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 = 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 const 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);