android_kernel_motorola_sm6225/fs/sysfs/file.c
NeilBrown 4508a7a734 [PATCH] sysfs: Allow sysfs attribute files to be pollable
It works like this:
  Open the file
  Read all the contents.
  Call poll requesting POLLERR or POLLPRI (so select/exceptfds works)
  When poll returns,
     close the file and go to top of loop.
   or lseek to start of file and go back to the 'read'.

Events are signaled by an object manager calling
   sysfs_notify(kobj, dir, attr);

If the dir is non-NULL, it is used to find a subdirectory which
contains the attribute (presumably created by sysfs_create_group).

This has a cost of one int  per attribute, one wait_queuehead per kobject,
one int per open file.

The name "sysfs_notify" may be confused with the inotify
functionality.  Maybe it would be nice to support inotify for sysfs
attributes as well?

This patch also uses sysfs_notify to allow /sys/block/md*/md/sync_action
to be pollable

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-04-14 11:41:24 -07:00

559 lines
14 KiB
C

/*
* 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 <asm/uaccess.h>
#include <asm/semaphore.h>
#include "sysfs.h"
#define to_subsys(k) container_of(k,struct subsystem,kset.kobj)
#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 subsystem * s = to_subsys(kobj);
struct subsys_attribute * sattr = to_sattr(attr);
ssize_t ret = -EIO;
if (sattr->show)
ret = sattr->show(s,page);
return ret;
}
static ssize_t
subsys_attr_store(struct kobject * kobj, struct attribute * attr,
const char * page, size_t count)
{
struct subsystem * s = to_subsys(kobj);
struct subsys_attribute * sattr = to_sattr(attr);
ssize_t ret = -EIO;
if (sattr->store)
ret = sattr->store(s,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 semaphore sem;
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.
*/
static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
struct sysfs_dirent * sd = dentry->d_fsdata;
struct attribute * attr = to_attr(dentry);
struct kobject * kobj = to_kobj(dentry->d_parent);
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;
buffer->event = atomic_read(&sd->s_event);
count = ops->show(kobj,attr,buffer->page);
buffer->needs_read_fill = 0;
BUG_ON(count > (ssize_t)PAGE_SIZE);
if (count >= 0)
buffer->count = count;
else
ret = count;
return ret;
}
/**
* flush_read_buffer - push buffer to userspace.
* @buffer: data buffer for file.
* @buf: user-passed buffer.
* @count: number of bytes requested.
* @ppos: file position.
*
* Copy the buffer we filled in fill_read_buffer() to userspace.
* This is done at the reader's leisure, copying and advancing
* the amount they specify each time.
* This may be called continuously until the buffer is empty.
*/
static int flush_read_buffer(struct sysfs_buffer * buffer, char __user * buf,
size_t count, loff_t * ppos)
{
int error;
if (*ppos > buffer->count)
return 0;
if (count > (buffer->count - *ppos))
count = buffer->count - *ppos;
error = copy_to_user(buf,buffer->page + *ppos,count);
if (!error)
*ppos += count;
return error ? -EFAULT : count;
}
/**
* 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;
down(&buffer->sem);
if (buffer->needs_read_fill) {
if ((retval = fill_read_buffer(file->f_dentry,buffer)))
goto out;
}
pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
__FUNCTION__,count,*ppos,buffer->page);
retval = flush_read_buffer(buffer,buf,count,ppos);
out:
up(&buffer->sem);
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;
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 attribute * attr = to_attr(dentry);
struct kobject * kobj = to_kobj(dentry->d_parent);
struct sysfs_ops * ops = buffer->ops;
return ops->store(kobj,attr,buffer->page,count);
}
/**
* 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;
down(&buffer->sem);
len = fill_write_buffer(buffer, buf, count);
if (len > 0)
len = flush_write_buffer(file->f_dentry, buffer, len);
if (len > 0)
*ppos += len;
up(&buffer->sem);
return len;
}
static int check_perm(struct inode * inode, struct file * file)
{
struct kobject *kobj = sysfs_get_kobject(file->f_dentry->d_parent);
struct attribute * attr = to_attr(file->f_dentry);
struct sysfs_buffer * buffer;
struct sysfs_ops * ops = NULL;
int error = 0;
if (!kobj || !attr)
goto Einval;
/* Grab the module reference for this attribute if we have one */
if (!try_module_get(attr->owner)) {
error = -ENODEV;
goto Done;
}
/* 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;
/* No sysfs operations, either from having no subsystem,
* or the subsystem have no operations.
*/
if (!ops)
goto Eaccess;
/* 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 Eaccess;
}
/* 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 Eaccess;
}
/* No error? Great, allocate a buffer for the file, and store it
* it in file->private_data for easy access.
*/
buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
if (buffer) {
init_MUTEX(&buffer->sem);
buffer->needs_read_fill = 1;
buffer->ops = ops;
file->private_data = buffer;
} else
error = -ENOMEM;
goto Done;
Einval:
error = -EINVAL;
goto Done;
Eaccess:
error = -EACCES;
module_put(attr->owner);
Done:
if (error && kobj)
kobject_put(kobj);
return error;
}
static int sysfs_open_file(struct inode * inode, struct file * filp)
{
return check_perm(inode,filp);
}
static int sysfs_release(struct inode * inode, struct file * filp)
{
struct kobject * kobj = to_kobj(filp->f_dentry->d_parent);
struct attribute * attr = to_attr(filp->f_dentry);
struct module * owner = attr->owner;
struct sysfs_buffer * buffer = filp->private_data;
if (kobj)
kobject_put(kobj);
/* After this point, attr should not be accessed. */
module_put(owner);
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 kobject * kobj = to_kobj(filp->f_dentry->d_parent);
struct sysfs_dirent * sd = filp->f_dentry->d_fsdata;
int res = 0;
poll_wait(filp, &kobj->poll, wait);
if (buffer->event != atomic_read(&sd->s_event)) {
res = POLLERR|POLLPRI;
buffer->needs_read_fill = 1;
}
return res;
}
static struct dentry *step_down(struct dentry *dir, const char * name)
{
struct dentry * de;
if (dir == NULL || dir->d_inode == NULL)
return NULL;
mutex_lock(&dir->d_inode->i_mutex);
de = lookup_one_len(name, dir, strlen(name));
mutex_unlock(&dir->d_inode->i_mutex);
dput(dir);
if (IS_ERR(de))
return NULL;
if (de->d_inode == NULL) {
dput(de);
return NULL;
}
return de;
}
void sysfs_notify(struct kobject * k, char *dir, char *attr)
{
struct dentry *de = k->dentry;
if (de)
dget(de);
if (de && dir)
de = step_down(de, dir);
if (de && attr)
de = step_down(de, attr);
if (de) {
struct sysfs_dirent * sd = de->d_fsdata;
if (sd)
atomic_inc(&sd->s_event);
wake_up_interruptible(&k->poll);
dput(de);
}
}
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 dentry * dir, const struct attribute * attr, int type)
{
struct sysfs_dirent * parent_sd = dir->d_fsdata;
umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
int error = -EEXIST;
mutex_lock(&dir->d_inode->i_mutex);
if (!sysfs_dirent_exist(parent_sd, attr->name))
error = sysfs_make_dirent(parent_sd, NULL, (void *)attr,
mode, type);
mutex_unlock(&dir->d_inode->i_mutex);
return error;
}
/**
* 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->dentry || !attr);
return sysfs_add_file(kobj->dentry, attr, SYSFS_KOBJ_ATTR);
}
/**
* 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 dentry * dir = kobj->dentry;
struct dentry * victim;
int res = -ENOENT;
mutex_lock(&dir->d_inode->i_mutex);
victim = lookup_one_len(attr->name, dir, strlen(attr->name));
if (!IS_ERR(victim)) {
/* make sure dentry is really there */
if (victim->d_inode &&
(victim->d_parent->d_inode == dir->d_inode)) {
victim->d_inode->i_mtime = CURRENT_TIME;
fsnotify_modify(victim);
/**
* Drop reference from initial sysfs_get_dentry().
*/
dput(victim);
res = 0;
} else
d_drop(victim);
/**
* Drop the reference acquired from sysfs_get_dentry() above.
*/
dput(victim);
}
mutex_unlock(&dir->d_inode->i_mutex);
return res;
}
/**
* 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 dentry *dir = kobj->dentry;
struct dentry *victim;
struct inode * inode;
struct iattr newattrs;
int res = -ENOENT;
mutex_lock(&dir->d_inode->i_mutex);
victim = lookup_one_len(attr->name, dir, strlen(attr->name));
if (!IS_ERR(victim)) {
if (victim->d_inode &&
(victim->d_parent->d_inode == dir->d_inode)) {
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;
res = notify_change(victim, &newattrs);
mutex_unlock(&inode->i_mutex);
}
dput(victim);
}
mutex_unlock(&dir->d_inode->i_mutex);
return res;
}
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->dentry,attr->name);
}
EXPORT_SYMBOL_GPL(sysfs_create_file);
EXPORT_SYMBOL_GPL(sysfs_remove_file);
EXPORT_SYMBOL_GPL(sysfs_update_file);