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 rtc_DP8570A_init(void);
  67 extern int rtc_MK48T08_init(void);
  68 extern int pmu_device_init(void);
  69
  70 #ifdef CONFIG_PROC_FS
  71 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  72 {
  73         struct miscdevice *p;
  74         loff_t off = 0;
  75
  76         down(&misc_sem);
  77         list_for_each_entry(p, &misc_list, list) {
  78                 if (*pos == off++)
  79                         return p;
  80         }
  81         return NULL;
  82 }
  83
  84 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  85 {
  86         struct list_head *n = ((struct miscdevice *)v)->list.next;
  87
  88         ++*pos;
  89
  90         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  91                  : NULL;
  92 }
  93
  94 static void misc_seq_stop(struct seq_file *seq, void *v)
  95 {
  96         up(&misc_sem);
  97 }
  98
  99 static int misc_seq_show(struct seq_file *seq, void *v)
 100 {
 101         const struct miscdevice *p = v;
 102
 103         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 104         return 0;
 105 }
 106
 107
 108 static struct seq_operations misc_seq_ops = {
 109         .start = misc_seq_start,
 110         .next  = misc_seq_next,
 111         .stop  = misc_seq_stop,
 112         .show  = misc_seq_show,
 113 };
 114
 115 static int misc_seq_open(struct inode *inode, struct file *file)
 116 {
 117         return seq_open(file, &misc_seq_ops);
 118 }
 119
 120 static struct file_operations misc_proc_fops = {
 121         .owner   = THIS_MODULE,
 122         .open    = misc_seq_open,
 123         .read    = seq_read,
 124         .llseek  = seq_lseek,
 125         .release = seq_release,
 126 };
 127 #endif
 128
 129 static int misc_open(struct inode * inode, struct file * file)
 130 {
 131         int minor = iminor(inode);
 132         struct miscdevice *c;
 133         int err = -ENODEV;
 134         struct file_operations *old_fops, *new_fops = NULL;
 135
 136         down(&misc_sem);
 137
 138         list_for_each_entry(c, &misc_list, list) {
 139                 if (c->minor == minor) {
 140                         new_fops = fops_get(c->fops);
 141                         break;
 142                 }
 143         }
 144
 145         if (!new_fops) {
 146                 up(&misc_sem);
 147                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 148                 down(&misc_sem);
 149
 150                 list_for_each_entry(c, &misc_list, list) {
 151                         if (c->minor == minor) {
 152                                 new_fops = fops_get(c->fops);
 153                                 break;
 154                         }
 155                 }
 156                 if (!new_fops)
 157                         goto fail;
 158         }
 159
 160         err = 0;
 161         old_fops = file->f_op;
 162         file->f_op = new_fops;
 163         if (file->f_op->open) {
 164                 err=file->f_op->open(inode,file);
 165                 if (err) {
 166                         fops_put(file->f_op);
 167                         file->f_op = fops_get(old_fops);
 168                 }
 169         }
 170         fops_put(old_fops);
 171 fail:
 172         up(&misc_sem);
 173         return err;
 174 }
 175
 176 /*
 177  * TODO for 2.7:
 178  *  - add a struct kref to struct miscdevice and make all usages of
 179  *    them dynamic.
 180  */
 181 static struct class *misc_class;
 182
 183 static struct file_operations misc_fops = {
 184         .owner          = THIS_MODULE,
 185         .open           = misc_open,
 186 };
 187
 188
 189 /**
 190  *      misc_register   -       register a miscellaneous device
 191  *      @misc: device structure
 192  *
 193  *      Register a miscellaneous device with the kernel. If the minor
 194  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 195  *      and placed in the minor field of the structure. For other cases
 196  *      the minor number requested is used.
 197  *
 198  *      The structure passed is linked into the kernel and may not be
 199  *      destroyed until it has been unregistered.
 200  *
 201  *      A zero is returned on success and a negative errno code for
 202  *      failure.
 203  */
 204
 205 int misc_register(struct miscdevice * misc)
 206 {
 207         struct miscdevice *c;
 208         dev_t dev;
 209         int err;
 210
 211         down(&misc_sem);
 212         list_for_each_entry(c, &misc_list, list) {
 213                 if (c->minor == misc->minor) {
 214                         up(&misc_sem);
 215                         return -EBUSY;
 216                 }
 217         }
 218
 219         if (misc->minor == MISC_DYNAMIC_MINOR) {
 220                 int i = DYNAMIC_MINORS;
 221                 while (--i >= 0)
 222                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 223                                 break;
 224                 if (i<0) {
 225                         up(&misc_sem);
 226                         return -EBUSY;
 227                 }
 228                 misc->minor = i;
 229         }
 230
 231         if (misc->minor < DYNAMIC_MINORS)
 232                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 233         if (misc->devfs_name[0] == '\0') {
 234                 snprintf(misc->devfs_name, sizeof(misc->devfs_name),
 235                                 "misc/%s", misc->name);
 236         }
 237         dev = MKDEV(MISC_MAJOR, misc->minor);
 238
 239         misc->class = class_device_create(misc_class, dev, misc->dev,
 240                                           "%s", misc->name);
 241         if (IS_ERR(misc->class)) {
 242                 err = PTR_ERR(misc->class);
 243                 goto out;
 244         }
 245
 246         err = devfs_mk_cdev(dev, S_IFCHR|S_IRUSR|S_IWUSR|S_IRGRP,
 247                             misc->devfs_name);
 248         if (err) {
 249                 class_device_destroy(misc_class, dev);
 250                 goto out;
 251         }
 252
 253         /*
 254          * Add it to the front, so that later devices can "override"
 255          * earlier defaults
 256          */
 257         list_add(&misc->list, &misc_list);
 258  out:
 259         up(&misc_sem);
 260         return err;
 261 }
 262
 263 /**
 264  *      misc_deregister - unregister a miscellaneous device
 265  *      @misc: device to unregister
 266  *
 267  *      Unregister a miscellaneous device that was previously
 268  *      successfully registered with misc_register(). Success
 269  *      is indicated by a zero return, a negative errno code
 270  *      indicates an error.
 271  */
 272
 273 int misc_deregister(struct miscdevice * misc)
 274 {
 275         int i = misc->minor;
 276
 277         if (list_empty(&misc->list))
 278                 return -EINVAL;
 279
 280         down(&misc_sem);
 281         list_del(&misc->list);
 282         class_device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 283         devfs_remove(misc->devfs_name);
 284         if (i < DYNAMIC_MINORS && i>0) {
 285                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 286         }
 287         up(&misc_sem);
 288         return 0;
 289 }
 290
 291 EXPORT_SYMBOL(misc_register);
 292 EXPORT_SYMBOL(misc_deregister);
 293
 294 static int __init misc_init(void)
 295 {
 296 #ifdef CONFIG_PROC_FS
 297         struct proc_dir_entry *ent;
 298
 299         ent = create_proc_entry("misc", 0, NULL);
 300         if (ent)
 301                 ent->proc_fops = &misc_proc_fops;
 302 #endif
 303         misc_class = class_create(THIS_MODULE, "misc");
 304         if (IS_ERR(misc_class))
 305                 return PTR_ERR(misc_class);
 306 #ifdef CONFIG_MVME16x
 307         rtc_MK48T08_init();
 308 #endif
 309 #ifdef CONFIG_BVME6000
 310         rtc_DP8570A_init();
 311 #endif
 312         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 313                 printk("unable to get major %d for misc devices\n",
 314                        MISC_MAJOR);
 315                 class_destroy(misc_class);
 316                 return -EIO;
 317         }
 318         return 0;
 319 }
 320 subsys_initcall(misc_init);