fs/char_dev.c

   1 /*
   2  *  linux/fs/char_dev.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/config.h>
   8 #include <linux/init.h>
   9 #include <linux/fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/string.h>
  12
  13 #include <linux/major.h>
  14 #include <linux/errno.h>
  15 #include <linux/module.h>
  16 #include <linux/smp_lock.h>
  17 #include <linux/devfs_fs_kernel.h>
  18 #include <linux/seq_file.h>
  19
  20 #include <linux/kobject.h>
  21 #include <linux/kobj_map.h>
  22 #include <linux/cdev.h>
  23 #include <linux/mutex.h>
  24
  25 #ifdef CONFIG_KMOD
  26 #include <linux/kmod.h>
  27 #endif
  28
  29 static struct kobj_map *cdev_map;
  30
  31 static DEFINE_MUTEX(chrdevs_lock);
  32
  33 static struct char_device_struct {
  34         struct char_device_struct *next;
  35         unsigned int major;
  36         unsigned int baseminor;
  37         int minorct;
  38         char name[64];
  39         struct file_operations *fops;
  40         struct cdev *cdev;              /* will die */
  41 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
  42
  43 /* index in the above */
  44 static inline int major_to_index(int major)
  45 {
  46         return major % CHRDEV_MAJOR_HASH_SIZE;
  47 }
  48
  49 #ifdef CONFIG_PROC_FS
  50
  51 void chrdev_show(struct seq_file *f, off_t offset)
  52 {
  53         struct char_device_struct *cd;
  54
  55         if (offset < CHRDEV_MAJOR_HASH_SIZE) {
  56                 mutex_lock(&chrdevs_lock);
  57                 for (cd = chrdevs[offset]; cd; cd = cd->next)
  58                         seq_printf(f, "%3d %s\n", cd->major, cd->name);
  59                 mutex_unlock(&chrdevs_lock);
  60         }
  61 }
  62
  63 #endif /* CONFIG_PROC_FS */
  64
  65 /*
  66  * Register a single major with a specified minor range.
  67  *
  68  * If major == 0 this functions will dynamically allocate a major and return
  69  * its number.
  70  *
  71  * If major > 0 this function will attempt to reserve the passed range of
  72  * minors and will return zero on success.
  73  *
  74  * Returns a -ve errno on failure.
  75  */
  76 static struct char_device_struct *
  77 __register_chrdev_region(unsigned int major, unsigned int baseminor,
  78                            int minorct, const char *name)
  79 {
  80         struct char_device_struct *cd, **cp;
  81         int ret = 0;
  82         int i;
  83
  84         cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
  85         if (cd == NULL)
  86                 return ERR_PTR(-ENOMEM);
  87
  88         mutex_lock(&chrdevs_lock);
  89
  90         /* temporary */
  91         if (major == 0) {
  92                 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
  93                         if (chrdevs[i] == NULL)
  94                                 break;
  95                 }
  96
  97                 if (i == 0) {
  98                         ret = -EBUSY;
  99                         goto out;
 100                 }
 101                 major = i;
 102                 ret = major;
 103         }
 104
 105         cd->major = major;
 106         cd->baseminor = baseminor;
 107         cd->minorct = minorct;
 108         strncpy(cd->name,name, 64);
 109
 110         i = major_to_index(major);
 111
 112         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 113                 if ((*cp)->major > major ||
 114                     ((*cp)->major == major && (*cp)->baseminor >= baseminor))
 115                         break;
 116         if (*cp && (*cp)->major == major &&
 117             (*cp)->baseminor < baseminor + minorct) {
 118                 ret = -EBUSY;
 119                 goto out;
 120         }
 121         cd->next = *cp;
 122         *cp = cd;
 123         mutex_unlock(&chrdevs_lock);
 124         return cd;
 125 out:
 126         mutex_unlock(&chrdevs_lock);
 127         kfree(cd);
 128         return ERR_PTR(ret);
 129 }
 130
 131 static struct char_device_struct *
 132 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 133 {
 134         struct char_device_struct *cd = NULL, **cp;
 135         int i = major_to_index(major);
 136
 137         mutex_lock(&chrdevs_lock);
 138         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 139                 if ((*cp)->major == major &&
 140                     (*cp)->baseminor == baseminor &&
 141                     (*cp)->minorct == minorct)
 142                         break;
 143         if (*cp) {
 144                 cd = *cp;
 145                 *cp = cd->next;
 146         }
 147         mutex_unlock(&chrdevs_lock);
 148         return cd;
 149 }
 150
 151 int register_chrdev_region(dev_t from, unsigned count, const char *name)
 152 {
 153         struct char_device_struct *cd;
 154         dev_t to = from + count;
 155         dev_t n, next;
 156
 157         for (n = from; n < to; n = next) {
 158                 next = MKDEV(MAJOR(n)+1, 0);
 159                 if (next > to)
 160                         next = to;
 161                 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
 162                                next - n, name);
 163                 if (IS_ERR(cd))
 164                         goto fail;
 165         }
 166         return 0;
 167 fail:
 168         to = n;
 169         for (n = from; n < to; n = next) {
 170                 next = MKDEV(MAJOR(n)+1, 0);
 171                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 172         }
 173         return PTR_ERR(cd);
 174 }
 175
 176 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
 177                         const char *name)
 178 {
 179         struct char_device_struct *cd;
 180         cd = __register_chrdev_region(0, baseminor, count, name);
 181         if (IS_ERR(cd))
 182                 return PTR_ERR(cd);
 183         *dev = MKDEV(cd->major, cd->baseminor);
 184         return 0;
 185 }
 186
 187 int register_chrdev(unsigned int major, const char *name,
 188                     const struct file_operations *fops)
 189 {
 190         struct char_device_struct *cd;
 191         struct cdev *cdev;
 192         char *s;
 193         int err = -ENOMEM;
 194
 195         cd = __register_chrdev_region(major, 0, 256, name);
 196         if (IS_ERR(cd))
 197                 return PTR_ERR(cd);
 198
 199         cdev = cdev_alloc();
 200         if (!cdev)
 201                 goto out2;
 202
 203         cdev->owner = fops->owner;
 204         cdev->ops = fops;
 205         kobject_set_name(&cdev->kobj, "%s", name);
 206         for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
 207                 *s = '!';
 208
 209         err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
 210         if (err)
 211                 goto out;
 212
 213         cd->cdev = cdev;
 214
 215         return major ? 0 : cd->major;
 216 out:
 217         kobject_put(&cdev->kobj);
 218 out2:
 219         kfree(__unregister_chrdev_region(cd->major, 0, 256));
 220         return err;
 221 }
 222
 223 void unregister_chrdev_region(dev_t from, unsigned count)
 224 {
 225         dev_t to = from + count;
 226         dev_t n, next;
 227
 228         for (n = from; n < to; n = next) {
 229                 next = MKDEV(MAJOR(n)+1, 0);
 230                 if (next > to)
 231                         next = to;
 232                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 233         }
 234 }
 235
 236 int unregister_chrdev(unsigned int major, const char *name)
 237 {
 238         struct char_device_struct *cd;
 239         cd = __unregister_chrdev_region(major, 0, 256);
 240         if (cd && cd->cdev)
 241                 cdev_del(cd->cdev);
 242         kfree(cd);
 243         return 0;
 244 }
 245
 246 static DEFINE_SPINLOCK(cdev_lock);
 247
 248 static struct kobject *cdev_get(struct cdev *p)
 249 {
 250         struct module *owner = p->owner;
 251         struct kobject *kobj;
 252
 253         if (owner && !try_module_get(owner))
 254                 return NULL;
 255         kobj = kobject_get(&p->kobj);
 256         if (!kobj)
 257                 module_put(owner);
 258         return kobj;
 259 }
 260
 261 void cdev_put(struct cdev *p)
 262 {
 263         if (p) {
 264                 struct module *owner = p->owner;
 265                 kobject_put(&p->kobj);
 266                 module_put(owner);
 267         }
 268 }
 269
 270 /*
 271  * Called every time a character special file is opened
 272  */
 273 int chrdev_open(struct inode * inode, struct file * filp)
 274 {
 275         struct cdev *p;
 276         struct cdev *new = NULL;
 277         int ret = 0;
 278
 279         spin_lock(&cdev_lock);
 280         p = inode->i_cdev;
 281         if (!p) {
 282                 struct kobject *kobj;
 283                 int idx;
 284                 spin_unlock(&cdev_lock);
 285                 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
 286                 if (!kobj)
 287                         return -ENXIO;
 288                 new = container_of(kobj, struct cdev, kobj);
 289                 spin_lock(&cdev_lock);
 290                 p = inode->i_cdev;
 291                 if (!p) {
 292                         inode->i_cdev = p = new;
 293                         inode->i_cindex = idx;
 294                         list_add(&inode->i_devices, &p->list);
 295                         new = NULL;
 296                 } else if (!cdev_get(p))
 297                         ret = -ENXIO;
 298         } else if (!cdev_get(p))
 299                 ret = -ENXIO;
 300         spin_unlock(&cdev_lock);
 301         cdev_put(new);
 302         if (ret)
 303                 return ret;
 304         filp->f_op = fops_get(p->ops);
 305         if (!filp->f_op) {
 306                 cdev_put(p);
 307                 return -ENXIO;
 308         }
 309         if (filp->f_op->open) {
 310                 lock_kernel();
 311                 ret = filp->f_op->open(inode,filp);
 312                 unlock_kernel();
 313         }
 314         if (ret)
 315                 cdev_put(p);
 316         return ret;
 317 }
 318
 319 void cd_forget(struct inode *inode)
 320 {
 321         spin_lock(&cdev_lock);
 322         list_del_init(&inode->i_devices);
 323         inode->i_cdev = NULL;
 324         spin_unlock(&cdev_lock);
 325 }
 326
 327 static void cdev_purge(struct cdev *cdev)
 328 {
 329         spin_lock(&cdev_lock);
 330         while (!list_empty(&cdev->list)) {
 331                 struct inode *inode;
 332                 inode = container_of(cdev->list.next, struct inode, i_devices);
 333                 list_del_init(&inode->i_devices);
 334                 inode->i_cdev = NULL;
 335         }
 336         spin_unlock(&cdev_lock);
 337 }
 338
 339 /*
 340  * Dummy default file-operations: the only thing this does
 341  * is contain the open that then fills in the correct operations
 342  * depending on the special file...
 343  */
 344 const struct file_operations def_chr_fops = {
 345         .open = chrdev_open,
 346 };
 347
 348 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 349 {
 350         struct cdev *p = data;
 351         return &p->kobj;
 352 }
 353
 354 static int exact_lock(dev_t dev, void *data)
 355 {
 356         struct cdev *p = data;
 357         return cdev_get(p) ? 0 : -1;
 358 }
 359
 360 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 361 {
 362         p->dev = dev;
 363         p->count = count;
 364         return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 365 }
 366
 367 static void cdev_unmap(dev_t dev, unsigned count)
 368 {
 369         kobj_unmap(cdev_map, dev, count);
 370 }
 371
 372 void cdev_del(struct cdev *p)
 373 {
 374         cdev_unmap(p->dev, p->count);
 375         kobject_put(&p->kobj);
 376 }
 377
 378
 379 static void cdev_default_release(struct kobject *kobj)
 380 {
 381         struct cdev *p = container_of(kobj, struct cdev, kobj);
 382         cdev_purge(p);
 383 }
 384
 385 static void cdev_dynamic_release(struct kobject *kobj)
 386 {
 387         struct cdev *p = container_of(kobj, struct cdev, kobj);
 388         cdev_purge(p);
 389         kfree(p);
 390 }
 391
 392 static struct kobj_type ktype_cdev_default = {
 393         .release        = cdev_default_release,
 394 };
 395
 396 static struct kobj_type ktype_cdev_dynamic = {
 397         .release        = cdev_dynamic_release,
 398 };
 399
 400 struct cdev *cdev_alloc(void)
 401 {
 402         struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
 403         if (p) {
 404                 p->kobj.ktype = &ktype_cdev_dynamic;
 405                 INIT_LIST_HEAD(&p->list);
 406                 kobject_init(&p->kobj);
 407         }
 408         return p;
 409 }
 410
 411 void cdev_init(struct cdev *cdev, const struct file_operations *fops)
 412 {
 413         memset(cdev, 0, sizeof *cdev);
 414         INIT_LIST_HEAD(&cdev->list);
 415         cdev->kobj.ktype = &ktype_cdev_default;
 416         kobject_init(&cdev->kobj);
 417         cdev->ops = fops;
 418 }
 419
 420 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 421 {
 422         if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
 423                 /* Make old-style 2.4 aliases work */
 424                 request_module("char-major-%d", MAJOR(dev));
 425         return NULL;
 426 }
 427
 428 void __init chrdev_init(void)
 429 {
 430         cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 431 }
 432
 433
 434 /* Let modules do char dev stuff */
 435 EXPORT_SYMBOL(register_chrdev_region);
 436 EXPORT_SYMBOL(unregister_chrdev_region);
 437 EXPORT_SYMBOL(alloc_chrdev_region);
 438 EXPORT_SYMBOL(cdev_init);
 439 EXPORT_SYMBOL(cdev_alloc);
 440 EXPORT_SYMBOL(cdev_del);
 441 EXPORT_SYMBOL(cdev_add);
 442 EXPORT_SYMBOL(register_chrdev);
 443 EXPORT_SYMBOL(unregister_chrdev);