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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/smp_lock.h> | |
17 | #include <linux/seq_file.h> | |
18 | ||
19 | #include <linux/kobject.h> | |
20 | #include <linux/kobj_map.h> | |
21 | #include <linux/cdev.h> | |
22 | #include <linux/mutex.h> | |
23 | #include <linux/backing-dev.h> | |
24 | ||
25 | #include "internal.h" | |
26 | ||
27 | /* | |
28 | * capabilities for /dev/mem, /dev/kmem and similar directly mappable character | |
29 | * devices | |
30 | * - permits shared-mmap for read, write and/or exec | |
31 | * - does not permit private mmap in NOMMU mode (can't do COW) | |
32 | * - no readahead or I/O queue unplugging required | |
33 | */ | |
34 | struct backing_dev_info directly_mappable_cdev_bdi = { | |
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() - Register a major number for character devices. | |
242 | * @major: major device number or 0 for dynamic allocation | |
243 | * @name: name of this range of devices | |
244 | * @fops: file operations associated with this devices | |
245 | * | |
246 | * If @major == 0 this functions will dynamically allocate a major and return | |
247 | * its number. | |
248 | * | |
249 | * If @major > 0 this function will attempt to reserve a device with the given | |
250 | * major number and will return zero on success. | |
251 | * | |
252 | * Returns a -ve errno on failure. | |
253 | * | |
254 | * The name of this device has nothing to do with the name of the device in | |
255 | * /dev. It only helps to keep track of the different owners of devices. If | |
256 | * your module name has only one type of devices it's ok to use e.g. the name | |
257 | * of the module here. | |
258 | * | |
259 | * This function registers a range of 256 minor numbers. The first minor number | |
260 | * is 0. | |
261 | */ | |
262 | int register_chrdev(unsigned int major, const char *name, | |
263 | const struct file_operations *fops) | |
264 | { | |
265 | struct char_device_struct *cd; | |
266 | struct cdev *cdev; | |
267 | char *s; | |
268 | int err = -ENOMEM; | |
269 | ||
270 | cd = __register_chrdev_region(major, 0, 256, name); | |
271 | if (IS_ERR(cd)) | |
272 | return PTR_ERR(cd); | |
273 | ||
274 | cdev = cdev_alloc(); | |
275 | if (!cdev) | |
276 | goto out2; | |
277 | ||
278 | cdev->owner = fops->owner; | |
279 | cdev->ops = fops; | |
280 | kobject_set_name(&cdev->kobj, "%s", name); | |
281 | for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) | |
282 | *s = '!'; | |
283 | ||
284 | err = cdev_add(cdev, MKDEV(cd->major, 0), 256); | |
285 | if (err) | |
286 | goto out; | |
287 | ||
288 | cd->cdev = cdev; | |
289 | ||
290 | return major ? 0 : cd->major; | |
291 | out: | |
292 | kobject_put(&cdev->kobj); | |
293 | out2: | |
294 | kfree(__unregister_chrdev_region(cd->major, 0, 256)); | |
295 | return err; | |
296 | } | |
297 | ||
298 | /** | |
299 | * unregister_chrdev_region() - return a range of device numbers | |
300 | * @from: the first in the range of numbers to unregister | |
301 | * @count: the number of device numbers to unregister | |
302 | * | |
303 | * This function will unregister a range of @count device numbers, | |
304 | * starting with @from. The caller should normally be the one who | |
305 | * allocated those numbers in the first place... | |
306 | */ | |
307 | void unregister_chrdev_region(dev_t from, unsigned count) | |
308 | { | |
309 | dev_t to = from + count; | |
310 | dev_t n, next; | |
311 | ||
312 | for (n = from; n < to; n = next) { | |
313 | next = MKDEV(MAJOR(n)+1, 0); | |
314 | if (next > to) | |
315 | next = to; | |
316 | kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); | |
317 | } | |
318 | } | |
319 | ||
320 | void unregister_chrdev(unsigned int major, const char *name) | |
321 | { | |
322 | struct char_device_struct *cd; | |
323 | cd = __unregister_chrdev_region(major, 0, 256); | |
324 | if (cd && cd->cdev) | |
325 | cdev_del(cd->cdev); | |
326 | kfree(cd); | |
327 | } | |
328 | ||
329 | static DEFINE_SPINLOCK(cdev_lock); | |
330 | ||
331 | static struct kobject *cdev_get(struct cdev *p) | |
332 | { | |
333 | struct module *owner = p->owner; | |
334 | struct kobject *kobj; | |
335 | ||
336 | if (owner && !try_module_get(owner)) | |
337 | return NULL; | |
338 | kobj = kobject_get(&p->kobj); | |
339 | if (!kobj) | |
340 | module_put(owner); | |
341 | return kobj; | |
342 | } | |
343 | ||
344 | void cdev_put(struct cdev *p) | |
345 | { | |
346 | if (p) { | |
347 | struct module *owner = p->owner; | |
348 | kobject_put(&p->kobj); | |
349 | module_put(owner); | |
350 | } | |
351 | } | |
352 | ||
353 | /* | |
354 | * Called every time a character special file is opened | |
355 | */ | |
356 | static int chrdev_open(struct inode *inode, struct file *filp) | |
357 | { | |
358 | struct cdev *p; | |
359 | struct cdev *new = NULL; | |
360 | int ret = 0; | |
361 | ||
362 | spin_lock(&cdev_lock); | |
363 | p = inode->i_cdev; | |
364 | if (!p) { | |
365 | struct kobject *kobj; | |
366 | int idx; | |
367 | spin_unlock(&cdev_lock); | |
368 | kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); | |
369 | if (!kobj) | |
370 | return -ENXIO; | |
371 | new = container_of(kobj, struct cdev, kobj); | |
372 | spin_lock(&cdev_lock); | |
373 | /* Check i_cdev again in case somebody beat us to it while | |
374 | we dropped the lock. */ | |
375 | p = inode->i_cdev; | |
376 | if (!p) { | |
377 | inode->i_cdev = p = new; | |
378 | inode->i_cindex = idx; | |
379 | list_add(&inode->i_devices, &p->list); | |
380 | new = NULL; | |
381 | } else if (!cdev_get(p)) | |
382 | ret = -ENXIO; | |
383 | } else if (!cdev_get(p)) | |
384 | ret = -ENXIO; | |
385 | spin_unlock(&cdev_lock); | |
386 | cdev_put(new); | |
387 | if (ret) | |
388 | return ret; | |
389 | ||
390 | ret = -ENXIO; | |
391 | filp->f_op = fops_get(p->ops); | |
392 | if (!filp->f_op) | |
393 | goto out_cdev_put; | |
394 | ||
395 | if (filp->f_op->open) { | |
396 | ret = filp->f_op->open(inode,filp); | |
397 | if (ret) | |
398 | goto out_cdev_put; | |
399 | } | |
400 | ||
401 | return 0; | |
402 | ||
403 | out_cdev_put: | |
404 | cdev_put(p); | |
405 | return ret; | |
406 | } | |
407 | ||
408 | void cd_forget(struct inode *inode) | |
409 | { | |
410 | spin_lock(&cdev_lock); | |
411 | list_del_init(&inode->i_devices); | |
412 | inode->i_cdev = NULL; | |
413 | spin_unlock(&cdev_lock); | |
414 | } | |
415 | ||
416 | static void cdev_purge(struct cdev *cdev) | |
417 | { | |
418 | spin_lock(&cdev_lock); | |
419 | while (!list_empty(&cdev->list)) { | |
420 | struct inode *inode; | |
421 | inode = container_of(cdev->list.next, struct inode, i_devices); | |
422 | list_del_init(&inode->i_devices); | |
423 | inode->i_cdev = NULL; | |
424 | } | |
425 | spin_unlock(&cdev_lock); | |
426 | } | |
427 | ||
428 | /* | |
429 | * Dummy default file-operations: the only thing this does | |
430 | * is contain the open that then fills in the correct operations | |
431 | * depending on the special file... | |
432 | */ | |
433 | const struct file_operations def_chr_fops = { | |
434 | .open = chrdev_open, | |
435 | }; | |
436 | ||
437 | static struct kobject *exact_match(dev_t dev, int *part, void *data) | |
438 | { | |
439 | struct cdev *p = data; | |
440 | return &p->kobj; | |
441 | } | |
442 | ||
443 | static int exact_lock(dev_t dev, void *data) | |
444 | { | |
445 | struct cdev *p = data; | |
446 | return cdev_get(p) ? 0 : -1; | |
447 | } | |
448 | ||
449 | /** | |
450 | * cdev_add() - add a char device to the system | |
451 | * @p: the cdev structure for the device | |
452 | * @dev: the first device number for which this device is responsible | |
453 | * @count: the number of consecutive minor numbers corresponding to this | |
454 | * device | |
455 | * | |
456 | * cdev_add() adds the device represented by @p to the system, making it | |
457 | * live immediately. A negative error code is returned on failure. | |
458 | */ | |
459 | int cdev_add(struct cdev *p, dev_t dev, unsigned count) | |
460 | { | |
461 | p->dev = dev; | |
462 | p->count = count; | |
463 | return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); | |
464 | } | |
465 | ||
466 | static void cdev_unmap(dev_t dev, unsigned count) | |
467 | { | |
468 | kobj_unmap(cdev_map, dev, count); | |
469 | } | |
470 | ||
471 | /** | |
472 | * cdev_del() - remove a cdev from the system | |
473 | * @p: the cdev structure to be removed | |
474 | * | |
475 | * cdev_del() removes @p from the system, possibly freeing the structure | |
476 | * itself. | |
477 | */ | |
478 | void cdev_del(struct cdev *p) | |
479 | { | |
480 | cdev_unmap(p->dev, p->count); | |
481 | kobject_put(&p->kobj); | |
482 | } | |
483 | ||
484 | ||
485 | static void cdev_default_release(struct kobject *kobj) | |
486 | { | |
487 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
488 | cdev_purge(p); | |
489 | } | |
490 | ||
491 | static void cdev_dynamic_release(struct kobject *kobj) | |
492 | { | |
493 | struct cdev *p = container_of(kobj, struct cdev, kobj); | |
494 | cdev_purge(p); | |
495 | kfree(p); | |
496 | } | |
497 | ||
498 | static struct kobj_type ktype_cdev_default = { | |
499 | .release = cdev_default_release, | |
500 | }; | |
501 | ||
502 | static struct kobj_type ktype_cdev_dynamic = { | |
503 | .release = cdev_dynamic_release, | |
504 | }; | |
505 | ||
506 | /** | |
507 | * cdev_alloc() - allocate a cdev structure | |
508 | * | |
509 | * Allocates and returns a cdev structure, or NULL on failure. | |
510 | */ | |
511 | struct cdev *cdev_alloc(void) | |
512 | { | |
513 | struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); | |
514 | if (p) { | |
515 | INIT_LIST_HEAD(&p->list); | |
516 | kobject_init(&p->kobj, &ktype_cdev_dynamic); | |
517 | } | |
518 | return p; | |
519 | } | |
520 | ||
521 | /** | |
522 | * cdev_init() - initialize a cdev structure | |
523 | * @cdev: the structure to initialize | |
524 | * @fops: the file_operations for this device | |
525 | * | |
526 | * Initializes @cdev, remembering @fops, making it ready to add to the | |
527 | * system with cdev_add(). | |
528 | */ | |
529 | void cdev_init(struct cdev *cdev, const struct file_operations *fops) | |
530 | { | |
531 | memset(cdev, 0, sizeof *cdev); | |
532 | INIT_LIST_HEAD(&cdev->list); | |
533 | kobject_init(&cdev->kobj, &ktype_cdev_default); | |
534 | cdev->ops = fops; | |
535 | } | |
536 | ||
537 | static struct kobject *base_probe(dev_t dev, int *part, void *data) | |
538 | { | |
539 | if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) | |
540 | /* Make old-style 2.4 aliases work */ | |
541 | request_module("char-major-%d", MAJOR(dev)); | |
542 | return NULL; | |
543 | } | |
544 | ||
545 | void __init chrdev_init(void) | |
546 | { | |
547 | cdev_map = kobj_map_init(base_probe, &chrdevs_lock); | |
548 | bdi_init(&directly_mappable_cdev_bdi); | |
549 | } | |
550 | ||
551 | ||
552 | /* Let modules do char dev stuff */ | |
553 | EXPORT_SYMBOL(register_chrdev_region); | |
554 | EXPORT_SYMBOL(unregister_chrdev_region); | |
555 | EXPORT_SYMBOL(alloc_chrdev_region); | |
556 | EXPORT_SYMBOL(cdev_init); | |
557 | EXPORT_SYMBOL(cdev_alloc); | |
558 | EXPORT_SYMBOL(cdev_del); | |
559 | EXPORT_SYMBOL(cdev_add); | |
560 | EXPORT_SYMBOL(register_chrdev); | |
561 | EXPORT_SYMBOL(unregister_chrdev); | |
562 | EXPORT_SYMBOL(directly_mappable_cdev_bdi); |