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 23 #ifdef CONFIG_KMOD 24 #include <linux/kmod.h> 25 #endif 26 27 static struct kobj_map *cdev_map; 28 29 #define MAX_PROBE_HASH 255 /* random */ 30 31 static DECLARE_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 const char *name; 39 struct file_operations *fops; 40 struct cdev *cdev; /* will die */ 41 } *chrdevs[MAX_PROBE_HASH]; 42 43 /* index in the above */ 44 static inline int major_to_index(int major) 45 { 46 return major % MAX_PROBE_HASH; 47 } 48 49 /* get char device names in somewhat random order */ 50 int get_chrdev_list(char *page) 51 { 52 struct char_device_struct *cd; 53 int i, len; 54 55 len = sprintf(page, "Character devices:\n"); 56 57 down(&chrdevs_lock); 58 for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) { 59 for (cd = chrdevs[i]; cd; cd = cd->next) { 60 /* 61 * if the current name, plus the 5 extra characters 62 * in the device line for this entry 63 * would run us off the page, we're done 64 */ 65 if ((len+strlen(cd->name) + 5) >= PAGE_SIZE) 66 goto page_full; 67 68 69 len += sprintf(page+len, "%3d %s\n", 70 cd->major, cd->name); 71 } 72 } 73 page_full: 74 up(&chrdevs_lock); 75 76 return len; 77 } 78 79 /* 80 * Register a single major with a specified minor range. 81 * 82 * If major == 0 this functions will dynamically allocate a major and return 83 * its number. 84 * 85 * If major > 0 this function will attempt to reserve the passed range of 86 * minors and will return zero on success. 87 * 88 * Returns a -ve errno on failure. 89 */ 90 static struct char_device_struct * 91 __register_chrdev_region(unsigned int major, unsigned int baseminor, 92 int minorct, const char *name) 93 { 94 struct char_device_struct *cd, **cp; 95 int ret = 0; 96 int i; 97 98 cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL); 99 if (cd == NULL) 100 return ERR_PTR(-ENOMEM); 101 102 memset(cd, 0, sizeof(struct char_device_struct)); 103 104 down(&chrdevs_lock); 105 106 /* temporary */ 107 if (major == 0) { 108 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) { 109 if (chrdevs[i] == NULL) 110 break; 111 } 112 113 if (i == 0) { 114 ret = -EBUSY; 115 goto out; 116 } 117 major = i; 118 ret = major; 119 } 120 121 cd->major = major; 122 cd->baseminor = baseminor; 123 cd->minorct = minorct; 124 cd->name = name; 125 126 i = major_to_index(major); 127 128 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) 129 if ((*cp)->major > major || 130 ((*cp)->major == major && (*cp)->baseminor >= baseminor)) 131 break; 132 if (*cp && (*cp)->major == major && 133 (*cp)->baseminor < baseminor + minorct) { 134 ret = -EBUSY; 135 goto out; 136 } 137 cd->next = *cp; 138 *cp = cd; 139 up(&chrdevs_lock); 140 return cd; 141 out: 142 up(&chrdevs_lock); 143 kfree(cd); 144 return ERR_PTR(ret); 145 } 146 147 static struct char_device_struct * 148 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) 149 { 150 struct char_device_struct *cd = NULL, **cp; 151 int i = major_to_index(major); 152 153 down(&chrdevs_lock); 154 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) 155 if ((*cp)->major == major && 156 (*cp)->baseminor == baseminor && 157 (*cp)->minorct == minorct) 158 break; 159 if (*cp) { 160 cd = *cp; 161 *cp = cd->next; 162 } 163 up(&chrdevs_lock); 164 return cd; 165 } 166 167 int register_chrdev_region(dev_t from, unsigned count, const char *name) 168 { 169 struct char_device_struct *cd; 170 dev_t to = from + count; 171 dev_t n, next; 172 173 for (n = from; n < to; n = next) { 174 next = MKDEV(MAJOR(n)+1, 0); 175 if (next > to) 176 next = to; 177 cd = __register_chrdev_region(MAJOR(n), MINOR(n), 178 next - n, name); 179 if (IS_ERR(cd)) 180 goto fail; 181 } 182 return 0; 183 fail: 184 to = n; 185 for (n = from; n < to; n = next) { 186 next = MKDEV(MAJOR(n)+1, 0); 187 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); 188 } 189 return PTR_ERR(cd); 190 } 191 192 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, 193 const char *name) 194 { 195 struct char_device_struct *cd; 196 cd = __register_chrdev_region(0, baseminor, count, name); 197 if (IS_ERR(cd)) 198 return PTR_ERR(cd); 199 *dev = MKDEV(cd->major, cd->baseminor); 200 return 0; 201 } 202 203 int register_chrdev(unsigned int major, const char *name, 204 struct file_operations *fops) 205 { 206 struct char_device_struct *cd; 207 struct cdev *cdev; 208 char *s; 209 int err = -ENOMEM; 210 211 cd = __register_chrdev_region(major, 0, 256, name); 212 if (IS_ERR(cd)) 213 return PTR_ERR(cd); 214 215 cdev = cdev_alloc(); 216 if (!cdev) 217 goto out2; 218 219 cdev->owner = fops->owner; 220 cdev->ops = fops; 221 kobject_set_name(&cdev->kobj, "%s", name); 222 for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) 223 *s = '!'; 224 225 err = cdev_add(cdev, MKDEV(cd->major, 0), 256); 226 if (err) 227 goto out; 228 229 cd->cdev = cdev; 230 231 return major ? 0 : cd->major; 232 out: 233 kobject_put(&cdev->kobj); 234 out2: 235 kfree(__unregister_chrdev_region(cd->major, 0, 256)); 236 return err; 237 } 238 239 void unregister_chrdev_region(dev_t from, unsigned count) 240 { 241 dev_t to = from + count; 242 dev_t n, next; 243 244 for (n = from; n < to; n = next) { 245 next = MKDEV(MAJOR(n)+1, 0); 246 if (next > to) 247 next = to; 248 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); 249 } 250 } 251 252 int unregister_chrdev(unsigned int major, const char *name) 253 { 254 struct char_device_struct *cd; 255 cd = __unregister_chrdev_region(major, 0, 256); 256 if (cd && cd->cdev) 257 cdev_del(cd->cdev); 258 kfree(cd); 259 return 0; 260 } 261 262 static DEFINE_SPINLOCK(cdev_lock); 263 264 static struct kobject *cdev_get(struct cdev *p) 265 { 266 struct module *owner = p->owner; 267 struct kobject *kobj; 268 269 if (owner && !try_module_get(owner)) 270 return NULL; 271 kobj = kobject_get(&p->kobj); 272 if (!kobj) 273 module_put(owner); 274 return kobj; 275 } 276 277 void cdev_put(struct cdev *p) 278 { 279 if (p) { 280 struct module *owner = p->owner; 281 kobject_put(&p->kobj); 282 module_put(owner); 283 } 284 } 285 286 /* 287 * Called every time a character special file is opened 288 */ 289 int chrdev_open(struct inode * inode, struct file * filp) 290 { 291 struct cdev *p; 292 struct cdev *new = NULL; 293 int ret = 0; 294 295 spin_lock(&cdev_lock); 296 p = inode->i_cdev; 297 if (!p) { 298 struct kobject *kobj; 299 int idx; 300 spin_unlock(&cdev_lock); 301 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); 302 if (!kobj) 303 return -ENXIO; 304 new = container_of(kobj, struct cdev, kobj); 305 spin_lock(&cdev_lock); 306 p = inode->i_cdev; 307 if (!p) { 308 inode->i_cdev = p = new; 309 inode->i_cindex = idx; 310 list_add(&inode->i_devices, &p->list); 311 new = NULL; 312 } else if (!cdev_get(p)) 313 ret = -ENXIO; 314 } else if (!cdev_get(p)) 315 ret = -ENXIO; 316 spin_unlock(&cdev_lock); 317 cdev_put(new); 318 if (ret) 319 return ret; 320 filp->f_op = fops_get(p->ops); 321 if (!filp->f_op) { 322 cdev_put(p); 323 return -ENXIO; 324 } 325 if (filp->f_op->open) { 326 lock_kernel(); 327 ret = filp->f_op->open(inode,filp); 328 unlock_kernel(); 329 } 330 if (ret) 331 cdev_put(p); 332 return ret; 333 } 334 335 void cd_forget(struct inode *inode) 336 { 337 spin_lock(&cdev_lock); 338 list_del_init(&inode->i_devices); 339 inode->i_cdev = NULL; 340 spin_unlock(&cdev_lock); 341 } 342 343 static void cdev_purge(struct cdev *cdev) 344 { 345 spin_lock(&cdev_lock); 346 while (!list_empty(&cdev->list)) { 347 struct inode *inode; 348 inode = container_of(cdev->list.next, struct inode, i_devices); 349 list_del_init(&inode->i_devices); 350 inode->i_cdev = NULL; 351 } 352 spin_unlock(&cdev_lock); 353 } 354 355 /* 356 * Dummy default file-operations: the only thing this does 357 * is contain the open that then fills in the correct operations 358 * depending on the special file... 359 */ 360 struct file_operations def_chr_fops = { 361 .open = chrdev_open, 362 }; 363 364 static struct kobject *exact_match(dev_t dev, int *part, void *data) 365 { 366 struct cdev *p = data; 367 return &p->kobj; 368 } 369 370 static int exact_lock(dev_t dev, void *data) 371 { 372 struct cdev *p = data; 373 return cdev_get(p) ? 0 : -1; 374 } 375 376 int cdev_add(struct cdev *p, dev_t dev, unsigned count) 377 { 378 p->dev = dev; 379 p->count = count; 380 return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); 381 } 382 383 static void cdev_unmap(dev_t dev, unsigned count) 384 { 385 kobj_unmap(cdev_map, dev, count); 386 } 387 388 void cdev_del(struct cdev *p) 389 { 390 cdev_unmap(p->dev, p->count); 391 kobject_put(&p->kobj); 392 } 393 394 395 static void cdev_default_release(struct kobject *kobj) 396 { 397 struct cdev *p = container_of(kobj, struct cdev, kobj); 398 cdev_purge(p); 399 } 400 401 static void cdev_dynamic_release(struct kobject *kobj) 402 { 403 struct cdev *p = container_of(kobj, struct cdev, kobj); 404 cdev_purge(p); 405 kfree(p); 406 } 407 408 static struct kobj_type ktype_cdev_default = { 409 .release = cdev_default_release, 410 }; 411 412 static struct kobj_type ktype_cdev_dynamic = { 413 .release = cdev_dynamic_release, 414 }; 415 416 struct cdev *cdev_alloc(void) 417 { 418 struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL); 419 if (p) { 420 memset(p, 0, sizeof(struct cdev)); 421 p->kobj.ktype = &ktype_cdev_dynamic; 422 INIT_LIST_HEAD(&p->list); 423 kobject_init(&p->kobj); 424 } 425 return p; 426 } 427 428 void cdev_init(struct cdev *cdev, struct file_operations *fops) 429 { 430 memset(cdev, 0, sizeof *cdev); 431 INIT_LIST_HEAD(&cdev->list); 432 cdev->kobj.ktype = &ktype_cdev_default; 433 kobject_init(&cdev->kobj); 434 cdev->ops = fops; 435 } 436 437 static struct kobject *base_probe(dev_t dev, int *part, void *data) 438 { 439 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) 440 /* Make old-style 2.4 aliases work */ 441 request_module("char-major-%d", MAJOR(dev)); 442 return NULL; 443 } 444 445 void __init chrdev_init(void) 446 { 447 cdev_map = kobj_map_init(base_probe, &chrdevs_lock); 448 } 449 450 451 /* Let modules do char dev stuff */ 452 EXPORT_SYMBOL(register_chrdev_region); 453 EXPORT_SYMBOL(unregister_chrdev_region); 454 EXPORT_SYMBOL(alloc_chrdev_region); 455 EXPORT_SYMBOL(cdev_init); 456 EXPORT_SYMBOL(cdev_alloc); 457 EXPORT_SYMBOL(cdev_del); 458 EXPORT_SYMBOL(cdev_add); 459 EXPORT_SYMBOL(register_chrdev); 460 EXPORT_SYMBOL(unregister_chrdev); 461