file.c

linux 内核源代码

	 */
	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:	attribute 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);