/*
   * linux/drivers/char/misc.c
   *
   * Generic misc open routine by Johan Myreen
   *
   * Based on code from Linus
   *
   * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
   *   changes incorporated into 0.97pl4
   *   by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
   *   See busmouse.c for particulars.
   *
   * Made things a lot mode modular - easy to compile in just one or two
   * of the misc drivers, as they are now completely independent. Linus.
   *
   * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
   *
   * Fixed a failing symbol register to free the device registration
   *		Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
   *
   * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
   *
   * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
   *
   * Handling of mouse minor numbers for kerneld:
   *  Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
   *  adapted by Bjorn Ekwall <bj0rn@blox.se>
   *  corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
   *
   * Changes for kmod (from kerneld):
   *	Cyrus Durgin <cider@speakeasy.org>
   *
   * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au>  10-Jan-1998
   */
  
  #include <linux/module.h>

  
  #include <linux/fs.h>
  #include <linux/errno.h>
  #include <linux/miscdevice.h>
  #include <linux/kernel.h>
  #include <linux/major.h>

  #include <linux/mutex.h>

  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>

  #include <linux/stat.h>
  #include <linux/init.h>
  #include <linux/device.h>
  #include <linux/tty.h>
  #include <linux/kmod.h>

  #include <linux/gfp.h>

  
  /*
   * Head entry for the doubly linked miscdevice list
   */
  static LIST_HEAD(misc_list);

  static DEFINE_MUTEX(misc_mtx);

  
  /*
   * Assigned numbers, used for dynamic minors
   */
  #define DYNAMIC_MINORS 64 /* like dynamic majors */

  static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);

  #ifdef CONFIG_PROC_FS
  static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  {

  	mutex_lock(&misc_mtx);

  	return seq_list_start(&misc_list, *pos);

  }
  
  static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {

  	return seq_list_next(v, &misc_list, pos);

  }
  
  static void misc_seq_stop(struct seq_file *seq, void *v)
  {

  	mutex_unlock(&misc_mtx);

  }
  
  static int misc_seq_show(struct seq_file *seq, void *v)
  {

  	const struct miscdevice *p = list_entry(v, struct miscdevice, list);

  
  	seq_printf(seq, "%3i %s
  ", p->minor, p->name ? p->name : "");
  	return 0;
  }

  static const struct seq_operations misc_seq_ops = {

  	.start = misc_seq_start,
  	.next  = misc_seq_next,
  	.stop  = misc_seq_stop,
  	.show  = misc_seq_show,
  };
  
  static int misc_seq_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &misc_seq_ops);
  }

  static const struct file_operations misc_proc_fops = {

  	.owner	 = THIS_MODULE,
  	.open    = misc_seq_open,
  	.read    = seq_read,
  	.llseek  = seq_lseek,
  	.release = seq_release,
  };
  #endif
  
  static int misc_open(struct inode * inode, struct file * file)
  {
  	int minor = iminor(inode);
  	struct miscdevice *c;
  	int err = -ENODEV;

  	const struct file_operations *old_fops, *new_fops = NULL;

  	mutex_lock(&misc_mtx);

  	
  	list_for_each_entry(c, &misc_list, list) {
  		if (c->minor == minor) {
  			new_fops = fops_get(c->fops);		
  			break;
  		}
  	}
  		
  	if (!new_fops) {

  		mutex_unlock(&misc_mtx);

  		request_module("char-major-%d-%d", MISC_MAJOR, minor);

  		mutex_lock(&misc_mtx);

  
  		list_for_each_entry(c, &misc_list, list) {
  			if (c->minor == minor) {
  				new_fops = fops_get(c->fops);
  				break;
  			}
  		}
  		if (!new_fops)
  			goto fail;
  	}
  
  	err = 0;
  	old_fops = file->f_op;
  	file->f_op = new_fops;
  	if (file->f_op->open) {

  		file->private_data = c;

  		err=file->f_op->open(inode,file);
  		if (err) {
  			fops_put(file->f_op);
  			file->f_op = fops_get(old_fops);
  		}
  	}
  	fops_put(old_fops);
  fail:

  	mutex_unlock(&misc_mtx);

  	return err;
  }

  static struct class *misc_class;

  static const struct file_operations misc_fops = {

  	.owner		= THIS_MODULE,
  	.open		= misc_open,

  	.llseek		= noop_llseek,

  };

  /**
   *	misc_register	-	register a miscellaneous device
   *	@misc: device structure
   *	
   *	Register a miscellaneous device with the kernel. If the minor
   *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
   *	and placed in the minor field of the structure. For other cases
   *	the minor number requested is used.
   *
   *	The structure passed is linked into the kernel and may not be
   *	destroyed until it has been unregistered.
   *
   *	A zero is returned on success and a negative errno code for
   *	failure.
   */
   
  int misc_register(struct miscdevice * misc)
  {
  	struct miscdevice *c;
  	dev_t dev;

  	int err = 0;

  	INIT_LIST_HEAD(&misc->list);

  	mutex_lock(&misc_mtx);

  	list_for_each_entry(c, &misc_list, list) {
  		if (c->minor == misc->minor) {

  			mutex_unlock(&misc_mtx);

  			return -EBUSY;
  		}
  	}
  
  	if (misc->minor == MISC_DYNAMIC_MINOR) {

  		int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
  		if (i >= DYNAMIC_MINORS) {

  			mutex_unlock(&misc_mtx);

  			return -EBUSY;
  		}

  		misc->minor = DYNAMIC_MINORS - i - 1;
  		set_bit(i, misc_minors);

  	}

  	dev = MKDEV(MISC_MAJOR, misc->minor);

  	misc->this_device = device_create(misc_class, misc->parent, dev,
  					  misc, "%s", misc->name);

  	if (IS_ERR(misc->this_device)) {

  		int i = DYNAMIC_MINORS - misc->minor - 1;

  		if (i < DYNAMIC_MINORS && i >= 0)

  			clear_bit(i, misc_minors);

  		err = PTR_ERR(misc->this_device);

  		goto out;
  	}

  	/*
  	 * Add it to the front, so that later devices can "override"
  	 * earlier defaults
  	 */
  	list_add(&misc->list, &misc_list);
   out:

  	mutex_unlock(&misc_mtx);

  	return err;
  }
  
  /**

   *	misc_deregister - unregister a miscellaneous device

   *	@misc: device to unregister
   *
   *	Unregister a miscellaneous device that was previously
   *	successfully registered with misc_register(). Success
   *	is indicated by a zero return, a negative errno code
   *	indicates an error.
   */

  int misc_deregister(struct miscdevice *misc)

  {

  	int i = DYNAMIC_MINORS - misc->minor - 1;

  	if (WARN_ON(list_empty(&misc->list)))

  		return -EINVAL;

  	mutex_lock(&misc_mtx);

  	list_del(&misc->list);

  	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));

  	if (i < DYNAMIC_MINORS && i >= 0)

  		clear_bit(i, misc_minors);

  	mutex_unlock(&misc_mtx);

  	return 0;
  }
  
  EXPORT_SYMBOL(misc_register);

  EXPORT_SYMBOL(misc_deregister);

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

  {
  	struct miscdevice *c = dev_get_drvdata(dev);

  	if (mode && c->mode)
  		*mode = c->mode;
  	if (c->nodename)
  		return kstrdup(c->nodename, GFP_KERNEL);

  	return NULL;
  }

  static int __init misc_init(void)
  {

  	int err;

  #ifdef CONFIG_PROC_FS
  	proc_create("misc", 0, NULL, &misc_proc_fops);

  #endif

  	misc_class = class_create(THIS_MODULE, "misc");

  	err = PTR_ERR(misc_class);

  	if (IS_ERR(misc_class))

  		goto fail_remove;

  	err = -EIO;
  	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
  		goto fail_printk;

  	misc_class->devnode = misc_devnode;

  	return 0;

  
  fail_printk:
  	printk("unable to get major %d for misc devices
  ", MISC_MAJOR);
  	class_destroy(misc_class);
  fail_remove:
  	remove_proc_entry("misc", NULL);
  	return err;

  }
  subsys_initcall(misc_init);