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