drivers/char/misc.c

   1 /*
   2  * linux/drivers/char/misc.c
   3  *
   4  * Generic misc open routine by Johan Myreen
   5  *
   6  * Based on code from Linus
   7  *
   8  * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
   9  *   changes incorporated into 0.97pl4
  10  *   by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
  11  *   See busmouse.c for particulars.
  12  *
  13  * Made things a lot mode modular - easy to compile in just one or two
  14  * of the misc drivers, as they are now completely independent. Linus.
  15  *
  16  * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
  17  *
  18  * Fixed a failing symbol register to free the device registration
  19  *              Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
  20  *
  21  * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
  22  *
  23  * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
  24  *
  25  * Handling of mouse minor numbers for kerneld:
  26  *  Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
  27  *  adapted by Bjorn Ekwall <bj0rn@blox.se>
  28  *  corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
  29  *
  30  * Changes for kmod (from kerneld):
  31  *      Cyrus Durgin <cider@speakeasy.org>
  32  *
  33  * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au>  10-Jan-1998
  34  */
  35
  36 #include <linux/module.h>
  37
  38 #include <linux/fs.h>
  39 #include <linux/errno.h>
  40 #include <linux/miscdevice.h>
  41 #include <linux/kernel.h>
  42 #include <linux/major.h>
  43 #include <linux/slab.h>
  44 #include <linux/mutex.h>
  45 #include <linux/proc_fs.h>
  46 #include <linux/seq_file.h>
  47 #include <linux/stat.h>
  48 #include <linux/init.h>
  49 #include <linux/device.h>
  50 #include <linux/tty.h>
  51 #include <linux/kmod.h>
  52
  53 /*
  54  * Head entry for the doubly linked miscdevice list
  55  */
  56 static LIST_HEAD(misc_list);
  57 static DEFINE_MUTEX(misc_mtx);
  58
  59 /*
  60  * Assigned numbers, used for dynamic minors
  61  */
  62 #define DYNAMIC_MINORS 64 /* like dynamic majors */
  63 static unsigned char misc_minors[DYNAMIC_MINORS / 8];
  64
  65 extern int pmu_device_init(void);
  66
  67 #ifdef CONFIG_PROC_FS
  68 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  69 {
  70         struct miscdevice *p;
  71         loff_t off = 0;
  72
  73         mutex_lock(&misc_mtx);
  74         list_for_each_entry(p, &misc_list, list) {
  75                 if (*pos == off++)
  76                         return p;
  77         }
  78         return NULL;
  79 }
  80
  81 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  82 {
  83         struct list_head *n = ((struct miscdevice *)v)->list.next;
  84
  85         ++*pos;
  86
  87         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  88                  : NULL;
  89 }
  90
  91 static void misc_seq_stop(struct seq_file *seq, void *v)
  92 {
  93         mutex_unlock(&misc_mtx);
  94 }
  95
  96 static int misc_seq_show(struct seq_file *seq, void *v)
  97 {
  98         const struct miscdevice *p = v;
  99
 100         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 101         return 0;
 102 }
 103
 104
 105 static struct seq_operations misc_seq_ops = {
 106         .start = misc_seq_start,
 107         .next  = misc_seq_next,
 108         .stop  = misc_seq_stop,
 109         .show  = misc_seq_show,
 110 };
 111
 112 static int misc_seq_open(struct inode *inode, struct file *file)
 113 {
 114         return seq_open(file, &misc_seq_ops);
 115 }
 116
 117 static const struct file_operations misc_proc_fops = {
 118         .owner   = THIS_MODULE,
 119         .open    = misc_seq_open,
 120         .read    = seq_read,
 121         .llseek  = seq_lseek,
 122         .release = seq_release,
 123 };
 124 #endif
 125
 126 static int misc_open(struct inode * inode, struct file * file)
 127 {
 128         int minor = iminor(inode);
 129         struct miscdevice *c;
 130         int err = -ENODEV;
 131         const struct file_operations *old_fops, *new_fops = NULL;
 132
 133         mutex_lock(&misc_mtx);
 134
 135         list_for_each_entry(c, &misc_list, list) {
 136                 if (c->minor == minor) {
 137                         new_fops = fops_get(c->fops);
 138                         break;
 139                 }
 140         }
 141
 142         if (!new_fops) {
 143                 mutex_unlock(&misc_mtx);
 144                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 145                 mutex_lock(&misc_mtx);
 146
 147                 list_for_each_entry(c, &misc_list, list) {
 148                         if (c->minor == minor) {
 149                                 new_fops = fops_get(c->fops);
 150                                 break;
 151                         }
 152                 }
 153                 if (!new_fops)
 154                         goto fail;
 155         }
 156
 157         err = 0;
 158         old_fops = file->f_op;
 159         file->f_op = new_fops;
 160         if (file->f_op->open) {
 161                 err=file->f_op->open(inode,file);
 162                 if (err) {
 163                         fops_put(file->f_op);
 164                         file->f_op = fops_get(old_fops);
 165                 }
 166         }
 167         fops_put(old_fops);
 168 fail:
 169         mutex_unlock(&misc_mtx);
 170         return err;
 171 }
 172
 173 static struct class *misc_class;
 174
 175 static const struct file_operations misc_fops = {
 176         .owner          = THIS_MODULE,
 177         .open           = misc_open,
 178 };
 179
 180
 181 /**
 182  *      misc_register   -       register a miscellaneous device
 183  *      @misc: device structure
 184  *
 185  *      Register a miscellaneous device with the kernel. If the minor
 186  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 187  *      and placed in the minor field of the structure. For other cases
 188  *      the minor number requested is used.
 189  *
 190  *      The structure passed is linked into the kernel and may not be
 191  *      destroyed until it has been unregistered.
 192  *
 193  *      A zero is returned on success and a negative errno code for
 194  *      failure.
 195  */
 196
 197 int misc_register(struct miscdevice * misc)
 198 {
 199         struct miscdevice *c;
 200         dev_t dev;
 201         int err = 0;
 202
 203         INIT_LIST_HEAD(&misc->list);
 204
 205         mutex_lock(&misc_mtx);
 206         list_for_each_entry(c, &misc_list, list) {
 207                 if (c->minor == misc->minor) {
 208                         mutex_unlock(&misc_mtx);
 209                         return -EBUSY;
 210                 }
 211         }
 212
 213         if (misc->minor == MISC_DYNAMIC_MINOR) {
 214                 int i = DYNAMIC_MINORS;
 215                 while (--i >= 0)
 216                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 217                                 break;
 218                 if (i<0) {
 219                         mutex_unlock(&misc_mtx);
 220                         return -EBUSY;
 221                 }
 222                 misc->minor = i;
 223         }
 224
 225         if (misc->minor < DYNAMIC_MINORS)
 226                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 227         dev = MKDEV(MISC_MAJOR, misc->minor);
 228
 229         misc->this_device = device_create(misc_class, misc->parent, dev,
 230                                           "%s", misc->name);
 231         if (IS_ERR(misc->this_device)) {
 232                 err = PTR_ERR(misc->this_device);
 233                 goto out;
 234         }
 235
 236         /*
 237          * Add it to the front, so that later devices can "override"
 238          * earlier defaults
 239          */
 240         list_add(&misc->list, &misc_list);
 241  out:
 242         mutex_unlock(&misc_mtx);
 243         return err;
 244 }
 245
 246 /**
 247  *      misc_deregister - unregister a miscellaneous device
 248  *      @misc: device to unregister
 249  *
 250  *      Unregister a miscellaneous device that was previously
 251  *      successfully registered with misc_register(). Success
 252  *      is indicated by a zero return, a negative errno code
 253  *      indicates an error.
 254  */
 255
 256 int misc_deregister(struct miscdevice * misc)
 257 {
 258         int i = misc->minor;
 259
 260         if (list_empty(&misc->list))
 261                 return -EINVAL;
 262
 263         mutex_lock(&misc_mtx);
 264         list_del(&misc->list);
 265         device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 266         if (i < DYNAMIC_MINORS && i>0) {
 267                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 268         }
 269         mutex_unlock(&misc_mtx);
 270         return 0;
 271 }
 272
 273 EXPORT_SYMBOL(misc_register);
 274 EXPORT_SYMBOL(misc_deregister);
 275
 276 static int __init misc_init(void)
 277 {
 278 #ifdef CONFIG_PROC_FS
 279         struct proc_dir_entry *ent;
 280
 281         ent = create_proc_entry("misc", 0, NULL);
 282         if (ent)
 283                 ent->proc_fops = &misc_proc_fops;
 284 #endif
 285         misc_class = class_create(THIS_MODULE, "misc");
 286         if (IS_ERR(misc_class))
 287                 return PTR_ERR(misc_class);
 288
 289         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 290                 printk("unable to get major %d for misc devices\n",
 291                        MISC_MAJOR);
 292                 class_destroy(misc_class);
 293                 return -EIO;
 294         }
 295         return 0;
 296 }
 297 subsys_initcall(misc_init);