blob: 89b718e326e5a0873ca0002cc76441a3c5469238 [file] [log] [blame]
/*
* linux/drivers/char/raw.c
*
* Front-end raw character devices. These can be bound to any block
* devices to provide genuine Unix raw character device semantics.
*
* We reserve minor number 0 for a control interface. ioctl()s on this
* device are used to bind the other minor numbers to block devices.
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/raw.h>
#include <linux/capability.h>
#include <linux/uio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
struct raw_device_data {
struct block_device *binding;
int inuse;
};
static struct class *raw_class;
static struct raw_device_data raw_devices[MAX_RAW_MINORS];
static DEFINE_MUTEX(raw_mutex);
static const struct file_operations raw_ctl_fops; /* forward declaration */
/*
* Open/close code for raw IO.
*
* We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
* point at the blockdev's address_space and set the file handle to use
* O_DIRECT.
*
* Set the device's soft blocksize to the minimum possible. This gives the
* finest possible alignment and has no adverse impact on performance.
*/
static int raw_open(struct inode *inode, struct file *filp)
{
const int minor = iminor(inode);
struct block_device *bdev;
int err;
if (minor == 0) { /* It is the control device */
filp->f_op = &raw_ctl_fops;
return 0;
}
mutex_lock(&raw_mutex);
/*
* All we need to do on open is check that the device is bound.
*/
bdev = raw_devices[minor].binding;
err = -ENODEV;
if (!bdev)
goto out;
igrab(bdev->bd_inode);
err = blkdev_get(bdev, filp->f_mode, 0);
if (err)
goto out;
err = bd_claim(bdev, raw_open);
if (err)
goto out1;
err = set_blocksize(bdev, bdev_hardsect_size(bdev));
if (err)
goto out2;
filp->f_flags |= O_DIRECT;
filp->f_mapping = bdev->bd_inode->i_mapping;
if (++raw_devices[minor].inuse == 1)
filp->f_dentry->d_inode->i_mapping =
bdev->bd_inode->i_mapping;
filp->private_data = bdev;
mutex_unlock(&raw_mutex);
return 0;
out2:
bd_release(bdev);
out1:
blkdev_put(bdev);
out:
mutex_unlock(&raw_mutex);
return err;
}
/*
* When the final fd which refers to this character-special node is closed, we
* make its ->mapping point back at its own i_data.
*/
static int raw_release(struct inode *inode, struct file *filp)
{
const int minor= iminor(inode);
struct block_device *bdev;
mutex_lock(&raw_mutex);
bdev = raw_devices[minor].binding;
if (--raw_devices[minor].inuse == 0) {
/* Here inode->i_mapping == bdev->bd_inode->i_mapping */
inode->i_mapping = &inode->i_data;
inode->i_mapping->backing_dev_info = &default_backing_dev_info;
}
mutex_unlock(&raw_mutex);
bd_release(bdev);
blkdev_put(bdev);
return 0;
}
/*
* Forward ioctls to the underlying block device.
*/
static int
raw_ioctl(struct inode *inode, struct file *filp,
unsigned int command, unsigned long arg)
{
struct block_device *bdev = filp->private_data;
return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
}
static void bind_device(struct raw_config_request *rq)
{
class_device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor),
NULL, "raw%d", rq->raw_minor);
}
/*
* Deal with ioctls against the raw-device control interface, to bind
* and unbind other raw devices.
*/
static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
unsigned int command, unsigned long arg)
{
struct raw_config_request rq;
struct raw_device_data *rawdev;
int err = 0;
switch (command) {
case RAW_SETBIND:
case RAW_GETBIND:
/* First, find out which raw minor we want */
if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
err = -EFAULT;
goto out;
}
if (rq.raw_minor < 0 || rq.raw_minor >= MAX_RAW_MINORS) {
err = -EINVAL;
goto out;
}
rawdev = &raw_devices[rq.raw_minor];
if (command == RAW_SETBIND) {
dev_t dev;
/*
* This is like making block devices, so demand the
* same capability
*/
if (!capable(CAP_SYS_ADMIN)) {
err = -EPERM;
goto out;
}
/*
* For now, we don't need to check that the underlying
* block device is present or not: we can do that when
* the raw device is opened. Just check that the
* major/minor numbers make sense.
*/
dev = MKDEV(rq.block_major, rq.block_minor);
if ((rq.block_major == 0 && rq.block_minor != 0) ||
MAJOR(dev) != rq.block_major ||
MINOR(dev) != rq.block_minor) {
err = -EINVAL;
goto out;
}
mutex_lock(&raw_mutex);
if (rawdev->inuse) {
mutex_unlock(&raw_mutex);
err = -EBUSY;
goto out;
}
if (rawdev->binding) {
bdput(rawdev->binding);
module_put(THIS_MODULE);
}
if (rq.block_major == 0 && rq.block_minor == 0) {
/* unbind */
rawdev->binding = NULL;
class_device_destroy(raw_class,
MKDEV(RAW_MAJOR, rq.raw_minor));
} else {
rawdev->binding = bdget(dev);
if (rawdev->binding == NULL)
err = -ENOMEM;
else {
__module_get(THIS_MODULE);
bind_device(&rq);
}
}
mutex_unlock(&raw_mutex);
} else {
struct block_device *bdev;
mutex_lock(&raw_mutex);
bdev = rawdev->binding;
if (bdev) {
rq.block_major = MAJOR(bdev->bd_dev);
rq.block_minor = MINOR(bdev->bd_dev);
} else {
rq.block_major = rq.block_minor = 0;
}
mutex_unlock(&raw_mutex);
if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
err = -EFAULT;
goto out;
}
}
break;
default:
err = -EINVAL;
break;
}
out:
return err;
}
static const struct file_operations raw_fops = {
.read = do_sync_read,
.aio_read = generic_file_aio_read,
.write = do_sync_write,
.aio_write = generic_file_aio_write_nolock,
.open = raw_open,
.release= raw_release,
.ioctl = raw_ioctl,
.owner = THIS_MODULE,
};
static const struct file_operations raw_ctl_fops = {
.ioctl = raw_ctl_ioctl,
.open = raw_open,
.owner = THIS_MODULE,
};
static struct cdev raw_cdev = {
.kobj = {.name = "raw", },
.owner = THIS_MODULE,
};
static int __init raw_init(void)
{
dev_t dev = MKDEV(RAW_MAJOR, 0);
int ret;
ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
if (ret)
goto error;
cdev_init(&raw_cdev, &raw_fops);
ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
if (ret) {
kobject_put(&raw_cdev.kobj);
goto error_region;
}
raw_class = class_create(THIS_MODULE, "raw");
if (IS_ERR(raw_class)) {
printk(KERN_ERR "Error creating raw class.\n");
cdev_del(&raw_cdev);
ret = PTR_ERR(raw_class);
goto error_region;
}
class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
return 0;
error_region:
unregister_chrdev_region(dev, MAX_RAW_MINORS);
error:
return ret;
}
static void __exit raw_exit(void)
{
class_device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
class_destroy(raw_class);
cdev_del(&raw_cdev);
unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
}
module_init(raw_init);
module_exit(raw_exit);
MODULE_LICENSE("GPL");