an appropriate error code). When in doubt, set a suitable timeout value.
391 static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
393 struct sysfs_buffer * buffer = filp->private_data;
394 struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
395 struct kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
397 /* need parent for the kobj, grab both */
398 if (!sysfs_get_active_two(attr_sd))
401 poll_wait(filp, &kobj->poll, wait);
403 sysfs_put_active_two(attr_sd);
405 if (buffer->event != atomic_read(&attr_sd->s_event))
411 buffer->needs_read_fill = 1;
412 return POLLERR|POLLPRI;
416 static struct dentry *step_down(struct dentry *dir, const char * name)
420 if (dir == NULL || dir->d_inode == NULL)
423 mutex_lock(&dir->d_inode->i_mutex);
424 de = lookup_one_len(name, dir, strlen(name));
425 mutex_unlock(&dir->d_inode->i_mutex);
429 if (de->d_inode == NULL) {
436 void sysfs_notify(struct kobject * k, char *dir, char *attr)
438 struct dentry *de = k->dentry;
442 de = step_down(de, dir);
444 de = step_down(de, attr);
446 struct sysfs_dirent * sd = de->d_fsdata;
448 atomic_inc(&sd->s_event);
449 wake_up_interruptible(&k->poll);
453 EXPORT_SYMBOL_GPL(sysfs_notify);
455 const struct file_operations sysfs_file_operations = {
456 .read = sysfs_read_file,
457 .write = sysfs_write_file,
458 .llseek = generic_file_llseek,
459 .open = sysfs_open_file,
460 .release = sysfs_release,
465 int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type)
467 struct sysfs_dirent * parent_sd = dir->d_fsdata;
468 umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
469 struct sysfs_dirent *sd;
472 mutex_lock(&dir->d_inode->i_mutex);
474 if (sysfs_dirent_exist(parent_sd, attr->name)) {
479 sd = sysfs_new_dirent(attr->name, mode, type);
484 sd->s_elem.attr.attr = (void *)attr;
485 sysfs_attach_dirent(sd, parent_sd, NULL);
488 mutex_unlock(&dir->d_inode->i_mutex);
494 * sysfs_create_file - create an attribute file for an object.
495 * @kobj: object we're creating for.
496 * @attr: atrribute descriptor.
499 int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
501 BUG_ON(!kobj || !kobj->dentry || !attr);
503 return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR);
509 * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
510 * @kobj: object we're acting for.
511 * @attr: attribute descriptor.
512 * @group: group name.
514 int sysfs_add_file_to_group(struct kobject *kobj,
515 const struct attribute *attr, const char *group)
520 dir = lookup_one_len(group, kobj->dentry, strlen(group));
522 error = PTR_ERR(dir);
524 error = sysfs_add_file(dir, attr, SYSFS_KOBJ_ATTR);
529 EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
533 * sysfs_update_file - update the modified timestamp on an object attribute.
534 * @kobj: object we're acting for.
535 * @attr: attribute descriptor.
537 int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
539 struct dentry * dir = kobj->dentry;
540 struct dentry * victim;
543 mutex_lock(&dir->d_inode->i_mutex);
544 victim = lookup_one_len(attr->name, dir, strlen(attr->name));
545 if (!IS_ERR(victim)) {
546 /* make sure dentry is really there */
547 if (victim->d_inode &&
548 (victim->d_parent->d_inode == dir->d_inode)) {
549 victim->d_inode->i_mtime = CURRENT_TIME;
550 fsnotify_modify(victim);
556 * Drop the reference acquired from lookup_one_len() above.
560 mutex_unlock(&dir->d_inode->i_mutex);
567 * sysfs_chmod_file - update the modified mode value on an object attribute.
568 * @kobj: object we're acting for.
569 * @attr: attribute descriptor.
570 * @mode: file permissions.
573 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
575 struct dentry *dir = kobj->dentry;
576 struct dentry *victim;
577 struct inode * inode;
578 struct iattr newattrs;
581 mutex_lock(&dir->d_inode->i_mutex);
582 victim = lookup_one_len(attr->name, dir, strlen(attr->name));
583 if (!IS_ERR(victim)) {
584 if (victim->d_inode &&
585 (victim->d_parent->d_inode == dir->d_inode)) {
586 inode = victim->d_inode;
587 mutex_lock(&inode->i_mutex);
588 newattrs.ia_mode = (mode & S_IALLUGO) |
589 (inode->i_mode & ~S_IALLUGO);
590 newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
591 res = notify_change(victim, &newattrs);
592 mutex_unlock(&inode->i_mutex);
596 mutex_unlock(&dir->d_inode->i_mutex);
600 EXPORT_SYMBOL_GPL(sysfs_chmod_file);
604 * sysfs_remove_file - remove an object attribute.
605 * @kobj: object we're acting for.
606 * @attr: attribute descriptor.
608 * Hash the attribute name and kill the victim.
611 void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
613 sysfs_hash_and_remove(kobj->dentry, attr->name);
618 * sysfs_remove_file_from_group - remove an attribute file from a group.
619 * @kobj: object we're acting for.
620 * @attr: attribute descriptor.
621 * @group: group name.
623 void sysfs_remove_file_from_group(struct kobject *kobj,
624 const struct attribute *attr, const char *group)
628 dir = lookup_one_len(group, kobj->dentry, strlen(group));
630 sysfs_hash_and_remove(dir, attr->name);
634 EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
636 struct sysfs_schedule_callback_struct {
637 struct kobject *kobj;
638 void (*func)(void *);
640 struct module *owner;
641 struct work_struct work;
644 static void sysfs_schedule_callback_work(struct work_struct *work)
646 struct sysfs_schedule_callback_struct *ss = container_of(work,
647 struct sysfs_schedule_callback_struct, work);
649 (ss->func)(ss->data);
650 kobject_put(ss->kobj);
651 module_put(ss->owner);
656 * sysfs_schedule_callback - helper to schedule a callback for a kobject
657 * @kobj: object we're acting for.
658 * @func: callback function to invoke later.
659 * @data: argument to pass to @func.
660 * @owner: module owning the callback code
662 * sysfs attribute methods must not unregister themselves or their parent
663 * kobject (which would amount to the same thing). Attempts to do so will
664 * deadlock, since unregistration is mutually exclusive with driver
667 * Instead methods can call this routine, which will attempt to allocate
668 * and schedule a workqueue request to call back @func with @data as its
669 * argument in the workqueue's process context. @kobj will be pinned
670 * until @func returns.
672 * Returns 0 if the request was submitted, -ENOMEM if storage could not
673 * be allocated, -ENODEV if a reference to @owner isn't available.
675 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
676 void *data, struct module *owner)
678 struct sysfs_schedule_callback_struct *ss;
680 if (!try_module_get(owner))
682 ss = kmalloc(sizeof(*ss), GFP_KERNEL);
692 INIT_WORK(&ss->work, sysfs_schedule_callback_work);
693 schedule_work(&ss->work);
696 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
699 EXPORT_SYMBOL_GPL(sysfs_create_file);
700 EXPORT_SYMBOL_GPL(sysfs_remove_file);
701 EXPORT_SYMBOL_GPL(sysfs_update_file);