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
  19 #include <linux/kobject.h>
  20 #include <linux/kobj_map.h>
  21 #include <linux/cdev.h>
  22 #include <linux/mutex.h>
  23
  24 #ifdef CONFIG_KMOD
  25 #include <linux/kmod.h>
  26 #endif
  27
  28 static struct kobj_map *cdev_map;
  29
  30 #define MAX_PROBE_HASH 255      /* random */
  31
  32 static DEFINE_MUTEX(chrdevs_lock);
  33
  34 static struct char_device_struct {
  35         struct char_device_struct *next;
  36         unsigned int major;
  37         unsigned int baseminor;
  38         int minorct;
  39         char name[64];
  40         struct file_operations *fops;
  41         struct cdev *cdev;              /* will die */
  42 } *chrdevs[MAX_PROBE_HASH];
  43
  44 /* index in the above */
  45 static inline int major_to_index(int major)
  46 {
  47         return major % MAX_PROBE_HASH;
  48 }
  49
  50 struct chrdev_info {
  51         int index;
  52         struct char_device_struct *cd;
  53 };
  54
  55 void *get_next_chrdev(void *dev)
  56 {
  57         struct chrdev_info *info;
  58
  59         if (dev == NULL) {
  60                 info = kmalloc(sizeof(*info), GFP_KERNEL);
  61                 if (!info)
  62                         goto out;
  63                 info->index=0;
  64                 info->cd = chrdevs[info->index];
  65                 if (info->cd)
  66                         goto out;
  67         } else {
  68                 info = dev;
  69         }
  70
  71         while (info->index < ARRAY_SIZE(chrdevs)) {
  72                 if (info->cd)
  73                         info->cd = info->cd->next;
  74                 if (info->cd)
  75                         goto out;
  76                 /*
  77                  * No devices on this chain, move to the next
  78                  */
  79                 info->index++;
  80                 info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
  81                         chrdevs[info->index] : NULL;
  82                 if (info->cd)
  83                         goto out;
  84         }
  85
  86 out:
  87         return info;
  88 }
  89
  90 void *acquire_chrdev_list(void)
  91 {
  92         mutex_lock(&chrdevs_lock);
  93         return get_next_chrdev(NULL);
  94 }
  95
  96 void release_chrdev_list(void *dev)
  97 {
  98         mutex_unlock(&chrdevs_lock);
  99         kfree(dev);
 100 }
 101
 102
 103 int count_chrdev_list(void)
 104 {
 105         struct char_device_struct *cd;
 106         int i, count;
 107
 108         count = 0;
 109
 110         for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
 111                 for (cd = chrdevs[i]; cd; cd = cd->next)
 112                         count++;
 113         }
 114
 115         return count;
 116 }
 117
 118 int get_chrdev_info(void *dev, int *major, char **name)
 119 {
 120         struct chrdev_info *info = dev;
 121
 122         if (info->cd == NULL)
 123                 return 1;
 124
 125         *major = info->cd->major;
 126         *name = info->cd->name;
 127         return 0;
 128 }
 129
 130 /*
 131  * Register a single major with a specified minor range.
 132  *
 133  * If major == 0 this functions will dynamically allocate a major and return
 134  * its number.
 135  *
 136  * If major > 0 this function will attempt to reserve the passed range of
 137  * minors and will return zero on success.
 138  *
 139  * Returns a -ve errno on failure.
 140  */
 141 static struct char_device_struct *
 142 __register_chrdev_region(unsigned int major, unsigned int baseminor,
 143                            int minorct, const char *name)
 144 {
 145         struct char_device_struct *cd, **cp;
 146         int ret = 0;
 147         int i;
 148
 149         cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
 150         if (cd == NULL)
 151                 return ERR_PTR(-ENOMEM);
 152
 153         memset(cd, 0, sizeof(struct char_device_struct));
 154
 155         mutex_lock(&chrdevs_lock);
 156
 157         /* temporary */
 158         if (major == 0) {
 159                 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
 160                         if (chrdevs[i] == NULL)
 161                                 break;
 162                 }
 163
 164                 if (i == 0) {
 165                         ret = -EBUSY;
 166                         goto out;
 167                 }
 168                 major = i;
 169                 ret = major;
 170         }
 171
 172         cd->major = major;
 173         cd->baseminor = baseminor;
 174         cd->minorct = minorct;
 175         strncpy(cd->name,name, 64);
 176
 177         i = major_to_index(major);
 178
 179         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 180                 if ((*cp)->major > major ||
 181                     ((*cp)->major == major && (*cp)->baseminor >= baseminor))
 182                         break;
 183         if (*cp && (*cp)->major == major &&
 184             (*cp)->baseminor < baseminor + minorct) {
 185                 ret = -EBUSY;
 186                 goto out;
 187         }
 188         cd->next = *cp;
 189         *cp = cd;
 190         mutex_unlock(&chrdevs_lock);
 191         return cd;
 192 out:
 193         mutex_unlock(&chrdevs_lock);
 194         kfree(cd);
 195         return ERR_PTR(ret);
 196 }
 197
 198 static struct char_device_struct *
 199 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 200 {
 201         struct char_device_struct *cd = NULL, **cp;
 202         int i = major_to_index(major);
 203
 204         mutex_lock(&chrdevs_lock);
 205         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 206                 if ((*cp)->major == major &&
 207                     (*cp)->baseminor == baseminor &&
 208                     (*cp)->minorct == minorct)
 209                         break;
 210         if (*cp) {
 211                 cd = *cp;
 212                 *cp = cd->next;
 213         }
 214         mutex_unlock(&chrdevs_lock);
 215         return cd;
 216 }
 217
 218 int register_chrdev_region(dev_t from, unsigned count, const char *name)
 219 {
 220         struct char_device_struct *cd;
 221         dev_t to = from + count;
 222         dev_t n, next;
 223
 224         for (n = from; n < to; n = next) {
 225                 next = MKDEV(MAJOR(n)+1, 0);
 226                 if (next > to)
 227                         next = to;
 228                 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
 229                                next - n, name);
 230                 if (IS_ERR(cd))
 231                         goto fail;
 232         }
 233         return 0;
 234 fail:
 235         to = n;
 236         for (n = from; n < to; n = next) {
 237                 next = MKDEV(MAJOR(n)+1, 0);
 238                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 239         }
 240         return PTR_ERR(cd);
 241 }
 242
 243 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
 244                         const char *name)
 245 {
 246         struct char_device_struct *cd;
 247         cd = __register_chrdev_region(0, baseminor, count, name);
 248         if (IS_ERR(cd))
 249                 return PTR_ERR(cd);
 250         *dev = MKDEV(cd->major, cd->baseminor);
 251         return 0;
 252 }
 253
 254 int register_chrdev(unsigned int major, const char *name,
 255                     struct file_operations *fops)
 256 {
 257         struct char_device_struct *cd;
 258         struct cdev *cdev;
 259         char *s;
 260         int err = -ENOMEM;
 261
 262         cd = __register_chrdev_region(major, 0, 256, name);
 263         if (IS_ERR(cd))
 264                 return PTR_ERR(cd);
 265
 266         cdev = cdev_alloc();
 267         if (!cdev)
 268                 goto out2;
 269
 270         cdev->owner = fops->owner;
 271         cdev->ops = fops;
 272         kobject_set_name(&cdev->kobj, "%s", name);
 273         for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
 274                 *s = '!';
 275
 276         err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
 277         if (err)
 278                 goto out;
 279
 280         cd->cdev = cdev;
 281
 282         return major ? 0 : cd->major;
 283 out:
 284         kobject_put(&cdev->kobj);
 285 out2:
 286         kfree(__unregister_chrdev_region(cd->major, 0, 256));
 287         return err;
 288 }
 289
 290 void unregister_chrdev_region(dev_t from, unsigned count)
 291 {
 292         dev_t to = from + count;
 293         dev_t n, next;
 294
 295         for (n = from; n < to; n = next) {
 296                 next = MKDEV(MAJOR(n)+1, 0);
 297                 if (next > to)
 298                         next = to;
 299                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 300         }
 301 }
 302
 303 int unregister_chrdev(unsigned int major, const char *name)
 304 {
 305         struct char_device_struct *cd;
 306         cd = __unregister_chrdev_region(major, 0, 256);
 307         if (cd && cd->cdev)
 308                 cdev_del(cd->cdev);
 309         kfree(cd);
 310         return 0;
 311 }
 312
 313 static DEFINE_SPINLOCK(cdev_lock);
 314
 315 static struct kobject *cdev_get(struct cdev *p)
 316 {
 317         struct module *owner = p->owner;
 318         struct kobject *kobj;
 319
 320         if (owner && !try_module_get(owner))
 321                 return NULL;
 322         kobj = kobject_get(&p->kobj);
 323         if (!kobj)
 324                 module_put(owner);
 325         return kobj;
 326 }
 327
 328 void cdev_put(struct cdev *p)
 329 {
 330         if (p) {
 331                 struct module *owner = p->owner;
 332                 kobject_put(&p->kobj);
 333                 module_put(owner);
 334         }
 335 }
 336
 337 /*
 338  * Called every time a character special file is opened
 339  */
 340 int chrdev_open(struct inode * inode, struct file * filp)
 341 {
 342         struct cdev *p;
 343         struct cdev *new = NULL;
 344         int ret = 0;
 345
 346         spin_lock(&cdev_lock);
 347         p = inode->i_cdev;
 348         if (!p) {
 349                 struct kobject *kobj;
 350                 int idx;
 351                 spin_unlock(&cdev_lock);
 352                 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
 353                 if (!kobj)
 354                         return -ENXIO;
 355                 new = container_of(kobj, struct cdev, kobj);
 356                 spin_lock(&cdev_lock);
 357                 p = inode->i_cdev;
 358                 if (!p) {
 359                         inode->i_cdev = p = new;
 360                         inode->i_cindex = idx;
 361                         list_add(&inode->i_devices, &p->list);
 362                         new = NULL;
 363                 } else if (!cdev_get(p))
 364                         ret = -ENXIO;
 365         } else if (!cdev_get(p))
 366                 ret = -ENXIO;
 367         spin_unlock(&cdev_lock);
 368         cdev_put(new);
 369         if (ret)
 370                 return ret;
 371         filp->f_op = fops_get(p->ops);
 372         if (!filp->f_op) {
 373                 cdev_put(p);
 374                 return -ENXIO;
 375         }
 376         if (filp->f_op->open) {
 377                 lock_kernel();
 378                 ret = filp->f_op->open(inode,filp);
 379                 unlock_kernel();
 380         }
 381         if (ret)
 382                 cdev_put(p);
 383         return ret;
 384 }
 385
 386 void cd_forget(struct inode *inode)
 387 {
 388         spin_lock(&cdev_lock);
 389         list_del_init(&inode->i_devices);
 390         inode->i_cdev = NULL;
 391         spin_unlock(&cdev_lock);
 392 }
 393
 394 static void cdev_purge(struct cdev *cdev)
 395 {
 396         spin_lock(&cdev_lock);
 397         while (!list_empty(&cdev->list)) {
 398                 struct inode *inode;
 399                 inode = container_of(cdev->list.next, struct inode, i_devices);
 400                 list_del_init(&inode->i_devices);
 401                 inode->i_cdev = NULL;
 402         }
 403         spin_unlock(&cdev_lock);
 404 }
 405
 406 /*
 407  * Dummy default file-operations: the only thing this does
 408  * is contain the open that then fills in the correct operations
 409  * depending on the special file...
 410  */
 411 struct file_operations def_chr_fops = {
 412         .open = chrdev_open,
 413 };
 414
 415 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 416 {
 417         struct cdev *p = data;
 418         return &p->kobj;
 419 }
 420
 421 static int exact_lock(dev_t dev, void *data)
 422 {
 423         struct cdev *p = data;
 424         return cdev_get(p) ? 0 : -1;
 425 }
 426
 427 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 428 {
 429         p->dev = dev;
 430         p->count = count;
 431         return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 432 }
 433
 434 static void cdev_unmap(dev_t dev, unsigned count)
 435 {
 436         kobj_unmap(cdev_map, dev, count);
 437 }
 438
 439 void cdev_del(struct cdev *p)
 440 {
 441         cdev_unmap(p->dev, p->count);
 442         kobject_put(&p->kobj);
 443 }
 444
 445
 446 static void cdev_default_release(struct kobject *kobj)
 447 {
 448         struct cdev *p = container_of(kobj, struct cdev, kobj);
 449         cdev_purge(p);
 450 }
 451
 452 static void cdev_dynamic_release(struct kobject *kobj)
 453 {
 454         struct cdev *p = container_of(kobj, struct cdev, kobj);
 455         cdev_purge(p);
 456         kfree(p);
 457 }
 458
 459 static struct kobj_type ktype_cdev_default = {
 460         .release        = cdev_default_release,
 461 };
 462
 463 static struct kobj_type ktype_cdev_dynamic = {
 464         .release        = cdev_dynamic_release,
 465 };
 466
 467 struct cdev *cdev_alloc(void)
 468 {
 469         struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 470         if (p) {
 471                 memset(p, 0, sizeof(struct cdev));
 472                 p->kobj.ktype = &ktype_cdev_dynamic;
 473                 INIT_LIST_HEAD(&p->list);
 474                 kobject_init(&p->kobj);
 475         }
 476         return p;
 477 }
 478
 479 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 480 {
 481         memset(cdev, 0, sizeof *cdev);
 482         INIT_LIST_HEAD(&cdev->list);
 483         cdev->kobj.ktype = &ktype_cdev_default;
 484         kobject_init(&cdev->kobj);
 485         cdev->ops = fops;
 486 }
 487
 488 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 489 {
 490         if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
 491                 /* Make old-style 2.4 aliases work */
 492                 request_module("char-major-%d", MAJOR(dev));
 493         return NULL;
 494 }
 495
 496 void __init chrdev_init(void)
 497 {
 498         cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 499 }
 500
 501
 502 /* Let modules do char dev stuff */
 503 EXPORT_SYMBOL(register_chrdev_region);
 504 EXPORT_SYMBOL(unregister_chrdev_region);
 505 EXPORT_SYMBOL(alloc_chrdev_region);
 506 EXPORT_SYMBOL(cdev_init);
 507 EXPORT_SYMBOL(cdev_alloc);
 508 EXPORT_SYMBOL(cdev_del);
 509 EXPORT_SYMBOL(cdev_add);
 510 EXPORT_SYMBOL(register_chrdev);
 511 EXPORT_SYMBOL(unregister_chrdev);