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         mutex_lock(&misc_mtx);
  71         return seq_list_start(&misc_list, *pos);
  72 }
  73
  74 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  75 {
  76         return seq_list_next(v, &misc_list, pos);
  77 }
  78
  79 static void misc_seq_stop(struct seq_file *seq, void *v)
  80 {
  81         mutex_unlock(&misc_mtx);
  82 }
  83
  84 static int misc_seq_show(struct seq_file *seq, void *v)
  85 {
  86         const struct miscdevice *p = list_entry(v, struct miscdevice, list);
  87
  88         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
  89         return 0;
  90 }
  91
  92
  93 static struct seq_operations misc_seq_ops = {
  94         .start = misc_seq_start,
  95         .next  = misc_seq_next,
  96         .stop  = misc_seq_stop,
  97         .show  = misc_seq_show,
  98 };
  99
 100 static int misc_seq_open(struct inode *inode, struct file *file)
 101 {
 102         return seq_open(file, &misc_seq_ops);
 103 }
 104
 105 static const struct file_operations misc_proc_fops = {
 106         .owner   = THIS_MODULE,
 107         .open    = misc_seq_open,
 108         .read    = seq_read,
 109         .llseek  = seq_lseek,
 110         .release = seq_release,
 111 };
 112 #endif
 113
 114 static int misc_open(struct inode * inode, struct file * file)
 115 {
 116         int minor = iminor(inode);
 117         struct miscdevice *c;
 118         int err = -ENODEV;
 119         const struct file_operations *old_fops, *new_fops = NULL;
 120
 121         mutex_lock(&misc_mtx);
 122
 123         list_for_each_entry(c, &misc_list, list) {
 124                 if (c->minor == minor) {
 125                         new_fops = fops_get(c->fops);
 126                         break;
 127                 }
 128         }
 129
 130         if (!new_fops) {
 131                 mutex_unlock(&misc_mtx);
 132                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 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                 if (!new_fops)
 142                         goto fail;
 143         }
 144
 145         err = 0;
 146         old_fops = file->f_op;
 147         file->f_op = new_fops;
 148         if (file->f_op->open) {
 149                 err=file->f_op->open(inode,file);
 150                 if (err) {
 151                         fops_put(file->f_op);
 152                         file->f_op = fops_get(old_fops);
 153                 }
 154         }
 155         fops_put(old_fops);
 156 fail:
 157         mutex_unlock(&misc_mtx);
 158         return err;
 159 }
 160
 161 static struct class *misc_class;
 162
 163 static const struct file_operations misc_fops = {
 164         .owner          = THIS_MODULE,
 165         .open           = misc_open,
 166 };
 167
 168
 169 /**
 170  *      misc_register   -       register a miscellaneous device
 171  *      @misc: device structure
 172  *
 173  *      Register a miscellaneous device with the kernel. If the minor
 174  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 175  *      and placed in the minor field of the structure. For other cases
 176  *      the minor number requested is used.
 177  *
 178  *      The structure passed is linked into the kernel and may not be
 179  *      destroyed until it has been unregistered.
 180  *
 181  *      A zero is returned on success and a negative errno code for
 182  *      failure.
 183  */
 184
 185 int misc_register(struct miscdevice * misc)
 186 {
 187         struct miscdevice *c;
 188         dev_t dev;
 189         int err = 0;
 190
 191         INIT_LIST_HEAD(&misc->list);
 192
 193         mutex_lock(&misc_mtx);
 194         list_for_each_entry(c, &misc_list, list) {
 195                 if (c->minor == misc->minor) {
 196                         mutex_unlock(&misc_mtx);
 197                         return -EBUSY;
 198                 }
 199         }
 200
 201         if (misc->minor == MISC_DYNAMIC_MINOR) {
 202                 int i = DYNAMIC_MINORS;
 203                 while (--i >= 0)
 204                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 205                                 break;
 206                 if (i<0) {
 207                         mutex_unlock(&misc_mtx);
 208                         return -EBUSY;
 209                 }
 210                 misc->minor = i;
 211         }
 212
 213         if (misc->minor < DYNAMIC_MINORS)
 214                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 215         dev = MKDEV(MISC_MAJOR, misc->minor);
 216
 217         misc->this_device = device_create(misc_class, misc->parent, dev,
 218                                           "%s", misc->name);
 219         if (IS_ERR(misc->this_device)) {
 220                 err = PTR_ERR(misc->this_device);
 221                 goto out;
 222         }
 223
 224         /*
 225          * Add it to the front, so that later devices can "override"
 226          * earlier defaults
 227          */
 228         list_add(&misc->list, &misc_list);
 229  out:
 230         mutex_unlock(&misc_mtx);
 231         return err;
 232 }
 233
 234 /**
 235  *      misc_deregister - unregister a miscellaneous device
 236  *      @misc: device to unregister
 237  *
 238  *      Unregister a miscellaneous device that was previously
 239  *      successfully registered with misc_register(). Success
 240  *      is indicated by a zero return, a negative errno code
 241  *      indicates an error.
 242  */
 243
 244 int misc_deregister(struct miscdevice * misc)
 245 {
 246         int i = misc->minor;
 247
 248         if (list_empty(&misc->list))
 249                 return -EINVAL;
 250
 251         mutex_lock(&misc_mtx);
 252         list_del(&misc->list);
 253         device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 254         if (i < DYNAMIC_MINORS && i>0) {
 255                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 256         }
 257         mutex_unlock(&misc_mtx);
 258         return 0;
 259 }
 260
 261 EXPORT_SYMBOL(misc_register);
 262 EXPORT_SYMBOL(misc_deregister);
 263
 264 static int __init misc_init(void)
 265 {
 266 #ifdef CONFIG_PROC_FS
 267         struct proc_dir_entry *ent;
 268
 269         ent = create_proc_entry("misc", 0, NULL);
 270         if (ent)
 271                 ent->proc_fops = &misc_proc_fops;
 272 #endif
 273         misc_class = class_create(THIS_MODULE, "misc");
 274         if (IS_ERR(misc_class))
 275                 return PTR_ERR(misc_class);
 276
 277         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 278                 printk("unable to get major %d for misc devices\n",
 279                        MISC_MAJOR);
 280                 class_destroy(misc_class);
 281                 return -EIO;
 282         }
 283         return 0;
 284 }
 285 subsys_initcall(misc_init);