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