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/*

 * 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/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);

        /*

         * The code works fine with PAGE_SIZE return but it's likely to

         * indicate truncated result or overflow in normal use cases.

         */

        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:  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;