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 #include <linux/config.h>
  38
  39 #include <linux/fs.h>
  40 #include <linux/errno.h>
  41 #include <linux/miscdevice.h>
  42 #include <linux/kernel.h>
  43 #include <linux/major.h>
  44 #include <linux/slab.h>
  45 #include <linux/proc_fs.h>
  46 #include <linux/seq_file.h>
  47 #include <linux/devfs_fs_kernel.h>
  48 #include <linux/stat.h>
  49 #include <linux/init.h>
  50 #include <linux/device.h>
  51 #include <linux/tty.h>
  52 #include <linux/kmod.h>
  53
  54 /*
  55  * Head entry for the doubly linked miscdevice list
  56  */
  57 static LIST_HEAD(misc_list);
  58 static DECLARE_MUTEX(misc_sem);
  59
  60 /*
  61  * Assigned numbers, used for dynamic minors
  62  */
  63 #define DYNAMIC_MINORS 64 /* like dynamic majors */
  64 static unsigned char misc_minors[DYNAMIC_MINORS / 8];
  65
  66 extern int pmu_device_init(void);
  67
  68 #ifdef CONFIG_PROC_FS
  69 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  70 {
  71         struct miscdevice *p;
  72         loff_t off = 0;
  73
  74         down(&misc_sem);
  75         list_for_each_entry(p, &misc_list, list) {
  76                 if (*pos == off++)
  77                         return p;
  78         }
  79         return NULL;
  80 }
  81
  82 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  83 {
  84         struct list_head *n = ((struct miscdevice *)v)->list.next;
  85
  86         ++*pos;
  87
  88         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  89                  : NULL;
  90 }
  91
  92 static void misc_seq_stop(struct seq_file *seq, void *v)
  93 {
  94         up(&misc_sem);
  95 }
  96
  97 static int misc_seq_show(struct seq_file *seq, void *v)
  98 {
  99         const struct miscdevice *p = v;
 100
 101         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 102         return 0;
 103 }
 104
 105
 106 static struct seq_operations misc_seq_ops = {
 107         .start = misc_seq_start,
 108         .next  = misc_seq_next,
 109         .stop  = misc_seq_stop,
 110         .show  = misc_seq_show,
 111 };
 112
 113 static int misc_seq_open(struct inode *inode, struct file *file)
 114 {
 115         return seq_open(file, &misc_seq_ops);
 116 }
 117
 118 static struct file_operations misc_proc_fops = {
 119         .owner   = THIS_MODULE,
 120         .open    = misc_seq_open,
 121         .read    = seq_read,
 122         .llseek  = seq_lseek,
 123         .release = seq_release,
 124 };
 125 #endif
 126
 127 static int misc_open(struct inode * inode, struct file * file)
 128 {
 129         int minor = iminor(inode);
 130         struct miscdevice *c;
 131         int err = -ENODEV;
 132         struct file_operations *old_fops, *new_fops = NULL;
 133
 134         down(&misc_sem);
 135
 136         list_for_each_entry(c, &misc_list, list) {
 137                 if (c->minor == minor) {
 138                         new_fops = fops_get(c->fops);
 139                         break;
 140                 }
 141         }
 142
 143         if (!new_fops) {
 144                 up(&misc_sem);
 145                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 146                 down(&misc_sem);
 147
 148                 list_for_each_entry(c, &misc_list, list) {
 149                         if (c->minor == minor) {
 150                                 new_fops = fops_get(c->fops);
 151                                 break;
 152                         }
 153                 }
 154                 if (!new_fops)
 155                         goto fail;
 156         }
 157
 158         err = 0;
 159         old_fops = file->f_op;
 160         file->f_op = new_fops;
 161         if (file->f_op->open) {
 162                 err=file->f_op->open(inode,file);
 163                 if (err) {
 164                         fops_put(file->f_op);
 165                         file->f_op = fops_get(old_fops);
 166                 }
 167         }
 168         fops_put(old_fops);
 169 fail:
 170         up(&misc_sem);
 171         return err;
 172 }
 173
 174 /*
 175  * TODO for 2.7:
 176  *  - add a struct kref to struct miscdevice and make all usages of
 177  *    them dynamic.
 178  */
 179 static struct class *misc_class;
 180
 181 static struct file_operations misc_fops = {
 182         .owner          = THIS_MODULE,
 183         .open           = misc_open,
 184 };
 185
 186
 187 /**
 188  *      misc_register   -       register a miscellaneous device
 189  *      @misc: device structure
 190  *
 191  *      Register a miscellaneous device with the kernel. If the minor
 192  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 193  *      and placed in the minor field of the structure. For other cases
 194  *      the minor number requested is used.
 195  *
 196  *      The structure passed is linked into the kernel and may not be
 197  *      destroyed until it has been unregistered.
 198  *
 199  *      A zero is returned on success and a negative errno code for
 200  *      failure.
 201  */
 202
 203 int misc_register(struct miscdevice * misc)
 204 {
 205         struct miscdevice *c;
 206         dev_t dev;
 207         int err;
 208
 209         down(&misc_sem);
 210         list_for_each_entry(c, &misc_list, list) {
 211                 if (c->minor == misc->minor) {
 212                         up(&misc_sem);
 213                         return -EBUSY;
 214                 }
 215         }
 216
 217         if (misc->minor == MISC_DYNAMIC_MINOR) {
 218                 int i = DYNAMIC_MINORS;
 219                 while (--i >= 0)
 220                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 221                                 break;
 222                 if (i<0) {
 223                         up(&misc_sem);
 224                         return -EBUSY;
 225                 }
 226                 misc->minor = i;
 227         }
 228
 229         if (misc->minor < DYNAMIC_MINORS)
 230                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 231         if (misc->devfs_name[0] == '\0') {
 232                 snprintf(misc->devfs_name, sizeof(misc->devfs_name),
 233                                 "misc/%s", misc->name);
 234         }
 235         dev = MKDEV(MISC_MAJOR, misc->minor);
 236
 237         misc->class = class_device_create(misc_class, dev, misc->dev,
 238                                           "%s", misc->name);
 239         if (IS_ERR(misc->class)) {
 240                 err = PTR_ERR(misc->class);
 241                 goto out;
 242         }
 243
 244         err = devfs_mk_cdev(dev, S_IFCHR|S_IRUSR|S_IWUSR|S_IRGRP,
 245                             misc->devfs_name);
 246         if (err) {
 247                 class_device_destroy(misc_class, dev);
 248                 goto out;
 249         }
 250
 251         /*
 252          * Add it to the front, so that later devices can "override"
 253          * earlier defaults
 254          */
 255         list_add(&misc->list, &misc_list);
 256  out:
 257         up(&misc_sem);
 258         return err;
 259 }
 260
 261 /**
 262  *      misc_deregister - unregister a miscellaneous device
 263  *      @misc: device to unregister
 264  *
 265  *      Unregister a miscellaneous device that was previously
 266  *      successfully registered with misc_register(). Success
 267  *      is indicated by a zero return, a negative errno code
 268  *      indicates an error.
 269  */
 270
 271 int misc_deregister(struct miscdevice * misc)
 272 {
 273         int i = misc->minor;
 274
 275         if (list_empty(&misc->list))
 276                 return -EINVAL;
 277
 278         down(&misc_sem);
 279         list_del(&misc->list);
 280         class_device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 281         devfs_remove(misc->devfs_name);
 282         if (i < DYNAMIC_MINORS && i>0) {
 283                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 284         }
 285         up(&misc_sem);
 286         return 0;
 287 }
 288
 289 EXPORT_SYMBOL(misc_register);
 290 EXPORT_SYMBOL(misc_deregister);
 291
 292 static int __init misc_init(void)
 293 {
 294 #ifdef CONFIG_PROC_FS
 295         struct proc_dir_entry *ent;
 296
 297         ent = create_proc_entry("misc", 0, NULL);
 298         if (ent)
 299                 ent->proc_fops = &misc_proc_fops;
 300 #endif
 301         misc_class = class_create(THIS_MODULE, "misc");
 302         if (IS_ERR(misc_class))
 303                 return PTR_ERR(misc_class);
 304
 305         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 306                 printk("unable to get major %d for misc devices\n",
 307                        MISC_MAJOR);
 308                 class_destroy(misc_class);
 309                 return -EIO;
 310         }
 311         return 0;
 312 }
 313 subsys_initcall(misc_init);