init android origin source code

1 files changed, 799 insertions, 0 deletions

diff --git a/ANDROID_3.4.5/fs/sysfs/file.c b/ANDROID_3.4.5/fs/sysfs/file.c
new file mode 100644
index 00000000..00012e31
--- /dev/null
+++ b/ANDROID_3.4.5/fs/sysfs/file.c
@@ -0,0 +1,799 @@
+/*
+ * fs/sysfs/file.c - sysfs regular (text) file implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/kallsyms.h>
+#include <linux/slab.h>
+#include <linux/fsnotify.h>
+#include <linux/namei.h>
+#include <linux/poll.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/limits.h>
+#include <asm/uaccess.h>
+
+#include "sysfs.h"
+
+/*
+ * 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 DEFINE_SPINLOCK(sysfs_open_dirent_lock);
+
+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;
+	const 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;
+	const 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(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(attr_sd);
+
+	/*
+	 * The code works fine with PAGE_SIZE return but it's likely to
+	 * indicate truncated result or overflow in normal use cases.
+	 */
+	if (count >= (ssize_t)PAGE_SIZE) {
+		print_symbol("fill_read_buffer: %s returned bad count\n",
+			(unsigned long)ops->show);
+		/* Try to struggle along */
+		count = PAGE_SIZE - 1;
+	}
+	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 || *ppos == 0) {
+		retval = fill_read_buffer(file->f_path.dentry,buffer);
+		if (retval)
+			goto out;
+	}
+	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
+		 __func__, 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;
+	const struct sysfs_ops * ops = buffer->ops;
+	int rc;
+
+	/* need attr_sd for attr and ops, its parent for kobj */
+	if (!sysfs_get_active(attr_sd))
+		return -ENODEV;
+
+	rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count);
+
+	sysfs_put_active(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_irq(&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_irq(&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;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
+
+	list_del(&buffer->list);
+	if (atomic_dec_and_test(&od->refcnt))
+		sd->s_attr.open = NULL;
+	else
+		od = NULL;
+
+	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
+
+	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;
+	const struct sysfs_ops *ops;
+	int error = -EACCES;
+
+	/* need attr_sd for attr and ops, its parent for kobj */
+	if (!sysfs_get_active(attr_sd))
+		return -ENODEV;
+
+	/* every kobject with an attribute needs a ktype assigned */
+	if (kobj->ktype && kobj->ktype->sysfs_ops)
+		ops = kobj->ktype->sysfs_ops;
+	else {
+		WARN(1, KERN_ERR "missing sysfs attribute operations for "
+		       "kobject: %s\n", kobject_name(kobj));
+		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(attr_sd);
+	return 0;
+
+ err_free:
+	kfree(buffer);
+ err_out:
+	sysfs_put_active(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, or seek to 0 and read again.
+ * 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(attr_sd))
+		goto trigger;
+
+	poll_wait(filp, &od->poll, wait);
+
+	sysfs_put_active(attr_sd);
+
+	if (buffer->event != atomic_read(&od->event))
+		goto trigger;
+
+	return DEFAULT_POLLMASK;
+
+ trigger:
+	buffer->needs_read_fill = 1;
+	return DEFAULT_POLLMASK|POLLERR|POLLPRI;
+}
+
+void sysfs_notify_dirent(struct sysfs_dirent *sd)
+{
+	struct sysfs_open_dirent *od;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sysfs_open_dirent_lock, flags);
+
+	od = sd->s_attr.open;
+	if (od) {
+		atomic_inc(&od->event);
+		wake_up_interruptible(&od->poll);
+	}
+
+	spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
+}
+EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
+
+void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
+{
+	struct sysfs_dirent *sd = k->sd;
+
+	mutex_lock(&sysfs_mutex);
+
+	if (sd && dir)
+		sd = sysfs_find_dirent(sd, NULL, dir);
+	if (sd && attr)
+		sd = sysfs_find_dirent(sd, NULL, attr);
+	if (sd)
+		sysfs_notify_dirent(sd);
+
+	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_attr_ns(struct kobject *kobj, const struct attribute *attr,
+		  const void **pns)
+{
+	struct sysfs_dirent *dir_sd = kobj->sd;
+	const struct sysfs_ops *ops;
+	const void *ns = NULL;
+	int err;
+
+	if (!dir_sd) {
+		WARN(1, KERN_ERR "sysfs: kobject %s without dirent\n",
+			kobject_name(kobj));
+		return -ENOENT;
+	}
+
+	err = 0;
+	if (!sysfs_ns_type(dir_sd))
+		goto out;
+
+	err = -EINVAL;
+	if (!kobj->ktype)
+		goto out;
+	ops = kobj->ktype->sysfs_ops;
+	if (!ops)
+		goto out;
+	if (!ops->namespace)
+		goto out;
+
+	err = 0;
+	ns = ops->namespace(kobj, attr);
+out:
+	if (err) {
+		WARN(1, KERN_ERR "missing sysfs namespace attribute operation for "
+		     "kobject: %s\n", kobject_name(kobj));
+	}
+	*pns = ns;
+	return err;
+}
+
+int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
+			const struct attribute *attr, int type, umode_t amode)
+{
+	umode_t mode = (amode & S_IALLUGO) | S_IFREG;
+	struct sysfs_addrm_cxt acxt;
+	struct sysfs_dirent *sd;
+	const void *ns;
+	int rc;
+
+	rc = sysfs_attr_ns(dir_sd->s_dir.kobj, attr, &ns);
+	if (rc)
+		return rc;
+
+	sd = sysfs_new_dirent(attr->name, mode, type);
+	if (!sd)
+		return -ENOMEM;
+
+	sd->s_ns = ns;
+	sd->s_attr.attr = (void *)attr;
+	sysfs_dirent_init_lockdep(sd);
+
+	sysfs_addrm_start(&acxt, dir_sd);
+	rc = sysfs_add_one(&acxt, sd);
+	sysfs_addrm_finish(&acxt);
+
+	if (rc)
+		sysfs_put(sd);
+
+	return rc;
+}
+
+
+int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
+		   int type)
+{
+	return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
+}
+
+
+/**
+ *	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);
+
+}
+
+int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
+{
+	int err = 0;
+	int i;
+
+	for (i = 0; ptr[i] && !err; i++)
+		err = sysfs_create_file(kobj, ptr[i]);
+	if (err)
+		while (--i >= 0)
+			sysfs_remove_file(kobj, ptr[i]);
+	return err;
+}
+
+/**
+ * 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;
+
+	if (group)
+		dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
+	else
+		dir_sd = sysfs_get(kobj->sd);
+
+	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, const struct attribute *attr,
+		     umode_t mode)
+{
+	struct sysfs_dirent *sd;
+	struct iattr newattrs;
+	const void *ns;
+	int rc;
+
+	rc = sysfs_attr_ns(kobj, attr, &ns);
+	if (rc)
+		return rc;
+
+	mutex_lock(&sysfs_mutex);
+
+	rc = -ENOENT;
+	sd = sysfs_find_dirent(kobj->sd, ns, attr->name);
+	if (!sd)
+		goto out;
+
+	newattrs.ia_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
+	newattrs.ia_valid = ATTR_MODE;
+	rc = sysfs_sd_setattr(sd, &newattrs);
+
+ out:
+	mutex_unlock(&sysfs_mutex);
+	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)
+{
+	const void *ns;
+
+	if (sysfs_attr_ns(kobj, attr, &ns))
+		return;
+
+	sysfs_hash_and_remove(kobj->sd, ns, attr->name);
+}
+
+void sysfs_remove_files(struct kobject * kobj, const struct attribute **ptr)
+{
+	int i;
+	for (i = 0; ptr[i]; i++)
+		sysfs_remove_file(kobj, ptr[i]);
+}
+
+/**
+ * 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;
+
+	if (group)
+		dir_sd = sysfs_get_dirent(kobj->sd, NULL, group);
+	else
+		dir_sd = sysfs_get(kobj->sd);
+	if (dir_sd) {
+		sysfs_hash_and_remove(dir_sd, NULL, attr->name);
+		sysfs_put(dir_sd);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
+
+struct sysfs_schedule_callback_struct {
+	struct list_head	workq_list;
+	struct kobject		*kobj;
+	void			(*func)(void *);
+	void			*data;
+	struct module		*owner;
+	struct work_struct	work;
+};
+
+static struct workqueue_struct *sysfs_workqueue;
+static DEFINE_MUTEX(sysfs_workq_mutex);
+static LIST_HEAD(sysfs_workq);
+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);
+	mutex_lock(&sysfs_workq_mutex);
+	list_del(&ss->workq_list);
+	mutex_unlock(&sysfs_workq_mutex);
+	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,
+ * -EAGAIN if a callback has already been scheduled for @kobj.
+ */
+int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
+		void *data, struct module *owner)
+{
+	struct sysfs_schedule_callback_struct *ss, *tmp;
+
+	if (!try_module_get(owner))
+		return -ENODEV;
+
+	mutex_lock(&sysfs_workq_mutex);
+	list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
+		if (ss->kobj == kobj) {
+			module_put(owner);
+			mutex_unlock(&sysfs_workq_mutex);
+			return -EAGAIN;
+		}
+	mutex_unlock(&sysfs_workq_mutex);
+
+	if (sysfs_workqueue == NULL) {
+		sysfs_workqueue = create_singlethread_workqueue("sysfsd");
+		if (sysfs_workqueue == NULL) {
+			module_put(owner);
+			return -ENOMEM;
+		}
+	}
+
+	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);
+	INIT_LIST_HEAD(&ss->workq_list);
+	mutex_lock(&sysfs_workq_mutex);
+	list_add_tail(&ss->workq_list, &sysfs_workq);
+	mutex_unlock(&sysfs_workq_mutex);
+	queue_work(sysfs_workqueue, &ss->work);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
+
+
+EXPORT_SYMBOL_GPL(sysfs_create_file);
+EXPORT_SYMBOL_GPL(sysfs_remove_file);
+EXPORT_SYMBOL_GPL(sysfs_remove_files);
+EXPORT_SYMBOL_GPL(sysfs_create_files);