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/proc_fs.h>
  45 #include <linux/seq_file.h>
  46 #include <linux/stat.h>
  47 #include <linux/init.h>
  48 #include <linux/device.h>
  49 #include <linux/tty.h>
  50 #include <linux/kmod.h>
  51
  52 /*
  53  * Head entry for the doubly linked miscdevice list
  54  */
  55 static LIST_HEAD(misc_list);
  56 static DECLARE_MUTEX(misc_sem);
  57
  58 /*
  59  * Assigned numbers, used for dynamic minors
  60  */
  61 #define DYNAMIC_MINORS 64 /* like dynamic majors */
  62 static unsigned char misc_minors[DYNAMIC_MINORS / 8];
  63
  64 extern int pmu_device_init(void);
  65
  66 #ifdef CONFIG_PROC_FS
  67 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  68 {
  69         struct miscdevice *p;
  70         loff_t off = 0;
  71
  72         down(&misc_sem);
  73         list_for_each_entry(p, &misc_list, list) {
  74                 if (*pos == off++)
  75                         return p;
  76         }
  77         return NULL;
  78 }
  79
  80 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  81 {
  82         struct list_head *n = ((struct miscdevice *)v)->list.next;
  83
  84         ++*pos;
  85
  86         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  87                  : NULL;
  88 }
  89
  90 static void misc_seq_stop(struct seq_file *seq, void *v)
  91 {
  92         up(&misc_sem);
  93 }
  94
  95 static int misc_seq_show(struct seq_file *seq, void *v)
  96 {
  97         const struct miscdevice *p = v;
  98
  99         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 100         return 0;
 101 }
 102
 103
 104 static struct seq_operations misc_seq_ops = {
 105         .start = misc_seq_start,
 106         .next  = misc_seq_next,
 107         .stop  = misc_seq_stop,
 108         .show  = misc_seq_show,
 109 };
 110
 111 static int misc_seq_open(struct inode *inode, struct file *file)
 112 {
 113         return seq_open(file, &misc_seq_ops);
 114 }
 115
 116 static const struct file_operations misc_proc_fops = {
 117         .owner   = THIS_MODULE,
 118         .open    = misc_seq_open,
 119         .read    = seq_read,
 120         .llseek  = seq_lseek,
 121         .release = seq_release,
 122 };
 123 #endif
 124
 125 static int misc_open(struct inode * inode, struct file * file)
 126 {
 127         int minor = iminor(inode);
 128         struct miscdevice *c;
 129         int err = -ENODEV;
 130         const struct file_operations *old_fops, *new_fops = NULL;
 131
 132         down(&misc_sem);
 133
 134         list_for_each_entry(c, &misc_list, list) {
 135                 if (c->minor == minor) {
 136                         new_fops = fops_get(c->fops);
 137                         break;
 138                 }
 139         }
 140
 141         if (!new_fops) {
 142                 up(&misc_sem);
 143                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 144                 down(&misc_sem);
 145
 146                 list_for_each_entry(c, &misc_list, list) {
 147                         if (c->minor == minor) {
 148                                 new_fops = fops_get(c->fops);
 149                                 break;
 150                         }
 151                 }
 152                 if (!new_fops)
 153                         goto fail;
 154         }
 155
 156         err = 0;
 157         old_fops = file->f_op;
 158         file->f_op = new_fops;
 159         if (file->f_op->open) {
 160                 err=file->f_op->open(inode,file);
 161                 if (err) {
 162                         fops_put(file->f_op);
 163                         file->f_op = fops_get(old_fops);
 164                 }
 165         }
 166         fops_put(old_fops);
 167 fail:
 168         up(&misc_sem);
 169         return err;
 170 }
 171
 172 /*
 173  * TODO for 2.7:
 174  *  - add a struct kref to struct miscdevice and make all usages of
 175  *    them dynamic.
 176  */
 177 static struct class *misc_class;
 178
 179 static const struct file_operations misc_fops = {
 180         .owner          = THIS_MODULE,
 181         .open           = misc_open,
 182 };
 183
 184
 185 /**
 186  *      misc_register   -       register a miscellaneous device
 187  *      @misc: device structure
 188  *
 189  *      Register a miscellaneous device with the kernel. If the minor
 190  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 191  *      and placed in the minor field of the structure. For other cases
 192  *      the minor number requested is used.
 193  *
 194  *      The structure passed is linked into the kernel and may not be
 195  *      destroyed until it has been unregistered.
 196  *
 197  *      A zero is returned on success and a negative errno code for
 198  *      failure.
 199  */
 200
 201 int misc_register(struct miscdevice * misc)
 202 {
 203         struct miscdevice *c;
 204         dev_t dev;
 205         int err = 0;
 206
 207         down(&misc_sem);
 208         list_for_each_entry(c, &misc_list, list) {
 209                 if (c->minor == misc->minor) {
 210                         up(&misc_sem);
 211                         return -EBUSY;
 212                 }
 213         }
 214
 215         if (misc->minor == MISC_DYNAMIC_MINOR) {
 216                 int i = DYNAMIC_MINORS;
 217                 while (--i >= 0)
 218                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 219                                 break;
 220                 if (i<0) {
 221                         up(&misc_sem);
 222                         return -EBUSY;
 223                 }
 224                 misc->minor = i;
 225         }
 226
 227         if (misc->minor < DYNAMIC_MINORS)
 228                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 229         dev = MKDEV(MISC_MAJOR, misc->minor);
 230
 231         misc->class = class_device_create(misc_class, NULL, dev, misc->dev,
 232                                           "%s", misc->name);
 233         if (IS_ERR(misc->class)) {
 234                 err = PTR_ERR(misc->class);
 235                 goto out;
 236         }
 237
 238         /*
 239          * Add it to the front, so that later devices can "override"
 240          * earlier defaults
 241          */
 242         list_add(&misc->list, &misc_list);
 243  out:
 244         up(&misc_sem);
 245         return err;
 246 }
 247
 248 /**
 249  *      misc_deregister - unregister a miscellaneous device
 250  *      @misc: device to unregister
 251  *
 252  *      Unregister a miscellaneous device that was previously
 253  *      successfully registered with misc_register(). Success
 254  *      is indicated by a zero return, a negative errno code
 255  *      indicates an error.
 256  */
 257
 258 int misc_deregister(struct miscdevice * misc)
 259 {
 260         int i = misc->minor;
 261
 262         if (list_empty(&misc->list))
 263                 return -EINVAL;
 264
 265         down(&misc_sem);
 266         list_del(&misc->list);
 267         class_device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 268         if (i < DYNAMIC_MINORS && i>0) {
 269                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 270         }
 271         up(&misc_sem);
 272         return 0;
 273 }
 274
 275 EXPORT_SYMBOL(misc_register);
 276 EXPORT_SYMBOL(misc_deregister);
 277
 278 static int __init misc_init(void)
 279 {
 280 #ifdef CONFIG_PROC_FS
 281         struct proc_dir_entry *ent;
 282
 283         ent = create_proc_entry("misc", 0, NULL);
 284         if (ent)
 285                 ent->proc_fops = &misc_proc_fops;
 286 #endif
 287         misc_class = class_create(THIS_MODULE, "misc");
 288         if (IS_ERR(misc_class))
 289                 return PTR_ERR(misc_class);
 290
 291         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 292                 printk("unable to get major %d for misc devices\n",
 293                        MISC_MAJOR);
 294                 class_destroy(misc_class);
 295                 return -EIO;
 296         }
 297         return 0;
 298 }
 299 subsys_initcall(misc_init);