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 #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         up(&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                 kobject_put(&p->kobj);
 281                 module_put(p->owner);
 282         }
 283 }
 284
 285 /*
 286  * Called every time a character special file is opened
 287  */
 288 int chrdev_open(struct inode * inode, struct file * filp)
 289 {
 290         struct cdev *p;
 291         struct cdev *new = NULL;
 292         int ret = 0;
 293
 294         spin_lock(&cdev_lock);
 295         p = inode->i_cdev;
 296         if (!p) {
 297                 struct kobject *kobj;
 298                 int idx;
 299                 spin_unlock(&cdev_lock);
 300                 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
 301                 if (!kobj)
 302                         return -ENXIO;
 303                 new = container_of(kobj, struct cdev, kobj);
 304                 spin_lock(&cdev_lock);
 305                 p = inode->i_cdev;
 306                 if (!p) {
 307                         inode->i_cdev = p = new;
 308                         inode->i_cindex = idx;
 309                         list_add(&inode->i_devices, &p->list);
 310                         new = NULL;
 311                 } else if (!cdev_get(p))
 312                         ret = -ENXIO;
 313         } else if (!cdev_get(p))
 314                 ret = -ENXIO;
 315         spin_unlock(&cdev_lock);
 316         cdev_put(new);
 317         if (ret)
 318                 return ret;
 319         filp->f_op = fops_get(p->ops);
 320         if (!filp->f_op) {
 321                 cdev_put(p);
 322                 return -ENXIO;
 323         }
 324         if (filp->f_op->open) {
 325                 lock_kernel();
 326                 ret = filp->f_op->open(inode,filp);
 327                 unlock_kernel();
 328         }
 329         if (ret)
 330                 cdev_put(p);
 331         return ret;
 332 }
 333
 334 void cd_forget(struct inode *inode)
 335 {
 336         spin_lock(&cdev_lock);
 337         list_del_init(&inode->i_devices);
 338         inode->i_cdev = NULL;
 339         spin_unlock(&cdev_lock);
 340 }
 341
 342 static void cdev_purge(struct cdev *cdev)
 343 {
 344         spin_lock(&cdev_lock);
 345         while (!list_empty(&cdev->list)) {
 346                 struct inode *inode;
 347                 inode = container_of(cdev->list.next, struct inode, i_devices);
 348                 list_del_init(&inode->i_devices);
 349                 inode->i_cdev = NULL;
 350         }
 351         spin_unlock(&cdev_lock);
 352 }
 353
 354 /*
 355  * Dummy default file-operations: the only thing this does
 356  * is contain the open that then fills in the correct operations
 357  * depending on the special file...
 358  */
 359 struct file_operations def_chr_fops = {
 360         .open = chrdev_open,
 361 };
 362
 363 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 364 {
 365         struct cdev *p = data;
 366         return &p->kobj;
 367 }
 368
 369 static int exact_lock(dev_t dev, void *data)
 370 {
 371         struct cdev *p = data;
 372         return cdev_get(p) ? 0 : -1;
 373 }
 374
 375 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 376 {
 377         p->dev = dev;
 378         p->count = count;
 379         return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 380 }
 381
 382 static void cdev_unmap(dev_t dev, unsigned count)
 383 {
 384         kobj_unmap(cdev_map, dev, count);
 385 }
 386
 387 void cdev_del(struct cdev *p)
 388 {
 389         cdev_unmap(p->dev, p->count);
 390         kobject_put(&p->kobj);
 391 }
 392
 393
 394 static void cdev_default_release(struct kobject *kobj)
 395 {
 396         struct cdev *p = container_of(kobj, struct cdev, kobj);
 397         cdev_purge(p);
 398 }
 399
 400 static void cdev_dynamic_release(struct kobject *kobj)
 401 {
 402         struct cdev *p = container_of(kobj, struct cdev, kobj);
 403         cdev_purge(p);
 404         kfree(p);
 405 }
 406
 407 static struct kobj_type ktype_cdev_default = {
 408         .release        = cdev_default_release,
 409 };
 410
 411 static struct kobj_type ktype_cdev_dynamic = {
 412         .release        = cdev_dynamic_release,
 413 };
 414
 415 struct cdev *cdev_alloc(void)
 416 {
 417         struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 418         if (p) {
 419                 memset(p, 0, sizeof(struct cdev));
 420                 p->kobj.ktype = &ktype_cdev_dynamic;
 421                 INIT_LIST_HEAD(&p->list);
 422                 kobject_init(&p->kobj);
 423         }
 424         return p;
 425 }
 426
 427 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 428 {
 429         memset(cdev, 0, sizeof *cdev);
 430         INIT_LIST_HEAD(&cdev->list);
 431         cdev->kobj.ktype = &ktype_cdev_default;
 432         kobject_init(&cdev->kobj);
 433         cdev->ops = fops;
 434 }
 435
 436 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 437 {
 438         if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
 439                 /* Make old-style 2.4 aliases work */
 440                 request_module("char-major-%d", MAJOR(dev));
 441         return NULL;
 442 }
 443
 444 void __init chrdev_init(void)
 445 {
 446         cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 447 }
 448
 449
 450 /* Let modules do char dev stuff */
 451 EXPORT_SYMBOL(register_chrdev_region);
 452 EXPORT_SYMBOL(unregister_chrdev_region);
 453 EXPORT_SYMBOL(alloc_chrdev_region);
 454 EXPORT_SYMBOL(cdev_init);
 455 EXPORT_SYMBOL(cdev_alloc);
 456 EXPORT_SYMBOL(cdev_del);
 457 EXPORT_SYMBOL(cdev_add);
 458 EXPORT_SYMBOL(register_chrdev);
 459 EXPORT_SYMBOL(unregister_chrdev);