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 tosh_init(void);
  70 extern int i8k_init(void);
  71
  72 #ifdef CONFIG_PROC_FS
  73 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
  74 {
  75         struct miscdevice *p;
  76         loff_t off = 0;
  77
  78         down(&misc_sem);
  79         list_for_each_entry(p, &misc_list, list) {
  80                 if (*pos == off++)
  81                         return p;
  82         }
  83         return NULL;
  84 }
  85
  86 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  87 {
  88         struct list_head *n = ((struct miscdevice *)v)->list.next;
  89
  90         ++*pos;
  91
  92         return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
  93                  : NULL;
  94 }
  95
  96 static void misc_seq_stop(struct seq_file *seq, void *v)
  97 {
  98         up(&misc_sem);
  99 }
 100
 101 static int misc_seq_show(struct seq_file *seq, void *v)
 102 {
 103         const struct miscdevice *p = v;
 104
 105         seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
 106         return 0;
 107 }
 108
 109
 110 static struct seq_operations misc_seq_ops = {
 111         .start = misc_seq_start,
 112         .next  = misc_seq_next,
 113         .stop  = misc_seq_stop,
 114         .show  = misc_seq_show,
 115 };
 116
 117 static int misc_seq_open(struct inode *inode, struct file *file)
 118 {
 119         return seq_open(file, &misc_seq_ops);
 120 }
 121
 122 static struct file_operations misc_proc_fops = {
 123         .owner   = THIS_MODULE,
 124         .open    = misc_seq_open,
 125         .read    = seq_read,
 126         .llseek  = seq_lseek,
 127         .release = seq_release,
 128 };
 129 #endif
 130
 131 static int misc_open(struct inode * inode, struct file * file)
 132 {
 133         int minor = iminor(inode);
 134         struct miscdevice *c;
 135         int err = -ENODEV;
 136         struct file_operations *old_fops, *new_fops = NULL;
 137
 138         down(&misc_sem);
 139
 140         list_for_each_entry(c, &misc_list, list) {
 141                 if (c->minor == minor) {
 142                         new_fops = fops_get(c->fops);
 143                         break;
 144                 }
 145         }
 146
 147         if (!new_fops) {
 148                 up(&misc_sem);
 149                 request_module("char-major-%d-%d", MISC_MAJOR, minor);
 150                 down(&misc_sem);
 151
 152                 list_for_each_entry(c, &misc_list, list) {
 153                         if (c->minor == minor) {
 154                                 new_fops = fops_get(c->fops);
 155                                 break;
 156                         }
 157                 }
 158                 if (!new_fops)
 159                         goto fail;
 160         }
 161
 162         err = 0;
 163         old_fops = file->f_op;
 164         file->f_op = new_fops;
 165         if (file->f_op->open) {
 166                 err=file->f_op->open(inode,file);
 167                 if (err) {
 168                         fops_put(file->f_op);
 169                         file->f_op = fops_get(old_fops);
 170                 }
 171         }
 172         fops_put(old_fops);
 173 fail:
 174         up(&misc_sem);
 175         return err;
 176 }
 177
 178 /*
 179  * TODO for 2.7:
 180  *  - add a struct class_device to struct miscdevice and make all usages of
 181  *    them dynamic.
 182  */
 183 static struct class_simple *misc_class;
 184
 185 static struct file_operations misc_fops = {
 186         .owner          = THIS_MODULE,
 187         .open           = misc_open,
 188 };
 189
 190
 191 /**
 192  *      misc_register   -       register a miscellaneous device
 193  *      @misc: device structure
 194  *
 195  *      Register a miscellaneous device with the kernel. If the minor
 196  *      number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
 197  *      and placed in the minor field of the structure. For other cases
 198  *      the minor number requested is used.
 199  *
 200  *      The structure passed is linked into the kernel and may not be
 201  *      destroyed until it has been unregistered.
 202  *
 203  *      A zero is returned on success and a negative errno code for
 204  *      failure.
 205  */
 206
 207 int misc_register(struct miscdevice * misc)
 208 {
 209         struct miscdevice *c;
 210         dev_t dev;
 211         int err;
 212
 213         down(&misc_sem);
 214         list_for_each_entry(c, &misc_list, list) {
 215                 if (c->minor == misc->minor) {
 216                         up(&misc_sem);
 217                         return -EBUSY;
 218                 }
 219         }
 220
 221         if (misc->minor == MISC_DYNAMIC_MINOR) {
 222                 int i = DYNAMIC_MINORS;
 223                 while (--i >= 0)
 224                         if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
 225                                 break;
 226                 if (i<0) {
 227                         up(&misc_sem);
 228                         return -EBUSY;
 229                 }
 230                 misc->minor = i;
 231         }
 232
 233         if (misc->minor < DYNAMIC_MINORS)
 234                 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 235         if (misc->devfs_name[0] == '\0') {
 236                 snprintf(misc->devfs_name, sizeof(misc->devfs_name),
 237                                 "misc/%s", misc->name);
 238         }
 239         dev = MKDEV(MISC_MAJOR, misc->minor);
 240
 241         misc->class = class_simple_device_add(misc_class, dev,
 242                                               misc->dev, misc->name);
 243         if (IS_ERR(misc->class)) {
 244                 err = PTR_ERR(misc->class);
 245                 goto out;
 246         }
 247
 248         err = devfs_mk_cdev(dev, S_IFCHR|S_IRUSR|S_IWUSR|S_IRGRP,
 249                             misc->devfs_name);
 250         if (err) {
 251                 class_simple_device_remove(dev);
 252                 goto out;
 253         }
 254
 255         /*
 256          * Add it to the front, so that later devices can "override"
 257          * earlier defaults
 258          */
 259         list_add(&misc->list, &misc_list);
 260  out:
 261         up(&misc_sem);
 262         return err;
 263 }
 264
 265 /**
 266  *      misc_deregister - unregister a miscellaneous device
 267  *      @misc: device to unregister
 268  *
 269  *      Unregister a miscellaneous device that was previously
 270  *      successfully registered with misc_register(). Success
 271  *      is indicated by a zero return, a negative errno code
 272  *      indicates an error.
 273  */
 274
 275 int misc_deregister(struct miscdevice * misc)
 276 {
 277         int i = misc->minor;
 278
 279         if (list_empty(&misc->list))
 280                 return -EINVAL;
 281
 282         down(&misc_sem);
 283         list_del(&misc->list);
 284         class_simple_device_remove(MKDEV(MISC_MAJOR, misc->minor));
 285         devfs_remove(misc->devfs_name);
 286         if (i < DYNAMIC_MINORS && i>0) {
 287                 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
 288         }
 289         up(&misc_sem);
 290         return 0;
 291 }
 292
 293 EXPORT_SYMBOL(misc_register);
 294 EXPORT_SYMBOL(misc_deregister);
 295
 296 static int __init misc_init(void)
 297 {
 298 #ifdef CONFIG_PROC_FS
 299         struct proc_dir_entry *ent;
 300
 301         ent = create_proc_entry("misc", 0, NULL);
 302         if (ent)
 303                 ent->proc_fops = &misc_proc_fops;
 304 #endif
 305         misc_class = class_simple_create(THIS_MODULE, "misc");
 306         if (IS_ERR(misc_class))
 307                 return PTR_ERR(misc_class);
 308 #ifdef CONFIG_MVME16x
 309         rtc_MK48T08_init();
 310 #endif
 311 #ifdef CONFIG_BVME6000
 312         rtc_DP8570A_init();
 313 #endif
 314 #ifdef CONFIG_PMAC_PBOOK
 315         pmu_device_init();
 316 #endif
 317 #ifdef CONFIG_TOSHIBA
 318         tosh_init();
 319 #endif
 320 #ifdef CONFIG_I8K
 321         i8k_init();
 322 #endif
 323         if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
 324                 printk("unable to get major %d for misc devices\n",
 325                        MISC_MAJOR);
 326                 class_simple_destroy(misc_class);
 327                 return -EIO;
 328         }
 329         return 0;
 330 }
 331 subsys_initcall(misc_init);