/*
   * 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/backing-dev.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/gfp.h>

  #include <linux/compat.h>

  #include <linux/vmalloc.h>

  #include <linux/uaccess.h>

  
  struct raw_device_data {
  	struct block_device *binding;
  	int inuse;
  };

  static struct class *raw_class;

  static struct raw_device_data *raw_devices;

  static DEFINE_MUTEX(raw_mutex);

  static const struct file_operations raw_ctl_fops; /* forward declaration */

  static int max_raw_minors = MAX_RAW_MINORS;
  
  module_param(max_raw_minors, int, 0);
  MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");

  /*
   * 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;

  	bdgrab(bdev);

  	err = blkdev_get(bdev, filp->f_mode | FMODE_EXCL, raw_open);

  	if (err)
  		goto out;

  	err = set_blocksize(bdev, bdev_logical_block_size(bdev));

  	if (err)

  		goto out1;

  	filp->f_flags |= O_DIRECT;
  	filp->f_mapping = bdev->bd_inode->i_mapping;
  	if (++raw_devices[minor].inuse == 1)

  		file_inode(filp)->i_mapping =

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

  	mutex_unlock(&raw_mutex);

  	return 0;

  out1:

  	blkdev_put(bdev, filp->f_mode | FMODE_EXCL);

  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;

  	mutex_unlock(&raw_mutex);

  	blkdev_put(bdev, filp->f_mode | FMODE_EXCL);

  	return 0;
  }
  
  /*
   * Forward ioctls to the underlying block device.
   */

  static long
  raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)

  {
  	struct block_device *bdev = filp->private_data;

  	return blkdev_ioctl(bdev, 0, command, arg);
  }
  
  static int bind_set(int number, u64 major, u64 minor)
  {
  	dev_t dev = MKDEV(major, minor);
  	struct raw_device_data *rawdev;
  	int err = 0;

  	if (number <= 0 || number >= max_raw_minors)

  		return -EINVAL;
  
  	if (MAJOR(dev) != major || MINOR(dev) != minor)
  		return -EINVAL;
  
  	rawdev = &raw_devices[number];

  	/*
  	 * This is like making block devices, so demand the
  	 * same capability
  	 */
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	/*
  	 * 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.
  	 */
  
  	if (MAJOR(dev) == 0 && dev != 0)
  		return -EINVAL;

  	mutex_lock(&raw_mutex);
  	if (rawdev->inuse) {
  		mutex_unlock(&raw_mutex);
  		return -EBUSY;
  	}
  	if (rawdev->binding) {
  		bdput(rawdev->binding);
  		module_put(THIS_MODULE);
  	}
  	if (!dev) {
  		/* unbind */
  		rawdev->binding = NULL;
  		device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
  	} else {
  		rawdev->binding = bdget(dev);
  		if (rawdev->binding == NULL) {
  			err = -ENOMEM;
  		} else {
  			dev_t raw = MKDEV(RAW_MAJOR, number);
  			__module_get(THIS_MODULE);
  			device_destroy(raw_class, raw);
  			device_create(raw_class, NULL, raw, NULL,
  				      "raw%d", number);
  		}
  	}
  	mutex_unlock(&raw_mutex);
  	return err;

  }

  static int bind_get(int number, dev_t *dev)

  {

  	struct raw_device_data *rawdev;
  	struct block_device *bdev;

  	if (number <= 0 || number >= max_raw_minors)

  		return -EINVAL;
  
  	rawdev = &raw_devices[number];
  
  	mutex_lock(&raw_mutex);
  	bdev = rawdev->binding;
  	*dev = bdev ? bdev->bd_dev : 0;
  	mutex_unlock(&raw_mutex);
  	return 0;

  }
  
  /*
   * Deal with ioctls against the raw-device control interface, to bind
   * and unbind other raw devices.
   */

  static long raw_ctl_ioctl(struct file *filp, unsigned int command,
  			  unsigned long arg)

  {
  	struct raw_config_request rq;

  	dev_t dev;
  	int err;

  
  	switch (command) {
  	case RAW_SETBIND:

  		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
  			return -EFAULT;
  
  		return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);

  	case RAW_GETBIND:

  		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
  			return -EFAULT;

  		err = bind_get(rq.raw_minor, &dev);
  		if (err)
  			return err;

  		rq.block_major = MAJOR(dev);
  		rq.block_minor = MINOR(dev);

  		if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
  			return -EFAULT;
  
  		return 0;

  	}

  
  	return -EINVAL;
  }
  
  #ifdef CONFIG_COMPAT
  struct raw32_config_request {
  	compat_int_t	raw_minor;
  	compat_u64	block_major;
  	compat_u64	block_minor;
  };
  
  static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
  				unsigned long arg)
  {
  	struct raw32_config_request __user *user_req = compat_ptr(arg);
  	struct raw32_config_request rq;
  	dev_t dev;
  	int err = 0;
  
  	switch (cmd) {
  	case RAW_SETBIND:
  		if (copy_from_user(&rq, user_req, sizeof(rq)))
  			return -EFAULT;
  
  		return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
  
  	case RAW_GETBIND:
  		if (copy_from_user(&rq, user_req, sizeof(rq)))
  			return -EFAULT;
  
  		err = bind_get(rq.raw_minor, &dev);
  		if (err)
  			return err;
  
  		rq.block_major = MAJOR(dev);
  		rq.block_minor = MINOR(dev);
  
  		if (copy_to_user(user_req, &rq, sizeof(rq)))
  			return -EFAULT;
  
  		return 0;
  	}
  
  	return -EINVAL;

  }

  #endif

  static const struct file_operations raw_fops = {

  	.read_iter	= blkdev_read_iter,

  	.write_iter	= blkdev_write_iter,

  	.fsync		= blkdev_fsync,
  	.open		= raw_open,
  	.release	= raw_release,
  	.unlocked_ioctl = raw_ioctl,

  	.llseek		= default_llseek,

  	.owner		= THIS_MODULE,

  };

  static const struct file_operations raw_ctl_fops = {

  	.unlocked_ioctl = raw_ctl_ioctl,

  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= raw_ctl_compat_ioctl,
  #endif

  	.open		= raw_open,
  	.owner		= THIS_MODULE,

  	.llseek		= noop_llseek,

  };

  static struct cdev raw_cdev;

  static char *raw_devnode(struct device *dev, umode_t *mode)

  {
  	return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
  }

  static int __init raw_init(void)
  {

  	dev_t dev = MKDEV(RAW_MAJOR, 0);

  	int ret;

  	if (max_raw_minors < 1 || max_raw_minors > 65536) {
  		printk(KERN_WARNING "raw: invalid max_raw_minors (must be"
  			" between 1 and 65536), using %d
  ", MAX_RAW_MINORS);
  		max_raw_minors = MAX_RAW_MINORS;
  	}

  	raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors);

  	if (!raw_devices) {
  		printk(KERN_ERR "Not enough memory for raw device structures
  ");
  		ret = -ENOMEM;
  		goto error;
  	}

  
  	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)

  		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;

  	}

  	raw_class->devnode = raw_devnode;

  	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

  	return 0;

  error_region:

  	unregister_chrdev_region(dev, max_raw_minors);

  error:

  	vfree(raw_devices);

  	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");