4 * Copyright (C) 1991, 1992 Linus Torvalds
7 #include <linux/init.h>
9 #include <linux/kdev_t.h>
10 #include <linux/slab.h>
11 #include <linux/string.h>
13 #include <linux/major.h>
14 #include <linux/errno.h>
15 #include <linux/module.h>
16 #include <linux/seq_file.h>
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>
27 static struct kobj_map *cdev_map;
29 static DEFINE_MUTEX(chrdevs_lock);
31 static struct char_device_struct {
32 struct char_device_struct *next;
34 unsigned int baseminor;
37 struct cdev *cdev; /* will die */
38 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
40 /* index in the above */
41 static inline int major_to_index(unsigned major)
43 return major % CHRDEV_MAJOR_HASH_SIZE;
48 void chrdev_show(struct seq_file *f, off_t offset)
50 struct char_device_struct *cd;
52 if (offset < CHRDEV_MAJOR_HASH_SIZE) {
53 mutex_lock(&chrdevs_lock);
54 for (cd = chrdevs[offset]; cd; cd = cd->next)
55 seq_printf(f, "%3d %s\n", cd->major, cd->name);
56 mutex_unlock(&chrdevs_lock);
60 #endif /* CONFIG_PROC_FS */
63 * Register a single major with a specified minor range.
65 * If major == 0 this functions will dynamically allocate a major and return
68 * If major > 0 this function will attempt to reserve the passed range of
69 * minors and will return zero on success.
71 * Returns a -ve errno on failure.
73 static struct char_device_struct *
74 __register_chrdev_region(unsigned int major, unsigned int baseminor,
75 int minorct, const char *name)
77 struct char_device_struct *cd, **cp;
81 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
83 return ERR_PTR(-ENOMEM);
85 mutex_lock(&chrdevs_lock);
89 for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
90 if (chrdevs[i] == NULL)
94 if (i < CHRDEV_MAJOR_DYN_END)
95 pr_warn("CHRDEV \"%s\" major number %d goes below the dynamic allocation range\n",
106 cd->baseminor = baseminor;
107 cd->minorct = minorct;
108 strlcpy(cd->name, name, sizeof(cd->name));
110 i = major_to_index(major);
112 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
113 if ((*cp)->major > major ||
114 ((*cp)->major == major &&
115 (((*cp)->baseminor >= baseminor) ||
116 ((*cp)->baseminor + (*cp)->minorct > baseminor))))
119 /* Check for overlapping minor ranges. */
120 if (*cp && (*cp)->major == major) {
121 int old_min = (*cp)->baseminor;
122 int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
123 int new_min = baseminor;
124 int new_max = baseminor + minorct - 1;
126 /* New driver overlaps from the left. */
127 if (new_max >= old_min && new_max <= old_max) {
132 /* New driver overlaps from the right. */
133 if (new_min <= old_max && new_min >= old_min) {
138 if (new_min < old_min && new_max > old_max) {
147 mutex_unlock(&chrdevs_lock);
150 mutex_unlock(&chrdevs_lock);
155 static struct char_device_struct *
156 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
158 struct char_device_struct *cd = NULL, **cp;
159 int i = major_to_index(major);
161 mutex_lock(&chrdevs_lock);
162 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
163 if ((*cp)->major == major &&
164 (*cp)->baseminor == baseminor &&
165 (*cp)->minorct == minorct)
171 mutex_unlock(&chrdevs_lock);
176 * register_chrdev_region() - register a range of device numbers
177 * @from: the first in the desired range of device numbers; must include
179 * @count: the number of consecutive device numbers required
180 * @name: the name of the device or driver.
182 * Return value is zero on success, a negative error code on failure.
184 int register_chrdev_region(dev_t from, unsigned count, const char *name)
186 struct char_device_struct *cd;
187 dev_t to = from + count;
190 for (n = from; n < to; n = next) {
191 next = MKDEV(MAJOR(n)+1, 0);
194 cd = __register_chrdev_region(MAJOR(n), MINOR(n),
202 for (n = from; n < to; n = next) {
203 next = MKDEV(MAJOR(n)+1, 0);
204 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
210 * alloc_chrdev_region() - register a range of char device numbers
211 * @dev: output parameter for first assigned number
212 * @baseminor: first of the requested range of minor numbers
213 * @count: the number of minor numbers required
214 * @name: the name of the associated device or driver
216 * Allocates a range of char device numbers. The major number will be
217 * chosen dynamically, and returned (along with the first minor number)
218 * in @dev. Returns zero or a negative error code.
220 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
223 struct char_device_struct *cd;
224 cd = __register_chrdev_region(0, baseminor, count, name);
227 *dev = MKDEV(cd->major, cd->baseminor);
232 * __register_chrdev() - create and register a cdev occupying a range of minors
233 * @major: major device number or 0 for dynamic allocation
234 * @baseminor: first of the requested range of minor numbers
235 * @count: the number of minor numbers required
236 * @name: name of this range of devices
237 * @fops: file operations associated with this devices
239 * If @major == 0 this functions will dynamically allocate a major and return
242 * If @major > 0 this function will attempt to reserve a device with the given
243 * major number and will return zero on success.
245 * Returns a -ve errno on failure.
247 * The name of this device has nothing to do with the name of the device in
248 * /dev. It only helps to keep track of the different owners of devices. If
249 * your module name has only one type of devices it's ok to use e.g. the name
250 * of the module here.
252 int __register_chrdev(unsigned int major, unsigned int baseminor,
253 unsigned int count, const char *name,
254 const struct file_operations *fops)
256 struct char_device_struct *cd;
260 cd = __register_chrdev_region(major, baseminor, count, name);
268 cdev->owner = fops->owner;
270 kobject_set_name(&cdev->kobj, "%s", name);
272 err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
278 return major ? 0 : cd->major;
280 kobject_put(&cdev->kobj);
282 kfree(__unregister_chrdev_region(cd->major, baseminor, count));
287 * unregister_chrdev_region() - unregister a range of device numbers
288 * @from: the first in the range of numbers to unregister
289 * @count: the number of device numbers to unregister
291 * This function will unregister a range of @count device numbers,
292 * starting with @from. The caller should normally be the one who
293 * allocated those numbers in the first place...
295 void unregister_chrdev_region(dev_t from, unsigned count)
297 dev_t to = from + count;
300 for (n = from; n < to; n = next) {
301 next = MKDEV(MAJOR(n)+1, 0);
304 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
309 * __unregister_chrdev - unregister and destroy a cdev
310 * @major: major device number
311 * @baseminor: first of the range of minor numbers
312 * @count: the number of minor numbers this cdev is occupying
313 * @name: name of this range of devices
315 * Unregister and destroy the cdev occupying the region described by
316 * @major, @baseminor and @count. This function undoes what
317 * __register_chrdev() did.
319 void __unregister_chrdev(unsigned int major, unsigned int baseminor,
320 unsigned int count, const char *name)
322 struct char_device_struct *cd;
324 cd = __unregister_chrdev_region(major, baseminor, count);
330 static DEFINE_SPINLOCK(cdev_lock);
332 static struct kobject *cdev_get(struct cdev *p)
334 struct module *owner = p->owner;
335 struct kobject *kobj;
337 if (owner && !try_module_get(owner))
339 kobj = kobject_get_unless_zero(&p->kobj);
345 void cdev_put(struct cdev *p)
348 struct module *owner = p->owner;
349 kobject_put(&p->kobj);
355 * Called every time a character special file is opened
357 static int chrdev_open(struct inode *inode, struct file *filp)
359 const struct file_operations *fops;
361 struct cdev *new = NULL;
364 spin_lock(&cdev_lock);
367 struct kobject *kobj;
369 spin_unlock(&cdev_lock);
370 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
373 new = container_of(kobj, struct cdev, kobj);
374 spin_lock(&cdev_lock);
375 /* Check i_cdev again in case somebody beat us to it while
376 we dropped the lock. */
379 inode->i_cdev = p = new;
380 list_add(&inode->i_devices, &p->list);
382 } else if (!cdev_get(p))
384 } else if (!cdev_get(p))
386 spin_unlock(&cdev_lock);
392 fops = fops_get(p->ops);
396 replace_fops(filp, fops);
397 if (filp->f_op->open) {
398 ret = filp->f_op->open(inode, filp);
410 void cd_forget(struct inode *inode)
412 spin_lock(&cdev_lock);
413 list_del_init(&inode->i_devices);
414 inode->i_cdev = NULL;
415 inode->i_mapping = &inode->i_data;
416 spin_unlock(&cdev_lock);
419 static void cdev_purge(struct cdev *cdev)
421 spin_lock(&cdev_lock);
422 while (!list_empty(&cdev->list)) {
424 inode = container_of(cdev->list.next, struct inode, i_devices);
425 list_del_init(&inode->i_devices);
426 inode->i_cdev = NULL;
428 spin_unlock(&cdev_lock);
432 * Dummy default file-operations: the only thing this does
433 * is contain the open that then fills in the correct operations
434 * depending on the special file...
436 const struct file_operations def_chr_fops = {
438 .llseek = noop_llseek,
441 static struct kobject *exact_match(dev_t dev, int *part, void *data)
443 struct cdev *p = data;
447 static int exact_lock(dev_t dev, void *data)
449 struct cdev *p = data;
450 return cdev_get(p) ? 0 : -1;
454 * cdev_add() - add a char device to the system
455 * @p: the cdev structure for the device
456 * @dev: the first device number for which this device is responsible
457 * @count: the number of consecutive minor numbers corresponding to this
460 * cdev_add() adds the device represented by @p to the system, making it
461 * live immediately. A negative error code is returned on failure.
463 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
470 error = kobj_map(cdev_map, dev, count, NULL,
471 exact_match, exact_lock, p);
475 kobject_get(p->kobj.parent);
481 * cdev_set_parent() - set the parent kobject for a char device
482 * @p: the cdev structure
483 * @kobj: the kobject to take a reference to
485 * cdev_set_parent() sets a parent kobject which will be referenced
486 * appropriately so the parent is not freed before the cdev. This
487 * should be called before cdev_add.
489 void cdev_set_parent(struct cdev *p, struct kobject *kobj)
491 WARN_ON(!kobj->state_initialized);
492 p->kobj.parent = kobj;
496 * cdev_device_add() - add a char device and it's corresponding
497 * struct device, linkink
498 * @dev: the device structure
499 * @cdev: the cdev structure
501 * cdev_device_add() adds the char device represented by @cdev to the system,
502 * just as cdev_add does. It then adds @dev to the system using device_add
503 * The dev_t for the char device will be taken from the struct device which
504 * needs to be initialized first. This helper function correctly takes a
505 * reference to the parent device so the parent will not get released until
506 * all references to the cdev are released.
508 * This helper uses dev->devt for the device number. If it is not set
509 * it will not add the cdev and it will be equivalent to device_add.
511 * This function should be used whenever the struct cdev and the
512 * struct device are members of the same structure whose lifetime is
513 * managed by the struct device.
515 * NOTE: Callers must assume that userspace was able to open the cdev and
516 * can call cdev fops callbacks at any time, even if this function fails.
518 int cdev_device_add(struct cdev *cdev, struct device *dev)
523 cdev_set_parent(cdev, &dev->kobj);
525 rc = cdev_add(cdev, dev->devt, 1);
530 rc = device_add(dev);
538 * cdev_device_del() - inverse of cdev_device_add
539 * @dev: the device structure
540 * @cdev: the cdev structure
542 * cdev_device_del() is a helper function to call cdev_del and device_del.
543 * It should be used whenever cdev_device_add is used.
545 * If dev->devt is not set it will not remove the cdev and will be equivalent
548 * NOTE: This guarantees that associated sysfs callbacks are not running
549 * or runnable, however any cdevs already open will remain and their fops
550 * will still be callable even after this function returns.
552 void cdev_device_del(struct cdev *cdev, struct device *dev)
559 static void cdev_unmap(dev_t dev, unsigned count)
561 kobj_unmap(cdev_map, dev, count);
565 * cdev_del() - remove a cdev from the system
566 * @p: the cdev structure to be removed
568 * cdev_del() removes @p from the system, possibly freeing the structure
571 * NOTE: This guarantees that cdev device will no longer be able to be
572 * opened, however any cdevs already open will remain and their fops will
573 * still be callable even after cdev_del returns.
575 void cdev_del(struct cdev *p)
577 cdev_unmap(p->dev, p->count);
578 kobject_put(&p->kobj);
582 static void cdev_default_release(struct kobject *kobj)
584 struct cdev *p = container_of(kobj, struct cdev, kobj);
585 struct kobject *parent = kobj->parent;
591 static void cdev_dynamic_release(struct kobject *kobj)
593 struct cdev *p = container_of(kobj, struct cdev, kobj);
594 struct kobject *parent = kobj->parent;
601 static struct kobj_type ktype_cdev_default = {
602 .release = cdev_default_release,
605 static struct kobj_type ktype_cdev_dynamic = {
606 .release = cdev_dynamic_release,
610 * cdev_alloc() - allocate a cdev structure
612 * Allocates and returns a cdev structure, or NULL on failure.
614 struct cdev *cdev_alloc(void)
616 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
618 INIT_LIST_HEAD(&p->list);
619 kobject_init(&p->kobj, &ktype_cdev_dynamic);
625 * cdev_init() - initialize a cdev structure
626 * @cdev: the structure to initialize
627 * @fops: the file_operations for this device
629 * Initializes @cdev, remembering @fops, making it ready to add to the
630 * system with cdev_add().
632 void cdev_init(struct cdev *cdev, const struct file_operations *fops)
634 memset(cdev, 0, sizeof *cdev);
635 INIT_LIST_HEAD(&cdev->list);
636 kobject_init(&cdev->kobj, &ktype_cdev_default);
640 static struct kobject *base_probe(dev_t dev, int *part, void *data)
642 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
643 /* Make old-style 2.4 aliases work */
644 request_module("char-major-%d", MAJOR(dev));
648 void __init chrdev_init(void)
650 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
654 /* Let modules do char dev stuff */
655 EXPORT_SYMBOL(register_chrdev_region);
656 EXPORT_SYMBOL(unregister_chrdev_region);
657 EXPORT_SYMBOL(alloc_chrdev_region);
658 EXPORT_SYMBOL(cdev_init);
659 EXPORT_SYMBOL(cdev_alloc);
660 EXPORT_SYMBOL(cdev_del);
661 EXPORT_SYMBOL(cdev_add);
662 EXPORT_SYMBOL(cdev_set_parent);
663 EXPORT_SYMBOL(cdev_device_add);
664 EXPORT_SYMBOL(cdev_device_del);
665 EXPORT_SYMBOL(__register_chrdev);
666 EXPORT_SYMBOL(__unregister_chrdev);