| /* |
| * file.c - operations for regular (text) files. |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/kobject.h> |
| #include <linux/namei.h> |
| #include <linux/poll.h> |
| #include <linux/list.h> |
| #include <linux/mutex.h> |
| #include <asm/uaccess.h> |
| |
| #include "sysfs.h" |
| |
| #define to_sattr(a) container_of(a,struct subsys_attribute, attr) |
| |
| /* |
| * Subsystem file operations. |
| * These operations allow subsystems to have files that can be |
| * read/written. |
| */ |
| static ssize_t |
| subsys_attr_show(struct kobject * kobj, struct attribute * attr, char * page) |
| { |
| struct kset *kset = to_kset(kobj); |
| struct subsys_attribute * sattr = to_sattr(attr); |
| ssize_t ret = -EIO; |
| |
| if (sattr->show) |
| ret = sattr->show(kset, page); |
| return ret; |
| } |
| |
| static ssize_t |
| subsys_attr_store(struct kobject * kobj, struct attribute * attr, |
| const char * page, size_t count) |
| { |
| struct kset *kset = to_kset(kobj); |
| struct subsys_attribute * sattr = to_sattr(attr); |
| ssize_t ret = -EIO; |
| |
| if (sattr->store) |
| ret = sattr->store(kset, page, count); |
| return ret; |
| } |
| |
| static struct sysfs_ops subsys_sysfs_ops = { |
| .show = subsys_attr_show, |
| .store = subsys_attr_store, |
| }; |
| |
| /* |
| * There's one sysfs_buffer for each open file and one |
| * sysfs_open_dirent for each sysfs_dirent with one or more open |
| * files. |
| * |
| * filp->private_data points to sysfs_buffer and |
| * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open |
| * is protected by sysfs_open_dirent_lock. |
| */ |
| static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED; |
| |
| struct sysfs_open_dirent { |
| atomic_t refcnt; |
| atomic_t event; |
| wait_queue_head_t poll; |
| struct list_head buffers; /* goes through sysfs_buffer.list */ |
| }; |
| |
| struct sysfs_buffer { |
| size_t count; |
| loff_t pos; |
| char * page; |
| struct sysfs_ops * ops; |
| struct mutex mutex; |
| int needs_read_fill; |
| int event; |
| struct list_head list; |
| }; |
| |
| /** |
| * fill_read_buffer - allocate and fill buffer from object. |
| * @dentry: dentry pointer. |
| * @buffer: data buffer for file. |
| * |
| * Allocate @buffer->page, if it hasn't been already, then call the |
| * kobject's show() method to fill the buffer with this attribute's |
| * data. |
| * This is called only once, on the file's first read unless an error |
| * is returned. |
| */ |
| static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer) |
| { |
| struct sysfs_dirent *attr_sd = dentry->d_fsdata; |
| struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; |
| struct sysfs_ops * ops = buffer->ops; |
| int ret = 0; |
| ssize_t count; |
| |
| if (!buffer->page) |
| buffer->page = (char *) get_zeroed_page(GFP_KERNEL); |
| if (!buffer->page) |
| return -ENOMEM; |
| |
| /* need attr_sd for attr and ops, its parent for kobj */ |
| if (!sysfs_get_active_two(attr_sd)) |
| return -ENODEV; |
| |
| buffer->event = atomic_read(&attr_sd->s_attr.open->event); |
| count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page); |
| |
| sysfs_put_active_two(attr_sd); |
| |
| BUG_ON(count > (ssize_t)PAGE_SIZE); |
| if (count >= 0) { |
| buffer->needs_read_fill = 0; |
| buffer->count = count; |
| } else { |
| ret = count; |
| } |
| return ret; |
| } |
| |
| /** |
| * sysfs_read_file - read an attribute. |
| * @file: file pointer. |
| * @buf: buffer to fill. |
| * @count: number of bytes to read. |
| * @ppos: starting offset in file. |
| * |
| * Userspace wants to read an attribute file. The attribute descriptor |
| * is in the file's ->d_fsdata. The target object is in the directory's |
| * ->d_fsdata. |
| * |
| * We call fill_read_buffer() to allocate and fill the buffer from the |
| * object's show() method exactly once (if the read is happening from |
| * the beginning of the file). That should fill the entire buffer with |
| * all the data the object has to offer for that attribute. |
| * We then call flush_read_buffer() to copy the buffer to userspace |
| * in the increments specified. |
| */ |
| |
| static ssize_t |
| sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) |
| { |
| struct sysfs_buffer * buffer = file->private_data; |
| ssize_t retval = 0; |
| |
| mutex_lock(&buffer->mutex); |
| if (buffer->needs_read_fill) { |
| retval = fill_read_buffer(file->f_path.dentry,buffer); |
| if (retval) |
| goto out; |
| } |
| pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n", |
| __FUNCTION__, count, *ppos, buffer->page); |
| retval = simple_read_from_buffer(buf, count, ppos, buffer->page, |
| buffer->count); |
| out: |
| mutex_unlock(&buffer->mutex); |
| return retval; |
| } |
| |
| /** |
| * fill_write_buffer - copy buffer from userspace. |
| * @buffer: data buffer for file. |
| * @buf: data from user. |
| * @count: number of bytes in @userbuf. |
| * |
| * Allocate @buffer->page if it hasn't been already, then |
| * copy the user-supplied buffer into it. |
| */ |
| |
| static int |
| fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count) |
| { |
| int error; |
| |
| if (!buffer->page) |
| buffer->page = (char *)get_zeroed_page(GFP_KERNEL); |
| if (!buffer->page) |
| return -ENOMEM; |
| |
| if (count >= PAGE_SIZE) |
| count = PAGE_SIZE - 1; |
| error = copy_from_user(buffer->page,buf,count); |
| buffer->needs_read_fill = 1; |
| /* if buf is assumed to contain a string, terminate it by \0, |
| so e.g. sscanf() can scan the string easily */ |
| buffer->page[count] = 0; |
| return error ? -EFAULT : count; |
| } |
| |
| |
| /** |
| * flush_write_buffer - push buffer to kobject. |
| * @dentry: dentry to the attribute |
| * @buffer: data buffer for file. |
| * @count: number of bytes |
| * |
| * Get the correct pointers for the kobject and the attribute we're |
| * dealing with, then call the store() method for the attribute, |
| * passing the buffer that we acquired in fill_write_buffer(). |
| */ |
| |
| static int |
| flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count) |
| { |
| struct sysfs_dirent *attr_sd = dentry->d_fsdata; |
| struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; |
| struct sysfs_ops * ops = buffer->ops; |
| int rc; |
| |
| /* need attr_sd for attr and ops, its parent for kobj */ |
| if (!sysfs_get_active_two(attr_sd)) |
| return -ENODEV; |
| |
| rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count); |
| |
| sysfs_put_active_two(attr_sd); |
| |
| return rc; |
| } |
| |
| |
| /** |
| * sysfs_write_file - write an attribute. |
| * @file: file pointer |
| * @buf: data to write |
| * @count: number of bytes |
| * @ppos: starting offset |
| * |
| * Similar to sysfs_read_file(), though working in the opposite direction. |
| * We allocate and fill the data from the user in fill_write_buffer(), |
| * then push it to the kobject in flush_write_buffer(). |
| * There is no easy way for us to know if userspace is only doing a partial |
| * write, so we don't support them. We expect the entire buffer to come |
| * on the first write. |
| * Hint: if you're writing a value, first read the file, modify only the |
| * the value you're changing, then write entire buffer back. |
| */ |
| |
| static ssize_t |
| sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) |
| { |
| struct sysfs_buffer * buffer = file->private_data; |
| ssize_t len; |
| |
| mutex_lock(&buffer->mutex); |
| len = fill_write_buffer(buffer, buf, count); |
| if (len > 0) |
| len = flush_write_buffer(file->f_path.dentry, buffer, len); |
| if (len > 0) |
| *ppos += len; |
| mutex_unlock(&buffer->mutex); |
| return len; |
| } |
| |
| /** |
| * sysfs_get_open_dirent - get or create sysfs_open_dirent |
| * @sd: target sysfs_dirent |
| * @buffer: sysfs_buffer for this instance of open |
| * |
| * If @sd->s_attr.open exists, increment its reference count; |
| * otherwise, create one. @buffer is chained to the buffers |
| * list. |
| * |
| * LOCKING: |
| * Kernel thread context (may sleep). |
| * |
| * RETURNS: |
| * 0 on success, -errno on failure. |
| */ |
| static int sysfs_get_open_dirent(struct sysfs_dirent *sd, |
| struct sysfs_buffer *buffer) |
| { |
| struct sysfs_open_dirent *od, *new_od = NULL; |
| |
| retry: |
| spin_lock(&sysfs_open_dirent_lock); |
| |
| if (!sd->s_attr.open && new_od) { |
| sd->s_attr.open = new_od; |
| new_od = NULL; |
| } |
| |
| od = sd->s_attr.open; |
| if (od) { |
| atomic_inc(&od->refcnt); |
| list_add_tail(&buffer->list, &od->buffers); |
| } |
| |
| spin_unlock(&sysfs_open_dirent_lock); |
| |
| if (od) { |
| kfree(new_od); |
| return 0; |
| } |
| |
| /* not there, initialize a new one and retry */ |
| new_od = kmalloc(sizeof(*new_od), GFP_KERNEL); |
| if (!new_od) |
| return -ENOMEM; |
| |
| atomic_set(&new_od->refcnt, 0); |
| atomic_set(&new_od->event, 1); |
| init_waitqueue_head(&new_od->poll); |
| INIT_LIST_HEAD(&new_od->buffers); |
| goto retry; |
| } |
| |
| /** |
| * sysfs_put_open_dirent - put sysfs_open_dirent |
| * @sd: target sysfs_dirent |
| * @buffer: associated sysfs_buffer |
| * |
| * Put @sd->s_attr.open and unlink @buffer from the buffers list. |
| * If reference count reaches zero, disassociate and free it. |
| * |
| * LOCKING: |
| * None. |
| */ |
| static void sysfs_put_open_dirent(struct sysfs_dirent *sd, |
| struct sysfs_buffer *buffer) |
| { |
| struct sysfs_open_dirent *od = sd->s_attr.open; |
| |
| spin_lock(&sysfs_open_dirent_lock); |
| |
| list_del(&buffer->list); |
| if (atomic_dec_and_test(&od->refcnt)) |
| sd->s_attr.open = NULL; |
| else |
| od = NULL; |
| |
| spin_unlock(&sysfs_open_dirent_lock); |
| |
| kfree(od); |
| } |
| |
| static int sysfs_open_file(struct inode *inode, struct file *file) |
| { |
| struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata; |
| struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; |
| struct sysfs_buffer * buffer; |
| struct sysfs_ops * ops = NULL; |
| int error; |
| |
| /* need attr_sd for attr and ops, its parent for kobj */ |
| if (!sysfs_get_active_two(attr_sd)) |
| return -ENODEV; |
| |
| /* if the kobject has no ktype, then we assume that it is a subsystem |
| * itself, and use ops for it. |
| */ |
| if (kobj->kset && kobj->kset->ktype) |
| ops = kobj->kset->ktype->sysfs_ops; |
| else if (kobj->ktype) |
| ops = kobj->ktype->sysfs_ops; |
| else |
| ops = &subsys_sysfs_ops; |
| |
| error = -EACCES; |
| |
| /* No sysfs operations, either from having no subsystem, |
| * or the subsystem have no operations. |
| */ |
| if (!ops) |
| goto err_out; |
| |
| /* File needs write support. |
| * The inode's perms must say it's ok, |
| * and we must have a store method. |
| */ |
| if (file->f_mode & FMODE_WRITE) { |
| if (!(inode->i_mode & S_IWUGO) || !ops->store) |
| goto err_out; |
| } |
| |
| /* File needs read support. |
| * The inode's perms must say it's ok, and we there |
| * must be a show method for it. |
| */ |
| if (file->f_mode & FMODE_READ) { |
| if (!(inode->i_mode & S_IRUGO) || !ops->show) |
| goto err_out; |
| } |
| |
| /* No error? Great, allocate a buffer for the file, and store it |
| * it in file->private_data for easy access. |
| */ |
| error = -ENOMEM; |
| buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL); |
| if (!buffer) |
| goto err_out; |
| |
| mutex_init(&buffer->mutex); |
| buffer->needs_read_fill = 1; |
| buffer->ops = ops; |
| file->private_data = buffer; |
| |
| /* make sure we have open dirent struct */ |
| error = sysfs_get_open_dirent(attr_sd, buffer); |
| if (error) |
| goto err_free; |
| |
| /* open succeeded, put active references */ |
| sysfs_put_active_two(attr_sd); |
| return 0; |
| |
| err_free: |
| kfree(buffer); |
| err_out: |
| sysfs_put_active_two(attr_sd); |
| return error; |
| } |
| |
| static int sysfs_release(struct inode *inode, struct file *filp) |
| { |
| struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata; |
| struct sysfs_buffer *buffer = filp->private_data; |
| |
| sysfs_put_open_dirent(sd, buffer); |
| |
| if (buffer->page) |
| free_page((unsigned long)buffer->page); |
| kfree(buffer); |
| |
| return 0; |
| } |
| |
| /* Sysfs attribute files are pollable. The idea is that you read |
| * the content and then you use 'poll' or 'select' to wait for |
| * the content to change. When the content changes (assuming the |
| * manager for the kobject supports notification), poll will |
| * return POLLERR|POLLPRI, and select will return the fd whether |
| * it is waiting for read, write, or exceptions. |
| * Once poll/select indicates that the value has changed, you |
| * need to close and re-open the file, as simply seeking and reading |
| * again will not get new data, or reset the state of 'poll'. |
| * Reminder: this only works for attributes which actively support |
| * it, and it is not possible to test an attribute from userspace |
| * to see if it supports poll (Neither 'poll' nor 'select' return |
| * an appropriate error code). When in doubt, set a suitable timeout value. |
| */ |
| static unsigned int sysfs_poll(struct file *filp, poll_table *wait) |
| { |
| struct sysfs_buffer * buffer = filp->private_data; |
| struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata; |
| struct sysfs_open_dirent *od = attr_sd->s_attr.open; |
| |
| /* need parent for the kobj, grab both */ |
| if (!sysfs_get_active_two(attr_sd)) |
| goto trigger; |
| |
| poll_wait(filp, &od->poll, wait); |
| |
| sysfs_put_active_two(attr_sd); |
| |
| if (buffer->event != atomic_read(&od->event)) |
| goto trigger; |
| |
| return 0; |
| |
| trigger: |
| buffer->needs_read_fill = 1; |
| return POLLERR|POLLPRI; |
| } |
| |
| void sysfs_notify(struct kobject *k, char *dir, char *attr) |
| { |
| struct sysfs_dirent *sd = k->sd; |
| |
| mutex_lock(&sysfs_mutex); |
| |
| if (sd && dir) |
| sd = sysfs_find_dirent(sd, dir); |
| if (sd && attr) |
| sd = sysfs_find_dirent(sd, attr); |
| if (sd) { |
| struct sysfs_open_dirent *od; |
| |
| spin_lock(&sysfs_open_dirent_lock); |
| |
| od = sd->s_attr.open; |
| if (od) { |
| atomic_inc(&od->event); |
| wake_up_interruptible(&od->poll); |
| } |
| |
| spin_unlock(&sysfs_open_dirent_lock); |
| } |
| |
| mutex_unlock(&sysfs_mutex); |
| } |
| EXPORT_SYMBOL_GPL(sysfs_notify); |
| |
| const struct file_operations sysfs_file_operations = { |
| .read = sysfs_read_file, |
| .write = sysfs_write_file, |
| .llseek = generic_file_llseek, |
| .open = sysfs_open_file, |
| .release = sysfs_release, |
| .poll = sysfs_poll, |
| }; |
| |
| |
| int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr, |
| int type) |
| { |
| umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG; |
| struct sysfs_addrm_cxt acxt; |
| struct sysfs_dirent *sd; |
| int rc; |
| |
| sd = sysfs_new_dirent(attr->name, mode, type); |
| if (!sd) |
| return -ENOMEM; |
| sd->s_attr.attr = (void *)attr; |
| |
| sysfs_addrm_start(&acxt, dir_sd); |
| rc = sysfs_add_one(&acxt, sd); |
| sysfs_addrm_finish(&acxt); |
| |
| if (rc) |
| sysfs_put(sd); |
| |
| return rc; |
| } |
| |
| |
| /** |
| * sysfs_create_file - create an attribute file for an object. |
| * @kobj: object we're creating for. |
| * @attr: atrribute descriptor. |
| */ |
| |
| int sysfs_create_file(struct kobject * kobj, const struct attribute * attr) |
| { |
| BUG_ON(!kobj || !kobj->sd || !attr); |
| |
| return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR); |
| |
| } |
| |
| |
| /** |
| * sysfs_add_file_to_group - add an attribute file to a pre-existing group. |
| * @kobj: object we're acting for. |
| * @attr: attribute descriptor. |
| * @group: group name. |
| */ |
| int sysfs_add_file_to_group(struct kobject *kobj, |
| const struct attribute *attr, const char *group) |
| { |
| struct sysfs_dirent *dir_sd; |
| int error; |
| |
| dir_sd = sysfs_get_dirent(kobj->sd, group); |
| if (!dir_sd) |
| return -ENOENT; |
| |
| error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR); |
| sysfs_put(dir_sd); |
| |
| return error; |
| } |
| EXPORT_SYMBOL_GPL(sysfs_add_file_to_group); |
| |
| /** |
| * sysfs_chmod_file - update the modified mode value on an object attribute. |
| * @kobj: object we're acting for. |
| * @attr: attribute descriptor. |
| * @mode: file permissions. |
| * |
| */ |
| int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode) |
| { |
| struct sysfs_dirent *victim_sd = NULL; |
| struct dentry *victim = NULL; |
| struct inode * inode; |
| struct iattr newattrs; |
| int rc; |
| |
| rc = -ENOENT; |
| victim_sd = sysfs_get_dirent(kobj->sd, attr->name); |
| if (!victim_sd) |
| goto out; |
| |
| mutex_lock(&sysfs_rename_mutex); |
| victim = sysfs_get_dentry(victim_sd); |
| mutex_unlock(&sysfs_rename_mutex); |
| if (IS_ERR(victim)) { |
| rc = PTR_ERR(victim); |
| victim = NULL; |
| goto out; |
| } |
| |
| inode = victim->d_inode; |
| |
| mutex_lock(&inode->i_mutex); |
| |
| newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO); |
| newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; |
| rc = notify_change(victim, &newattrs); |
| |
| if (rc == 0) { |
| mutex_lock(&sysfs_mutex); |
| victim_sd->s_mode = newattrs.ia_mode; |
| mutex_unlock(&sysfs_mutex); |
| } |
| |
| mutex_unlock(&inode->i_mutex); |
| out: |
| dput(victim); |
| sysfs_put(victim_sd); |
| return rc; |
| } |
| EXPORT_SYMBOL_GPL(sysfs_chmod_file); |
| |
| |
| /** |
| * sysfs_remove_file - remove an object attribute. |
| * @kobj: object we're acting for. |
| * @attr: attribute descriptor. |
| * |
| * Hash the attribute name and kill the victim. |
| */ |
| |
| void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr) |
| { |
| sysfs_hash_and_remove(kobj->sd, attr->name); |
| } |
| |
| |
| /** |
| * sysfs_remove_file_from_group - remove an attribute file from a group. |
| * @kobj: object we're acting for. |
| * @attr: attribute descriptor. |
| * @group: group name. |
| */ |
| void sysfs_remove_file_from_group(struct kobject *kobj, |
| const struct attribute *attr, const char *group) |
| { |
| struct sysfs_dirent *dir_sd; |
| |
| dir_sd = sysfs_get_dirent(kobj->sd, group); |
| if (dir_sd) { |
| sysfs_hash_and_remove(dir_sd, attr->name); |
| sysfs_put(dir_sd); |
| } |
| } |
| EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group); |
| |
| struct sysfs_schedule_callback_struct { |
| struct kobject *kobj; |
| void (*func)(void *); |
| void *data; |
| struct module *owner; |
| struct work_struct work; |
| }; |
| |
| static void sysfs_schedule_callback_work(struct work_struct *work) |
| { |
| struct sysfs_schedule_callback_struct *ss = container_of(work, |
| struct sysfs_schedule_callback_struct, work); |
| |
| (ss->func)(ss->data); |
| kobject_put(ss->kobj); |
| module_put(ss->owner); |
| kfree(ss); |
| } |
| |
| /** |
| * sysfs_schedule_callback - helper to schedule a callback for a kobject |
| * @kobj: object we're acting for. |
| * @func: callback function to invoke later. |
| * @data: argument to pass to @func. |
| * @owner: module owning the callback code |
| * |
| * sysfs attribute methods must not unregister themselves or their parent |
| * kobject (which would amount to the same thing). Attempts to do so will |
| * deadlock, since unregistration is mutually exclusive with driver |
| * callbacks. |
| * |
| * Instead methods can call this routine, which will attempt to allocate |
| * and schedule a workqueue request to call back @func with @data as its |
| * argument in the workqueue's process context. @kobj will be pinned |
| * until @func returns. |
| * |
| * Returns 0 if the request was submitted, -ENOMEM if storage could not |
| * be allocated, -ENODEV if a reference to @owner isn't available. |
| */ |
| int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *), |
| void *data, struct module *owner) |
| { |
| struct sysfs_schedule_callback_struct *ss; |
| |
| if (!try_module_get(owner)) |
| return -ENODEV; |
| ss = kmalloc(sizeof(*ss), GFP_KERNEL); |
| if (!ss) { |
| module_put(owner); |
| return -ENOMEM; |
| } |
| kobject_get(kobj); |
| ss->kobj = kobj; |
| ss->func = func; |
| ss->data = data; |
| ss->owner = owner; |
| INIT_WORK(&ss->work, sysfs_schedule_callback_work); |
| schedule_work(&ss->work); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(sysfs_schedule_callback); |
| |
| |
| EXPORT_SYMBOL_GPL(sysfs_create_file); |
| EXPORT_SYMBOL_GPL(sysfs_remove_file); |