/*
   * 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 <linux/smp_lock.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;
  	}

  	lock_kernel();

  	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);

  	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_path.dentry->d_inode->i_mapping =

  			bdev->bd_inode->i_mapping;
  	filp->private_data = bdev;

  	mutex_unlock(&raw_mutex);

  	unlock_kernel();

  	return 0;
  
  out2:
  	bd_release(bdev);
  out1:

  	blkdev_put(bdev, filp->f_mode);

  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, filp->f_mode);

  	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, 0, command, arg);

  }
  
  static void bind_device(struct raw_config_request *rq)
  {

  	device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));

  	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;

  				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;

  
  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.
  ");
  		cdev_del(&raw_cdev);

  		ret = PTR_ERR(raw_class);
  		goto error_region;

  	}

  	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)
  {

  	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");