Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * linux/fs/char_dev.c
4 : *
5 : * Copyright (C) 1991, 1992 Linus Torvalds
6 : */
7 :
8 : #include <linux/init.h>
9 : #include <linux/fs.h>
10 : #include <linux/kdev_t.h>
11 : #include <linux/slab.h>
12 : #include <linux/string.h>
13 :
14 : #include <linux/major.h>
15 : #include <linux/errno.h>
16 : #include <linux/module.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 : #include <linux/tty.h>
25 :
26 : #include "internal.h"
27 :
28 : static struct kobj_map *cdev_map;
29 :
30 : static DEFINE_MUTEX(chrdevs_lock);
31 :
32 : #define CHRDEV_MAJOR_HASH_SIZE 255
33 :
34 : static struct char_device_struct {
35 : struct char_device_struct *next;
36 : unsigned int major;
37 : unsigned int baseminor;
38 : int minorct;
39 : char name[64];
40 : struct cdev *cdev; /* will die */
41 : } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
42 :
43 : /* index in the above */
44 : static inline int major_to_index(unsigned major)
45 : {
46 13 : return major % CHRDEV_MAJOR_HASH_SIZE;
47 : }
48 :
49 : #ifdef CONFIG_PROC_FS
50 :
51 0 : void chrdev_show(struct seq_file *f, off_t offset)
52 : {
53 : struct char_device_struct *cd;
54 :
55 0 : mutex_lock(&chrdevs_lock);
56 0 : for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {
57 0 : if (cd->major == offset)
58 0 : seq_printf(f, "%3d %s\n", cd->major, cd->name);
59 : }
60 0 : mutex_unlock(&chrdevs_lock);
61 0 : }
62 :
63 : #endif /* CONFIG_PROC_FS */
64 :
65 0 : static int find_dynamic_major(void)
66 : {
67 : int i;
68 : struct char_device_struct *cd;
69 :
70 0 : for (i = ARRAY_SIZE(chrdevs)-1; i >= CHRDEV_MAJOR_DYN_END; i--) {
71 0 : if (chrdevs[i] == NULL)
72 : return i;
73 : }
74 :
75 0 : for (i = CHRDEV_MAJOR_DYN_EXT_START;
76 0 : i >= CHRDEV_MAJOR_DYN_EXT_END; i--) {
77 0 : for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)
78 0 : if (cd->major == i)
79 : break;
80 :
81 0 : if (cd == NULL)
82 : return i;
83 : }
84 :
85 : return -EBUSY;
86 : }
87 :
88 : /*
89 : * Register a single major with a specified minor range.
90 : *
91 : * If major == 0 this function will dynamically allocate an unused major.
92 : * If major > 0 this function will attempt to reserve the range of minors
93 : * with given major.
94 : *
95 : */
96 : static struct char_device_struct *
97 13 : __register_chrdev_region(unsigned int major, unsigned int baseminor,
98 : int minorct, const char *name)
99 : {
100 13 : struct char_device_struct *cd, *curr, *prev = NULL;
101 : int ret;
102 : int i;
103 :
104 13 : if (major >= CHRDEV_MAJOR_MAX) {
105 0 : pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
106 : name, major, CHRDEV_MAJOR_MAX-1);
107 0 : return ERR_PTR(-EINVAL);
108 : }
109 :
110 13 : if (minorct > MINORMASK + 1 - baseminor) {
111 0 : pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
112 : name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
113 0 : return ERR_PTR(-EINVAL);
114 : }
115 :
116 13 : cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
117 13 : if (cd == NULL)
118 : return ERR_PTR(-ENOMEM);
119 :
120 13 : mutex_lock(&chrdevs_lock);
121 :
122 13 : if (major == 0) {
123 0 : ret = find_dynamic_major();
124 0 : if (ret < 0) {
125 0 : pr_err("CHRDEV \"%s\" dynamic allocation region is full\n",
126 : name);
127 0 : goto out;
128 : }
129 0 : major = ret;
130 : }
131 :
132 13 : ret = -EBUSY;
133 13 : i = major_to_index(major);
134 16 : for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
135 3 : if (curr->major < major)
136 0 : continue;
137 :
138 3 : if (curr->major > major)
139 : break;
140 :
141 3 : if (curr->baseminor + curr->minorct <= baseminor)
142 3 : continue;
143 :
144 0 : if (curr->baseminor >= baseminor + minorct)
145 : break;
146 :
147 : goto out;
148 : }
149 :
150 13 : cd->major = major;
151 13 : cd->baseminor = baseminor;
152 13 : cd->minorct = minorct;
153 26 : strscpy(cd->name, name, sizeof(cd->name));
154 :
155 13 : if (!prev) {
156 11 : cd->next = curr;
157 11 : chrdevs[i] = cd;
158 : } else {
159 2 : cd->next = prev->next;
160 2 : prev->next = cd;
161 : }
162 :
163 13 : mutex_unlock(&chrdevs_lock);
164 13 : return cd;
165 : out:
166 0 : mutex_unlock(&chrdevs_lock);
167 0 : kfree(cd);
168 0 : return ERR_PTR(ret);
169 : }
170 :
171 : static struct char_device_struct *
172 0 : __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
173 : {
174 0 : struct char_device_struct *cd = NULL, **cp;
175 0 : int i = major_to_index(major);
176 :
177 0 : mutex_lock(&chrdevs_lock);
178 0 : for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
179 0 : if ((*cp)->major == major &&
180 0 : (*cp)->baseminor == baseminor &&
181 0 : (*cp)->minorct == minorct)
182 : break;
183 0 : if (*cp) {
184 0 : cd = *cp;
185 0 : *cp = cd->next;
186 : }
187 0 : mutex_unlock(&chrdevs_lock);
188 0 : return cd;
189 : }
190 :
191 : /**
192 : * register_chrdev_region() - register a range of device numbers
193 : * @from: the first in the desired range of device numbers; must include
194 : * the major number.
195 : * @count: the number of consecutive device numbers required
196 : * @name: the name of the device or driver.
197 : *
198 : * Return value is zero on success, a negative error code on failure.
199 : */
200 9 : int register_chrdev_region(dev_t from, unsigned count, const char *name)
201 : {
202 : struct char_device_struct *cd;
203 9 : dev_t to = from + count;
204 : dev_t n, next;
205 :
206 27 : for (n = from; n < to; n = next) {
207 9 : next = MKDEV(MAJOR(n)+1, 0);
208 9 : if (next > to)
209 7 : next = to;
210 9 : cd = __register_chrdev_region(MAJOR(n), MINOR(n),
211 9 : next - n, name);
212 9 : if (IS_ERR(cd))
213 : goto fail;
214 : }
215 : return 0;
216 : fail:
217 : to = n;
218 0 : for (n = from; n < to; n = next) {
219 0 : next = MKDEV(MAJOR(n)+1, 0);
220 0 : kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
221 : }
222 0 : return PTR_ERR(cd);
223 : }
224 :
225 : /**
226 : * alloc_chrdev_region() - register a range of char device numbers
227 : * @dev: output parameter for first assigned number
228 : * @baseminor: first of the requested range of minor numbers
229 : * @count: the number of minor numbers required
230 : * @name: the name of the associated device or driver
231 : *
232 : * Allocates a range of char device numbers. The major number will be
233 : * chosen dynamically, and returned (along with the first minor number)
234 : * in @dev. Returns zero or a negative error code.
235 : */
236 0 : int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
237 : const char *name)
238 : {
239 : struct char_device_struct *cd;
240 0 : cd = __register_chrdev_region(0, baseminor, count, name);
241 0 : if (IS_ERR(cd))
242 0 : return PTR_ERR(cd);
243 0 : *dev = MKDEV(cd->major, cd->baseminor);
244 0 : return 0;
245 : }
246 :
247 : /**
248 : * __register_chrdev() - create and register a cdev occupying a range of minors
249 : * @major: major device number or 0 for dynamic allocation
250 : * @baseminor: first of the requested range of minor numbers
251 : * @count: the number of minor numbers required
252 : * @name: name of this range of devices
253 : * @fops: file operations associated with this devices
254 : *
255 : * If @major == 0 this functions will dynamically allocate a major and return
256 : * its number.
257 : *
258 : * If @major > 0 this function will attempt to reserve a device with the given
259 : * major number and will return zero on success.
260 : *
261 : * Returns a -ve errno on failure.
262 : *
263 : * The name of this device has nothing to do with the name of the device in
264 : * /dev. It only helps to keep track of the different owners of devices. If
265 : * your module name has only one type of devices it's ok to use e.g. the name
266 : * of the module here.
267 : */
268 4 : int __register_chrdev(unsigned int major, unsigned int baseminor,
269 : unsigned int count, const char *name,
270 : const struct file_operations *fops)
271 : {
272 : struct char_device_struct *cd;
273 : struct cdev *cdev;
274 4 : int err = -ENOMEM;
275 :
276 4 : cd = __register_chrdev_region(major, baseminor, count, name);
277 4 : if (IS_ERR(cd))
278 0 : return PTR_ERR(cd);
279 :
280 4 : cdev = cdev_alloc();
281 4 : if (!cdev)
282 : goto out2;
283 :
284 4 : cdev->owner = fops->owner;
285 4 : cdev->ops = fops;
286 4 : kobject_set_name(&cdev->kobj, "%s", name);
287 :
288 4 : err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
289 4 : if (err)
290 : goto out;
291 :
292 4 : cd->cdev = cdev;
293 :
294 4 : return major ? 0 : cd->major;
295 : out:
296 0 : kobject_put(&cdev->kobj);
297 : out2:
298 0 : kfree(__unregister_chrdev_region(cd->major, baseminor, count));
299 0 : return err;
300 : }
301 :
302 : /**
303 : * unregister_chrdev_region() - unregister a range of device numbers
304 : * @from: the first in the range of numbers to unregister
305 : * @count: the number of device numbers to unregister
306 : *
307 : * This function will unregister a range of @count device numbers,
308 : * starting with @from. The caller should normally be the one who
309 : * allocated those numbers in the first place...
310 : */
311 0 : void unregister_chrdev_region(dev_t from, unsigned count)
312 : {
313 0 : dev_t to = from + count;
314 : dev_t n, next;
315 :
316 0 : for (n = from; n < to; n = next) {
317 0 : next = MKDEV(MAJOR(n)+1, 0);
318 0 : if (next > to)
319 0 : next = to;
320 0 : kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
321 : }
322 0 : }
323 :
324 : /**
325 : * __unregister_chrdev - unregister and destroy a cdev
326 : * @major: major device number
327 : * @baseminor: first of the range of minor numbers
328 : * @count: the number of minor numbers this cdev is occupying
329 : * @name: name of this range of devices
330 : *
331 : * Unregister and destroy the cdev occupying the region described by
332 : * @major, @baseminor and @count. This function undoes what
333 : * __register_chrdev() did.
334 : */
335 0 : void __unregister_chrdev(unsigned int major, unsigned int baseminor,
336 : unsigned int count, const char *name)
337 : {
338 : struct char_device_struct *cd;
339 :
340 0 : cd = __unregister_chrdev_region(major, baseminor, count);
341 0 : if (cd && cd->cdev)
342 0 : cdev_del(cd->cdev);
343 0 : kfree(cd);
344 0 : }
345 :
346 : static DEFINE_SPINLOCK(cdev_lock);
347 :
348 : static struct kobject *cdev_get(struct cdev *p)
349 : {
350 0 : struct module *owner = p->owner;
351 : struct kobject *kobj;
352 :
353 : if (owner && !try_module_get(owner))
354 : return NULL;
355 0 : kobj = kobject_get_unless_zero(&p->kobj);
356 : if (!kobj)
357 : module_put(owner);
358 : return kobj;
359 : }
360 :
361 0 : void cdev_put(struct cdev *p)
362 : {
363 0 : if (p) {
364 0 : struct module *owner = p->owner;
365 0 : kobject_put(&p->kobj);
366 0 : module_put(owner);
367 : }
368 0 : }
369 :
370 : /*
371 : * Called every time a character special file is opened
372 : */
373 0 : static int chrdev_open(struct inode *inode, struct file *filp)
374 : {
375 : const struct file_operations *fops;
376 : struct cdev *p;
377 0 : struct cdev *new = NULL;
378 0 : int ret = 0;
379 :
380 0 : spin_lock(&cdev_lock);
381 0 : p = inode->i_cdev;
382 0 : if (!p) {
383 : struct kobject *kobj;
384 : int idx;
385 0 : spin_unlock(&cdev_lock);
386 0 : kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
387 0 : if (!kobj)
388 0 : return -ENXIO;
389 0 : new = container_of(kobj, struct cdev, kobj);
390 0 : spin_lock(&cdev_lock);
391 : /* Check i_cdev again in case somebody beat us to it while
392 : we dropped the lock. */
393 0 : p = inode->i_cdev;
394 0 : if (!p) {
395 0 : inode->i_cdev = p = new;
396 0 : list_add(&inode->i_devices, &p->list);
397 0 : new = NULL;
398 0 : } else if (!cdev_get(p))
399 0 : ret = -ENXIO;
400 0 : } else if (!cdev_get(p))
401 0 : ret = -ENXIO;
402 0 : spin_unlock(&cdev_lock);
403 0 : cdev_put(new);
404 0 : if (ret)
405 : return ret;
406 :
407 0 : ret = -ENXIO;
408 0 : fops = fops_get(p->ops);
409 0 : if (!fops)
410 : goto out_cdev_put;
411 :
412 0 : replace_fops(filp, fops);
413 0 : if (filp->f_op->open) {
414 0 : ret = filp->f_op->open(inode, filp);
415 0 : if (ret)
416 : goto out_cdev_put;
417 : }
418 :
419 : return 0;
420 :
421 : out_cdev_put:
422 : cdev_put(p);
423 : return ret;
424 : }
425 :
426 0 : void cd_forget(struct inode *inode)
427 : {
428 0 : spin_lock(&cdev_lock);
429 0 : list_del_init(&inode->i_devices);
430 0 : inode->i_cdev = NULL;
431 0 : inode->i_mapping = &inode->i_data;
432 0 : spin_unlock(&cdev_lock);
433 0 : }
434 :
435 : static void cdev_purge(struct cdev *cdev)
436 : {
437 : spin_lock(&cdev_lock);
438 0 : while (!list_empty(&cdev->list)) {
439 : struct inode *inode;
440 0 : inode = container_of(cdev->list.next, struct inode, i_devices);
441 0 : list_del_init(&inode->i_devices);
442 0 : inode->i_cdev = NULL;
443 : }
444 0 : spin_unlock(&cdev_lock);
445 : }
446 :
447 : /*
448 : * Dummy default file-operations: the only thing this does
449 : * is contain the open that then fills in the correct operations
450 : * depending on the special file...
451 : */
452 : const struct file_operations def_chr_fops = {
453 : .open = chrdev_open,
454 : .llseek = noop_llseek,
455 : };
456 :
457 0 : static struct kobject *exact_match(dev_t dev, int *part, void *data)
458 : {
459 0 : struct cdev *p = data;
460 0 : return &p->kobj;
461 : }
462 :
463 0 : static int exact_lock(dev_t dev, void *data)
464 : {
465 0 : struct cdev *p = data;
466 0 : return cdev_get(p) ? 0 : -1;
467 : }
468 :
469 : /**
470 : * cdev_add() - add a char device to the system
471 : * @p: the cdev structure for the device
472 : * @dev: the first device number for which this device is responsible
473 : * @count: the number of consecutive minor numbers corresponding to this
474 : * device
475 : *
476 : * cdev_add() adds the device represented by @p to the system, making it
477 : * live immediately. A negative error code is returned on failure.
478 : */
479 12 : int cdev_add(struct cdev *p, dev_t dev, unsigned count)
480 : {
481 : int error;
482 :
483 12 : p->dev = dev;
484 12 : p->count = count;
485 :
486 12 : if (WARN_ON(dev == WHITEOUT_DEV)) {
487 : error = -EBUSY;
488 : goto err;
489 : }
490 :
491 12 : error = kobj_map(cdev_map, dev, count, NULL,
492 : exact_match, exact_lock, p);
493 12 : if (error)
494 : goto err;
495 :
496 12 : kobject_get(p->kobj.parent);
497 :
498 12 : return 0;
499 :
500 : err:
501 0 : kfree_const(p->kobj.name);
502 0 : p->kobj.name = NULL;
503 0 : return error;
504 : }
505 :
506 : /**
507 : * cdev_set_parent() - set the parent kobject for a char device
508 : * @p: the cdev structure
509 : * @kobj: the kobject to take a reference to
510 : *
511 : * cdev_set_parent() sets a parent kobject which will be referenced
512 : * appropriately so the parent is not freed before the cdev. This
513 : * should be called before cdev_add.
514 : */
515 0 : void cdev_set_parent(struct cdev *p, struct kobject *kobj)
516 : {
517 0 : WARN_ON(!kobj->state_initialized);
518 0 : p->kobj.parent = kobj;
519 0 : }
520 :
521 : /**
522 : * cdev_device_add() - add a char device and it's corresponding
523 : * struct device, linkink
524 : * @dev: the device structure
525 : * @cdev: the cdev structure
526 : *
527 : * cdev_device_add() adds the char device represented by @cdev to the system,
528 : * just as cdev_add does. It then adds @dev to the system using device_add
529 : * The dev_t for the char device will be taken from the struct device which
530 : * needs to be initialized first. This helper function correctly takes a
531 : * reference to the parent device so the parent will not get released until
532 : * all references to the cdev are released.
533 : *
534 : * This helper uses dev->devt for the device number. If it is not set
535 : * it will not add the cdev and it will be equivalent to device_add.
536 : *
537 : * This function should be used whenever the struct cdev and the
538 : * struct device are members of the same structure whose lifetime is
539 : * managed by the struct device.
540 : *
541 : * NOTE: Callers must assume that userspace was able to open the cdev and
542 : * can call cdev fops callbacks at any time, even if this function fails.
543 : */
544 0 : int cdev_device_add(struct cdev *cdev, struct device *dev)
545 : {
546 0 : int rc = 0;
547 :
548 0 : if (dev->devt) {
549 0 : cdev_set_parent(cdev, &dev->kobj);
550 :
551 0 : rc = cdev_add(cdev, dev->devt, 1);
552 0 : if (rc)
553 : return rc;
554 : }
555 :
556 0 : rc = device_add(dev);
557 0 : if (rc && dev->devt)
558 0 : cdev_del(cdev);
559 :
560 : return rc;
561 : }
562 :
563 : /**
564 : * cdev_device_del() - inverse of cdev_device_add
565 : * @dev: the device structure
566 : * @cdev: the cdev structure
567 : *
568 : * cdev_device_del() is a helper function to call cdev_del and device_del.
569 : * It should be used whenever cdev_device_add is used.
570 : *
571 : * If dev->devt is not set it will not remove the cdev and will be equivalent
572 : * to device_del.
573 : *
574 : * NOTE: This guarantees that associated sysfs callbacks are not running
575 : * or runnable, however any cdevs already open will remain and their fops
576 : * will still be callable even after this function returns.
577 : */
578 0 : void cdev_device_del(struct cdev *cdev, struct device *dev)
579 : {
580 0 : device_del(dev);
581 0 : if (dev->devt)
582 0 : cdev_del(cdev);
583 0 : }
584 :
585 : static void cdev_unmap(dev_t dev, unsigned count)
586 : {
587 0 : kobj_unmap(cdev_map, dev, count);
588 : }
589 :
590 : /**
591 : * cdev_del() - remove a cdev from the system
592 : * @p: the cdev structure to be removed
593 : *
594 : * cdev_del() removes @p from the system, possibly freeing the structure
595 : * itself.
596 : *
597 : * NOTE: This guarantees that cdev device will no longer be able to be
598 : * opened, however any cdevs already open will remain and their fops will
599 : * still be callable even after cdev_del returns.
600 : */
601 0 : void cdev_del(struct cdev *p)
602 : {
603 0 : cdev_unmap(p->dev, p->count);
604 0 : kobject_put(&p->kobj);
605 0 : }
606 :
607 :
608 0 : static void cdev_default_release(struct kobject *kobj)
609 : {
610 0 : struct cdev *p = container_of(kobj, struct cdev, kobj);
611 0 : struct kobject *parent = kobj->parent;
612 :
613 0 : cdev_purge(p);
614 0 : kobject_put(parent);
615 0 : }
616 :
617 0 : static void cdev_dynamic_release(struct kobject *kobj)
618 : {
619 0 : struct cdev *p = container_of(kobj, struct cdev, kobj);
620 0 : struct kobject *parent = kobj->parent;
621 :
622 0 : cdev_purge(p);
623 0 : kfree(p);
624 0 : kobject_put(parent);
625 0 : }
626 :
627 : static struct kobj_type ktype_cdev_default = {
628 : .release = cdev_default_release,
629 : };
630 :
631 : static struct kobj_type ktype_cdev_dynamic = {
632 : .release = cdev_dynamic_release,
633 : };
634 :
635 : /**
636 : * cdev_alloc() - allocate a cdev structure
637 : *
638 : * Allocates and returns a cdev structure, or NULL on failure.
639 : */
640 9 : struct cdev *cdev_alloc(void)
641 : {
642 9 : struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
643 9 : if (p) {
644 18 : INIT_LIST_HEAD(&p->list);
645 9 : kobject_init(&p->kobj, &ktype_cdev_dynamic);
646 : }
647 9 : return p;
648 : }
649 :
650 : /**
651 : * cdev_init() - initialize a cdev structure
652 : * @cdev: the structure to initialize
653 : * @fops: the file_operations for this device
654 : *
655 : * Initializes @cdev, remembering @fops, making it ready to add to the
656 : * system with cdev_add().
657 : */
658 3 : void cdev_init(struct cdev *cdev, const struct file_operations *fops)
659 : {
660 6 : memset(cdev, 0, sizeof *cdev);
661 6 : INIT_LIST_HEAD(&cdev->list);
662 3 : kobject_init(&cdev->kobj, &ktype_cdev_default);
663 3 : cdev->ops = fops;
664 3 : }
665 :
666 0 : static struct kobject *base_probe(dev_t dev, int *part, void *data)
667 : {
668 0 : if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
669 : /* Make old-style 2.4 aliases work */
670 : request_module("char-major-%d", MAJOR(dev));
671 0 : return NULL;
672 : }
673 :
674 1 : void __init chrdev_init(void)
675 : {
676 1 : cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
677 1 : }
678 :
679 :
680 : /* Let modules do char dev stuff */
681 : EXPORT_SYMBOL(register_chrdev_region);
682 : EXPORT_SYMBOL(unregister_chrdev_region);
683 : EXPORT_SYMBOL(alloc_chrdev_region);
684 : EXPORT_SYMBOL(cdev_init);
685 : EXPORT_SYMBOL(cdev_alloc);
686 : EXPORT_SYMBOL(cdev_del);
687 : EXPORT_SYMBOL(cdev_add);
688 : EXPORT_SYMBOL(cdev_set_parent);
689 : EXPORT_SYMBOL(cdev_device_add);
690 : EXPORT_SYMBOL(cdev_device_del);
691 : EXPORT_SYMBOL(__register_chrdev);
692 : EXPORT_SYMBOL(__unregister_chrdev);
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