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misc.c

/*
 * 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/slab.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>

/*
 * 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 unsigned char misc_minors[DYNAMIC_MINORS / 8];

extern int pmu_device_init(void);

#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\n", p->minor, p->name ? p->name : "");
      return 0;
}


static 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) {
            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,
};


/**
 *    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 = DYNAMIC_MINORS;
            while (--i >= 0)
                  if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
                        break;
            if (i<0) {
                  mutex_unlock(&misc_mtx);
                  return -EBUSY;
            }
            misc->minor = i;
      }

      if (misc->minor < DYNAMIC_MINORS)
            misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
      dev = MKDEV(MISC_MAJOR, misc->minor);

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

      if (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) {
            misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
      }
      mutex_unlock(&misc_mtx);
      return 0;
}

EXPORT_SYMBOL(misc_register);
EXPORT_SYMBOL(misc_deregister);

static int __init misc_init(void)
{
#ifdef CONFIG_PROC_FS
      struct proc_dir_entry *ent;

      ent = create_proc_entry("misc", 0, NULL);
      if (ent)
            ent->proc_fops = &misc_proc_fops;
#endif
      misc_class = class_create(THIS_MODULE, "misc");
      if (IS_ERR(misc_class))
            return PTR_ERR(misc_class);

      if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
            printk("unable to get major %d for misc devices\n",
                   MISC_MAJOR);
            class_destroy(misc_class);
            return -EIO;
      }
      return 0;
}
subsys_initcall(misc_init);

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