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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * linux/fs/char_dev.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | */ | |
6 | ||
1da177e4 LT |
7 | #include <linux/init.h> |
8 | #include <linux/fs.h> | |
b446b60e | 9 | #include <linux/kdev_t.h> |
1da177e4 LT |
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> | |
68eef3b4 | 17 | #include <linux/seq_file.h> |
1da177e4 LT |
18 | |
19 | #include <linux/kobject.h> | |
20 | #include <linux/kobj_map.h> | |
21 | #include <linux/cdev.h> | |
58383af6 | 22 | #include <linux/mutex.h> |
5da6185b | 23 | #include <linux/backing-dev.h> |
1da177e4 LT |
24 | |
25 | #ifdef CONFIG_KMOD | |
26 | #include <linux/kmod.h> | |
27 | #endif | |
07f3f05c | 28 | #include "internal.h" |
1da177e4 | 29 | |
5da6185b DH |
30 | /* |
31 | * capabilities for /dev/mem, /dev/kmem and similar directly mappable character | |
32 | * devices | |
33 | * - permits shared-mmap for read, write and/or exec | |
34 | * - does not permit private mmap in NOMMU mode (can't do COW) | |
35 | * - no readahead or I/O queue unplugging required | |
36 | */ | |
37 | struct backing_dev_info directly_mappable_cdev_bdi = { | |
38 | .capabilities = ( | |
39 | #ifdef CONFIG_MMU | |
40 | /* permit private copies of the data to be taken */ | |
41 | BDI_CAP_MAP_COPY | | |
42 | #endif | |
43 | /* permit direct mmap, for read, write or exec */ | |
44 | BDI_CAP_MAP_DIRECT | | |
45 | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP), | |
46 | }; | |
47 | ||
1da177e4 LT |
48 | static struct kobj_map *cdev_map; |
49 | ||
58383af6 | 50 | static DEFINE_MUTEX(chrdevs_lock); |
1da177e4 LT |
51 | |
52 | static struct char_device_struct { | |
53 | struct char_device_struct *next; | |
54 | unsigned int major; | |
55 | unsigned int baseminor; | |
56 | int minorct; | |
7170be5f | 57 | char name[64]; |
1da177e4 | 58 | struct cdev *cdev; /* will die */ |
68eef3b4 | 59 | } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; |
1da177e4 LT |
60 | |
61 | /* index in the above */ | |
62 | static inline int major_to_index(int major) | |
63 | { | |
68eef3b4 | 64 | return major % CHRDEV_MAJOR_HASH_SIZE; |
7170be5f NH |
65 | } |
66 | ||
68eef3b4 | 67 | #ifdef CONFIG_PROC_FS |
7170be5f | 68 | |
68eef3b4 | 69 | void chrdev_show(struct seq_file *f, off_t offset) |
7170be5f NH |
70 | { |
71 | struct char_device_struct *cd; | |
7170be5f | 72 | |
68eef3b4 JK |
73 | if (offset < CHRDEV_MAJOR_HASH_SIZE) { |
74 | mutex_lock(&chrdevs_lock); | |
75 | for (cd = chrdevs[offset]; cd; cd = cd->next) | |
76 | seq_printf(f, "%3d %s\n", cd->major, cd->name); | |
77 | mutex_unlock(&chrdevs_lock); | |
1da177e4 | 78 | } |
7170be5f NH |
79 | } |
80 | ||
68eef3b4 | 81 | #endif /* CONFIG_PROC_FS */ |
1da177e4 LT |
82 | |
83 | /* | |
84 | * Register a single major with a specified minor range. | |
85 | * | |
86 | * If major == 0 this functions will dynamically allocate a major and return | |
87 | * its number. | |
88 | * | |
89 | * If major > 0 this function will attempt to reserve the passed range of | |
90 | * minors and will return zero on success. | |
91 | * | |
92 | * Returns a -ve errno on failure. | |
93 | */ | |
94 | static struct char_device_struct * | |
95 | __register_chrdev_region(unsigned int major, unsigned int baseminor, | |
96 | int minorct, const char *name) | |
97 | { | |
98 | struct char_device_struct *cd, **cp; | |
99 | int ret = 0; | |
100 | int i; | |
101 | ||
11b0b5ab | 102 | cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL); |
1da177e4 LT |
103 | if (cd == NULL) |
104 | return ERR_PTR(-ENOMEM); | |
105 | ||
58383af6 | 106 | mutex_lock(&chrdevs_lock); |
1da177e4 LT |
107 | |
108 | /* temporary */ | |
109 | if (major == 0) { | |
110 | for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) { | |
111 | if (chrdevs[i] == NULL) | |
112 | break; | |
113 | } | |
114 | ||
115 | if (i == 0) { | |
116 | ret = -EBUSY; | |
117 | goto out; | |
118 | } | |
119 | major = i; | |
120 | ret = major; | |
121 | } | |
122 | ||
123 | cd->major = major; | |
124 | cd->baseminor = baseminor; | |
125 | cd->minorct = minorct; | |
7170be5f | 126 | strncpy(cd->name,name, 64); |
1da177e4 LT |
127 | |
128 | i = major_to_index(major); | |
129 | ||
130 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) | |
131 | if ((*cp)->major > major || | |
01d553d0 AW |
132 | ((*cp)->major == major && |
133 | (((*cp)->baseminor >= baseminor) || | |
134 | ((*cp)->baseminor + (*cp)->minorct > baseminor)))) | |
1da177e4 | 135 | break; |
01d553d0 AW |
136 | |
137 | /* Check for overlapping minor ranges. */ | |
138 | if (*cp && (*cp)->major == major) { | |
139 | int old_min = (*cp)->baseminor; | |
140 | int old_max = (*cp)->baseminor + (*cp)->minorct - 1; | |
141 | int new_min = baseminor; | |
142 | int new_max = baseminor + minorct - 1; | |
143 | ||
144 | /* New driver overlaps from the left. */ | |
145 | if (new_max >= old_min && new_max <= old_max) { | |
146 | ret = -EBUSY; | |
147 | goto out; | |
148 | } | |
149 | ||
150 | /* New driver overlaps from the right. */ | |
151 | if (new_min <= old_max && new_min >= old_min) { | |
152 | ret = -EBUSY; | |
153 | goto out; | |
154 | } | |
1da177e4 | 155 | } |
01d553d0 | 156 | |
1da177e4 LT |
157 | cd->next = *cp; |
158 | *cp = cd; | |
58383af6 | 159 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
160 | return cd; |
161 | out: | |
58383af6 | 162 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
163 | kfree(cd); |
164 | return ERR_PTR(ret); | |
165 | } | |
166 | ||
167 | static struct char_device_struct * | |
168 | __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) | |
169 | { | |
170 | struct char_device_struct *cd = NULL, **cp; | |
171 | int i = major_to_index(major); | |
172 | ||
58383af6 | 173 | mutex_lock(&chrdevs_lock); |
1da177e4 LT |
174 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
175 | if ((*cp)->major == major && | |
176 | (*cp)->baseminor == baseminor && | |
177 | (*cp)->minorct == minorct) | |
178 | break; | |
179 | if (*cp) { | |
180 | cd = *cp; | |
181 | *cp = cd->next; | |
182 | } | |
58383af6 | 183 | mutex_unlock(&chrdevs_lock); |
1da177e4 LT |
184 | return cd; |
185 | } | |
186 | ||
cf3e43db JC |
187 | /** |
188 | * register_chrdev_region() - register a range of device numbers | |
189 | * @from: the first in the desired range of device numbers; must include | |
190 | * the major number. | |
191 | * @count: the number of consecutive device numbers required | |
192 | * @name: the name of the device or driver. | |
193 | * | |
194 | * Return value is zero on success, a negative error code on failure. | |
195 | */ | |
1da177e4 LT |
196 | int register_chrdev_region(dev_t from, unsigned count, const char *name) |
197 | { | |
198 | struct char_device_struct *cd; | |
199 | dev_t to = from + count; | |
200 | dev_t n, next; | |
201 | ||
202 | for (n = from; n < to; n = next) { | |
203 | next = MKDEV(MAJOR(n)+1, 0); | |
204 | if (next > to) | |
205 | next = to; | |
206 | cd = __register_chrdev_region(MAJOR(n), MINOR(n), | |
207 | next - n, name); | |
208 | if (IS_ERR(cd)) | |
209 | goto fail; | |
210 | } | |
211 | return 0; | |
212 | fail: | |
213 | to = n; | |
214 | for (n = from; n < to; n = next) { | |
215 | next = MKDEV(MAJOR(n)+1, 0); | |
216 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); | |
217 | } | |
218 | return PTR_ERR(cd); | |
219 | } | |
220 | ||
cf3e43db JC |
221 | /** |
222 | * alloc_chrdev_region() - register a range of char device numbers | |
223 | * @dev: output parameter for first assigned number | |
224 | * @baseminor: first of the requested range of minor numbers | |
225 | * @count: the number of minor numbers required | |
226 | * @name: the name of the associated device or driver | |
227 | * | |
228 | * Allocates a range of char device numbers. The major number will be | |
229 | * chosen dynamically, and returned (along with the first minor number) | |
230 | * in @dev. Returns zero or a negative error code. | |
231 | */ | |
1da177e4 LT |
232 | int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, |
233 | const char *name) | |
234 | { | |
235 | struct char_device_struct *cd; | |
236 | cd = __register_chrdev_region(0, baseminor, count, name); | |
237 | if (IS_ERR(cd)) | |
238 | return PTR_ERR(cd); | |
239 | *dev = MKDEV(cd->major, cd->baseminor); | |
240 | return 0; | |
241 | } | |
242 | ||
d247e2c6 REB |
243 | /** |
244 | * register_chrdev() - Register a major number for character devices. | |
245 | * @major: major device number or 0 for dynamic allocation | |
246 | * @name: name of this range of devices | |
247 | * @fops: file operations associated with this devices | |
248 | * | |
249 | * If @major == 0 this functions will dynamically allocate a major and return | |
250 | * its number. | |
251 | * | |
252 | * If @major > 0 this function will attempt to reserve a device with the given | |
253 | * major number and will return zero on success. | |
254 | * | |
255 | * Returns a -ve errno on failure. | |
256 | * | |
257 | * The name of this device has nothing to do with the name of the device in | |
258 | * /dev. It only helps to keep track of the different owners of devices. If | |
259 | * your module name has only one type of devices it's ok to use e.g. the name | |
260 | * of the module here. | |
261 | * | |
262 | * This function registers a range of 256 minor numbers. The first minor number | |
263 | * is 0. | |
264 | */ | |
1da177e4 | 265 | int register_chrdev(unsigned int major, const char *name, |
99ac48f5 | 266 | const struct file_operations *fops) |
1da177e4 LT |
267 | { |
268 | struct char_device_struct *cd; | |
269 | struct cdev *cdev; | |
270 | char *s; | |
271 | int err = -ENOMEM; | |
272 | ||
273 | cd = __register_chrdev_region(major, 0, 256, name); | |
274 | if (IS_ERR(cd)) | |
275 | return PTR_ERR(cd); | |
276 | ||
277 | cdev = cdev_alloc(); | |
278 | if (!cdev) | |
279 | goto out2; | |
280 | ||
281 | cdev->owner = fops->owner; | |
282 | cdev->ops = fops; | |
283 | kobject_set_name(&cdev->kobj, "%s", name); | |
284 | for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) | |
285 | *s = '!'; | |
286 | ||
287 | err = cdev_add(cdev, MKDEV(cd->major, 0), 256); | |
288 | if (err) | |
289 | goto out; | |
290 | ||
291 | cd->cdev = cdev; | |
292 | ||
293 | return major ? 0 : cd->major; | |
294 | out: | |
295 | kobject_put(&cdev->kobj); | |
296 | out2: | |
297 | kfree(__unregister_chrdev_region(cd->major, 0, 256)); | |
298 | return err; | |
299 | } | |
300 | ||
cf3e43db JC |
301 | /** |
302 | * unregister_chrdev_region() - return a range of device numbers | |
303 | * @from: the first in the range of numbers to unregister | |
304 | * @count: the number of device numbers to unregister | |
305 | * | |
306 | * This function will unregister a range of @count device numbers, | |
307 | * starting with @from. The caller should normally be the one who | |
308 | * allocated those numbers in the first place... | |
309 | */ | |
1da177e4 LT |
310 | void unregister_chrdev_region(dev_t from, unsigned count) |
311 | { | |
312 | dev_t to = from + count; | |
313 | dev_t n, next; | |
314 | ||
315 | for (n = from; n < to; n = next) { | |
316 | next = MKDEV(MAJOR(n)+1, 0); | |
317 | if (next > to) | |
318 | next = to; | |
319 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); | |
320 | } | |
321 | } | |
322 | ||
e53252d9 | 323 | void unregister_chrdev(unsigned int major, const char *name) |
1da177e4 LT |
324 | { |
325 | struct char_device_struct *cd; | |
326 | cd = __unregister_chrdev_region(major, 0, 256); | |
327 | if (cd && cd->cdev) | |
328 | cdev_del(cd->cdev); | |
329 | kfree(cd); | |
1da177e4 LT |
330 | } |
331 | ||
332 | static DEFINE_SPINLOCK(cdev_lock); | |
333 | ||
334 | static struct kobject *cdev_get(struct cdev *p) | |
335 | { | |
336 | struct module *owner = p->owner; | |
337 | struct kobject *kobj; | |
338 | ||
339 | if (owner && !try_module_get(owner)) | |
340 | return NULL; | |
341 | kobj = kobject_get(&p->kobj); | |
342 | if (!kobj) | |
343 | module_put(owner); | |
344 | return kobj; | |
345 | } | |
346 | ||
347 | void cdev_put(struct cdev *p) | |
348 | { | |
349 | if (p) { | |
7da6844c | 350 | struct module *owner = p->owner; |
1da177e4 | 351 | kobject_put(&p->kobj); |
7da6844c | 352 | module_put(owner); |
1da177e4 LT |
353 | } |
354 | } | |
355 | ||
356 | /* | |
357 | * Called every time a character special file is opened | |
358 | */ | |
922f9cfa | 359 | static int chrdev_open(struct inode *inode, struct file *filp) |
1da177e4 LT |
360 | { |
361 | struct cdev *p; | |
362 | struct cdev *new = NULL; | |
363 | int ret = 0; | |
364 | ||
365 | spin_lock(&cdev_lock); | |
366 | p = inode->i_cdev; | |
367 | if (!p) { | |
368 | struct kobject *kobj; | |
369 | int idx; | |
370 | spin_unlock(&cdev_lock); | |
371 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); | |
372 | if (!kobj) | |
373 | return -ENXIO; | |
374 | new = container_of(kobj, struct cdev, kobj); | |
375 | spin_lock(&cdev_lock); | |
a30427d9 JC |
376 | /* Check i_cdev again in case somebody beat us to it while |
377 | we dropped the lock. */ | |
1da177e4 LT |
378 | p = inode->i_cdev; |
379 | if (!p) { | |
380 | inode->i_cdev = p = new; | |
381 | inode->i_cindex = idx; | |
382 | list_add(&inode->i_devices, &p->list); | |
383 | new = NULL; | |
384 | } else if (!cdev_get(p)) | |
385 | ret = -ENXIO; | |
386 | } else if (!cdev_get(p)) | |
387 | ret = -ENXIO; | |
388 | spin_unlock(&cdev_lock); | |
389 | cdev_put(new); | |
390 | if (ret) | |
391 | return ret; | |
392 | filp->f_op = fops_get(p->ops); | |
393 | if (!filp->f_op) { | |
394 | cdev_put(p); | |
395 | return -ENXIO; | |
396 | } | |
9514dff9 | 397 | if (filp->f_op->open) |
1da177e4 | 398 | ret = filp->f_op->open(inode,filp); |
1da177e4 LT |
399 | if (ret) |
400 | cdev_put(p); | |
401 | return ret; | |
402 | } | |
403 | ||
404 | void cd_forget(struct inode *inode) | |
405 | { | |
406 | spin_lock(&cdev_lock); | |
407 | list_del_init(&inode->i_devices); | |
408 | inode->i_cdev = NULL; | |
409 | spin_unlock(&cdev_lock); | |
410 | } | |
411 | ||
75c96f85 | 412 | static void cdev_purge(struct cdev *cdev) |
1da177e4 LT |
413 | { |
414 | spin_lock(&cdev_lock); | |
415 | while (!list_empty(&cdev->list)) { | |
416 | struct inode *inode; | |
417 | inode = container_of(cdev->list.next, struct inode, i_devices); | |
418 | list_del_init(&inode->i_devices); | |
419 | inode->i_cdev = NULL; | |
420 | } | |
421 | spin_unlock(&cdev_lock); | |
422 | } | |
423 | ||
424 | /* | |
425 | * Dummy default file-operations: the only thing this does | |
426 | * is contain the open that then fills in the correct operations | |
427 | * depending on the special file... | |
428 | */ | |
4b6f5d20 | 429 | const struct file_operations def_chr_fops = { |
1da177e4 LT |
430 | .open = chrdev_open, |
431 | }; | |
432 | ||
433 | static struct kobject *exact_match(dev_t dev, int *part, void *data) | |
434 | { | |
435 | struct cdev *p = data; | |
436 | return &p->kobj; | |
437 | } | |
438 | ||
439 | static int exact_lock(dev_t dev, void *data) | |
440 | { | |
441 | struct cdev *p = data; | |
442 | return cdev_get(p) ? 0 : -1; | |
443 | } | |
444 | ||
cf3e43db JC |
445 | /** |
446 | * cdev_add() - add a char device to the system | |
447 | * @p: the cdev structure for the device | |
448 | * @dev: the first device number for which this device is responsible | |
449 | * @count: the number of consecutive minor numbers corresponding to this | |
450 | * device | |
451 | * | |
452 | * cdev_add() adds the device represented by @p to the system, making it | |
453 | * live immediately. A negative error code is returned on failure. | |
454 | */ | |
1da177e4 LT |
455 | int cdev_add(struct cdev *p, dev_t dev, unsigned count) |
456 | { | |
457 | p->dev = dev; | |
458 | p->count = count; | |
459 | return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); | |
460 | } | |
461 | ||
462 | static void cdev_unmap(dev_t dev, unsigned count) | |
463 | { | |
464 | kobj_unmap(cdev_map, dev, count); | |
465 | } | |
466 | ||
cf3e43db JC |
467 | /** |
468 | * cdev_del() - remove a cdev from the system | |
469 | * @p: the cdev structure to be removed | |
470 | * | |
471 | * cdev_del() removes @p from the system, possibly freeing the structure | |
472 | * itself. | |
473 | */ | |
1da177e4 LT |
474 | void cdev_del(struct cdev *p) |
475 | { | |
476 | cdev_unmap(p->dev, p->count); | |
477 | kobject_put(&p->kobj); | |
478 | } | |
479 | ||
480 | ||
481 | static void cdev_default_release(struct kobject *kobj) | |
482 | { | |
483 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
484 | cdev_purge(p); | |
485 | } | |
486 | ||
487 | static void cdev_dynamic_release(struct kobject *kobj) | |
488 | { | |
489 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
490 | cdev_purge(p); | |
491 | kfree(p); | |
492 | } | |
493 | ||
494 | static struct kobj_type ktype_cdev_default = { | |
495 | .release = cdev_default_release, | |
496 | }; | |
497 | ||
498 | static struct kobj_type ktype_cdev_dynamic = { | |
499 | .release = cdev_dynamic_release, | |
500 | }; | |
501 | ||
cf3e43db JC |
502 | /** |
503 | * cdev_alloc() - allocate a cdev structure | |
504 | * | |
505 | * Allocates and returns a cdev structure, or NULL on failure. | |
506 | */ | |
1da177e4 LT |
507 | struct cdev *cdev_alloc(void) |
508 | { | |
11b0b5ab | 509 | struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); |
1da177e4 | 510 | if (p) { |
1da177e4 | 511 | INIT_LIST_HEAD(&p->list); |
f9cb074b | 512 | kobject_init(&p->kobj, &ktype_cdev_dynamic); |
1da177e4 LT |
513 | } |
514 | return p; | |
515 | } | |
516 | ||
cf3e43db JC |
517 | /** |
518 | * cdev_init() - initialize a cdev structure | |
519 | * @cdev: the structure to initialize | |
520 | * @fops: the file_operations for this device | |
521 | * | |
522 | * Initializes @cdev, remembering @fops, making it ready to add to the | |
523 | * system with cdev_add(). | |
524 | */ | |
99ac48f5 | 525 | void cdev_init(struct cdev *cdev, const struct file_operations *fops) |
1da177e4 LT |
526 | { |
527 | memset(cdev, 0, sizeof *cdev); | |
528 | INIT_LIST_HEAD(&cdev->list); | |
f9cb074b | 529 | kobject_init(&cdev->kobj, &ktype_cdev_default); |
1da177e4 LT |
530 | cdev->ops = fops; |
531 | } | |
532 | ||
533 | static struct kobject *base_probe(dev_t dev, int *part, void *data) | |
534 | { | |
535 | if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) | |
536 | /* Make old-style 2.4 aliases work */ | |
537 | request_module("char-major-%d", MAJOR(dev)); | |
538 | return NULL; | |
539 | } | |
540 | ||
541 | void __init chrdev_init(void) | |
542 | { | |
543 | cdev_map = kobj_map_init(base_probe, &chrdevs_lock); | |
e0bf68dd | 544 | bdi_init(&directly_mappable_cdev_bdi); |
1da177e4 LT |
545 | } |
546 | ||
547 | ||
548 | /* Let modules do char dev stuff */ | |
549 | EXPORT_SYMBOL(register_chrdev_region); | |
550 | EXPORT_SYMBOL(unregister_chrdev_region); | |
551 | EXPORT_SYMBOL(alloc_chrdev_region); | |
552 | EXPORT_SYMBOL(cdev_init); | |
553 | EXPORT_SYMBOL(cdev_alloc); | |
554 | EXPORT_SYMBOL(cdev_del); | |
555 | EXPORT_SYMBOL(cdev_add); | |
556 | EXPORT_SYMBOL(register_chrdev); | |
557 | EXPORT_SYMBOL(unregister_chrdev); | |
5da6185b | 558 | EXPORT_SYMBOL(directly_mappable_cdev_bdi); |