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1 | /* |
2 | * linux/fs/char_dev.c |
3 | * |
4 | * Copyright (C) 1991, 1992 Linus Torvalds |
5 | */ |
6 | |
7 | #include <linux/init.h> |
8 | #include <linux/fs.h> |
9 | #include <linux/kdev_t.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/seq_file.h> |
17 | |
18 | #include <linux/kobject.h> |
19 | #include <linux/kobj_map.h> |
20 | #include <linux/cdev.h> |
21 | #include <linux/mutex.h> |
22 | #include <linux/backing-dev.h> |
23 | |
24 | #include "internal.h" |
25 | |
26 | /* |
27 | * capabilities for /dev/mem, /dev/kmem and similar directly mappable character |
28 | * devices |
29 | * - permits shared-mmap for read, write and/or exec |
30 | * - does not permit private mmap in NOMMU mode (can't do COW) |
31 | * - no readahead or I/O queue unplugging required |
32 | */ |
33 | struct backing_dev_info directly_mappable_cdev_bdi = { |
34 | .name = "char", |
35 | .capabilities = ( |
36 | #ifdef CONFIG_MMU |
37 | /* permit private copies of the data to be taken */ |
38 | BDI_CAP_MAP_COPY | |
39 | #endif |
40 | /* permit direct mmap, for read, write or exec */ |
41 | BDI_CAP_MAP_DIRECT | |
42 | BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP), |
43 | }; |
44 | |
45 | static struct kobj_map *cdev_map; |
46 | |
47 | static DEFINE_MUTEX(chrdevs_lock); |
48 | |
49 | static struct char_device_struct { |
50 | struct char_device_struct *next; |
51 | unsigned int major; |
52 | unsigned int baseminor; |
53 | int minorct; |
54 | char name[64]; |
55 | struct cdev *cdev; /* will die */ |
56 | } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; |
57 | |
58 | /* index in the above */ |
59 | static inline int major_to_index(int major) |
60 | { |
61 | return major % CHRDEV_MAJOR_HASH_SIZE; |
62 | } |
63 | |
64 | #ifdef CONFIG_PROC_FS |
65 | |
66 | void chrdev_show(struct seq_file *f, off_t offset) |
67 | { |
68 | struct char_device_struct *cd; |
69 | |
70 | if (offset < CHRDEV_MAJOR_HASH_SIZE) { |
71 | mutex_lock(&chrdevs_lock); |
72 | for (cd = chrdevs[offset]; cd; cd = cd->next) |
73 | seq_printf(f, "%3d %s\n", cd->major, cd->name); |
74 | mutex_unlock(&chrdevs_lock); |
75 | } |
76 | } |
77 | |
78 | #endif /* CONFIG_PROC_FS */ |
79 | |
80 | /* |
81 | * Register a single major with a specified minor range. |
82 | * |
83 | * If major == 0 this functions will dynamically allocate a major and return |
84 | * its number. |
85 | * |
86 | * If major > 0 this function will attempt to reserve the passed range of |
87 | * minors and will return zero on success. |
88 | * |
89 | * Returns a -ve errno on failure. |
90 | */ |
91 | static struct char_device_struct * |
92 | __register_chrdev_region(unsigned int major, unsigned int baseminor, |
93 | int minorct, const char *name) |
94 | { |
95 | struct char_device_struct *cd, **cp; |
96 | int ret = 0; |
97 | int i; |
98 | |
99 | cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL); |
100 | if (cd == NULL) |
101 | return ERR_PTR(-ENOMEM); |
102 | |
103 | mutex_lock(&chrdevs_lock); |
104 | |
105 | /* temporary */ |
106 | if (major == 0) { |
107 | for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) { |
108 | if (chrdevs[i] == NULL) |
109 | break; |
110 | } |
111 | |
112 | if (i == 0) { |
113 | ret = -EBUSY; |
114 | goto out; |
115 | } |
116 | major = i; |
117 | ret = major; |
118 | } |
119 | |
120 | cd->major = major; |
121 | cd->baseminor = baseminor; |
122 | cd->minorct = minorct; |
123 | strlcpy(cd->name, name, sizeof(cd->name)); |
124 | |
125 | i = major_to_index(major); |
126 | |
127 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
128 | if ((*cp)->major > major || |
129 | ((*cp)->major == major && |
130 | (((*cp)->baseminor >= baseminor) || |
131 | ((*cp)->baseminor + (*cp)->minorct > baseminor)))) |
132 | break; |
133 | |
134 | /* Check for overlapping minor ranges. */ |
135 | if (*cp && (*cp)->major == major) { |
136 | int old_min = (*cp)->baseminor; |
137 | int old_max = (*cp)->baseminor + (*cp)->minorct - 1; |
138 | int new_min = baseminor; |
139 | int new_max = baseminor + minorct - 1; |
140 | |
141 | /* New driver overlaps from the left. */ |
142 | if (new_max >= old_min && new_max <= old_max) { |
143 | ret = -EBUSY; |
144 | goto out; |
145 | } |
146 | |
147 | /* New driver overlaps from the right. */ |
148 | if (new_min <= old_max && new_min >= old_min) { |
149 | ret = -EBUSY; |
150 | goto out; |
151 | } |
152 | } |
153 | |
154 | cd->next = *cp; |
155 | *cp = cd; |
156 | mutex_unlock(&chrdevs_lock); |
157 | return cd; |
158 | out: |
159 | mutex_unlock(&chrdevs_lock); |
160 | kfree(cd); |
161 | return ERR_PTR(ret); |
162 | } |
163 | |
164 | static struct char_device_struct * |
165 | __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) |
166 | { |
167 | struct char_device_struct *cd = NULL, **cp; |
168 | int i = major_to_index(major); |
169 | |
170 | mutex_lock(&chrdevs_lock); |
171 | for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) |
172 | if ((*cp)->major == major && |
173 | (*cp)->baseminor == baseminor && |
174 | (*cp)->minorct == minorct) |
175 | break; |
176 | if (*cp) { |
177 | cd = *cp; |
178 | *cp = cd->next; |
179 | } |
180 | mutex_unlock(&chrdevs_lock); |
181 | return cd; |
182 | } |
183 | |
184 | /** |
185 | * register_chrdev_region() - register a range of device numbers |
186 | * @from: the first in the desired range of device numbers; must include |
187 | * the major number. |
188 | * @count: the number of consecutive device numbers required |
189 | * @name: the name of the device or driver. |
190 | * |
191 | * Return value is zero on success, a negative error code on failure. |
192 | */ |
193 | int register_chrdev_region(dev_t from, unsigned count, const char *name) |
194 | { |
195 | struct char_device_struct *cd; |
196 | dev_t to = from + count; |
197 | dev_t n, next; |
198 | |
199 | for (n = from; n < to; n = next) { |
200 | next = MKDEV(MAJOR(n)+1, 0); |
201 | if (next > to) |
202 | next = to; |
203 | cd = __register_chrdev_region(MAJOR(n), MINOR(n), |
204 | next - n, name); |
205 | if (IS_ERR(cd)) |
206 | goto fail; |
207 | } |
208 | return 0; |
209 | fail: |
210 | to = n; |
211 | for (n = from; n < to; n = next) { |
212 | next = MKDEV(MAJOR(n)+1, 0); |
213 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); |
214 | } |
215 | return PTR_ERR(cd); |
216 | } |
217 | |
218 | /** |
219 | * alloc_chrdev_region() - register a range of char device numbers |
220 | * @dev: output parameter for first assigned number |
221 | * @baseminor: first of the requested range of minor numbers |
222 | * @count: the number of minor numbers required |
223 | * @name: the name of the associated device or driver |
224 | * |
225 | * Allocates a range of char device numbers. The major number will be |
226 | * chosen dynamically, and returned (along with the first minor number) |
227 | * in @dev. Returns zero or a negative error code. |
228 | */ |
229 | int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, |
230 | const char *name) |
231 | { |
232 | struct char_device_struct *cd; |
233 | cd = __register_chrdev_region(0, baseminor, count, name); |
234 | if (IS_ERR(cd)) |
235 | return PTR_ERR(cd); |
236 | *dev = MKDEV(cd->major, cd->baseminor); |
237 | return 0; |
238 | } |
239 | |
240 | /** |
241 | * __register_chrdev() - create and register a cdev occupying a range of minors |
242 | * @major: major device number or 0 for dynamic allocation |
243 | * @baseminor: first of the requested range of minor numbers |
244 | * @count: the number of minor numbers required |
245 | * @name: name of this range of devices |
246 | * @fops: file operations associated with this devices |
247 | * |
248 | * If @major == 0 this functions will dynamically allocate a major and return |
249 | * its number. |
250 | * |
251 | * If @major > 0 this function will attempt to reserve a device with the given |
252 | * major number and will return zero on success. |
253 | * |
254 | * Returns a -ve errno on failure. |
255 | * |
256 | * The name of this device has nothing to do with the name of the device in |
257 | * /dev. It only helps to keep track of the different owners of devices. If |
258 | * your module name has only one type of devices it's ok to use e.g. the name |
259 | * of the module here. |
260 | */ |
261 | int __register_chrdev(unsigned int major, unsigned int baseminor, |
262 | unsigned int count, const char *name, |
263 | const struct file_operations *fops) |
264 | { |
265 | struct char_device_struct *cd; |
266 | struct cdev *cdev; |
267 | int err = -ENOMEM; |
268 | |
269 | cd = __register_chrdev_region(major, baseminor, count, name); |
270 | if (IS_ERR(cd)) |
271 | return PTR_ERR(cd); |
272 | |
273 | cdev = cdev_alloc(); |
274 | if (!cdev) |
275 | goto out2; |
276 | |
277 | cdev->owner = fops->owner; |
278 | cdev->ops = fops; |
279 | kobject_set_name(&cdev->kobj, "%s", name); |
280 | |
281 | err = cdev_add(cdev, MKDEV(cd->major, baseminor), count); |
282 | if (err) |
283 | goto out; |
284 | |
285 | cd->cdev = cdev; |
286 | |
287 | return major ? 0 : cd->major; |
288 | out: |
289 | kobject_put(&cdev->kobj); |
290 | out2: |
291 | kfree(__unregister_chrdev_region(cd->major, baseminor, count)); |
292 | return err; |
293 | } |
294 | |
295 | /** |
296 | * unregister_chrdev_region() - return a range of device numbers |
297 | * @from: the first in the range of numbers to unregister |
298 | * @count: the number of device numbers to unregister |
299 | * |
300 | * This function will unregister a range of @count device numbers, |
301 | * starting with @from. The caller should normally be the one who |
302 | * allocated those numbers in the first place... |
303 | */ |
304 | void unregister_chrdev_region(dev_t from, unsigned count) |
305 | { |
306 | dev_t to = from + count; |
307 | dev_t n, next; |
308 | |
309 | for (n = from; n < to; n = next) { |
310 | next = MKDEV(MAJOR(n)+1, 0); |
311 | if (next > to) |
312 | next = to; |
313 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); |
314 | } |
315 | } |
316 | |
317 | /** |
318 | * __unregister_chrdev - unregister and destroy a cdev |
319 | * @major: major device number |
320 | * @baseminor: first of the range of minor numbers |
321 | * @count: the number of minor numbers this cdev is occupying |
322 | * @name: name of this range of devices |
323 | * |
324 | * Unregister and destroy the cdev occupying the region described by |
325 | * @major, @baseminor and @count. This function undoes what |
326 | * __register_chrdev() did. |
327 | */ |
328 | void __unregister_chrdev(unsigned int major, unsigned int baseminor, |
329 | unsigned int count, const char *name) |
330 | { |
331 | struct char_device_struct *cd; |
332 | |
333 | cd = __unregister_chrdev_region(major, baseminor, count); |
334 | if (cd && cd->cdev) |
335 | cdev_del(cd->cdev); |
336 | kfree(cd); |
337 | } |
338 | |
339 | static DEFINE_SPINLOCK(cdev_lock); |
340 | |
341 | static struct kobject *cdev_get(struct cdev *p) |
342 | { |
343 | struct module *owner = p->owner; |
344 | struct kobject *kobj; |
345 | |
346 | if (owner && !try_module_get(owner)) |
347 | return NULL; |
348 | kobj = kobject_get(&p->kobj); |
349 | if (!kobj) |
350 | module_put(owner); |
351 | return kobj; |
352 | } |
353 | |
354 | void cdev_put(struct cdev *p) |
355 | { |
356 | if (p) { |
357 | struct module *owner = p->owner; |
358 | kobject_put(&p->kobj); |
359 | module_put(owner); |
360 | } |
361 | } |
362 | |
363 | /* |
364 | * Called every time a character special file is opened |
365 | */ |
366 | static int chrdev_open(struct inode *inode, struct file *filp) |
367 | { |
368 | struct cdev *p; |
369 | struct cdev *new = NULL; |
370 | int ret = 0; |
371 | |
372 | spin_lock(&cdev_lock); |
373 | p = inode->i_cdev; |
374 | if (!p) { |
375 | struct kobject *kobj; |
376 | int idx; |
377 | spin_unlock(&cdev_lock); |
378 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); |
379 | if (!kobj) |
380 | return -ENXIO; |
381 | new = container_of(kobj, struct cdev, kobj); |
382 | spin_lock(&cdev_lock); |
383 | /* Check i_cdev again in case somebody beat us to it while |
384 | we dropped the lock. */ |
385 | p = inode->i_cdev; |
386 | if (!p) { |
387 | inode->i_cdev = p = new; |
388 | list_add(&inode->i_devices, &p->list); |
389 | new = NULL; |
390 | } else if (!cdev_get(p)) |
391 | ret = -ENXIO; |
392 | } else if (!cdev_get(p)) |
393 | ret = -ENXIO; |
394 | spin_unlock(&cdev_lock); |
395 | cdev_put(new); |
396 | if (ret) |
397 | return ret; |
398 | |
399 | ret = -ENXIO; |
400 | filp->f_op = fops_get(p->ops); |
401 | if (!filp->f_op) |
402 | goto out_cdev_put; |
403 | |
404 | if (filp->f_op->open) { |
405 | ret = filp->f_op->open(inode,filp); |
406 | if (ret) |
407 | goto out_cdev_put; |
408 | } |
409 | |
410 | return 0; |
411 | |
412 | out_cdev_put: |
413 | cdev_put(p); |
414 | return ret; |
415 | } |
416 | |
417 | int cdev_index(struct inode *inode) |
418 | { |
419 | int idx; |
420 | struct kobject *kobj; |
421 | |
422 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); |
423 | if (!kobj) |
424 | return -1; |
425 | kobject_put(kobj); |
426 | return idx; |
427 | } |
428 | |
429 | void cd_forget(struct inode *inode) |
430 | { |
431 | spin_lock(&cdev_lock); |
432 | list_del_init(&inode->i_devices); |
433 | inode->i_cdev = NULL; |
434 | spin_unlock(&cdev_lock); |
435 | } |
436 | |
437 | static void cdev_purge(struct cdev *cdev) |
438 | { |
439 | spin_lock(&cdev_lock); |
440 | while (!list_empty(&cdev->list)) { |
441 | struct inode *inode; |
442 | inode = container_of(cdev->list.next, struct inode, i_devices); |
443 | list_del_init(&inode->i_devices); |
444 | inode->i_cdev = NULL; |
445 | } |
446 | spin_unlock(&cdev_lock); |
447 | } |
448 | |
449 | /* |
450 | * Dummy default file-operations: the only thing this does |
451 | * is contain the open that then fills in the correct operations |
452 | * depending on the special file... |
453 | */ |
454 | const struct file_operations def_chr_fops = { |
455 | .open = chrdev_open, |
456 | }; |
457 | |
458 | static struct kobject *exact_match(dev_t dev, int *part, void *data) |
459 | { |
460 | struct cdev *p = data; |
461 | return &p->kobj; |
462 | } |
463 | |
464 | static int exact_lock(dev_t dev, void *data) |
465 | { |
466 | struct cdev *p = data; |
467 | return cdev_get(p) ? 0 : -1; |
468 | } |
469 | |
470 | /** |
471 | * cdev_add() - add a char device to the system |
472 | * @p: the cdev structure for the device |
473 | * @dev: the first device number for which this device is responsible |
474 | * @count: the number of consecutive minor numbers corresponding to this |
475 | * device |
476 | * |
477 | * cdev_add() adds the device represented by @p to the system, making it |
478 | * live immediately. A negative error code is returned on failure. |
479 | */ |
480 | int cdev_add(struct cdev *p, dev_t dev, unsigned count) |
481 | { |
482 | p->dev = dev; |
483 | p->count = count; |
484 | return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); |
485 | } |
486 | |
487 | static void cdev_unmap(dev_t dev, unsigned count) |
488 | { |
489 | kobj_unmap(cdev_map, dev, count); |
490 | } |
491 | |
492 | /** |
493 | * cdev_del() - remove a cdev from the system |
494 | * @p: the cdev structure to be removed |
495 | * |
496 | * cdev_del() removes @p from the system, possibly freeing the structure |
497 | * itself. |
498 | */ |
499 | void cdev_del(struct cdev *p) |
500 | { |
501 | cdev_unmap(p->dev, p->count); |
502 | kobject_put(&p->kobj); |
503 | } |
504 | |
505 | |
506 | static void cdev_default_release(struct kobject *kobj) |
507 | { |
508 | struct cdev *p = container_of(kobj, struct cdev, kobj); |
509 | cdev_purge(p); |
510 | } |
511 | |
512 | static void cdev_dynamic_release(struct kobject *kobj) |
513 | { |
514 | struct cdev *p = container_of(kobj, struct cdev, kobj); |
515 | cdev_purge(p); |
516 | kfree(p); |
517 | } |
518 | |
519 | static struct kobj_type ktype_cdev_default = { |
520 | .release = cdev_default_release, |
521 | }; |
522 | |
523 | static struct kobj_type ktype_cdev_dynamic = { |
524 | .release = cdev_dynamic_release, |
525 | }; |
526 | |
527 | /** |
528 | * cdev_alloc() - allocate a cdev structure |
529 | * |
530 | * Allocates and returns a cdev structure, or NULL on failure. |
531 | */ |
532 | struct cdev *cdev_alloc(void) |
533 | { |
534 | struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); |
535 | if (p) { |
536 | INIT_LIST_HEAD(&p->list); |
537 | kobject_init(&p->kobj, &ktype_cdev_dynamic); |
538 | } |
539 | return p; |
540 | } |
541 | |
542 | /** |
543 | * cdev_init() - initialize a cdev structure |
544 | * @cdev: the structure to initialize |
545 | * @fops: the file_operations for this device |
546 | * |
547 | * Initializes @cdev, remembering @fops, making it ready to add to the |
548 | * system with cdev_add(). |
549 | */ |
550 | void cdev_init(struct cdev *cdev, const struct file_operations *fops) |
551 | { |
552 | memset(cdev, 0, sizeof *cdev); |
553 | INIT_LIST_HEAD(&cdev->list); |
554 | kobject_init(&cdev->kobj, &ktype_cdev_default); |
555 | cdev->ops = fops; |
556 | } |
557 | |
558 | static struct kobject *base_probe(dev_t dev, int *part, void *data) |
559 | { |
560 | if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) |
561 | /* Make old-style 2.4 aliases work */ |
562 | request_module("char-major-%d", MAJOR(dev)); |
563 | return NULL; |
564 | } |
565 | |
566 | void __init chrdev_init(void) |
567 | { |
568 | cdev_map = kobj_map_init(base_probe, &chrdevs_lock); |
569 | bdi_init(&directly_mappable_cdev_bdi); |
570 | } |
571 | |
572 | |
573 | /* Let modules do char dev stuff */ |
574 | EXPORT_SYMBOL(register_chrdev_region); |
575 | EXPORT_SYMBOL(unregister_chrdev_region); |
576 | EXPORT_SYMBOL(alloc_chrdev_region); |
577 | EXPORT_SYMBOL(cdev_init); |
578 | EXPORT_SYMBOL(cdev_alloc); |
579 | EXPORT_SYMBOL(cdev_del); |
580 | EXPORT_SYMBOL(cdev_add); |
581 | EXPORT_SYMBOL(cdev_index); |
582 | EXPORT_SYMBOL(__register_chrdev); |
583 | EXPORT_SYMBOL(__unregister_chrdev); |
584 | EXPORT_SYMBOL(directly_mappable_cdev_bdi); |
585 |
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