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