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 #include <linux/seq_file.h>
  19
  20 #include <linux/kobject.h>
  21 #include <linux/kobj_map.h>
  22 #include <linux/cdev.h>
  23
  24 #ifdef CONFIG_KMOD
  25 #include <linux/kmod.h>
  26 #endif
  27
  28 static struct kobj_map *cdev_map;
  29
  30 static DECLARE_MUTEX(chrdevs_lock);
  31
  32 static struct char_device_struct {
  33         struct char_device_struct *next;
  34         unsigned int major;
  35         unsigned int baseminor;
  36         int minorct;
  37         char name[64];
  38         struct file_operations *fops;
  39         struct cdev *cdev;              /* will die */
  40 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
  41
  42 /* index in the above */
  43 static inline int major_to_index(int major)
  44 {
  45         return major % CHRDEV_MAJOR_HASH_SIZE;
  46 }
  47
  48 #ifdef CONFIG_PROC_FS
  49
  50 void chrdev_show(struct seq_file *f, off_t offset)
  51 {
  52         struct char_device_struct *cd;
  53
  54         if (offset < CHRDEV_MAJOR_HASH_SIZE) {
  55                 down(&chrdevs_lock);
  56                 for (cd = chrdevs[offset]; cd; cd = cd->next)
  57                         seq_printf(f, "%3d %s\n", cd->major, cd->name);
  58                 up(&chrdevs_lock);
  59         }
  60 }
  61
  62 #endif /* CONFIG_PROC_FS */
  63
  64 /*
  65  * Register a single major with a specified minor range.
  66  *
  67  * If major == 0 this functions will dynamically allocate a major and return
  68  * its number.
  69  *
  70  * If major > 0 this function will attempt to reserve the passed range of
  71  * minors and will return zero on success.
  72  *
  73  * Returns a -ve errno on failure.
  74  */
  75 static struct char_device_struct *
  76 __register_chrdev_region(unsigned int major, unsigned int baseminor,
  77                            int minorct, const char *name)
  78 {
  79         struct char_device_struct *cd, **cp;
  80         int ret = 0;
  81         int i;
  82
  83         cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
  84         if (cd == NULL)
  85                 return ERR_PTR(-ENOMEM);
  86
  87         memset(cd, 0, sizeof(struct char_device_struct));
  88
  89         down(&chrdevs_lock);
  90
  91         /* temporary */
  92         if (major == 0) {
  93                 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
  94                         if (chrdevs[i] == NULL)
  95                                 break;
  96                 }
  97
  98                 if (i == 0) {
  99                         ret = -EBUSY;
 100                         goto out;
 101                 }
 102                 major = i;
 103                 ret = major;
 104         }
 105
 106         cd->major = major;
 107         cd->baseminor = baseminor;
 108         cd->minorct = minorct;
 109         strncpy(cd->name,name, 64);
 110
 111         i = major_to_index(major);
 112
 113         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 114                 if ((*cp)->major > major ||
 115                     ((*cp)->major == major && (*cp)->baseminor >= baseminor))
 116                         break;
 117         if (*cp && (*cp)->major == major &&
 118             (*cp)->baseminor < baseminor + minorct) {
 119                 ret = -EBUSY;
 120                 goto out;
 121         }
 122         cd->next = *cp;
 123         *cp = cd;
 124         up(&chrdevs_lock);
 125         return cd;
 126 out:
 127         up(&chrdevs_lock);
 128         kfree(cd);
 129         return ERR_PTR(ret);
 130 }
 131
 132 static struct char_device_struct *
 133 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 134 {
 135         struct char_device_struct *cd = NULL, **cp;
 136         int i = major_to_index(major);
 137
 138         down(&chrdevs_lock);
 139         for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
 140                 if ((*cp)->major == major &&
 141                     (*cp)->baseminor == baseminor &&
 142                     (*cp)->minorct == minorct)
 143                         break;
 144         if (*cp) {
 145                 cd = *cp;
 146                 *cp = cd->next;
 147         }
 148         up(&chrdevs_lock);
 149         return cd;
 150 }
 151
 152 int register_chrdev_region(dev_t from, unsigned count, const char *name)
 153 {
 154         struct char_device_struct *cd;
 155         dev_t to = from + count;
 156         dev_t n, next;
 157
 158         for (n = from; n < to; n = next) {
 159                 next = MKDEV(MAJOR(n)+1, 0);
 160                 if (next > to)
 161                         next = to;
 162                 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
 163                                next - n, name);
 164                 if (IS_ERR(cd))
 165                         goto fail;
 166         }
 167         return 0;
 168 fail:
 169         to = n;
 170         for (n = from; n < to; n = next) {
 171                 next = MKDEV(MAJOR(n)+1, 0);
 172                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 173         }
 174         return PTR_ERR(cd);
 175 }
 176
 177 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
 178                         const char *name)
 179 {
 180         struct char_device_struct *cd;
 181         cd = __register_chrdev_region(0, baseminor, count, name);
 182         if (IS_ERR(cd))
 183                 return PTR_ERR(cd);
 184         *dev = MKDEV(cd->major, cd->baseminor);
 185         return 0;
 186 }
 187
 188 int register_chrdev(unsigned int major, const char *name,
 189                     struct file_operations *fops)
 190 {
 191         struct char_device_struct *cd;
 192         struct cdev *cdev;
 193         char *s;
 194         int err = -ENOMEM;
 195
 196         cd = __register_chrdev_region(major, 0, 256, name);
 197         if (IS_ERR(cd))
 198                 return PTR_ERR(cd);
 199
 200         cdev = cdev_alloc();
 201         if (!cdev)
 202                 goto out2;
 203
 204         cdev->owner = fops->owner;
 205         cdev->ops = fops;
 206         kobject_set_name(&cdev->kobj, "%s", name);
 207         for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
 208                 *s = '!';
 209
 210         err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
 211         if (err)
 212                 goto out;
 213
 214         cd->cdev = cdev;
 215
 216         return major ? 0 : cd->major;
 217 out:
 218         kobject_put(&cdev->kobj);
 219 out2:
 220         kfree(__unregister_chrdev_region(cd->major, 0, 256));
 221         return err;
 222 }
 223
 224 void unregister_chrdev_region(dev_t from, unsigned count)
 225 {
 226         dev_t to = from + count;
 227         dev_t n, next;
 228
 229         for (n = from; n < to; n = next) {
 230                 next = MKDEV(MAJOR(n)+1, 0);
 231                 if (next > to)
 232                         next = to;
 233                 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
 234         }
 235 }
 236
 237 int unregister_chrdev(unsigned int major, const char *name)
 238 {
 239         struct char_device_struct *cd;
 240         cd = __unregister_chrdev_region(major, 0, 256);
 241         if (cd && cd->cdev)
 242                 cdev_del(cd->cdev);
 243         kfree(cd);
 244         return 0;
 245 }
 246
 247 static DEFINE_SPINLOCK(cdev_lock);
 248
 249 static struct kobject *cdev_get(struct cdev *p)
 250 {
 251         struct module *owner = p->owner;
 252         struct kobject *kobj;
 253
 254         if (owner && !try_module_get(owner))
 255                 return NULL;
 256         kobj = kobject_get(&p->kobj);
 257         if (!kobj)
 258                 module_put(owner);
 259         return kobj;
 260 }
 261
 262 void cdev_put(struct cdev *p)
 263 {
 264         if (p) {
 265                 struct module *owner = p->owner;
 266                 kobject_put(&p->kobj);
 267                 module_put(owner);
 268         }
 269 }
 270
 271 /*
 272  * Called every time a character special file is opened
 273  */
 274 int chrdev_open(struct inode * inode, struct file * filp)
 275 {
 276         struct cdev *p;
 277         struct cdev *new = NULL;
 278         int ret = 0;
 279
 280         spin_lock(&cdev_lock);
 281         p = inode->i_cdev;
 282         if (!p) {
 283                 struct kobject *kobj;
 284                 int idx;
 285                 spin_unlock(&cdev_lock);
 286                 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
 287                 if (!kobj)
 288                         return -ENXIO;
 289                 new = container_of(kobj, struct cdev, kobj);
 290                 spin_lock(&cdev_lock);
 291                 p = inode->i_cdev;
 292                 if (!p) {
 293                         inode->i_cdev = p = new;
 294                         inode->i_cindex = idx;
 295                         list_add(&inode->i_devices, &p->list);
 296                         new = NULL;
 297                 } else if (!cdev_get(p))
 298                         ret = -ENXIO;
 299         } else if (!cdev_get(p))
 300                 ret = -ENXIO;
 301         spin_unlock(&cdev_lock);
 302         cdev_put(new);
 303         if (ret)
 304                 return ret;
 305         filp->f_op = fops_get(p->ops);
 306         if (!filp->f_op) {
 307                 cdev_put(p);
 308                 return -ENXIO;
 309         }
 310         if (filp->f_op->open) {
 311                 lock_kernel();
 312                 ret = filp->f_op->open(inode,filp);
 313                 unlock_kernel();
 314         }
 315         if (ret)
 316                 cdev_put(p);
 317         return ret;
 318 }
 319
 320 void cd_forget(struct inode *inode)
 321 {
 322         spin_lock(&cdev_lock);
 323         list_del_init(&inode->i_devices);
 324         inode->i_cdev = NULL;
 325         spin_unlock(&cdev_lock);
 326 }
 327
 328 static void cdev_purge(struct cdev *cdev)
 329 {
 330         spin_lock(&cdev_lock);
 331         while (!list_empty(&cdev->list)) {
 332                 struct inode *inode;
 333                 inode = container_of(cdev->list.next, struct inode, i_devices);
 334                 list_del_init(&inode->i_devices);
 335                 inode->i_cdev = NULL;
 336         }
 337         spin_unlock(&cdev_lock);
 338 }
 339
 340 /*
 341  * Dummy default file-operations: the only thing this does
 342  * is contain the open that then fills in the correct operations
 343  * depending on the special file...
 344  */
 345 struct file_operations def_chr_fops = {
 346         .open = chrdev_open,
 347 };
 348
 349 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 350 {
 351         struct cdev *p = data;
 352         return &p->kobj;
 353 }
 354
 355 static int exact_lock(dev_t dev, void *data)
 356 {
 357         struct cdev *p = data;
 358         return cdev_get(p) ? 0 : -1;
 359 }
 360
 361 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 362 {
 363         p->dev = dev;
 364         p->count = count;
 365         return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
 366 }
 367
 368 static void cdev_unmap(dev_t dev, unsigned count)
 369 {
 370         kobj_unmap(cdev_map, dev, count);
 371 }
 372
 373 void cdev_del(struct cdev *p)
 374 {
 375         cdev_unmap(p->dev, p->count);
 376         kobject_put(&p->kobj);
 377 }
 378
 379
 380 static void cdev_default_release(struct kobject *kobj)
 381 {
 382         struct cdev *p = container_of(kobj, struct cdev, kobj);
 383         cdev_purge(p);
 384 }
 385
 386 static void cdev_dynamic_release(struct kobject *kobj)
 387 {
 388         struct cdev *p = container_of(kobj, struct cdev, kobj);
 389         cdev_purge(p);
 390         kfree(p);
 391 }
 392
 393 static struct kobj_type ktype_cdev_default = {
 394         .release        = cdev_default_release,
 395 };
 396
 397 static struct kobj_type ktype_cdev_dynamic = {
 398         .release        = cdev_dynamic_release,
 399 };
 400
 401 struct cdev *cdev_alloc(void)
 402 {
 403         struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
 404         if (p) {
 405                 memset(p, 0, sizeof(struct cdev));
 406                 p->kobj.ktype = &ktype_cdev_dynamic;
 407                 INIT_LIST_HEAD(&p->list);
 408                 kobject_init(&p->kobj);
 409         }
 410         return p;
 411 }
 412
 413 void cdev_init(struct cdev *cdev, struct file_operations *fops)
 414 {
 415         memset(cdev, 0, sizeof *cdev);
 416         INIT_LIST_HEAD(&cdev->list);
 417         cdev->kobj.ktype = &ktype_cdev_default;
 418         kobject_init(&cdev->kobj);
 419         cdev->ops = fops;
 420 }
 421
 422 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 423 {
 424         if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
 425                 /* Make old-style 2.4 aliases work */
 426                 request_module("char-major-%d", MAJOR(dev));
 427         return NULL;
 428 }
 429
 430 void __init chrdev_init(void)
 431 {
 432         cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 433 }
 434
 435
 436 /* Let modules do char dev stuff */
 437 EXPORT_SYMBOL(register_chrdev_region);
 438 EXPORT_SYMBOL(unregister_chrdev_region);
 439 EXPORT_SYMBOL(alloc_chrdev_region);
 440 EXPORT_SYMBOL(cdev_init);
 441 EXPORT_SYMBOL(cdev_alloc);
 442 EXPORT_SYMBOL(cdev_del);
 443 EXPORT_SYMBOL(cdev_add);
 444 EXPORT_SYMBOL(register_chrdev);
 445 EXPORT_SYMBOL(unregister_chrdev);