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 extern int i8k_init(void);
  70
  71 #ifdef CONFIG_PROC_FS
  72 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  73 {
  74         struct miscdevice *p;
  75         loff_t off = 0;
  76
  77         down(&misc_sem);
  78         list_for_each_entry(p, &misc_list, list) {
  79                 if (*pos == off++)
  80                         return p;
  81         }
  82         return NULL;
  83 }
  84
  85 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  86 {
  87         struct list_head *n = ((struct miscdevice *)v)->list.next;
  88
  89         ++*pos;
  90
  91         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  92                  : NULL;
  93 }
  94
  95 static void misc_seq_stop(struct seq_file *seq, void *v)
  96 {
  97         up(&misc_sem);
  98 }
  99
 100 static int misc_seq_show(struct seq_file *seq, void *v)
 101 {
 102         const struct miscdevice *p = v;
 103
 104         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 105         return 0;
 106 }
 107
 108
 109 static struct seq_operations misc_seq_ops = {
 110         .start = misc_seq_start,
 111         .next  = misc_seq_next,
 112         .stop  = misc_seq_stop,
 113         .show  = misc_seq_show,
 114 };
 115
 116 static int misc_seq_open(struct inode *inode, struct file *file)
 117 {
 118         return seq_open(file, &misc_seq_ops);
 119 }
 120
 121 static struct file_operations misc_proc_fops = {
 122         .owner   = THIS_MODULE,
 123         .open    = misc_seq_open,
 124         .read    = seq_read,
 125         .llseek  = seq_lseek,
 126         .release = seq_release,
 127 };
 128 #endif
 129
 130 static int misc_open(struct inode * inode, struct file * file)
 131 {
 132         int minor = iminor(inode);
 133         struct miscdevice *c;
 134         int err = -ENODEV;
 135         struct file_operations *old_fops, *new_fops = NULL;
 136
 137         down(&misc_sem);
 138
 139         list_for_each_entry(c, &misc_list, list) {
 140                 if (c->minor == minor) {
 141                         new_fops = fops_get(c->fops);
 142                         break;
 143                 }
 144         }
 145
 146         if (!new_fops) {
 147                 up(&misc_sem);
 148                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 149                 down(&misc_sem);
 150
 151                 list_for_each_entry(c, &misc_list, list) {
 152                         if (c->minor == minor) {
 153                                 new_fops = fops_get(c->fops);
 154                                 break;
 155                         }
 156                 }
 157                 if (!new_fops)
 158                         goto fail;
 159         }
 160
 161         err = 0;
 162         old_fops = file->f_op;
 163         file->f_op = new_fops;
 164         if (file->f_op->open) {
 165                 err=file->f_op->open(inode,file);
 166                 if (err) {
 167                         fops_put(file->f_op);
 168                         file->f_op = fops_get(old_fops);
 169                 }
 170         }
 171         fops_put(old_fops);
 172 fail:
 173         up(&misc_sem);
 174         return err;
 175 }
 176
 177 /*
 178  * TODO for 2.7:
 179  *  - add a struct kref to struct miscdevice and make all usages of
 180  *    them dynamic.
 181  */
 182 static struct class *misc_class;
 183
 184 static struct file_operations misc_fops = {
 185         .owner          = THIS_MODULE,
 186         .open           = misc_open,
 187 };
 188
 189
 190 /**
 191  *      misc_register   -       register a miscellaneous device
 192  *      @misc: device structure
 193  *
 194  *      Register a miscellaneous device with the kernel. If the minor
 195  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 196  *      and placed in the minor field of the structure. For other cases
 197  *      the minor number requested is used.
 198  *
 199  *      The structure passed is linked into the kernel and may not be
 200  *      destroyed until it has been unregistered.
 201  *
 202  *      A zero is returned on success and a negative errno code for
 203  *      failure.
 204  */
 205
 206 int misc_register(struct miscdevice * misc)
 207 {
 208         struct miscdevice *c;
 209         dev_t dev;
 210         int err;
 211
 212         down(&misc_sem);
 213         list_for_each_entry(c, &misc_list, list) {
 214                 if (c->minor == misc->minor) {
 215                         up(&misc_sem);
 216                         return -EBUSY;
 217                 }
 218         }
 219
 220         if (misc->minor == MISC_DYNAMIC_MINOR) {
 221                 int i = DYNAMIC_MINORS;
 222                 while (--i >= 0)
 223                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 224                                 break;
 225                 if (i<0) {
 226                         up(&misc_sem);
 227                         return -EBUSY;
 228                 }
 229                 misc->minor = i;
 230         }
 231
 232         if (misc->minor < DYNAMIC_MINORS)
 233                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 234         if (misc->devfs_name[0] == '\0') {
 235                 snprintf(misc->devfs_name, sizeof(misc->devfs_name),
 236                                 "misc/%s", misc->name);
 237         }
 238         dev = MKDEV(MISC_MAJOR, misc->minor);
 239
 240         misc->class = class_device_create(misc_class, dev, misc->dev,
 241                                           "%s", misc->name);
 242         if (IS_ERR(misc->class)) {
 243                 err = PTR_ERR(misc->class);
 244                 goto out;
 245         }
 246
 247         err = devfs_mk_cdev(dev, S_IFCHR|S_IRUSR|S_IWUSR|S_IRGRP,
 248                             misc->devfs_name);
 249         if (err) {
 250                 class_device_destroy(misc_class, dev);
 251                 goto out;
 252         }
 253
 254         /*
 255          * Add it to the front, so that later devices can "override"
 256          * earlier defaults
 257          */
 258         list_add(&misc->list, &misc_list);
 259  out:
 260         up(&misc_sem);
 261         return err;
 262 }
 263
 264 /**
 265  *      misc_deregister - unregister a miscellaneous device
 266  *      @misc: device to unregister
 267  *
 268  *      Unregister a miscellaneous device that was previously
 269  *      successfully registered with misc_register(). Success
 270  *      is indicated by a zero return, a negative errno code
 271  *      indicates an error.
 272  */
 273
 274 int misc_deregister(struct miscdevice * misc)
 275 {
 276         int i = misc->minor;
 277
 278         if (list_empty(&misc->list))
 279                 return -EINVAL;
 280
 281         down(&misc_sem);
 282         list_del(&misc->list);
 283         class_device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 284         devfs_remove(misc->devfs_name);
 285         if (i < DYNAMIC_MINORS && i>0) {
 286                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 287         }
 288         up(&misc_sem);
 289         return 0;
 290 }
 291
 292 EXPORT_SYMBOL(misc_register);
 293 EXPORT_SYMBOL(misc_deregister);
 294
 295 static int __init misc_init(void)
 296 {
 297 #ifdef CONFIG_PROC_FS
 298         struct proc_dir_entry *ent;
 299
 300         ent = create_proc_entry("misc", 0, NULL);
 301         if (ent)
 302                 ent->proc_fops = &misc_proc_fops;
 303 #endif
 304         misc_class = class_create(THIS_MODULE, "misc");
 305         if (IS_ERR(misc_class))
 306                 return PTR_ERR(misc_class);
 307 #ifdef CONFIG_MVME16x
 308         rtc_MK48T08_init();
 309 #endif
 310 #ifdef CONFIG_BVME6000
 311         rtc_DP8570A_init();
 312 #endif
 313 #ifdef CONFIG_PMAC_PBOOK
 314         pmu_device_init();
 315 #endif
 316 #ifdef CONFIG_I8K
 317         i8k_init();
 318 #endif
 319         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 320                 printk("unable to get major %d for misc devices\n",
 321                        MISC_MAJOR);
 322                 class_destroy(misc_class);
 323                 return -EIO;
 324         }
 325         return 0;
 326 }
 327 subsys_initcall(misc_init);