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 = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL); 150 if (cd == NULL) 151 return ERR_PTR(-ENOMEM); 152 153 mutex_lock(&chrdevs_lock); 154 155 /* temporary */ 156 if (major == 0) { 157 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) { 158 if (chrdevs[i] == NULL) 159 break; 160 } 161 162 if (i == 0) { 163 ret = -EBUSY; 164 goto out; 165 } 166 major = i; 167 ret = major; 168 } 169 170 cd->major = major; 171 cd->baseminor = baseminor; 172 cd->minorct = minorct; 173 strncpy(cd->name,name, 64); 174 175 i = major_to_index(major); 176 177 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) 178 if ((*cp)->major > major || 179 ((*cp)->major == major && (*cp)->baseminor >= baseminor)) 180 break; 181 if (*cp && (*cp)->major == major && 182 (*cp)->baseminor < baseminor + minorct) { 183 ret = -EBUSY; 184 goto out; 185 } 186 cd->next = *cp; 187 *cp = cd; 188 mutex_unlock(&chrdevs_lock); 189 return cd; 190 out: 191 mutex_unlock(&chrdevs_lock); 192 kfree(cd); 193 return ERR_PTR(ret); 194 } 195 196 static struct char_device_struct * 197 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) 198 { 199 struct char_device_struct *cd = NULL, **cp; 200 int i = major_to_index(major); 201 202 mutex_lock(&chrdevs_lock); 203 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) 204 if ((*cp)->major == major && 205 (*cp)->baseminor == baseminor && 206 (*cp)->minorct == minorct) 207 break; 208 if (*cp) { 209 cd = *cp; 210 *cp = cd->next; 211 } 212 mutex_unlock(&chrdevs_lock); 213 return cd; 214 } 215 216 int register_chrdev_region(dev_t from, unsigned count, const char *name) 217 { 218 struct char_device_struct *cd; 219 dev_t to = from + count; 220 dev_t n, next; 221 222 for (n = from; n < to; n = next) { 223 next = MKDEV(MAJOR(n)+1, 0); 224 if (next > to) 225 next = to; 226 cd = __register_chrdev_region(MAJOR(n), MINOR(n), 227 next - n, name); 228 if (IS_ERR(cd)) 229 goto fail; 230 } 231 return 0; 232 fail: 233 to = n; 234 for (n = from; n < to; n = next) { 235 next = MKDEV(MAJOR(n)+1, 0); 236 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); 237 } 238 return PTR_ERR(cd); 239 } 240 241 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, 242 const char *name) 243 { 244 struct char_device_struct *cd; 245 cd = __register_chrdev_region(0, baseminor, count, name); 246 if (IS_ERR(cd)) 247 return PTR_ERR(cd); 248 *dev = MKDEV(cd->major, cd->baseminor); 249 return 0; 250 } 251 252 int register_chrdev(unsigned int major, const char *name, 253 const struct file_operations *fops) 254 { 255 struct char_device_struct *cd; 256 struct cdev *cdev; 257 char *s; 258 int err = -ENOMEM; 259 260 cd = __register_chrdev_region(major, 0, 256, name); 261 if (IS_ERR(cd)) 262 return PTR_ERR(cd); 263 264 cdev = cdev_alloc(); 265 if (!cdev) 266 goto out2; 267 268 cdev->owner = fops->owner; 269 cdev->ops = fops; 270 kobject_set_name(&cdev->kobj, "%s", name); 271 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) 272 *s = '!'; 273 274 err = cdev_add(cdev, MKDEV(cd->major, 0), 256); 275 if (err) 276 goto out; 277 278 cd->cdev = cdev; 279 280 return major ? 0 : cd->major; 281 out: 282 kobject_put(&cdev->kobj); 283 out2: 284 kfree(__unregister_chrdev_region(cd->major, 0, 256)); 285 return err; 286 } 287 288 void unregister_chrdev_region(dev_t from, unsigned count) 289 { 290 dev_t to = from + count; 291 dev_t n, next; 292 293 for (n = from; n < to; n = next) { 294 next = MKDEV(MAJOR(n)+1, 0); 295 if (next > to) 296 next = to; 297 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); 298 } 299 } 300 301 int unregister_chrdev(unsigned int major, const char *name) 302 { 303 struct char_device_struct *cd; 304 cd = __unregister_chrdev_region(major, 0, 256); 305 if (cd && cd->cdev) 306 cdev_del(cd->cdev); 307 kfree(cd); 308 return 0; 309 } 310 311 static DEFINE_SPINLOCK(cdev_lock); 312 313 static struct kobject *cdev_get(struct cdev *p) 314 { 315 struct module *owner = p->owner; 316 struct kobject *kobj; 317 318 if (owner && !try_module_get(owner)) 319 return NULL; 320 kobj = kobject_get(&p->kobj); 321 if (!kobj) 322 module_put(owner); 323 return kobj; 324 } 325 326 void cdev_put(struct cdev *p) 327 { 328 if (p) { 329 struct module *owner = p->owner; 330 kobject_put(&p->kobj); 331 module_put(owner); 332 } 333 } 334 335 /* 336 * Called every time a character special file is opened 337 */ 338 int chrdev_open(struct inode * inode, struct file * filp) 339 { 340 struct cdev *p; 341 struct cdev *new = NULL; 342 int ret = 0; 343 344 spin_lock(&cdev_lock); 345 p = inode->i_cdev; 346 if (!p) { 347 struct kobject *kobj; 348 int idx; 349 spin_unlock(&cdev_lock); 350 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); 351 if (!kobj) 352 return -ENXIO; 353 new = container_of(kobj, struct cdev, kobj); 354 spin_lock(&cdev_lock); 355 p = inode->i_cdev; 356 if (!p) { 357 inode->i_cdev = p = new; 358 inode->i_cindex = idx; 359 list_add(&inode->i_devices, &p->list); 360 new = NULL; 361 } else if (!cdev_get(p)) 362 ret = -ENXIO; 363 } else if (!cdev_get(p)) 364 ret = -ENXIO; 365 spin_unlock(&cdev_lock); 366 cdev_put(new); 367 if (ret) 368 return ret; 369 filp->f_op = fops_get(p->ops); 370 if (!filp->f_op) { 371 cdev_put(p); 372 return -ENXIO; 373 } 374 if (filp->f_op->open) { 375 lock_kernel(); 376 ret = filp->f_op->open(inode,filp); 377 unlock_kernel(); 378 } 379 if (ret) 380 cdev_put(p); 381 return ret; 382 } 383 384 void cd_forget(struct inode *inode) 385 { 386 spin_lock(&cdev_lock); 387 list_del_init(&inode->i_devices); 388 inode->i_cdev = NULL; 389 spin_unlock(&cdev_lock); 390 } 391 392 static void cdev_purge(struct cdev *cdev) 393 { 394 spin_lock(&cdev_lock); 395 while (!list_empty(&cdev->list)) { 396 struct inode *inode; 397 inode = container_of(cdev->list.next, struct inode, i_devices); 398 list_del_init(&inode->i_devices); 399 inode->i_cdev = NULL; 400 } 401 spin_unlock(&cdev_lock); 402 } 403 404 /* 405 * Dummy default file-operations: the only thing this does 406 * is contain the open that then fills in the correct operations 407 * depending on the special file... 408 */ 409 struct file_operations def_chr_fops = { 410 .open = chrdev_open, 411 }; 412 413 static struct kobject *exact_match(dev_t dev, int *part, void *data) 414 { 415 struct cdev *p = data; 416 return &p->kobj; 417 } 418 419 static int exact_lock(dev_t dev, void *data) 420 { 421 struct cdev *p = data; 422 return cdev_get(p) ? 0 : -1; 423 } 424 425 int cdev_add(struct cdev *p, dev_t dev, unsigned count) 426 { 427 p->dev = dev; 428 p->count = count; 429 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); 430 } 431 432 static void cdev_unmap(dev_t dev, unsigned count) 433 { 434 kobj_unmap(cdev_map, dev, count); 435 } 436 437 void cdev_del(struct cdev *p) 438 { 439 cdev_unmap(p->dev, p->count); 440 kobject_put(&p->kobj); 441 } 442 443 444 static void cdev_default_release(struct kobject *kobj) 445 { 446 struct cdev *p = container_of(kobj, struct cdev, kobj); 447 cdev_purge(p); 448 } 449 450 static void cdev_dynamic_release(struct kobject *kobj) 451 { 452 struct cdev *p = container_of(kobj, struct cdev, kobj); 453 cdev_purge(p); 454 kfree(p); 455 } 456 457 static struct kobj_type ktype_cdev_default = { 458 .release = cdev_default_release, 459 }; 460 461 static struct kobj_type ktype_cdev_dynamic = { 462 .release = cdev_dynamic_release, 463 }; 464 465 struct cdev *cdev_alloc(void) 466 { 467 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); 468 if (p) { 469 p->kobj.ktype = &ktype_cdev_dynamic; 470 INIT_LIST_HEAD(&p->list); 471 kobject_init(&p->kobj); 472 } 473 return p; 474 } 475 476 void cdev_init(struct cdev *cdev, const struct file_operations *fops) 477 { 478 memset(cdev, 0, sizeof *cdev); 479 INIT_LIST_HEAD(&cdev->list); 480 cdev->kobj.ktype = &ktype_cdev_default; 481 kobject_init(&cdev->kobj); 482 cdev->ops = fops; 483 } 484 485 static struct kobject *base_probe(dev_t dev, int *part, void *data) 486 { 487 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) 488 /* Make old-style 2.4 aliases work */ 489 request_module("char-major-%d", MAJOR(dev)); 490 return NULL; 491 } 492 493 void __init chrdev_init(void) 494 { 495 cdev_map = kobj_map_init(base_probe, &chrdevs_lock); 496 } 497 498 499 /* Let modules do char dev stuff */ 500 EXPORT_SYMBOL(register_chrdev_region); 501 EXPORT_SYMBOL(unregister_chrdev_region); 502 EXPORT_SYMBOL(alloc_chrdev_region); 503 EXPORT_SYMBOL(cdev_init); 504 EXPORT_SYMBOL(cdev_alloc); 505 EXPORT_SYMBOL(cdev_del); 506 EXPORT_SYMBOL(cdev_add); 507 EXPORT_SYMBOL(register_chrdev); 508 EXPORT_SYMBOL(unregister_chrdev); 509