/*
* file.c - operations for regular (text) files.
*/
#include <linux/module.h>
#include <linux/fsnotify.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,
};
struct sysfs_buffer {
size_t count;
loff_t pos;
char * page;
struct sysfs_ops * ops;
struct mutex mutex;
int needs_read_fill;
int event;
};
/**
* 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_elem.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_event);
count = ops->show(kobj, attr_sd->s_elem.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_elem.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_elem.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;
}
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_elem.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;
/* open succeeded, put active references and pin attr_sd */
sysfs_put_active_two(attr_sd);
sysfs_get(attr_sd);
return 0;
err_out:
sysfs_put_active_two(attr_sd);
return error;
}
static int sysfs_release(struct inode * inode, struct file * filp)
{
struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
struct sysfs_buffer *buffer = filp->private_data;
sysfs_put(attr_sd);
if (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 (Nether 'poll' or '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 kobject *kobj = attr_sd->s_parent->s_elem.dir.kobj;
/* need parent for the kobj, grab both */
if (!sysfs_get_active_two(attr_sd))
goto trigger;
poll_wait(filp, &kobj->poll, wait);
sysfs_put_active_two(attr_sd);
if (buffer->event != atomic_read(&attr_sd->s_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) {
atomic_inc(&sd->s_event);
wake_up_interruptible(&k->poll);
}
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;
sd = sysfs_new_dirent(attr->name, mode, type);
if (!sd)
return -ENOMEM;
sd->s_elem.attr.attr = (void *)attr;
sysfs_addrm_start(&acxt, dir_sd);
if (!sysfs_find_dirent(dir_sd, attr->name)) {
sysfs_add_one(&acxt, sd);
sysfs_link_sibling(sd);
}
if (!sysfs_addrm_finish(&acxt)) {
sysfs_put(sd);
return -EEXIST;
}
return 0;
}
/**
* 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_update_file - update the modified timestamp on an object attribute.
* @kobj: object we're acting for.
* @attr: attribute descriptor.
*/
int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
{
struct sysfs_dirent *victim_sd = NULL;
struct dentry *victim = NULL;
int rc;
rc = -ENOENT;
victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
if (!victim_sd)
goto out;
victim = sysfs_get_dentry(victim_sd);
if (IS_ERR(victim)) {
rc = PTR_ERR(victim);
victim = NULL;
goto out;
}
mutex_lock(&victim->d_inode->i_mutex);
victim->d_inode->i_mtime = CURRENT_TIME;
fsnotify_modify(victim);
mutex_unlock(&victim->d_inode->i_mutex);
rc = 0;
out:
dput(victim);
sysfs_put(victim_sd);
return rc;
}
/**
* 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;
victim = sysfs_get_dentry(victim_sd);
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);
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);
EXPORT_SYMBOL_GPL(sysfs_update_file);
