Am Mittwoch, 4. Oktober 2006 22:15 schrieb Takashi Iwai:
>
> This looks like a good optoin. But one thing we have to be careful
> about is the module counter since the owner is different between the
> old f_op and disconnect_f_op...
>
here is rc1, will test later.
Feel free to pick it apart ;-)
-----------------------------------------------
/* virtual device
hides a real device's f_ops,
except for release
* Copyright (c) by Karsten Wiese <[email protected]>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/module.h>
struct snd_disconnected_file {
struct file *file;
int (*release) (struct inode *, struct file *);
struct snd_disconnected_file *next;
};
static struct snd_disconnected_file *disconnecting_files;
static struct file_operations snd_disconnect_f_ops;
static DEFINE_MUTEX(mutex);
void snd_disconnect_file(struct file *file, int (*release) (struct inode *, struct file *))
{
struct snd_disconnected_file *df, **_dfs;
df = kmalloc(sizeof(struct snd_disconnected_file), GFP_ATOMIC);
if (df == NULL)
panic("Atomic allocation failed for snd_disconnected_file!");
df->file = file;
df->release = release;
df->next = NULL;
mutex_lock(&mutex);
_dfs = &disconnecting_files;
while (*_dfs != NULL)
_dfs = &(*_dfs)->next;
*_dfs = df;
mutex_unlock(&mutex);
{
const struct file_operations *old_f_op = file->f_op;
fops_get(&snd_disconnect_f_ops);
file->f_op = &snd_disconnect_f_ops;
fops_put(old_f_op);
}
}
EXPORT_SYMBOL(snd_disconnect_file);
static loff_t snd_disconnect_llseek(struct file *file, loff_t offset, int orig)
{
return -ENODEV;
}
static ssize_t snd_disconnect_read(struct file *file, char __user *buf,
size_t count, loff_t *offset)
{
return -ENODEV;
}
static ssize_t snd_disconnect_write(struct file *file, const char __user *buf,
size_t count, loff_t *offset)
{
return -ENODEV;
}
static int snd_disconnect_release(struct inode *inode, struct file *file)
{
struct snd_disconnected_file *df, **_dfs, **__dfs;
int err = 0;
__dfs = _dfs = &disconnecting_files;
mutex_lock(&mutex);
while ((df = *_dfs))
if (df->file == file) {
*__dfs = df->next;
break;
} else {
__dfs = _dfs;
_dfs = &df->next;
}
mutex_unlock(&mutex);
if (df != NULL) {
err = df->release(inode, file);
kfree(df);
return err;
}
panic("%s(%p, %p) failed!", __FUNCTION__, inode, file);
}
static unsigned int snd_disconnect_poll(struct file * file, poll_table * wait)
{
return POLLERR | POLLNVAL;
}
static long snd_disconnect_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
return -ENODEV;
}
static int snd_disconnect_mmap(struct file *file, struct vm_area_struct *vma)
{
return -ENODEV;
}
static int snd_disconnect_fasync(int fd, struct file *file, int on)
{
return -ENODEV;
}
static struct file_operations snd_disconnect_f_ops =
{
.owner = THIS_MODULE,
.llseek = snd_disconnect_llseek,
.read = snd_disconnect_read,
.write = snd_disconnect_write,
.release = snd_disconnect_release,
.poll = snd_disconnect_poll,
.unlocked_ioctl = snd_disconnect_ioctl,
.compat_ioctl = snd_disconnect_ioctl,
.mmap = snd_disconnect_mmap,
.fasync = snd_disconnect_fasync
};
--------------------------------------------------------
Karsten
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