| 1 | /* |
| 2 | * linux/fs/char_dev.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | */ |
| 6 | |
| 7 | #include <linux/init.h> |
| 8 | #include <linux/fs.h> |
| 9 | #include <linux/kdev_t.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/seq_file.h> |
| 17 | |
| 18 | #include <linux/kobject.h> |
| 19 | #include <linux/kobj_map.h> |
| 20 | #include <linux/cdev.h> |
| 21 | #include <linux/mutex.h> |
| 22 | #include <linux/backing-dev.h> |
| 23 | #include <linux/tty.h> |
| 24 | |
| 25 | #include "internal.h" |
| 26 | |
| 27 | static struct kobj_map *cdev_map; |
| 28 | |
| 29 | static DEFINE_MUTEX(chrdevs_lock); |
| 30 | |
| 31 | static struct char_device_struct { |
| 32 | struct char_device_struct *next; |
| 33 | unsigned int major; |
| 34 | unsigned int baseminor; |
| 35 | int minorct; |
| 36 | char name[64]; |
| 37 | struct cdev *cdev; /* will die */ |
| 38 | } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; |
| 39 | |
| 40 | /* index in the above */ |
| 41 | static inline int major_to_index(unsigned major) |
| 42 | { |
| 43 | return major % CHRDEV_MAJOR_HASH_SIZE; |
| 44 | } |
| 45 | |
| 46 | #ifdef CONFIG_PROC_FS |
| 47 | |
| 48 | void chrdev_show(struct seq_file *f, off_t offset) |
| 49 | { |
| 50 | struct char_device_struct *cd; |
| 51 | |
| 52 | if (offset < CHRDEV_MAJOR_HASH_SIZE) { |
| 53 | mutex_lock(&chrdevs_lock); |
| 54 | for (cd = chrdevs[offset]; cd; cd = cd->next) |
| 55 | seq_printf(f, "%3d %s\n", cd->major, cd->name); |
| 56 | mutex_unlock(&chrdevs_lock); |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | #endif /* CONFIG_PROC_FS */ |
| 61 | |
| 62 | /* |
| 63 | * Register a single major with a specified minor range. |
| 64 | * |
| 65 | * If major == 0 this functions will dynamically allocate a major and return |
| 66 | * its number. |
| 67 | * |
| 68 | * If major > 0 this function will attempt to reserve the passed range of |
| 69 | * minors and will return zero on success. |
| 70 | * |
| 71 | * Returns a -ve errno on failure. |
| 72 | */ |
| 73 | static struct char_device_struct * |
| 74 | __register_chrdev_region(unsigned int major, unsigned int baseminor, |
| 75 | int minorct, const char *name) |
| 76 | { |
| 77 | struct char_device_struct *cd, **cp; |
| 78 | int ret = 0; |
| 79 | int i; |
| 80 | |
| 81 | cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL); |
| 82 | if (cd == NULL) |
| 83 | return ERR_PTR(-ENOMEM); |
| 84 | |
| 85 | mutex_lock(&chrdevs_lock); |
| 86 | |
| 87 | /* temporary */ |
| 88 | if (major == 0) { |
| 89 | for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) { |
| 90 | if (chrdevs[i] == NULL) |
| 91 | break; |
| 92 | } |
| 93 | |
| 94 | if (i == 0) { |
| 95 | ret = -EBUSY; |
| 96 | goto out; |
| 97 | } |
| 98 | major = i; |
| 99 | } |
| 100 | |
| 101 | cd->major = major; |
| 102 | cd->baseminor = baseminor; |
| 103 | cd->minorct = minorct; |
| 104 | strlcpy(cd->name, name, sizeof(cd->name)); |
| 105 | |
| 106 | i = major_to_index(major); |
| 107 | |
| 108 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
| 109 | if ((*cp)->major > major || |
| 110 | ((*cp)->major == major && |
| 111 | (((*cp)->baseminor >= baseminor) || |
| 112 | ((*cp)->baseminor + (*cp)->minorct > baseminor)))) |
| 113 | break; |
| 114 | |
| 115 | /* Check for overlapping minor ranges. */ |
| 116 | if (*cp && (*cp)->major == major) { |
| 117 | int old_min = (*cp)->baseminor; |
| 118 | int old_max = (*cp)->baseminor + (*cp)->minorct - 1; |
| 119 | int new_min = baseminor; |
| 120 | int new_max = baseminor + minorct - 1; |
| 121 | |
| 122 | /* New driver overlaps from the left. */ |
| 123 | if (new_max >= old_min && new_max <= old_max) { |
| 124 | ret = -EBUSY; |
| 125 | goto out; |
| 126 | } |
| 127 | |
| 128 | /* New driver overlaps from the right. */ |
| 129 | if (new_min <= old_max && new_min >= old_min) { |
| 130 | ret = -EBUSY; |
| 131 | goto out; |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | cd->next = *cp; |
| 136 | *cp = cd; |
| 137 | mutex_unlock(&chrdevs_lock); |
| 138 | return cd; |
| 139 | out: |
| 140 | mutex_unlock(&chrdevs_lock); |
| 141 | kfree(cd); |
| 142 | return ERR_PTR(ret); |
| 143 | } |
| 144 | |
| 145 | static struct char_device_struct * |
| 146 | __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) |
| 147 | { |
| 148 | struct char_device_struct *cd = NULL, **cp; |
| 149 | int i = major_to_index(major); |
| 150 | |
| 151 | mutex_lock(&chrdevs_lock); |
| 152 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
| 153 | if ((*cp)->major == major && |
| 154 | (*cp)->baseminor == baseminor && |
| 155 | (*cp)->minorct == minorct) |
| 156 | break; |
| 157 | if (*cp) { |
| 158 | cd = *cp; |
| 159 | *cp = cd->next; |
| 160 | } |
| 161 | mutex_unlock(&chrdevs_lock); |
| 162 | return cd; |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * register_chrdev_region() - register a range of device numbers |
| 167 | * @from: the first in the desired range of device numbers; must include |
| 168 | * the major number. |
| 169 | * @count: the number of consecutive device numbers required |
| 170 | * @name: the name of the device or driver. |
| 171 | * |
| 172 | * Return value is zero on success, a negative error code on failure. |
| 173 | */ |
| 174 | int register_chrdev_region(dev_t from, unsigned count, const char *name) |
| 175 | { |
| 176 | struct char_device_struct *cd; |
| 177 | dev_t to = from + count; |
| 178 | dev_t n, next; |
| 179 | |
| 180 | for (n = from; n < to; n = next) { |
| 181 | next = MKDEV(MAJOR(n)+1, 0); |
| 182 | if (next > to) |
| 183 | next = to; |
| 184 | cd = __register_chrdev_region(MAJOR(n), MINOR(n), |
| 185 | next - n, name); |
| 186 | if (IS_ERR(cd)) |
| 187 | goto fail; |
| 188 | } |
| 189 | return 0; |
| 190 | fail: |
| 191 | to = n; |
| 192 | for (n = from; n < to; n = next) { |
| 193 | next = MKDEV(MAJOR(n)+1, 0); |
| 194 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); |
| 195 | } |
| 196 | return PTR_ERR(cd); |
| 197 | } |
| 198 | |
| 199 | /** |
| 200 | * alloc_chrdev_region() - register a range of char device numbers |
| 201 | * @dev: output parameter for first assigned number |
| 202 | * @baseminor: first of the requested range of minor numbers |
| 203 | * @count: the number of minor numbers required |
| 204 | * @name: the name of the associated device or driver |
| 205 | * |
| 206 | * Allocates a range of char device numbers. The major number will be |
| 207 | * chosen dynamically, and returned (along with the first minor number) |
| 208 | * in @dev. Returns zero or a negative error code. |
| 209 | */ |
| 210 | int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, |
| 211 | const char *name) |
| 212 | { |
| 213 | struct char_device_struct *cd; |
| 214 | cd = __register_chrdev_region(0, baseminor, count, name); |
| 215 | if (IS_ERR(cd)) |
| 216 | return PTR_ERR(cd); |
| 217 | *dev = MKDEV(cd->major, cd->baseminor); |
| 218 | return 0; |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * __register_chrdev() - create and register a cdev occupying a range of minors |
| 223 | * @major: major device number or 0 for dynamic allocation |
| 224 | * @baseminor: first of the requested range of minor numbers |
| 225 | * @count: the number of minor numbers required |
| 226 | * @name: name of this range of devices |
| 227 | * @fops: file operations associated with this devices |
| 228 | * |
| 229 | * If @major == 0 this functions will dynamically allocate a major and return |
| 230 | * its number. |
| 231 | * |
| 232 | * If @major > 0 this function will attempt to reserve a device with the given |
| 233 | * major number and will return zero on success. |
| 234 | * |
| 235 | * Returns a -ve errno on failure. |
| 236 | * |
| 237 | * The name of this device has nothing to do with the name of the device in |
| 238 | * /dev. It only helps to keep track of the different owners of devices. If |
| 239 | * your module name has only one type of devices it's ok to use e.g. the name |
| 240 | * of the module here. |
| 241 | */ |
| 242 | int __register_chrdev(unsigned int major, unsigned int baseminor, |
| 243 | unsigned int count, const char *name, |
| 244 | const struct file_operations *fops) |
| 245 | { |
| 246 | struct char_device_struct *cd; |
| 247 | struct cdev *cdev; |
| 248 | int err = -ENOMEM; |
| 249 | |
| 250 | cd = __register_chrdev_region(major, baseminor, count, name); |
| 251 | if (IS_ERR(cd)) |
| 252 | return PTR_ERR(cd); |
| 253 | |
| 254 | cdev = cdev_alloc(); |
| 255 | if (!cdev) |
| 256 | goto out2; |
| 257 | |
| 258 | cdev->owner = fops->owner; |
| 259 | cdev->ops = fops; |
| 260 | kobject_set_name(&cdev->kobj, "%s", name); |
| 261 | |
| 262 | err = cdev_add(cdev, MKDEV(cd->major, baseminor), count); |
| 263 | if (err) |
| 264 | goto out; |
| 265 | |
| 266 | cd->cdev = cdev; |
| 267 | |
| 268 | return major ? 0 : cd->major; |
| 269 | out: |
| 270 | kobject_put(&cdev->kobj); |
| 271 | out2: |
| 272 | kfree(__unregister_chrdev_region(cd->major, baseminor, count)); |
| 273 | return err; |
| 274 | } |
| 275 | |
| 276 | /** |
| 277 | * unregister_chrdev_region() - return a range of device numbers |
| 278 | * @from: the first in the range of numbers to unregister |
| 279 | * @count: the number of device numbers to unregister |
| 280 | * |
| 281 | * This function will unregister a range of @count device numbers, |
| 282 | * starting with @from. The caller should normally be the one who |
| 283 | * allocated those numbers in the first place... |
| 284 | */ |
| 285 | void unregister_chrdev_region(dev_t from, unsigned count) |
| 286 | { |
| 287 | dev_t to = from + count; |
| 288 | dev_t n, next; |
| 289 | |
| 290 | for (n = from; n < to; n = next) { |
| 291 | next = MKDEV(MAJOR(n)+1, 0); |
| 292 | if (next > to) |
| 293 | next = to; |
| 294 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); |
| 295 | } |
| 296 | } |
| 297 | |
| 298 | /** |
| 299 | * __unregister_chrdev - unregister and destroy a cdev |
| 300 | * @major: major device number |
| 301 | * @baseminor: first of the range of minor numbers |
| 302 | * @count: the number of minor numbers this cdev is occupying |
| 303 | * @name: name of this range of devices |
| 304 | * |
| 305 | * Unregister and destroy the cdev occupying the region described by |
| 306 | * @major, @baseminor and @count. This function undoes what |
| 307 | * __register_chrdev() did. |
| 308 | */ |
| 309 | void __unregister_chrdev(unsigned int major, unsigned int baseminor, |
| 310 | unsigned int count, const char *name) |
| 311 | { |
| 312 | struct char_device_struct *cd; |
| 313 | |
| 314 | cd = __unregister_chrdev_region(major, baseminor, count); |
| 315 | if (cd && cd->cdev) |
| 316 | cdev_del(cd->cdev); |
| 317 | kfree(cd); |
| 318 | } |
| 319 | |
| 320 | static DEFINE_SPINLOCK(cdev_lock); |
| 321 | |
| 322 | static struct kobject *cdev_get(struct cdev *p) |
| 323 | { |
| 324 | struct module *owner = p->owner; |
| 325 | struct kobject *kobj; |
| 326 | |
| 327 | if (owner && !try_module_get(owner)) |
| 328 | return NULL; |
| 329 | kobj = kobject_get(&p->kobj); |
| 330 | if (!kobj) |
| 331 | module_put(owner); |
| 332 | return kobj; |
| 333 | } |
| 334 | |
| 335 | void cdev_put(struct cdev *p) |
| 336 | { |
| 337 | if (p) { |
| 338 | struct module *owner = p->owner; |
| 339 | kobject_put(&p->kobj); |
| 340 | module_put(owner); |
| 341 | } |
| 342 | } |
| 343 | |
| 344 | /* |
| 345 | * Called every time a character special file is opened |
| 346 | */ |
| 347 | static int chrdev_open(struct inode *inode, struct file *filp) |
| 348 | { |
| 349 | const struct file_operations *fops; |
| 350 | struct cdev *p; |
| 351 | struct cdev *new = NULL; |
| 352 | int ret = 0; |
| 353 | |
| 354 | spin_lock(&cdev_lock); |
| 355 | p = inode->i_cdev; |
| 356 | if (!p) { |
| 357 | struct kobject *kobj; |
| 358 | int idx; |
| 359 | spin_unlock(&cdev_lock); |
| 360 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); |
| 361 | if (!kobj) |
| 362 | return -ENXIO; |
| 363 | new = container_of(kobj, struct cdev, kobj); |
| 364 | spin_lock(&cdev_lock); |
| 365 | /* Check i_cdev again in case somebody beat us to it while |
| 366 | we dropped the lock. */ |
| 367 | p = inode->i_cdev; |
| 368 | if (!p) { |
| 369 | inode->i_cdev = p = new; |
| 370 | list_add(&inode->i_devices, &p->list); |
| 371 | new = NULL; |
| 372 | } else if (!cdev_get(p)) |
| 373 | ret = -ENXIO; |
| 374 | } else if (!cdev_get(p)) |
| 375 | ret = -ENXIO; |
| 376 | spin_unlock(&cdev_lock); |
| 377 | cdev_put(new); |
| 378 | if (ret) |
| 379 | return ret; |
| 380 | |
| 381 | ret = -ENXIO; |
| 382 | fops = fops_get(p->ops); |
| 383 | if (!fops) |
| 384 | goto out_cdev_put; |
| 385 | |
| 386 | replace_fops(filp, fops); |
| 387 | if (filp->f_op->open) { |
| 388 | ret = filp->f_op->open(inode, filp); |
| 389 | if (ret) |
| 390 | goto out_cdev_put; |
| 391 | } |
| 392 | |
| 393 | return 0; |
| 394 | |
| 395 | out_cdev_put: |
| 396 | cdev_put(p); |
| 397 | return ret; |
| 398 | } |
| 399 | |
| 400 | void cd_forget(struct inode *inode) |
| 401 | { |
| 402 | spin_lock(&cdev_lock); |
| 403 | list_del_init(&inode->i_devices); |
| 404 | inode->i_cdev = NULL; |
| 405 | spin_unlock(&cdev_lock); |
| 406 | } |
| 407 | |
| 408 | static void cdev_purge(struct cdev *cdev) |
| 409 | { |
| 410 | spin_lock(&cdev_lock); |
| 411 | while (!list_empty(&cdev->list)) { |
| 412 | struct inode *inode; |
| 413 | inode = container_of(cdev->list.next, struct inode, i_devices); |
| 414 | list_del_init(&inode->i_devices); |
| 415 | inode->i_cdev = NULL; |
| 416 | } |
| 417 | spin_unlock(&cdev_lock); |
| 418 | } |
| 419 | |
| 420 | /* |
| 421 | * Dummy default file-operations: the only thing this does |
| 422 | * is contain the open that then fills in the correct operations |
| 423 | * depending on the special file... |
| 424 | */ |
| 425 | const struct file_operations def_chr_fops = { |
| 426 | .open = chrdev_open, |
| 427 | .llseek = noop_llseek, |
| 428 | }; |
| 429 | |
| 430 | static struct kobject *exact_match(dev_t dev, int *part, void *data) |
| 431 | { |
| 432 | struct cdev *p = data; |
| 433 | return &p->kobj; |
| 434 | } |
| 435 | |
| 436 | static int exact_lock(dev_t dev, void *data) |
| 437 | { |
| 438 | struct cdev *p = data; |
| 439 | return cdev_get(p) ? 0 : -1; |
| 440 | } |
| 441 | |
| 442 | /** |
| 443 | * cdev_add() - add a char device to the system |
| 444 | * @p: the cdev structure for the device |
| 445 | * @dev: the first device number for which this device is responsible |
| 446 | * @count: the number of consecutive minor numbers corresponding to this |
| 447 | * device |
| 448 | * |
| 449 | * cdev_add() adds the device represented by @p to the system, making it |
| 450 | * live immediately. A negative error code is returned on failure. |
| 451 | */ |
| 452 | int cdev_add(struct cdev *p, dev_t dev, unsigned count) |
| 453 | { |
| 454 | int error; |
| 455 | |
| 456 | p->dev = dev; |
| 457 | p->count = count; |
| 458 | |
| 459 | error = kobj_map(cdev_map, dev, count, NULL, |
| 460 | exact_match, exact_lock, p); |
| 461 | if (error) |
| 462 | return error; |
| 463 | |
| 464 | kobject_get(p->kobj.parent); |
| 465 | |
| 466 | return 0; |
| 467 | } |
| 468 | |
| 469 | static void cdev_unmap(dev_t dev, unsigned count) |
| 470 | { |
| 471 | kobj_unmap(cdev_map, dev, count); |
| 472 | } |
| 473 | |
| 474 | /** |
| 475 | * cdev_del() - remove a cdev from the system |
| 476 | * @p: the cdev structure to be removed |
| 477 | * |
| 478 | * cdev_del() removes @p from the system, possibly freeing the structure |
| 479 | * itself. |
| 480 | */ |
| 481 | void cdev_del(struct cdev *p) |
| 482 | { |
| 483 | cdev_unmap(p->dev, p->count); |
| 484 | kobject_put(&p->kobj); |
| 485 | } |
| 486 | |
| 487 | |
| 488 | static void cdev_default_release(struct kobject *kobj) |
| 489 | { |
| 490 | struct cdev *p = container_of(kobj, struct cdev, kobj); |
| 491 | struct kobject *parent = kobj->parent; |
| 492 | |
| 493 | cdev_purge(p); |
| 494 | kobject_put(parent); |
| 495 | } |
| 496 | |
| 497 | static void cdev_dynamic_release(struct kobject *kobj) |
| 498 | { |
| 499 | struct cdev *p = container_of(kobj, struct cdev, kobj); |
| 500 | struct kobject *parent = kobj->parent; |
| 501 | |
| 502 | cdev_purge(p); |
| 503 | kfree(p); |
| 504 | kobject_put(parent); |
| 505 | } |
| 506 | |
| 507 | static struct kobj_type ktype_cdev_default = { |
| 508 | .release = cdev_default_release, |
| 509 | }; |
| 510 | |
| 511 | static struct kobj_type ktype_cdev_dynamic = { |
| 512 | .release = cdev_dynamic_release, |
| 513 | }; |
| 514 | |
| 515 | /** |
| 516 | * cdev_alloc() - allocate a cdev structure |
| 517 | * |
| 518 | * Allocates and returns a cdev structure, or NULL on failure. |
| 519 | */ |
| 520 | struct cdev *cdev_alloc(void) |
| 521 | { |
| 522 | struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); |
| 523 | if (p) { |
| 524 | INIT_LIST_HEAD(&p->list); |
| 525 | kobject_init(&p->kobj, &ktype_cdev_dynamic); |
| 526 | } |
| 527 | return p; |
| 528 | } |
| 529 | |
| 530 | /** |
| 531 | * cdev_init() - initialize a cdev structure |
| 532 | * @cdev: the structure to initialize |
| 533 | * @fops: the file_operations for this device |
| 534 | * |
| 535 | * Initializes @cdev, remembering @fops, making it ready to add to the |
| 536 | * system with cdev_add(). |
| 537 | */ |
| 538 | void cdev_init(struct cdev *cdev, const struct file_operations *fops) |
| 539 | { |
| 540 | memset(cdev, 0, sizeof *cdev); |
| 541 | INIT_LIST_HEAD(&cdev->list); |
| 542 | kobject_init(&cdev->kobj, &ktype_cdev_default); |
| 543 | cdev->ops = fops; |
| 544 | } |
| 545 | |
| 546 | static struct kobject *base_probe(dev_t dev, int *part, void *data) |
| 547 | { |
| 548 | if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) |
| 549 | /* Make old-style 2.4 aliases work */ |
| 550 | request_module("char-major-%d", MAJOR(dev)); |
| 551 | return NULL; |
| 552 | } |
| 553 | |
| 554 | void __init chrdev_init(void) |
| 555 | { |
| 556 | cdev_map = kobj_map_init(base_probe, &chrdevs_lock); |
| 557 | } |
| 558 | |
| 559 | |
| 560 | /* Let modules do char dev stuff */ |
| 561 | EXPORT_SYMBOL(register_chrdev_region); |
| 562 | EXPORT_SYMBOL(unregister_chrdev_region); |
| 563 | EXPORT_SYMBOL(alloc_chrdev_region); |
| 564 | EXPORT_SYMBOL(cdev_init); |
| 565 | EXPORT_SYMBOL(cdev_alloc); |
| 566 | EXPORT_SYMBOL(cdev_del); |
| 567 | EXPORT_SYMBOL(cdev_add); |
| 568 | EXPORT_SYMBOL(__register_chrdev); |
| 569 | EXPORT_SYMBOL(__unregister_chrdev); |